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Complementary Therapies in Clinical Practice 24 (2016) 50e56

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Complementary Therapies in Clinical Practice

journal homepage: www.elsevier.com/locate/ctcp

Yoga reduces perceived stress and exhaustion levels in healthy elderly individuals

Eric Lindahl a, 2, Katherine Tilton a, Nicole Eickholt b, Lisa Ferguson-Stegall a, *, 1

a Integrative Physiology Lab, Dept. of Biology, Hamline University, 1536 Hewitt Ave, Saint Paul, MN 55102, USA b Century College, 3300 Century Ave N, Saint Paul, MN 55110, USA

a r t i c l e i n f o

Article history: Received 24 March 2016 Received in revised form 7 May 2016 Accepted 7 May 2016

Keywords: Yoga Elderly Emotional wellness Stress Exhaustion

* Corresponding author. Hamline University, 1536 Paul, MN 55104, USA.

E-mail addresses: [email protected] (E. Lin (K. Tilton), [email protected] (N. Eickho (L. Ferguson-Stegall).

1 Dr. Ferguson-Stegall directs the Public Health S University. Her Integrative Physiology Laboratory focu physical function and mobility, as well as systemi response to exercise training. She earned her PhD in University of Texas at Austin. She received further tra Fellow at the University of Minnesota Medical Scho aging biology.

2 Eric Lindahl completed his undergraduate educ where he received a B.S. in Biology and a B.A. in Publ Ridgway Research Fellow. He will begin studies in the at the University of Kentucky in the fall of 2016.

http://dx.doi.org/10.1016/j.ctcp.2016.05.007 1744-3881/© 2016 Elsevier Ltd. All rights reserved.

a b s t r a c t

This study investigated whether a 7-week yoga intervention could improve physical function, perceived stress, and mental/emotional wellness in elderly participants. Methods: 8 participants (66.5 ± 0.3 years) attended 2 60-min Hatha yoga sessions/week for 7 weeks, and performed pre- and post-intervention assessments. Balance was assessed using a 5-test battery. Flexi- bility was measured by sit-and-reach and shoulder flexibility tests. Functional mobility tests included 8- ft up-and-go, 5 chair stands, and 4-m walk. Participants completed SF-12, exhaustion level, and Perceived Stress Scale (PSS) questionnaires. Results: SF-12 Mental Component Summary scores, exhaustion levels, and PSS scores improved post- intervention. No differences were found for physical function measures. Conclusions: Yoga participation can improve mental/emotional wellness, exhaustion levels, and stress levels in elderly individuals, even without measurable improvements in physical function. Clinicians and health practitioners who work with the elderly should consider yoga as a potential therapeutic modality for improving important aspects of quality of life in this population.

© 2016 Elsevier Ltd. All rights reserved.

1. Introduction

Aging is associated with a decline in physical function, which can lead to loss of independence, low quality of life, and increased morbidity and mortality. This physical decline is primarily due to sarcopenia, which is the combination of a loss of muscle mass and reduced muscle function (strength and functional performance)

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[1]. Many types of interventions have been studied with the goal of ameliorating this progressive decline. It is well known that resis- tance exercise (i.e., strength training) can significantly improve muscle mass, strength, and physical function [2,3]. Aerobic exercise has also been shown to improve the plasticity and metabolic function of skeletal muscle [4], as well as increase muscle mass in elderly individuals [5]. While most interventions have focused on these traditional exercise modalities, the effectiveness of yoga as an intervention to improve physical function in the elderly is less well characterized.

Yoga has become popular as a therapeutic intervention amongst all age groups, including the elderly. While there are many types and styles of yoga, typical practices combine stretching and holding various poses (called asanas) with deep, diaphragmatic breathing and meditation, with the physical goal of increasing flexibility and strength in skeletal muscles, the spine, and joints [6]. The pur- ported overall health benefits of yoga are wide-ranging, and to date there are many investigations that have demonstrated improve- ments in a multitude of conditions in response to yoga participa- tion. Specifically in the elderly, studies of yoga have shown significant improvements in cardiorespiratory fitness [7,8], respi- ratory function [9,10], and cognitive function [11,12], although this

E. Lindahl et al. / Complementary Therapies in Clinical Practice 24 (2016) 50e56 51

list is not all inclusive (for a comprehensive review, please see Field, 2011 [6]).

Studies of the effects of yoga on physical function in the elderly have mainly focused on balance and flexibility as primary outcome measures. Several have reported improved balance [7,13e15] and flexibility [7,8,14,16,17] in response to yoga interventions. Others have notedimprovedgaitspeed[15,18],aswellasimprovedenduranceand muscle strength [7,8]. Self-reported pain levels have also been shown to significantly improve with yoga participation [19].

In addition to the reported physiological benefits, yoga is often practiced to reduce stress, and to improve aspects of mental and emotional health, such as symptoms of depression. Indeed, in- vestigations have reported significant improvements in depression symptoms [20,21] and improvements in sympathovagal balance and autonomic function [10,22] in response to yoga participation. While reductions in cortisol levels in response to yoga have been documented in adults [22e24], few studies have investigated this outcome measure specifically in the elderly. In addition, only one study to our knowledge assessed perceived stress levels before and after yoga intervention, finding significant improvements in response to the intervention [25]. However, the participant group was middle aged (40e60 yrs) females [25], so the results cannot be generalized to a wider elderly (65 yrs and older) population.

Therefore, the present study sought to better characterize the potential benefits of yoga as a therapeutic intervention in community-dwelling elderly individuals. While there have been many investigations on the effects of yoga on measures of physical function, few have examined a range of functional performance measures directly relevant to performance of activities of daily living (ADLs) in elderly individuals. Additionally, few studies have exam- ined participants' perceptions of their overall, physical and mental/ emotional health, or their perceived levels of stress and exhaustion e all aspects that are important for a high quality of life e in response to participating in a yoga intervention. Thus, the purpose of our study was to determine the effects of a 7-week Hatha yoga inter- vention on measures of physical function and perceived physical health and mental/emotional wellness, exhaustion levels, and stress in elderly participants. We hypothesized that measures of physical function and perceptions of overall health and mental/emotional wellness would improve in response to the intervention. We further hypothesized that perceptions of exhaustion and perceived stress levels would significantly decrease as well.

2. Materials and methods

2.1. Participants

8 community-dwelling participants (6 males, 2 females;

Table 1 Participant characteristics.

Baseline End

Age (yrs) 66.5 ± 0.3 66.5 ± 0.3 Height (cm) 174.8 ± 2.6 174.8 ± 2.6 Weight (kg) 82.02 ± 5.15 80.99 ± 5.02 BMI (kg/m2) 26.7 ± 1.4 26.4 ± 1.3 Systolic blood pressure (mmHg) 120.00 ± 3.64 126.88 ± 3.95 Diastolic blood pressure (mmHg) 74.88 ± 3.86 78.13 ± 4.00 Resting heart rate (bpm) 66.63 ± 3.35 65.13 ± 4.92 Metabolic Profile Glucose (mg/dL) 95.25 ± 2.85 96.75 ± 2.76 Total cholesterol (mg/dL) 177.38 ± 9.55 177.13 ± 16.97 HDL (mg/dL) 48.50 ± 4.74 50.38 ± 4.25 LDL (mg/dL) 110.50 ± 10.08 107.50 ± 16.87 Triglycerides (mg/dL) 92.00 ± 9.13 96.75 ± 14.24

Values are mean ± SE.

66.5 ± 0.3 years) completed the study. Participant characteristics are listed in Table 1. To be eligible for the study, participants were required to be over the age of 60, not have participated in yoga or any other exercise training programs (including aerobic or strength training) regularly within the last year, and have no current injury or illness that would prevent safe participation. Written informed consent was obtained from all participants, and the study was approved by the Hamline University Institutional Review Board. This study was conducted with the ethical standards outlined in the Helsinki Declaration of 1975.

2.2. Research design

Participants completed a 7-week yoga intervention, which consisted of 2 60-min Hatha (combination of physical poses and deep breathing) yoga sessions per week. Baseline testing was per- formed 3e5 days prior to beginning the intervention, and the same tests were repeated within 3e5 days after the intervention ended.

2.3. Intervention

The twice-weekly sessions were led by the same certified yoga instructor with experience in teaching yoga to the elderly. Each 60 min session included several rounds of Surya Namaskar (sun salutations), followed by standing asanas such as Virabhadrasana I, II, and III (Warrior 1e3), seated spinal twists such as Ardha Mat- syendrasana (half twist pose), prone asanas such as Bhujangasana (cobra pose) and Dhanurasana (bow pose), supine asanas such as Setu Bandha Sarvangasana (bridge pose) and Supta Kapotasana (supine pigeon pose), and ended with mindful relaxation in Sava- sana (corpse pose). Deep, diaphragmatic breathing was encouraged throughout each session. Participants were allowed to miss only one class, and a make-up session was offered in the event that one additional class was missed.

2.4. Assessments

2.4.1. Metabolic profile and resting measurements Fasting blood lipids (levels of total cholesterol, HDL cholesterol,

triglycerides, and an indirect estimation of LDL cholesterol) and glucose were taken after an overnight fast. Briefly, the participant's finger was cleaned with alcohol, and a blood sample was taken using a single-use lancing device and a capillary tube. Samples were immediately analyzed using Alere Cholestech LDX Lipid Profile þ Glucose cassettes with the Alere Cholestech LDX system (Alere, San Diego, CA).

Resting blood pressure and heart rate were measured after participants had been seated quietly for 10 min using an Omron BP760 Automatic Blood Pressure Monitor (Omron Healthcare, Lake Forest, IL).

2.4.2. Self-reported perceptions of health, exhaustion, and stress Three survey instruments (questionnaires) - the SF-12, an

exhaustion questionnaire, and Cohen's Perceived Stress Scale (PSS) - were used to assess participants' self-reported perceptions of overall health (both physical and mental/emotional), exhaustion levels while performing activities of daily living, and stress levels, respectively. The questionnaires were completed by the partici- pants while seated alone at a desk in the laboratory prior to their pre- and post-testing sessions. After explaining each of the ques- tionnaires thoroughly and answering any questions about how to complete them, the investigators stepped away to give the partic- ipants privacy. The room was kept quiet and any potential dis- tractions, such as noise in the hallway, was minimized while the questionnaires were being completed.

E. Lindahl et al. / Complementary Therapies in Clinical Practice 24 (2016) 50e5652

The SF-12 is a widely used survey instrument that examines an individual's perception of his or her health status [26]. Using the information from the 12 questions, two sub-scores, a mental component score (MCS) and a physical component score (PCS) are calculated, in addition to a total score. The scores are reported on a 0e100 scale. Higher scores indicate perception of better overall, physical, and mental/emotional health [26].

Participants were asked to rate their perceived exhaustion level by answering the following question, which was provided to them in written form along with the 2 other questionnaires: “When you do basic, day-to-day physical activity (such as walking through your home, doing laundry, cooking, or walking through the grocery store) how often do you feel exhausted by the physical activity?” The answer choices were “never, rarely, sometimes, often, always.” These were coded numerically from 1 to 5, respectively.

Perceived stress levels were assessed using Cohen's Perceived Stress Scale (PSS) [27]. The PSS is a widely used self-report battery of 10 questions that assesses the individual's perception of how much stress is occurring or has occurred in the person's life over the last 4 weeks. Each question is rated on a 0e4 Likert scale, and a total score is calculated by summing the responses as directed in the test instructions [27]. The range of possible scores is from 0 to 40, and higher scores indicate greater perceived stress levels.

2.4.3. Salivary cortisol Saliva samples were taken at 3 time points during one day and

night before the intervention, and during one day and night at the end of the intervention. The time points were: (1) immediately upon waking, (2) 45 min after waking (without brushing teeth or drinking anything other than water), and (3) immediately before bed. Participants were given oral saliva collection swabs and pre- labeled storage tubes (Salimetrics, State College, PA), and the collection procedures were explained and demonstrated by an investigator. The participants also received printed instructions with pictures detailing the proper collection method. The pre- intervention collection occurred within 3 days of the first yoga session, and the post-intervention collection occurred the day before the final session of the intervention. Participants were instructed to refrigerate the samples after collection and deliver them to investigators at the first and final yoga sessions of the intervention.

Samples were stored in a �20 �C laboratory freezer until anal- ysis. They were then thawed and centrifuged according to the manufacturer's instructions (Salimetrics, State College, PA). Salivary cortisol concentrations were determined by high sensitivity competitive enzyme-linked immunosorbent assay (ELISA) accord- ing to the manufacturer's protocol (Salimetrics, State College, PA). Samples were analyzed in duplicate.

2.4.4. Physical function measures Physical function outcome measures were divided into 3

assessment areas: balance, flexibility, and functional mobility. Balance was assessed using 4 progressively difficult standing

balance tests adapted from the Fullerton Advanced Balance Test battery [28], plus a coordinated stability test [29]. The battery of standing tests were performed without shoes, and consisted of (in order of performance): feet together with eyes closed (FTEC), feet together on foam (FTOF), standing on one leg (SOOL), and the near- tandem balance test (NTB).

The FTEC test was performed with participants standing with the feet together and arms crossed over the chest, maintaining their balance with their eyes closed. The FTOF test was performed while standing on an 8-inch thick foam pad in order to challenge balance. For the SOOL test, participants were asked to fold their arms across the chest, lift their preferred leg off of the floor, and maintain

balance standing on one leg. In the NTB test, participants were asked to stand in a near-tandem stance on a non-slip grid with their feet separated laterally by 2.5 cm, and with the great toe of the rear foot placed 2.5 cm behind the heel of the front foot. The grid was marked with correct spacing and placement. Participants were allowed to choose which foot was placed in front. For each balance test, the time (sec) that the participant was able to stand in each position without moving the arms or feet (or opening the eyes in the FTEC test) was recorded as the test measure. The maximum time for each test was 30 sec. If 5 sec or less were achieved, par- ticipants were allowed a second trial and the higher score was used as the test measure.

Coordinated stability was assessed using a Swaymeter test [29]. The Swaymeter device was custom-built in our lab based on the design of Butler and colleagues, and their previously described test protocol was used [29]. The number of deviations was recorded as the test measure.

Flexibility was assessed using chair sit-and-reach and shoulder flexibility tests. For the chair sit-and-reach test, the participant started from a seated position, extended the leg of their choice, pointed the toes of that leg toward the ceiling, and reached with their overlapped hands as far as possible toward the toes while keeping the leg straight. The distance (gap or overlap, in cm) be- tween the tip of the extended middle fingers and the participant's toes was measured to the nearest half cm. For the shoulder flexi- bility test, participants were asked to raise one arm straight up and reach behind the neck, aiming to place the palm near the shoulder blades. Then, they reached the opposite hand down and behind the back with the palm facing out, aiming to touch the fingers of the other hand. The amount of gap or overlap (cm) was recorded. For both of these tests, participants were asked to choose which arm would be raised and which leg would be extended based on com- fort and/or previous injury, and this preference was recorded and repeated in the post-tests. Two familiarization tests were per- formed first, and the third test was recorded as the outcome measure for both of the above tests.

Functional mobility was assessed using 5 timed mobility tests: the 8-foot timed up-and-go (TUG), 4-m walk, stair ascent, stair descent, and the 5 chair stands tests. Each test was measured with a stopwatch with an accuracy of 0.01 s.

For the TUG, participants were instructed to rise from a seated position in a chair with their arms folded across the chest, walk to and around a cone placed 8 feet away, and return back to the seated position in the chair as quickly as possible. The time (sec) taken to complete this task was used as the test measure.

The 4-m walk was performed in a flat, well-lit corridor. Partic- ipants were asked to stand with the front of the toes touching a starting line of black tape on the floor. A finish line was pointed out, marked with orange tape. This line was 2 m past the actual 4 m mark, which was evident only to the investigators. Participants were instructed to walk at their usual, normal walking pace from the start line to the finish line. The time taken from when the first foot lifted to when the trailing foot crossed actual 4 m mark was recorded, and gait speed (m/sec) was calculated and used as the test measure.

The stair ascent and descent tests were performed on well-lit indoor stairs covered with non-slip linoleum, and equipped with a handrail. Starting at the bottom of the flight of 8 stairs, partici- pants were asked to walk up the 8 stairs as quickly as possible, using the handrail if necessary. Timing began when the first foot was lifted off the ground, and stopped when the trailing foot was placed on the 8th step (a landing). After a short rest (~15 s), par- ticipants were then asked to walk back down the stairs as quickly as possible and stop at the bottom, using the handrail if needed. As before, timing began with the lifting of the first foot, and stopped

Fig. 1. Self-reported daily exhaustion levels before and after the yoga intervention. Values are mean ± SE. Significant difference: *p � 0.05.

E. Lindahl et al. / Complementary Therapies in Clinical Practice 24 (2016) 50e56 53

when the trailing foot was placed on the floor. The time (sec) it took to complete the ascent and the descent, respectively, were used as the test measures.

The 5-chair stands test measured the time taken to stand from a seated position with arms folded across the chest, and return to the seated position a total of 5 times as quickly as possible. Elapsed time (sec) was used as the test measure.

2.5. Statistical analysis

Continuous and ordinal variables were analyzed using paired t- tests, and categorical variables were analyzed by a Wilcoxon Signed- Ranks Test. Salivary cortisol was analyzed using 2-way repeated measures ANOVA. Differences were considered significant at p � 0.05. Data were expressed as mean ± SE. All statistical analyses were performed using IBM SPSS Statistics for Windows, version 21 (IBM Corp., Armonk, NY). In addition, effect sizes (Cohen's d) were calculated using an online effect size calculator [30].

3. Results

Nine participants were admitted into the study; however, one voluntarily withdrew due to difficulty scheduling the post-testing session within a reasonable time frame. The baseline and post- intervention characteristics of the 8 participants who completed the yoga intervention are shown in Table 1, including metabolic profile results. The intervention adherence rate was 96%. No in- juries occurred during or as a result of the intervention, or from the testing procedures.

3.1. Metabolic profile and resting blood pressure

Fasting blood lipids (total cholesterol, HDL, estimated LDL, and triglycerides) and glucose levels are shown in Table 1. There were no significant differences between the baseline and post- intervention values. There were also no significant differences in resting blood pressure or heart rate (Table 1).

3.2. Self-reported perceptions of health, exhaustion, and stress

The SF-12 total, mental component (MCS), and physical component (PCS) scores are shown in Table 2. The SF-12 MCS significantly improved after the yoga intervention (p ¼ 0.029), with a large effect size (d ¼ 1.27). In addition, the total/overall SF-12 score trended towards significance (p ¼ 0.054), with a large effect size (d ¼ 1.30). The SF-12 physical component score (PCS) was not significantly different after the intervention.

Self-reported levels of exhaustion also significantly improved after the yoga intervention (Fig. 1; p ¼ 0.046). As described previ- ously in the Methods section, participants were asked how often they felt exhausted by physically performing activities of daily living before and after the 7-week intervention. The answer choices were “never, rarely, sometimes, often, always.” Prior to the inter- vention, 4 participants answered “never”; 3 responded “some- times”, 1 answered “often”, and 0 responded “always.” After the

Table 2 SF-12 results.

Baseline End p value Effect size

SF-12 e Total 98.5 ± 3.2 108.2 ± 1.9 0.054 1.30 SF-12 e MCS 48.8 ± 3.3 57.6 ± 1.2 § 0.029 1.27 SF-12 e PCS 49.8 ± 2.4 50.6 ± 2.3 0.781 0.12

MCS, Mental Component Score; PCS, Physical Component Score. Values are mean ± SE. Significant differences: §p � 0.05.

intervention, 7 answered “never”; 1 responded “sometimes”, and 0 answered “often” or “always.” Fig. 1 displays the numerically coded responses.

As shown in Fig. 2, perceived stress levels as assessed by the PSS significantly decreased after the intervention (Pre, 13.6 ± 1.2 vs Post, 8.9 ± 1.2, p ¼ 0.005), with a very large effect size of 1.38.

3.3. Salivary cortisol

As shown in Fig. 3, there were no differences in salivary cortisol levels after the intervention, compared with pre-intervention values. As expected due to the normal diurnal pattern of cortisol release, there is a significant time effect between the AM 1, AM 2, and PM time points.

3.4. Physical function testing

Balance, flexibility, and functional mobility outcome measures are shown in Table 3. A trend towards significance existed for the 5 chair stands test (Pre, 16.36 ± 0.96 vs Post, 14.02 ± 0.74 s, p ¼ 0.08), with a large effect size of 0.96. A trend also existed for the shoulder flexibility test (Pre, �10.51 ± 4.65 vs Post, �7.13 ± 3.94 cm, p ¼ 0.07), but the effect size was small (d ¼ 0.3). As shown in Table 3, effect sizes were medium for changes in the TUG and the stair descent. However, none of the differences in any of the physical testing outcome measures reached statistical significance.

Fig. 2. Perceived Stress Scale (PSS) scores before and after the yoga intervention. Values are mean ± SE. Significant difference: *p � 0.05.

Fig. 3. Diurnal salivary cortisol pattern over a one-day/night period before and after the yoga intervention. Saliva samples were taken immediately upon waking (AM 1), 45 min later (AM 2), and immediately before going to bed (PM). Values are mean ± SE. No significant change was found in the diurnal pattern in response to the intervention, or in comparing pre- and post-intervention values at any of the individual time points measured.

E. Lindahl et al. / Complementary Therapies in Clinical Practice 24 (2016) 50e5654

4. Discussion

This study aimed to determine the effects of a 7-week Hatha yoga intervention (2 60-min sessions/week) on measures of phys- ical function as well as self-reported perceptions of overall health, mental/emotional wellness, exhaustion levels, and perceived stress levels in a cohort of elderly community-dwelling participants. The most notable finding was that perceived mental/emotional well- ness, exhaustion levels, and perceived stress levels significantly improved in response to the yoga intervention. This is an important finding, considering the essential aspect of these outcomes to overall quality of life.

Our finding of improvement in perception of mental/emotional health is supported by other recent yoga intervention studies. Halpern and colleagues conducted a 12-week yoga intervention with 67 community-dwelling elderly participants who suffered from insomnia [31], and reported significant improvements in emotional health (as assessed by the SF-36, which is a more comprehensive version of the shorter SF-12), and reduced feelings of stress, anxiety, and depression. The investigators also reported improvements in the SF-36 physical health score in the yoga group as well, although the general health score did not significantly

Table 3 Balance, flexibility, and functional mobility.

Baseline

Balance FTEC (sec) 30.00 ± 0.00 FTOF (sec) 30.00 ± 0.00 SOOL (sec) 17.17 ± 1.53 NTB (sec) 25.66 ± 2.99 Coord. stability (# dev.) 2.50 ± 1.02

Flexibility Chair sit-and-reach (cm) �2.06 ± 4.36 Shoulder flexibility (cm) �10.51 ± 4.65

Functional Mobility TUG (sec) 8.78 ± 0.48 4-m walk (m/sec) 0.89 ± 0.04 Stair ascent (sec) 5.30 ± 0.28 Stair descent (sec) 4.79 ± 0.35 5 chair stands (sec) 16.36 ± 0.96

Values are mean ± SE.

improve [31]. In contrast, we saw no change in the SF-12 physical component score (PCS). However, a strong trend (p ¼ 0.054) existed for improvement the overall/total SF-12 score in our participants after the yoga intervention, and the very large effect size (d ¼ 1.30) indicates that this may be clinically relevant. The results of our study and that of Halpern and colleagues suggests that a yoga intervention can improve some aspects of perceived health and wellness, and the degree of improvement (or lack thereof) likely depends on the baseline characteristics of the participant group.

Findings of improvements in mental/emotional, physical, and general health perceptions are not consistent amongst yoga inter- vention studies. For example, Oken and colleagues reported improved general health perception as assessed using the SF-36 questionnaire [14]. However, others reported no change in either mental or physical SF-12 scores after yoga interventions in elderly participants [15]. While the discrepancy in study results may often be due to differences in the survey instrument used or to partici- pant characteristics at baseline, there are also vast differences in sample size and intervention length reported in the literature. Oken et al. used 135 participants in their 6-month intervention [14]; Halpern and colleges had 67 participants for 12 weeks [31]; Tie- demann and colleagues, who reported no differences in SF-12 scores, had 14 participants for 12 weeks [15]; and we had 8 par- ticipants for our 7-week intervention period. Therefore, when comparing intervention studies, it is important to consider the differences in study design when interpreting results. However, it should be noted that the magnitude of the treatment effects of our yoga intervention was very high for the mental/emotional health component, as well as the total/general SF-12 score, evidenced by effect sizes >1.0, which indicates that significant changes in some outcome measures can be found after only 7 weeks, and in a rela- tively small sample group.

Compared to use of perceived health status as an outcome measure, self-reported levels of fatigue or exhaustion are less prevalent in the yoga intervention literature. Some investigations have assessed perception of vitality or energy via the SF-36, reporting either a significant increase in Ref. [14] or no difference [31] in vitality, while some demonstrated significant improvement in fatigue levels using the POMS fatigue questionnaire [31]. Given that there are many ways to define and assess an individual's perception of exhaustion (fatigue is often the descriptive measure), it is difficult to compare this outcome measure across studies. However, our finding of improved exhaustion when performing activities of daily living certainly adds to this body of knowledge. Future studies should attempt to define and assess this outcome measure more clearly (i.e., fatigue vs exhaustion vs vitality).

End p value Effect size

30.00 ± 0.00 e e 30.00 ± 0.00 e e 18.34 ± 0.93 0.34 0.32 24.68 ± 3.54 0.60 0.11 2.25 ± 0.37 0.85 0.12

�2.19 ± 5.81 0.97 0.01 �7.13 ± 3.94 0.07 0.30

8.10 ± 0.34 0.10 0.58 0.93 ± 0.04 0.48 0.34 5.13 ± 0.16 0.28 0.26 4.37 ± 0.16 0.19 0.55

14.02 ± 0.74 0.08 0.96

E. Lindahl et al. / Complementary Therapies in Clinical Practice 24 (2016) 50e56 55

We should point out that our finding of decreased exhaustion levels when performing activities of daily living occurred without a significant increase in measures of physical function or in the perception of physical health status. Given the high level of physical function and activity level in our sample group, however, this is not surprising, as will be explained further below.

Our finding of significantly improved perceived stress levels after the yoga intervention as assessed by the PSS questionnaire is novel in an elderly-only sample group. Halpern and colleagues reported a significant reduction in self-reported stress levels in their elderly study population using the DASS-42 questionnaire [31], but to our knowledge, only one study has assessed perceived stress levels using the PSS before and after a yoga intervention, reporting significant improvements in response to the 8-week intervention [25]. However, since all participants were female and middle aged (40e60 yrs), generalizing the results to an elderly population of both sexes is difficult.

Although we found significantly improved perceived stress levels in response to the yoga intervention, this occurred without a concomitant change in salivary cortisol levels. However, the par- ticipants' pre-intervention levels were already in the lower end of the normal range for the morning and night time points, according to the manufacturer's expected ranges for salivary cortisol levels in adults aged 51e70 yrs. Our seemingly contradictory finding is not without precedent, however. While reductions in cortisol in adult and older individuals have been reported after yoga interventions [6,22,23], Bosch and colleagues did not find a change in the cortisol awakening nor the diurnal pattern in their sample group of older women with rheumatoid arthritis after 10 weeks of yoga [19]. However, they reported decreased perceptions of pain and depression, which are positive findings for improved quality of life [19]. It is also important to note that, despite the well-known role of cortisol as a stress hormone, not all investigations agree that increased levels of stress are actually evidenced by elevated cortisol levels [32]. Therefore, the lack of a change in cortisol may be less important from a clinical standpoint than are the improvements in perceived stress in our study cohort.

Despite the confirmation of our hypothesis regarding improve- ments in perceptions of mental/emotional health, exhaustion, and stress, our hypothesis regarding improvements in physical function outcome measures was not supported by our data. We found no significant differences in any balance, flexibility, or functional mobility measures, although a trend towards significance existed for the 5 chair stands test (with a large effect size), as well as the shoulder flexibility test. Balance and flexibility are the most commonly tested physical function measures in yoga intervention studies in the elderly, and most yoga intervention investigations report significant improvements in balance [7,13e15] and flexibility [7,8,14,16,17]. As will be discussed in the study limitations below, our participants were very physically active and not characterized as frail. Therefore, their balance and flexibility were already rela- tively normal for their age.

Surprisingly, very few studies have examined the effects of yoga on functional mobility outcome measures in elderly participants. The lack of measurable improvement in our functional mobility measures is contrary to some interventions that have demon- strated improvements in gait speed [15,18] and TUG time [18,33]. In a study of 14 frail participants, Galantino and colleagues assessed functional mobility and fear of falling before and after an 8-week chair yoga intervention, reporting that fear of falling significantly decreased, concomitant with an increase in TUG performance [33]. In support of our findings, however, others have reported no sig- nificant change in the 5 chair stands test or in gait speed after a 6- month intervention [14], or in timed sit-to-stand and TUG times after an 8-week yoga intervention [34]. Taken together, these

results would suggest that, while some improvements in functional performance are indeed possible, even in a relatively short- duration program such as ours, it is likely that the degree of improvement depends greatly on the baseline functional condition of the participants. As such, it is highly likely that measurable im- provements in functional performance may be best detected in a less physically robust sample group, such as those already classified as frail.

There are several limitations to this study. The most obvious limitation is that our sample size was small (n ¼ 8). This was due to limited space to hold the yoga sessions, as well as a limited time period in which to conduct the intervention. Future studies should recruit a larger group in order to increase statistical power. How- ever, the most important limitation was the physical robustness of our participants. While all participants met the study requirements for age and previous yoga experience, and were not participating in any exercise programs, analysis of the medical history and physical activity questionnaires revealed that the majority of the partici- pants were highly active individuals, participating in at least some form of physical activity such as golf or tennis on a regular basis. We speculate that for this primary reason, we were unable to detect any significant improvements in the functional mobility measures in our participant group. Therefore, future investigations should screen potential participants more stringently to control for non- structured physical activity levels, and focus on recruiting in- dividuals who are more sedentary or already classified as frail, especially if assessing physical function is a primary outcome measure.

Another potential limitation is the relatively short time period of our intervention. While it is possible that more significant im- provements could have occurred had our intervention period been longer than 7 weeks, we believe that this is unlikely, given the robustness of our participants. Most of the yoga interventions noted in the literature have been either 8 weeks [25,33,34] or 12 weeks [7,15,18,31], with only a few lasting 6 months to a year [14,17]. However, it should be noted that interventions that lasted only one week longer than the present study demonstrated sig- nificant improvements in several outcome measures of physical function, although in study populations that were much less physically robust than that reported here [33,34].

Lastly, another limitation to this and many other yoga inter- vention studies is the lack of a comparable alternate intervention group, such as an aerobic or resistance exercise group (or both). Without another treatment group, it is hard to draw conclusions that would lead us to recommend yoga instead of another form of exercise in this population. However, some have reported that yoga can improve measures of physical function and quality of life compared to an aerobic exercise intervention [14] or to a calis- thenics program [17]. Patel and colleagues compared the effec- tiveness of yoga with other exercise interventions for older adults, using outcome measures of health and physical functioning [35]. Their analysis of 18 qualified studies suggested that the benefits of yoga may even exceed those of traditional exercise interventions on outcome measures of aerobic fitness, strength, and self-reported health status in the elderly. The effect sizes were modest, howev- er, and evidence for yoga's beneficial effect on other aspects of wellness such as depression and sleep quality was mixed [35]. Based on the results of our present study, we concur with the conclusions of Patel and colleagues that larger comparative studies are necessary to better define the conditions in which yoga is most beneficial in the elderly population. Compared to aerobic and resistance training, the lower impact and possibly lower overall risk are ideal for elderly individuals who may be unable or unwilling to participate in more intense exercise programs.

E. Lindahl et al. / Complementary Therapies in Clinical Practice 24 (2016) 50e5656

5. Conclusions

In conclusion, Hatha yoga participation can be effective and beneficial in improving self-perceptions of mental/emotional health, exhaustion levels, and perceived stress levels in healthy elderly participants, even without significant changes in physical function. Clinicians and health practitioners who work with elderly individuals should consider yoga as a potential therapeutic mo- dality for improving important aspects of quality of life in this population.

Conflicts of interest

None.

Role of funding source

The funding source had no role in the design, data collection, analysis or interpretation of this study.

Funding

This project was supported by a grant from the Howard Hughes Medical Institute to the Hamline Biology Department.

Acknowledgements

The authors wish to thank the participants in this study for their time, dedication, and enthusiasm. We also thank The Richardsons for providing the space for the yoga sessions, and L. Petit for her expert yoga instruction. We gratefully acknowledge the Hamline University Biology Dept. (52007543), and Hamline's Collaborative Research program for support of our work.

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