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The positive impact of physical activity on cognition during adulthood: a review of underlying mechanisms, evidence and recommendations

John J. Ratey 1, * and James E. Loehr 2

1 Harvard Medical School , 328 Broadway, Cambridge, MA 02139 , USA 2 Human Performance Institute , Orlando, FL 32827 , USA

* Corresponding author e-mail: [email protected]

Abstract

A growing body of literature suggests that physical activity ben- efi cially infl uences brain function during adulthood, particularly frontal lobe-mediated cognitive processes, such as planning, scheduling, inhibition, and working memory. For our hunter- gatherer ancestors, times of famine interspersed with times of feast necessitated bouts of intense physical activity balanced by periods of rest. However, the sedentary lifestyle that pervades modern society has overridden the necessity for a physically active lifestyle. The impact of inactivity on disease processes has been the focus of much attention; the growing understand- ing that physical activity also has the benefi t of enhancing cog- nitive performance strengthens the imperative for interventions that are successful in increasing physical activity, with the out- comes of promoting health and productivity. Population health and performance programs that promote physical activity pro- vide benefi ts for employees and employers through improve- ments in worker health and performance and fi nancial returns for the company. In this review, we examine the mechanisms by which physical activity improves cognition. We also review studies that evaluate the effects of physical activity on cogni- tive executive performance in adulthood, including longitudi- nal studies that address the impact of physical activity during early adulthood and midlife on preservation of cognition later in life. This is of particular importance given that adulthood represents prime working years and that physical activity promotion is a key component of population health and per- formance programs. Finally, we provide recommendations for maximizing the lasting benefi ts of movement and physical activity on cognition in adulthood.

Keywords: cognition; cognitive reserve; executive function; exercise; movement; physical activity; population health.

Introduction

A growing body of literature indicates that physical activ- ity is associated with improvements in brain function

and cognition during childhood (Sibley and Etnier , 2003 ; Hillman et al. , 2008 ) and throughout adulthood (Colcombe and Kramer , 2003 ; Cotman et al. , 2007 ; Angevaren et al. , 2008 ; Hillman et al. , 2008 ; Smith et al. , 2010 ). Studies in older adults suggest that aerobic activity robustly and preferentially improves performance on tasks that involve executive cognition function, such as planning, schedul- ing, inhibition, and working memory (Kramer et al. , 1999 ; Colcombe and Kramer , 2003 ). Executive cognitive pro- cesses are mediated by the frontal lobes of the brain and are subject to age-related declines (Hillman et al. , 2008 ). Physical activity is an important component of healthy aging and preservation of cognitive function (Colcombe et al. , 2006 ; Kramer et al. , 2006 ; Larson et al. , 2006 ). For example, better aerobic fi tness in older adults reduces loss of brain volume in regions that mediate executive cognitive function (Colcombe et al. , 2003 ; Colcombe et al. , 2006 ) and is associated with more effi cient performance of executive function tasks and increased activity in brain regions that subserve such tasks (Colcombe et al. , 2004) . Similarly, older adults with better aerobic fi tness demonstrate better spatial memory performance and related increases in hippocampal volume (Erickson et al. , 2009 ).

In addition to preservation of cognition during older adulthood, it is important to examine the acute and lasting effects of physical activity on cognition during early adult- hood and midlife. In this review, we will examine potential mechanisms by which exercise and physical activity improve brain function, particularly with regard to executive processes and performance. We will also review studies evaluating the effects of acute bouts of exercise and longer-term physical activity interventions on cognitive performance in adulthood, as well as longitudinal studies that address the role of physi- cal activity during early adulthood and midlife in preserving cognition later in life. Finally, we will provide evidence and recommendations for maximizing the benefi ts of physical activity on cognition through full engagement in physical activity programs, including population health and perfor- mance programs in the workplace. Population health and performance programs that promote physical activity have reported positive effects on employee health and productivity (Conn et al. , 2009 ; Pronk , 2009 ; Pronk and Kottke , 2009 ) that translate into fi nancial savings for employers (Pronk , 2009 ; Baicker et al. , 2010 ). In light of the growing evidence that improved cognitive performance is one of the many benefi ts related to physical activity, workplace interventions that are successful in increasing physical activity can promote both physical and mental health. The rationale for population

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172 J.J. Ratey and J.E. Loehr

health and performance programs is further strengthened by their potential to optimize cognitive performance in addition to employee health.

Evolutionary perspective on physical activity

and cognition

From an evolutionary perspective, the need for movement is probably programmed into our genes (Booth et al. , 2002 ). Physical activity was required by our hunter-gatherer ancestors to compete for energy resources for survival. It is probable that the human genome evolved to support increased metabolic demands associated with hunting and foraging for food. Moreover, ‘ thrifty ’ genotypes (Neel , 1962 ) that maximized the human body ’ s ability to effi - ciently store and utilize fuel sources such as muscle glyco- gen and triglycerides probably evolved to support survival during periods of famine (Chakravarthy and Booth , 2004 ). In other words, the intake of glucose and fat when food was plentiful allowed our hunter-gatherer ancestors to store fuel sources in adipose tissue during periods when little physical activity was required (i.e., feast). Periods of feast were balanced by periods of famine that required physical activity for food procurement; during periods of famine, fuel sources in adipose tissue were metabolized by skeletal muscle.

Thus, the human genome has adapted to support a con- stant demand for movement as well as bursts of physical activity and metabolic fl uxes associated with proper energy homeostasis during periods of feast and famine (Booth et al. , 2002 ; Chakravarthy and Booth , 2004 ). Although the human genome has remained relatively unchanged for the past 10 000 years, the sedentary lifestyle that pervades modern society, along with the unlimited food supply, has overridden the necessity for a physically active lifestyle and natural metabolic fl uxes. The disruption of naturally evolved energy homeostasis brought on by physical inac- tivity contributes to the growing incidence of metabolic diseases (e.g., diabetes, obesity) in today ’ s sedentary soci- ety (Booth et al. , 2002; Chakravarthy and Booth, 2004; Dishman et al., 2006; Hamilton et al., 2007 ). According to data from the National Center for Health Statistics, physical inactivity accounts for approximately 200 000 or 1 in 10 disease-specifi c deaths each year in the US adult population (Danaei et al. , 2009 ). In addition to being an individual risk factor for disease-specifi c deaths, physical inactivity con- tributes to other dietary, lifestyle, and metabolic risk factors for chronic diseases through effects on body mass index (BMI), blood pressure, glucose, and low-density lipopro- tein cholesterol.

Physical activity can be evolutionarily related to cognition in that the need to generate movements for the purpose of suc- cessful food foraging could have necessitated mental activ- ity (Vaynman and Gomez -Pinilla, 2006 ). As Rudolfo Llin á s articulates in I of the Vortex: From Neurons to Self (Llin á s, 2001 ), successful movements led to our thinking brain: ‘ That which we call thinking is the evolutionary internalization of movement ’ .

Systems • Attention • Learning • Memory

Cellular • Synaptic plasticity • Neurogenesis • Angiogenesis

Molecular • Neurotrophins (BDNF) • Growth factors (IGF-1, FGF-2, VEGF)

Figure 1 Exercise exerts systemic, molecular, and cellular effects to mediate executive cognitive function. At the systems level, electrophysiologic and neuroimaging studies have shown that physical activity improves cognitive performance by increasing neuroelectric activity, brain volume, and blood fl ow in brain networks that mediate attention, learning, and memory. At the molecular level, physical activity increases the availability of neurotrophins and growth factors in the brain. Signaling cascades induced by these factors regulate cellular effects that support brain function, including synaptic plasticity, neurogenesis, and angiogen- esis. BDNF, brain-derived neurotrophic factor; FGF-2, fi broblast growth factor-2; IGF-1, insulin-like growth factor-1; VEGF, vascular endothelial growth factor.

Potential mechanisms that mediate the

benefi cial effects of physical activity on

cognition and performance

The effects of physical activity on cognition are seen at the systemic, molecular, and cellular levels (Figure 1 ). At the systems level, electrophysiologic and neuroimaging stud- ies have shown that neural systems that underlie attention, learning, and memory are primed for effi cient and fl exible functioning by physical activity. At the molecular level, physical activity increases the availability of neurotrophins and growth factors in the brain. Signaling cascades induced by these factors regulate cellular effects that support brain function, including synaptic plasticity, neurogenesis, and angiogenesis.

Systems level: increased activity in brain regions

mediating attention, learning, and memory

Many studies have shown that physical activity infl uences neural systems involved in attention, learning, and memory. Electrophysiologic studies have provided insight into the effects of exercise and fi tness on cognition by using elec- trodes placed on the scalp to record event-related brain poten- tials, a measure of electrocortical activity. In particular, P300 is a well-studied component of event-related brain potentials

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Physical activity and cognition 173

that occurs approximately 300 – 800 ms after stimulus onset and provides an indication of attentional resources allocated to the stimulus (Pontifex et al. , 2009 ). This attention-driven neural activity signal is thought to be generated by multiple brain regions involved in information processing and mem- ory encoding, including the frontal lobes, anterior cingulate cortex, temporal lobe, and parietal cortex (Polich , 2007 ). The frontal lobes mediate tasks that require executive cognitive function, such as planning, scheduling, inhibition, and work- ing memory (Kramer et al., 1999; Etnier and Chang , 2009 ). The anterior cingulate cortex is a limbic structure in the medial wall of the brain and is thought to monitor response confl ict and signal the need for adaptation in the attentional network (Colcombe et al. , 2004 ). Temporoparietal activity is thought to be associated with attention and subsequent mem- ory processing, particularly by the hippocampal formation in the medial temporal lobe (Polich , 2007 ).

The amplitude of P300 is proportional to the amount of attention needed to encode the stimulus in working memory, whereas the latency of P300 refl ects the speed of cognitive evaluation of the stimulus (Hillman et al. , 2003 ). In an elec- trophysiologic study of 20 young adults, Hillman et al. (2003) recorded P300 amplitude and latency during an executive cognitive task performed at baseline and after a single bout of treadmill exercise. Results indicated that P300 amplitude during task performance was larger after the exercise session than at baseline, suggesting that exercise increased allocation of attention and memory resources at the neuroelectric level. Other studies have reported that adults with better physical fi tness have larger P300 amplitudes and shorter P300 laten- cies than less fi t adults while they perform executive tasks (Polich and Lardon , 1997 ; Hillman et al. , 2006a ; Pontifex et al. , 2009 ; Kamijo and Takeda , 2010 ). These studies support a role for physical activity in improving cognitive function through attentional mechanisms.

In addition to fi ndings from electrophysiologic studies, neuroimaging studies have provided insights into the effects of physical activity on brain activity and cognition. Structural magnetic resonance imaging (MRI) studies in older adults have revealed that physical fi tness is related to preservation of brain volume. Adults with better fi tness have signifi cantly greater brain volume in frontal, temporal, and parietal cor- tices compared with less fi t adults (Colcombe et al. , 2003 ; Gordon et al. , 2008 ). Moreover, older adults who participated in a 6-month regimen of aerobic training had signifi cant pres- ervation of these brain areas (Colcombe et al. , 2006 ). A recent study provided a more direct link between brain volume and preservation of cognition during aging; older adults with bet- ter aerobic fi tness not only had increased hippocampal volume compared with less fi t adults but also had better performance on a task of spatial memory, a cognitive process subserved by the hippocampus (Erickson et al. , 2009 ).

Functional MRI studies support and extend the fi ndings that exercise affects brain structure, by demonstrating changes in brain function/activity after participating in a regimen of physical exercise. Colcombe et al. (2004) observed increased brain activity coupled with better cognitive performance in older adults who were more fi t or who underwent 6 months of

aerobic training compared with less fi t or untrained study par- ticipants. Participants underwent functional MRI while they performed an executive/attention task known as the Eriksen fl anker task, a task-switching test in which a target stimulus (e.g., B) is fl anked by congruent (e.g., BBBBB) or incongru- ent (e.g., AABAA) stimuli. A correct response during the incongruent condition requires participants to inhibit or fi lter misleading information (i.e., the incongruent fl anking cues); successful inhibition of the misleading information is signi- fi ed by faster reaction time to the incongruent cues. Highly fi t and aerobically trained adults had faster reaction times during the incongruent condition of the task, indicating that these participants processed confl icting cues more effi ciently than less fi t and untrained participants. In addition, highly fi t and aerobically trained adults had greater activity during the task in the attentional circuitry of the brain, including key regions of the frontal and parietal cortices. Thus, improved fi tness was associated with better task performance, as well as enhancements in structure and function of brain areas thought to underlie executive functions.

In another study, 11 adults aged 21 – 45 years partici- pated in a 3-month aerobic exercise regimen (Pereira et al. , 2007 ). Performance on a word recall memory task, the Rey Auditory Verbal Learning Test, along with changes in regional cerebral blood volume (CBV) in the hippocam- pus, was assessed before and after the exercise training period. CBV in the hippocampal dentate gyrus signifi - cantly increased after aerobic training and was positively associated with the fi tness level achieved (as assessed by the maximum volume of oxygen consumption). Moreover, performance on the Rey Auditory Verbal Learning Test improved after exercise training and correlated with den- tate gyrus CBV. Thus, exercise induced a selective increase in CBV that correlated with fi tness level and cognitive per- formance (Figure 2 ). The dentate gyrus is a hippocampal structure to which new neurons are added throughout life (Eriksson et al. , 1998 ); the potential role of neurogenesis in mediating exercise-induced changes in the brain is dis- cussed in more detail later.

Molecular level: neurotrophins and growth factors

In addition to studies reporting that neural systems underly- ing attention, learning, and memory are primed for effi cient and fl exible functioning after physical activity interventions, other studies have begun to elucidate molecular mechanisms by which physical activity affects cognition. Among vari- ous potential molecular mediators of the effect of exercise on cognition (Vaynman and Gomez -Pinilla, 2006 ; Cotman et al. , 2007 ), two well-studied candidates are brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1).

Studies in rats and mice (Cotman and Berchtold , 2002 ) have shown that voluntary exercise on a running wheel increases hippocampal levels of BDNF, a molecule important for syn- aptic plasticity, learning, and memory. Animal studies have shown that exercise improves performance on the Morris water maze, a task that involves spatial learning and memory,

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174 J.J. Ratey and J.E. Loehr

and that injection of a drug that blocks BDNF activity in the hippocampus also blocked the benefi t of exercise on the water maze task (Vaynman et al. , 2004 ; Gomez -Pinilla et al., 2008 ). In exercising mice, hippocampal BDNF levels increased immediately after exercise and remained elevated for several weeks before returning to baseline levels (Berchtold et al. , 2010 ). Moreover, the cognitive improvement in water maze training and memory performance paralleled the time course of hippocampal BDNF availability. In humans, acute exercise increased serum BDNF levels in young adults (Ferris et al. , 2007 ). In older women (but not older men), decreased levels of plasma BDNF were signifi cantly associated with poorer performance on multiple cognitive tasks (Komulainen , et al., 2008 ). Thus, the effects of BDNF on hippocampal function, learning, and plasticity make it a potentially important fac- tor in the mediation of the effects of exercise on cognition (Cotman et al. , 2007 ).

IGF-1 is produced mainly in the liver and works closely with growth hormone to mediate somatic growth and tissue remodeling (Trejo et al. , 2001 ; Torres -Aleman, 2010 ). IGF-1 also provides trophic support to the brain, both through serum IGF-1 that crosses the blood-brain barrier and through IGF-1 produced locally in the brain (Torres -Aleman, 2010 ). Animal studies have shown that exercise stimulates uptake of IGF-1 from the bloodstream into specifi c brain areas, including the hippocampus, and that blocking IGF-1 uptake in the brain also blocks exercise-mediated increases in adult neurogen- esis (Trejo et al. , 2001 ). Animals with decreased IGF-1 levels have impaired learning and memory (Trejo et al. , 2008 ). In humans, IGF-1 levels decrease with age, and in older adults, serum IGF-1 levels are positively correlated with cognitive performance (Arwert et al. , 2005 ).

BDNF and IGF-1 appear to act in concert to mediate exercise-induced effects on the brain (Cotman et al. , 2007 ). For example, IGF-1 infl uences BDNF production in the hip- pocampus in response to exercise. Other growth factors also contribute to the benefi cial effects of exercise on the brain. For example, vascular endothelial growth factor (VEGF) can work together with IGF-1 to mediate exercise-induced

vascular changes in the brain (Cotman et al. , 2007 ). Moreover, experimentally increasing VEGF levels in the hippocampus in rats resulted in a 2-fold increase in neurogenesis that was associated with improved performance on the Morris water maze, and blocking VEGF levels inhibited both neurogen- esis and learning (During and Cao , 2006 ). Fibroblast growth factor-2 (FGF-2) is another growth factor with effects on neu- rogenesis; animal studies have shown that FGF-2 increases neurogenesis in the hippocampus of adult and aged animals (Jin et al. , 2003 ; Mud ò et al., 2009 ). Similar to IGF-1, VEGF and FGF-2 exhibit age-related declines in the rat hippocam- pus, and the loss of growth factor activity with aging could contribute to age-related decreases in neurogenesis and brain function (Shetty et al. , 2005 ).

Cellular level: synaptic plasticity, neurogenesis,

and angiogenesis

Neurotrophins and growth factors can promote a cellular environment that supports cognition by increasing synaptic plasticity, neurogenesis, and vascular function (Cotman et al. , 2007 ).

Exercise increases long-term potentiation (LTP) in the hip- pocampus, a neural correlate of learning (Farmer et al. , 2004 ); rats given access to a running wheel had signifi cantly greater LTP induction than did sedentary litter mates, indicating that exercise lowers the threshold for synaptic plasticity. In addi- tion, expression of BDNF and specifi c glutamate receptor subtypes in the hippocampal dentate gyrus was increased in running rats, indicating that increased BDNF signaling and glutamate-mediated synaptic transmission could have con- tributed to the exercise-induced enhancement of synaptic plasticity. Additional research has shown that exercise affects synaptic plasticity through BDNF- and IGF-1-activated kinase signaling cascades (e.g., mitogen-activated protein kinase, calcium/calmodulin protein kinase II), which in turn promote transmission at the synapse through upregulation of synaptic proteins, such as synapsin I (Vaynman and Gomez - Pinilla, 2006 ).

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Figure 2 Increased CBV in the hippocampal dentate gyrus in adults who participated in a 12-week exercise training program. (A) Relative CBV (rCBV) in the dentate gyrus selectively increased after exercise training, whereas exercise did not signifi cantly affect CBV in other hippocampal subregions. (B) A high-resolution MRI taken after exercise training in one of the adult participants shows the hippocam- pus (left image) with depiction of individual subregions (middle image). Higher CBV (indicated by warmer colors) is evident in the dentate gyrus (right image). CA1, Cornu Ammonis 1; CBV, cerebral blood volume; DG, dentate gyrus; EC, entorhinal cortex; Sub, subiculum. Figure reproduced with permission from Pereira et al. (2007) . Figure used with permission from Pereira et al. (2007) National Academy of Sciences, USA, Copyright 2007.

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Physical activity and cognition 175

Research studies in rodents have demonstrated that volun- tary running increases the production of new neurons in the dentate gyrus of the hippocampus (van Praag et al. , 1999a,b ). Moreover, running increases neurogenesis in aged mice that had been sedentary until old age (van Praag et al. , 2005 ). Mice with access to a running wheel also had better performance on the Morris water maze than did non-running controls. Running increases neurogenesis in mice through effects on cell proliferation (McAlpine et al. , 2007 ), cell survival (van Praag et al. , 1999a,b, 2005 ; Snyder et al. , 2009 ), and func- tional maturation and incorporation of newly generated cells into hippocampal circuitry (Snyder et al. , 2009 ).

Exercise can promote the survival of newly generated cells in the dentate gyrus through effects on the phosphatidylinosi- tol 3-kinase/protein kinase B (PI3K-Akt) signaling pathway (Bruel -Jungerman et al., 2009 ). A recent rodent study found that phosphorylation/activation of Akt and several of its downstream antiapoptotic targets occurs in the dentate gyrus in response to running wheel exercise and that inhibiting PI3K blocks exercise-induced activation of these prosurvival proteins as well as reduces exercise-induced neurogenesis (Bruel -Jungerman et al., 2009 ). In addition, inhibition of PI3K blocked LTP induction, indicating that synaptic plasticity in the dentate gyrus depends on PI3K signaling. These results collectively suggest that neurogenesis is a key mechanism by which physical activity can improve synaptic plasticity and cognition and that growth factor cascades such as the PI3K- Akt signaling pathway induced by IGF-1 (Bondy and Cheng , 2004 ) can contribute to the exercise-induced effects on cogni- tion (Trejo et al. , 2008 ; Bruel -Jungerman et al., 2009 ).

Running increases the growth of new microvessels in the cerebral vasculature of young and old rats (Swain et al. , 2003 ; Ding et al. , 2006 ). In addition, angiogenesis is coupled with neurogenesis; the vascular environment in the dentate gyrus can help circulating growth factors infl uence the proliferation and survival of newly generated cells (Palmer et al. , 2000 ). Expression of VEGF is increased in running rats (Ding et al. , 2006 ), and blocking VEGF abolishes the exercise-induced increase in neurogenesis in running animals (Fabel et al. , 2003 ). Exercise increases the size of blood vessels in the den- tate gyrus in mice, potentially increasing the blood supply to support neurogenesis (van Praag et al. , 2005 ).

Mice with low levels of circulating IGF-1 (and thus reduced uptake of IGF-1 into the brain) have defi ciencies in both angiogenesis (Lopez -Lopez et al., 2004 ) and neu- rogenesis (Trejo et al. , 2001 ), suggesting that the vascular environment in the hippocampus affects the delivery of important, neurogenic growth factors to the dentate gyrus. Consistent with these fi ndings, another study showed that exercising mice have increased CBV and neurogenesis in the dentate gyrus (Pereira et al. , 2007 ). Blocking neurogene- sis by exposing the mice to irradiation also blocked changes in CBV, suggesting that neurogenesis is the mechanism by which exercise directs blood fl ow to the dentate gyrus. Taken together, these studies indicate that exercise promotes angiogenesis by increasing the effects of VEGF and IGF-1 on vessel growth (Cotman et al. , 2007 ) and that angiogen- esis is linked with neurogenesis.

Overall, mechanistic studies have demonstrated that physi- cal activity has a role in priming mental function at the sys- tems level and directly infl uencing cognition at the molecular and cellular levels, maximizing the potential of the brain to process new information (Ratey and Hagerman , 2008 ). Studies that have evaluated the connection between physical activity and cognitive performance on a variety of tasks in humans are discussed in detail later.

Benefi cial effects of physical activity

on cognition and performance

Published studies on the impact of physical activity on cogni- tive performance generally have two types of designs: con- trolled studies of the effects of exercise interventions and studies of the correlation between exercise and cognitive performance. Exercise interventions range from a single bout of acute exercise to weeks-long fi tness programs. Correlation studies have addressed whether adults who are already physi- cally active are more likely than inactive adults to have better performance on various cognitive tasks, or whether better fi t- ness in early adulthood and midlife is associated with better cognition later in life.

A single bout of exercise can improve specifi c aspects

of cognition

Studies have shown that a single bout of exercise, such as 30 min of cycling or running, can improve automatic aspects of cognition such as reaction time and speed of information processing (Hogervorst et al. , 1996 ; McMorris and Graydon , 1997 ; Audiffren et al. , 2008 ; Joyce et al. , 2009 ). Acute exer- cise also improves performance on higher-order cognitive processes, including executive cognitive tasks such as plan- ning, scheduling, inhibition, and working memory (Kramer et al. , 1999 ).

One common test of attention and executive function that has been used to measure the effects of exercise is the Stroop test (Stroop , 1935 ). This test measures the amount of time it takes to do three tasks: reading words, naming ink colors, and naming the ink color of words that are color names (e.g., the word ‘ red ’ printed in green ink). Although people fi nd the fi rst two tasks to be simple, the third is much more dif- fi cult because it involves inhibiting the automatic response to read the word rather than name the color. Thus, whereas the word and color subtasks of the Stroop test evaluate speed of information processing, the incongruent color-word subtask assesses the executive functions of selective attention, shift- ing, and inhibition of habitual responses (Chang and Etnier , 2009b ).

Improved executive function as demonstrated by bet- ter performance on the Stroop color-word subtask has been shown in young adults after a single bout of aerobic exercise (Hogervorst et al. , 1996 ; Sibley et al. , 2006 ) or resistance exer- cise (Chang and Etnier , 2009b ). In a study of 41 middle-aged adults (mean age: 49 years), improvement in information pro- cessing speed and a trend toward improvement in executive

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176 J.J. Ratey and J.E. Loehr

function were found after resistance exercise (Chang and Etnier , 2009a ). Other studies have shown increased working memory performance (e.g., verbal memory, visual memory) after acute aerobic exercise in young adults (Sibley and Beilock , 2007 ; Winter et al. , 2007 ; Coles and Tomporowski , 2008 ) and enhanced cognitive fl exibility (i.e., thinking beyond conventional uses of objects to alternate uses) after acute aer- obic exercise in middle-aged adults (aged 50 – 64 years) (Netz et al. , 2007 ).

Longer-term exercise interventions improve cognition

Prospective studies have shown that exercise interventions that range from 2 to 12 weeks can effectively improve cogni- tive function. In a report published more than 30 years ago, Young (1979) found that a 10-week exercise program for 32 adults aged 23 – 62 years improved performance on execu- tive function tasks, including the Wechsler Adult Intelligence Scale Digit Symbol and Block Design subtests and the Trail Making Test, along with other tests of learning and informa- tion processing speed (Figure 3 ). In addition, participants reported improved health status and decreased levels of anxi- ety at the end of the program.

In another study of 66 adults aged 18 – 48 years, participants who improved 15 % or more in physical fi tness after a 10- to 12-week exercise regimen had more effi cient information

processing compared with adults with stable fi tness levels (Blomquist and Danner , 1987 ). Similarly, a smaller study of 30 women aged 27 – 66 years showed that participation in a physical fi tness program consisting of three exercise sessions per week for 8 months improved physical fi tness by 17 % and was associated with signifi cant gains in information pro- cessing and decision-making capabilities (Suominen -Troyer et al., 1986 ).

A short-term exercise program can also be an effective way to improve working memory and cognitive fl exibility. A 14-day healthy lifestyle program that combined mental and physical exercise, stress reduction, and healthy diet was asso- ciated with signifi cant improvement in a verbal fl uency test of working memory in 17 adults aged 35 – 69 years with mild self-reported memory problems (Small et al. , 2006 ). Another study reported that 6 weeks of running (30 min three times weekly) by 14 adults aged 17 – 29 years improved visuospa- tial memory and positive mood (Stroth et al. , 2009 ). Another recent study of 91 adults aged 18 – 70 years randomized partic- ipants to minimal aerobic exercise (0 – 2 days/week, the con- trol group), moderate aerobic exercise (3 – 4 days/week), or high aerobic exercise (5 – 7 days/week) for 10 weeks (Masley et al. , 2009 ). Participants took the CNS Vital Signs battery of cognitive tests at study entry and after the 10-week inter- vention. Compared with the control group, the moderate and high exercise groups had signifi cantly improved cognitive

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Figure 3 Improved executive function after exercise intervention. The mean performance on various tasks of executive function improved after a 10-week exercise program in young (A, B) and middle-aged (C, D) adults. Across all four groups, regardless of age or sex, signifi cant improvement was observed after the exercise intervention on all tasks except the Visual Reproduction Memory task. Data are reproduced with permission from Young (1979) . Reproduced with permission from BMJ Publishing Group Ltd., Copyright 1979.

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Physical activity and cognition 177

fl exibility. In addition, participants who exercised 5 – 7 days per week had better reaction time, attention, and cognitive fl exibility than participants who exercised 3 – 4 days per week (Masley et al. , 2009 ).

Higher levels of physical activity are associated

with better cognition

In addition to promising results from randomized studies of short-term exercise interventions, correlation studies have shown that adults who are generally more physically active are more likely than adults who are generally inactive to have better performance on various cognitive tasks, includ- ing those involving executive functions. In a study of 241 community-dwelling individuals aged 15 – 71 years, Hillman et al. (2006b) evaluated whether participants ’ self-reported physical activity levels were associated with performance on the Eriksen fl anker task, a task that requires focusing atten- tion and inhibiting responses to the incongruent stimuli. The authors found that younger (mean age: 26 years) and older (mean age: 50 years) participants who participated in more physical activity had faster reaction times for congruent and incongruent conditions of the fl anker task. In addition, older participants with higher physical activity levels dis- played better response accuracy on the incongruent condi- tion (Hillman et al. , 2006b ). Smaller studies in young adults showed an association between physical activity and task- switching performance (Themanson et al. , 2008 ; Kamijo and Takeda , 2010 ); together, these studies provide evidence that regular physical activity during adulthood improves execu- tive function.

In a study that used a battery of neuropsychological tests on 1927 healthy adults aged 45 – 70 years revealed that indi- viduals with more intense weekly physical activity had better processing speed, memory, mental fl exibility, and overall cog- nitive function (Angevaren et al. , 2007 ). In addition, partici- pation in a greater variety of activities (e.g., walking, cycling, housekeeping, doing odd jobs, gardening, sports activities) was associated with signifi cantly better performance on all evaluated cognitive domains.

Furthermore, in a prospective, occupational cohort study of 10 308 adults aged 46 – 68 years who were employed by 20 London-based civil servant departments revealed that those who reported lower levels of physical activity had lower scores on various cognitive tests of executive function, including measures of inductive reasoning and verbal fl uency (Singh -Manoux et al., 2005 ).

Physical activity in early and middle adulthood can

preserve cognition in later life

Several studies have investigated the lasting benefi t of physi- cal activity on cognition in later years. The largest study included a population-based analysis of all Swedish men born from 1950 to 1976 who enlisted for military service at the age of 18 years (n = 1 221 727) ( Å berg et al., 2009 ). This large population represented approximately 97 % of the male Swedish population born from 1950 to 1976. Cardiovascular

fi tness was measured with ergometer cycling, and cogni- tive ability and performance were assessed with a combina- tion of four tests: a logical performance test, a verbal test of synonyms and opposites, a test of visuospatial/geometric perception, and a test of technical/mechanical skills with mathematical/physics problems, as measures of general cognitive ability. Cardiovascular fi tness as well as perfor- mance on the individual cognitive domains (logic, verbal, visuospatial, and technical) at age 18 years was signifi cantly associated with general cognitive ability. Interestingly, additional analyses of brother pairs (n = 268 496) and twin pairs (n = 3147, of which 1432 were monozygotic twin pairs) showed that the positive correlation between fi tness and cog- nition was mainly due to environmental rather than genetic factors. The authors also examined the longitudinal effect of cardiovascular fi tness on cognitive performance. They found that changes in fi tness from 15 to 18 years of age were linked to changes in cognition; participants with improved fi tness had better scores on global, logic, verbal, visuospatial, and technical cognitive tests compared with participants with a decline in fi tness levels. Finally, cardiovascular fi tness at age 18 years predicted educational attainment (university vs. high school) and socioeconomic status (professions ranked with high vs. low socioeconomic index) later in life ( Å berg et al., 2009 ).

In addition to this large, longitudinal study of young adults ( Å berg et al., 2009 ), other studies have found that physical activity during midlife can preserve cognition later in life (Bosma et al. , 2002 ; Richards et al. , 2003 ; Rovio et al. , 2005 ; Singh -Manoux et al., 2005 ; Andel et al. , 2008 ; Hassing et al. , 2009 ; Sabia et al. , 2009 ; Geda et al. , 2010 ). These studies, outlined in Table 1 , report that participa- tion in physical activity can signifi cantly slow the rate of cognitive decline during later adulthood (Bosma et al. , 2002 ; Richards et al. , 2003 ; Singh -Manoux et al., 2005 ) or reduce the risk of developing dementia or Alzheimer ’ s disease (Rovio et al. , 2005 Andel et al. , 2008; Geda et al., 2010 ) and that being overweight or obese during midlife can be associated with poorer cognition or increased odds of developing dementia later in life (Hassing et al. , 2009 ; Sabia et al. , 2009 ).

Additional insights and recommendations for

maximizing the benefi ts of physical activity on

cognition

The American College of Sports Medicine and the American Heart Association recommend that to promote and maintain health, all healthy adults aged 18 – 65 years should partake in a minimum of 150 min per week (i.e., 30 min for 5 days) of moderate-intensity aerobic physical activity as well as at least 2 days per week of muscle-strengthening activities that work the major muscle groups (Haskell et al. , 2007 ). Unfortunately, most adults in the United States currently do not obtain the recommended level of physical activity (Troiano et al. , 2008 ). In light of the large body of evidence that supports the positive effects of physical activity on

AUTHOR’S COPY | AUTORENEXEMPLAR

178 J.J. Ratey and J.E. Loehr

T ab

le 1

hy si

ca l

ac ti

vi ty

d ur

in g

m id

li fe

p re

se rv

es c

og ni

ti on

i n

la te

r ad

ul th

oo d.

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dy P

ar ti

ci p

an ts

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es sm

en ts

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u lt

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el e

t al

. (2

0 0

8 )

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n io

rs w

it h

d em

en ti

a an

d 2

87 0

co nt

ro ls

ro ll

ed i

n th

e H

A R

M O

N Y

s tu

dy , w

h ic

h in

cl ud

ed m

em b

er s

of t

h e

S w

ed is

h T

w in

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is tr

y w

ho w

er e

ag ed

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s an

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i n

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es sm

en t

of d

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ti a

o cc

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ed a

n av

er ag

e of

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te r

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vo lv

in g

sp or

ts ;

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li g

ht e

xe rc

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a s

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k in

g or

g ar

d en

in g

; 3)

h ar

d ly

a ny

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rc is

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pa re

d w

it h

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an ts

w ho

r ep

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d ly

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ho se

w ho

r ep

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n ifi

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tl y

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d ev

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y ea

rs l

at er

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m a

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2 0

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ed 4

9 –

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ea rs

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th e

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st ri

ch t

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in g

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dy .

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ti ci

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ts w

it h

no e

ng ag

em en

t vs

. a t

le as

t 1

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ee k

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te st

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ne a

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ll ow

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3 ye

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la te

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s ix

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s (S

tr o

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o rd

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ru en

t ta

sk , R

ey A

ud it

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ba l

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es t,

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te r

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it C

o d

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t, W

o rd

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t, a

nd M

M S

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pa re

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it h

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p ar

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p an

ts , t

ho se

w ho

p o

rt ed

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le as

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li n

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f A

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ti ci

p an

ts r

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rt ed

t h

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l of

p hy

si ca

l ex

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li g

ht ,

m o

d er

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v ig

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d u

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m id

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( ag

ed 5

0 –

65 y

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(m em

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is uo

sp at

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ls ).

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in m

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a ss

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; ex

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se r

ed uc

ed t

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ri sk

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I by

3 9

% .

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si ng

e t

al . (

2 0

0 9

) 11

52 a

du lt

s, i

n cl

ud in

g 31

2 w

it h

d em

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a an

d 18

1 w

it h

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h ei

m er

’ s d

is ea

se , f

ro m

t h

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w ed

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in R

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tr y

w ho

p ar

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p at

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n a

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rv ey

1 9

63 a

nd w

er e

ag ed

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– 65

y ea

rs i

n 19

63 .

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p an

ts w

er e

sc re

en ed

f o

r d

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cl ud

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m er

’ s

d is

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r a

fo ll

ow -u

p p

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4 0

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s. C

o rr

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to d

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( B

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2 6.

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n cr

ea se

d th

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of d

ev el

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9 %

g re

at er

r is

or A

lz h

ei m

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d is

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( 71

% g

re at

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h ar

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2 0

03 )

19 19

a du

lt s

en ro

ll ed

i n

th e

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ea rc

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n ci

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rv ey

o f

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lt h

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t (t

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B ri

ti sh

1 9

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bi rt

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ti ci

p an

ts r

ep o

rt ed

t h

ei r

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l of

p hy

si ca

l ex

er ci

se (

e. g.

, ae

ro bi

c ac

ti v

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p or

ts )

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sp ar

e- ti

m e

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v it

ie s

(e .g

., so

ci al

ti v

it ie

s) a

t ag

e 36

y ea

rs . V

er ba

l m

em or

y w

as a

ss es

se d

at a

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43 a

nd 5

3 ye

ar s

u si

ng a

w o

rd -l

ea rn

in g

ta sk

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ag em

en t

in p

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ca l

ex er

ci se

a nd

s pa

re -t

im e

ac ti

v it

y at

a ge

3 6

ye ar

s w

as s

ig n

ifi c

an tl

y as

so ci

at ed

w it

h b

et te

r ve

rb al

m em

or y

at a

ge 4

3 ye

ar s.

I n

ad d

it io

n , p

ar ti

ci p

an ts

ho r

ep o

rt ed

e ng

ag in

g in

p hy

si ca

l ex

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se a

t ag

e 36

y ea

rs h

ad a

s ig

n ifi

c an

tl y

sl ow

er r

at e

of d

ec li

n e

m em

or y

fr om

a ge

s 43

t o

53 y

ea rs

. M or

eo ve

r, p

ro te

ct io

n ag

ai n

st m

em or

y d

ec li

n e

w as

e v

id en

t in

p ar

ti ci

p an

w ho

r ep

o rt

ed e

ng ag

in g

in p

hy si

ca l

ex er

ci se

a t

ag e

ye ar

s (e

it h

er n

ew o

r co

nt in

u in

g ex

er ci

se rs

) bu

t no

t in

p ar

ti ci

p an

ts w

ho g

av e

up e

xe rc

is e

af te

r 36

y ea

rs ,

su g

ge st

in g

th at

c o

nt in

u in

g ph

ys ic

al e

xe rc

is e

af te

r ag

e 36

ar s

w as

i m

p o

rt an

t fo

r p

ro te

ct io

n of

c og

n it

io n.

R ov

io e

t al

. (2

0 05

) 14

49 a

du lt

s, i

n cl

ud in

g 11

7 w

ho d

ev el

op ed

em en

ti a

an d

76 w

ho d

ev el

op ed

A lz

h ei

m er

’ s

d is

ea se

, i n

th e

F in

n is

h C

A ID

E s

tu dy

w ho

h ad

se ss

m en

ts a

t m

id li

fe (

m ea

n ag

e, 5

1 ye

ar s)

a nd

ll ow

-u p

(m ea

n ag

e, 7

2 ye

ar s)

P ar

ti ci

p an

ts r

ep o

rt ed

t h

ei r

le ve

l of

p hy

si ca

l ac

ti v

it y

an d

w er

e ca

te go

ri ze

d as

a ct

iv e

(p ar

ti ci

pa te

d in

l ei

su re

-t im

e ph

ys ic

ac ti

v it

y at

l ea

st t

w ic

e a

w ee

k) o

r se

d en

ta ry

( pa

rt ic

ip at

ed i

n le

is u

re -t

im e

ph ys

ic al

a ct

iv it

y le

ss t

h an

t w

ic e

a w

ee k)

. C

o rr

el at

io n

an al

ys es

w er

e co

nd uc

te d

to d

et er

m in

e w

h et

h er

ga ge

m en

t in

p hy

si ca

l ac

ti v

it y

d ec

re as

ed t

h e

ri sk

o f

d ev

el op

in g

d em

en ti

a o

r A

lz h

ei m

er ’ s

d is

ea se

C om

pa re

d w

it h

th e

se d

en ta

ry g

ro up

, p ar

ti ci

p an

ts w

re p

o rt

ed e

ng ag

in g

in p

hy si

ca l

ac ti

v it

y at

l ea

st t

w ic

e a

w ee

k du

ri ng

m id

li fe

h ad

a s

ig n

ifi c

an tl

y re

du ce

d ri

sk o

f d

ev el

op in

g d

em en

ti a

(5 2

% l

es se

r ri

sk )

or A

lz h

ei m

er ’ s

is ea

se (

6 0

% l

es se

r ri

sk ).

AUTHOR’S COPY | AUTORENEXEMPLAR

Physical activity and cognition 179

S tu

dy P

ar ti

ci p

an ts

A ss

es sm

en ts

R es

u lt

S ab

ia e

t al

. (2

0 0

9 )

51 31

c iv

il s

er va

nt s

in L

on do

n w

ho p

ar ti

ci p

at ed

t h

e W

h it

eh al

l II

s tu

dy .

B M

I w

as s

el f-

re p

or te

d or

m ea

su re

d at

a ge

2 5

ye ar

s (e

ar ly

a du

lt -

ho o

d) , e

ar ly

m id

li fe

( m

ea n

ag e:

4 4

ye ar

s) , a

nd l

at e

m id

li fe

( 61

ar s)

. C og

n it

io n

w as

a ss

es se

d at

l at

e m

id li

fe u

si ng

a b

at te

ry o

f te

st s

an d

ca te

go ri

ze d

as m

ea su

ri ng

g lo

ba l

co g

n it

io n

(M M

S E

m em

or y

(2 0

-w o

rd f

re e

re ca

ll t

es t)

, a nd

e xe

cu ti

ve f

u nc

ti on

li ce

H ei

m 4

-I t

es t

of i

nd uc

ti ve

r ea

so n

in g

an d

te st

s of

v er

ba l

fl ue

nc y)

B ei

ng o

b es

e (B

M I ≥

3 0

k g

/m 2 )

a t

la te

m id

li fe

w as

so ci

at ed

w it

h p

o o

re r

co g

n it

io n

on a

ll m

ea su

re s

(M M

S E

, m em

or y,

a nd

e xe

cu ti

ve f

u nc

ti on

t es

ts ).

I n

ad d

it io

n , c

u m

u la

ti ve

o b

es it

y (b

ei ng

o b

es e

at t

w o

th re

e of

t h

e st

ud y

ti m

e p

oi nt

s) w

as a

ss o

ci at

ed w

it h

lo w

er M

M S

E , m

em or

y, a

nd e

xe cu

ti ve

f u

nc ti

on s

co re

su g

ge st

in g

th at

t h

e ef

fe ct

o f

ob es

it y

on c

og n

it io

n ac

cu m

u la

te s

ov er

t h

e ad

u lt

l if

e co

u rs

e, e

x am

in ed

o ve

r a

m ea

n du

ra ti

on o

f 36

y ea

rs i

n th

is s

tu dy

. S

in g

h -

M an

o u

x et

. ( 2

0 05

)

10 3

0 8

ci v

il s

er va

nt s

in L

on do

n w

pa rt

ic ip

at ed

i n

th e

W h

it eh

al l

II s

tu dy

, a

p ro

sp ec

ti ve

, o cc

up at

io n

al c

o ho

rt s

tu dy

t h

b eg

an i

n 19

85 , w

h en

p ar

ti ci

p an

ts w

er e

ag ed

– 5 5

ye ar

P ar

ti ci

p an

ts r

ep o

rt ed

t h

ei r

le ve

l of

p hy

si ca

l ac

ti v

it y

(l ow

, m

ed iu

m , o

r h

ig h)

a t

st ud

y ba

se li

ne a

nd o

th er

t im

e p

oi nt

C og

n it

iv e

fu nc

ti on

w as

a ss

es se

d fr

om 1

9 9

7 to

1 9

9 9,

w h

en t

h e

pa rt

ic ip

an ts

w er

e ag

ed 4

6 –

68 y

ea rs

, u si

ng a

b at

te ry

o f

te st

s th

in cl

ud ed

m ea

su re

s of

fl u

id i

nt el

li ge

nc e

(i .e

., A

li ce

H ei

m 4

-I t

es t

of i

nd uc

ti ve

r ea

so n

in g)

a nd

v er

ba l

fl ue

nc y.

A l

ow l

ev el

o f

ph ys

ic al

a ct

iv it

y at

s tu

dy b

as el

in e

w as

g n

ifi c

an tl

y as

so ci

at ed

w it

h p

o o

re r

p er

fo rm

an ce

o n

a m

ea su

re o

f fl

u id

i nt

el li

ge nc

e (w

h ic

h in

vo lv

es s

ho rt

-t er

m em

or y,

a b

st ra

ct t

h in

k in

g, c

re at

iv it

y, a

bi li

ty t

o so

lv e

no ve

l p

ro bl

em s,

a nd

r ea

ct io

n ti

m e)

1 1

ye ar

s la

te r,

w h

w o

rk er

s w

er e

ag ed

4 6

– 68

y ea

rs .

B M

I, B

od y

m as

s in

de x;

C A

ID E

, c ar

di ov

as cu

la r

ri sk

f ac

to rs

, a gi

ng a

nd i

nc id

en ce

o f

de m

en ti

a; M

C I,

m il

d co

gn it

iv e

im pa

ir m

en t;

M M

S E

, m in

i- m

en ta

l st

at e

ex am

in at

io n.

T ab

le 1

( C

on ti

nu ed

)

cognition, and the ample evidence of the impact of exercise on physical health and disease, effective interventions to increase level of exercise and effectiveness of exercise regi- mens are needed. In this section, we will discuss evidence that engaging in focused periods of exercise and rest, along with avoiding prolonged periods of sedentary behavior at work and at home, can improve physical health and cognitive performance. We also review evidence supporting participa- tion in population health and performance programs that promote physical activity. Given that employed adults spend around half of their waking hours at work (Conn et al. , 2009 ) and that the nature of contemporary work is increasingly sed- entary owing to automation and process effi ciencies (Pronk , 2009 ), workplace interventions that promote physical activ- ity are urgently needed and uniquely positioned to impact employee health and productivity. Our recommendations for focused periods of exercise and participation in workplace programs support both physical and mental health benefi ts (Table 2 ).

Engage in focused periods of exercise and rest

The recommended amount of weekly physical activity for healthy adults is a minimum of 150 min of moderate-inten- sity aerobic physical activity or 60 min of vigorous-intensity activity in addition to muscle-strengthening activities on 2 or more days (Haskell et al. , 2007 ). The level of inten- sity of physical activity can affect cognitive performance. Although the impact of exercise on cognition is not uniform across individuals (Sibley and Beilock , 2007 ), several stud- ies have suggested a dose-response relationship between exercise intensity and cognitive function (Themanson et al. , 2008 ; Chang and Etnier , 2009b ). Among 1927 adults aged 45 – 70 years, individuals with more intense weekly physical activity (assessed by summing weekly physical activities and calculating the metabolic equivalent value of the summed activity) had better processing speed, memory, mental fl ex- ibility, and overall cognitive function (Themanson et al. , 2008 ). However, the time spent weekly on physical activities did not affect cognitive performance, suggesting a selective effect of exercise intensity on cognitive function. A more recent study reported that the relationship between exercise intensity and cognitive performance depended on the type of cognitive task (Chang and Etnier , 2009b ); in this study of 68 adults (mean age: 26 years) who participated in an acute bout of resistance exercise, high-intensity exercise was found to benefi t speed of information processing, whereas moderate-intensity exercise was most benefi cial for execu- tive performance (i.e., inhibition, working memory, atten- tional fl exibility).

Regardless of the level of intensity applied during physi- cal activity, a highly focused, purposeful routine can provide motivation to stay engaged in an exercise regimen over the long-term (Loehr and Schwartz , 2003 ). A study of 50 adults aged 20 – 40 years reported that mindfulness was associated with better cognitive function. The study included medita- tors and non-meditators across a wide range of professions and reported that mindfulness was associated with better

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180 J.J. Ratey and J.E. Loehr

performance on the Stroop task and d2-concentration and endurance test (Moore and Malinowski , 2009 ). Meditators demonstrated greater mindfulness than did non-meditators and had better attentional control, accuracy, and cognitive fl exibility. Practical suggestions for increasing mindfulness during physical activity include commitment, focus, and elimination of distractions during the exercise period.

Periods of intense physical activity should be balanced by periods of rest and energy renewal (Loehr and Schwartz , 2003 ). Balance is key, because prolonged periods of sed- entary behavior during waking hours have been associated with poorer health (Healy et al. , 2008 ). Healy et al. (2008) reported an association between metabolic health and avoid- ance of prolonged periods of sitting in 168 adults aged 30 – 87 years (mean age: 53 years). Sedentary time and physical activity breaks (i.e., avoiding prolonged periods of physical inactivity) were monitored during waking hours for 7 days, and biomarkers of metabolic risk were assessed. Findings indicated that the number of physical activity breaks was associated with lower waist circumference, BMI, triglycer- ides, and 2-h plasma glucose levels. The recorded breaks were relatively short in duration and light in intensity, sug- gesting that brief, simple disruptions in sedentary time can have a signifi cant impact on metabolic health. The authors provided practical suggestions for implementing easy physi- cal activity breaks at home and in the workplace, such as taking brief ambulatory breaks during commercial breaks on television and during prolonged periods of sitting at work. Other approaches for avoiding prolonged periods of seden- tary behavior at work by expending energy in the offi ce set- ting include innovative offi ce equipment, such as treadmill workstations, or holding meetings while walking (Levine et al. , 2006 ; Levine and Miller , 2007 ; McAlpine et al. , 2007 ; John et al. , 2009 ).

In a study of 20 self-professed ‘ couch potatoes ’ , includ- ing 10 lean (BMI, 23 ± 2 kg/m 2 ) and 10 mildly obese (BMI, 33 ± 2 kg/m 2 ) participants, Levine et al. (2005) used microsen- sors to record participants ’ movements and body positions every 0.5 s for 10 days. Obese participants were seated an average of 2 h longer per day than lean participants. This result is consistent with the fi nding that prolonged sedentary time has detrimental effects on physical health. Moreover,

in light of evidence that being overweight or obese during midlife is associated with poorer cognition or increased odds of developing dementia later in life (Hassing et al. , 2009 ; Sabia et al. , 2009 ), these fi ndings suggest that avoiding prolonged periods of sedentary behavior can have positive effects not only on physical health but also on preservation of cognition.

In addition to evidence supporting intense physical activity and avoidance of prolonged sedentary time, other studies have reported positive associations between par- ticipation in leisure activities and cognition. Studies in middle-aged adults have shown that participation in leisure activities involving mental engagement (e.g., brain teasers, courses or evening classes, playing chess or bridge), social engagement (e.g., volunteer work, attending the cinema, theatre, or concerts), or spiritual engagement (e.g., church or religious activities) improved performance on various cognitive tests of executive function, including measures of inductive reasoning and memory (Richards et al. , 2003 ; Singh -Manoux et al., 2003 ; Small et al. , 2006 ). Moreover, participation in mental, social, and physical activities pro- tected against cognitive decline in 830 adults aged 49 – 81 years assessed at baseline and 3 years later (Bosma et al. , 2002 ).

Engaging in physical and leisure activities affects not only cognitive function but also emotional satisfaction and qual- ity of life. The association between exercise participation and well-being was assessed in approximately 8000 adults aged 18 – 65 years from the Netherlands Twin Registry. Exercisers were more satisfi ed with their life and happier than non-ex- ercisers at all ages (Stubbe et al. , 2007 ). A systematic review of 14 studies related to physical activity and health-related quality of life reported that higher levels of physical activity in healthy adults were linked to better health-related quality of life outcomes (Bize et al. , 2007 ).

Taken together, these studies suggest that engaging in focused periods of physical activity and rest has signifi cant physical and mental health benefi ts. In addition, the likeli- hood of preserving physical health and cognition throughout adulthood can be maximized by avoiding prolonged seden- tary time and participating in leisure activities that provide

Table 2 Recommendations for maximizing the benefi ts of physical activity on physical and mental health.

Recommendation Rationale

Engage in focused periods of physical activity and rest

• Exercise intensity is related to information processing speed, memory, mental fl exibility, and overall cognitive function (Angevaren et al. , 2007 ; Chang and Etnier , 2009b ).

• Taking frequent physical activity breaks (i.e., avoiding prolonged periods of uninterrupted sitting) has important health benefi ts (Healy et al. , 2008 ) that could promote preservation of cognitive performance.

• Participation in mental, social, and physical activities preserves cognitive function (Bosma et al. , 2002 ; Richards et al. , 2003 ; Singh -Manoux et al., 2003 ; Small et al. , 2006 ) and improves emotional satisfaction and health-related quality of life (Bize et al. , 2007 ; Stubbe et al. , 2007) .

Participate in workplace wellness programs

• Participation in wellness programs that promote physical activity improves worker health and productivity (Benedict and Arterburn , 2008 ; Anderson et al. , 2009 ; Conn et al. , 2009 ; Pronk , 2009 ).

• Financial gains for employers include decreased medical costs and reduced absenteeism costs (Baicker et al. , 2010 ).

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Physical activity and cognition 181

opportunities for physical, emotional, mental, and spiritual engagement.

Participate in workplace wellness programs

An increasing body of evidence suggests that promoting phys- ical activity in the workplace has a signifi cant positive effect on worker health and productivity (Conn et al. , 2009 ; Pronk , 2009 ). The workplace is an opportune setting for implement- ing and monitoring physical activity interventions that sup- port the employee population and, indirectly, their families (Pronk and Kottke , 2009 ). The corporate environment is well suited to leverage resources to increase employees ’ awareness of the benefi ts of physical activity and to encourage adoption and maintenance of physical activity regimens. For example, companies can use e-mail communications, departmental meetings, and online programs to promote tailored strategies (e.g., walking programs, integrated work breaks, comprehen- sive population health and performance programs) to increase physical activity and improve employee health and perfor- mance. Companies can also provide meaningful incentives and awards (e.g., fi nancial incentives, health insurance benefi ts) to promote ongoing participation in health risk assessments and physical activity programs (Pronk and Kottke , 2009 ).

In a comprehensive meta-analysis summarizing health and physical activity behavior outcomes associated with workplace wellness programs, Conn et al. (2009) reviewed nearly 150 reports including more than 38 000 participants. Signifi cant improvements were observed for physical activ- ity behavior, fi tness, lipids, anthropometric measures, work attendance, and job stress (Figure 4 ). Other systematic reviews reported that wellness programs are effective for improving weight loss and BMI (Benedict and Arterburn ,

2008 ; Anderson et al. , 2009 ). Taken together, studies of pop- ulation health and performance programs provide evidence that workplace interventions can successfully increase the physical activity behavior of employees. Moreover, these pro- grams can provide signifi cant benefi ts in terms of employee health and productivity. Although wellness programs gener- ally do not assess cognitive function as an outcome measure, the growing body of literature that connects physical activ- ity with cognition suggests that workplace programs that promote engagement in physical activity can also promote improved cognitive performance among employees.

Workplace wellness programs have signifi cant benefi ts for employers as well as employees. A meta-analysis evaluating the costs and savings associated with workplace wellness pro- grams showed that medical costs decrease by approximately $3.27 for every dollar spent on wellness programs and that absenteeism costs decrease by approximately $2.73 for every dollar spent (Baicker et al. , 2010 ). Thus, integrated popula- tion health and performance programs that promote physi- cal activity provide benefi ts for employees and employers through improvements in worker health and performance and fi nancial returns for the company. In light of the increasing evidence that improved cognitive performance is one of the many benefi ts related to physical activity, workplace inter- ventions that promote physical activity are likely to have lasting benefi ts on employees ’ physical fi tness and cognitive productivity.

Conclusion

Extensive evidence suggests that physical activity benefi cially infl uences brain function and executive cognitive processes in

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iz e

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Physical activity

behavior

Fitness Job stress Anthropometric measures

Lipid measures Diabetes riskWork attendance

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Figure 4 Meta-analytic fi ndings of effects of workplace physical activity interventions on physical activity behavior, health, and work-related outcomes. A meta-analysis of the effects of workplace physical activity interventions reported signifi cant benefi ts on physical activity behavior, fi t- ness (oxygen consumption), work attendance (derived from company records), job stress (self-reported), anthropometric measures (BMI, weight, abdominal girth, and percent body fat), lipid measures (total cholesterol, high-density lipoproteins, or the ratio of total cholesterol to high-density lipoproteins), and diabetes risk (fasting glucose or insulin levels). Data are reproduced with permission from Conn et al. (2009) . Reproduced with permission from Elsevier, Copyright 2009.

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182 J.J. Ratey and J.E. Loehr

particular. The effects of physical activity on cognition are exerted at the systemic, molecular, and cellular levels and are associated with changes in brain volume, cerebral blood fl ow, and growth factor availability and signaling cascades. Published studies suggest that physical activity in adulthood has a signifi cant, lasting impact on cognition. Not only does acute exercise improve executive cognitive performance but regular physical activity in midlife has a protective effect against cognitive decline in later adulthood. Recommendations for maximizing the lasting benefi ts of movement and physical activity on cognition in adulthood include bouts of intense exercise, avoidance of prolonged periods of sedentary behav- ior (i.e., sitting), engagement in leisure activities, and par- ticipation in workplace wellness programs. Population health and performance programs that promote physical activity can provide lasting benefi ts for employees in terms of physical health and brain function, translating into improved employee performance and increased fi nancial returns for the company. In summary, humans were designed to move. Movement improves cognitive performance and delays age-related cog- nitive declines through multiple neural mechanisms that sup- port improved brain function. Additional insights from future studies will continue to clarify the benefi cial effects of physi- cal activity – and the detrimental effects of inactivity – on cognitive performance throughout adulthood.

Acknowledgments

Medical writing assistance was provided by Robin L. Stromberg, PhD, of JK Associates, Inc., and was supported by Wellness & Prevention, Inc., a Johnson & Johnson company.

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