Discussion 13

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/279305983

Gait modifications to change lower extremity gait biomechanics in runners: A

systematic review

Article  in  British Journal of Sports Medicine · June 2015

DOI: 10.1136/bjsports-2014-094393 · Source: PubMed

CITATIONS

21

4 authors, including:

Some of the authors of this publication are also working on these related projects:

FKB project / research View project

PhD Thesis: Gait retraining to reduce biomechanical risk factors in novice recreational runners View project

Chris Napier

University of British Columbia - Vancouver

14 PUBLICATIONS   198 CITATIONS   

SEE PROFILE

Jack E Taunton

University of British Columbia - Vancouver

219 PUBLICATIONS   7,412 CITATIONS   

SEE PROFILE

Michael Hunt

University of British Columbia - Vancouver

157 PUBLICATIONS   3,705 CITATIONS   

SEE PROFILE

All content following this page was uploaded by Chris Napier on 09 March 2016.

The user has requested enhancement of the downloaded file.

Gait modifications to change lower extremity gait biomechanics in runners: a systematic review Christopher Napier,1 Christopher K Cochrane,1 Jack E Taunton,2 Michael A Hunt1

▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ bjsports-2014-094393). 1Faculty of Medicine, Department of Physical Therapy, University of British Columbia, Vancouver, British Columbia, Canada 2Faculty of Medicine, Division of Sports Medicine, Department of Family Practice, University of British Columbia, Vancouver, British Columbia, Canada

Correspondence to Dr Michael A Hunt, Department of Physical Therapy, University of British Columbia, 212-2177 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 1Z3; michael.hunt@ubc.ca

Received 5 November 2014 Revised 6 May 2015 Accepted 28 May 2015

To cite: Napier C, Cochrane CK, Taunton JE, et al. Br J Sports Med Published Online First: [please include Day Month Year] doi:10.1136/bjsports- 2014-094393

ABSTRACT Background Abnormal biomechanics have been cited as a potential risk factor for running-related injury. Many modifiable biomechanical risk factors have also been proposed in the literature as interventions via gait retraining. Aim To determine which interventions have successfully modified biomechanical variables linked to running- related injury. Study design Systematic literature review. Methods MEDLINE, EMBASE, CINAHL, SportDiscus and PSYCINFO were searched using key terms related to running biomechanics and gait retraining. Quality of included studies was assessed using the modified Downs and Black Quality Index and a best evidence synthesis was performed. Results 27 studies investigating the effect of biomechanical interventions on kinetic, kinematic and spatiotemporal variables were included in this review. Foot strike manipulation had the greatest effect on kinematic measures (conflicting evidence for proximal joint angles; strong evidence for distal joint angles), real- time feedback had the greatest effect on kinetic measures (ranging from conflicting to strong evidence), and combined training protocols had the greatest effect on spatiotemporal measures (limited to moderate evidence). Conclusions Overall, this systematic review shows that many biomechanical parameters can be altered by running modification training programmes. These interventions result in short term small to large effects on kinetic, kinematic and spatiotemporal outcomes during running. In general, runners tend to employ a distal strategy of gait modification unless given specific cues. The most effective strategy for reducing high-risk factors for running-related injury—such as impact loading—was through real-time feedback of kinetics and/or kinematics.

The incidence of running-related injury varies from 19% to 85%1–4 and this rate has not decreased appreciably in the past 30 years.4 A significant portion of runners who become injured do not return to running.1

Abnormal biomechanics have long been pro- posed as a potential risk factor for running-related injury.3 5 6 For example, several measures—includ- ing rearfoot eversion,7–11 vertical loading rate12–16

and foot strike index17—have all demonstrated a significant association with running-related injury. Given the possible links between faulty lower limb biomechanics and injury risk during running, many interventions have been aimed at modifying these biomechanical risk factors through the varied use of orthotics,18 shoes, the absences of shoes,19

changing surfaces and other structural interventions in an effort either to treat running-related injury or lower injury risk.20–25 Some of these biomechanical variables—such as cadence and foot strike—may be modifiable via specific interventions while others may not. To know which interventions may be effective in treating running-related injury, it is important to know which biomechanical variables have been successfully modified during running gait. To date, only one paper has reviewed the influence of stride frequency/length on running mechanics, finding that an increased stride fre- quency reduced the magnitude of several biomech- anical variables associated with running-related injury.26 However, none have looked at the effect of other commonly used clinical interventions on running gait. The aim of this systematic review, therefore, was to determine which interventions have successfully modified individual kinetic, kine- matic and spatiotemporal variables. For practical reasons, only the most commonly reported bio- mechanical variables will be included.

METHODS Identification and selection of the literature This systematic review was conducted and reported according to the PRISMA protocol. A search strat- egy was devised for electronic databases (MEDLINE, EMBASE, CINAHL, SportDiscus and PSYCINFO), with restrictions for English language and publication type (reviews and conference abstracts excluded). No date restrictions were included. The final search was completed on 22 July 2014 and involved the following search strat- egy (identical for all databases): (1) Biomechanics/ or Kinetics/, (2) Biomechanic$.mp, (3) Kinetic$.ti, ab or Kinematic$.ti,ab, (4) 1 or 2 or 3, (5) running/ or jogging/, (6) runner$.ti,ab or running.ti,ab, (7) 5 or 6, (8) 4 and 7, (9) Animals/, (10) 8 not 9. Titles and abstracts of all identified citations were

screened by two reviewers (CN and CKC), with the full-text of articles meeting the initial inclusion cri- teria retrieved for further screening. Reference lists of all publications considered for inclusion were further reviewed and a manual search of one author’s (CN) private collection was conducted until no additional eligible publications were identi- fied. In cases of disagreement between the first two reviewers, a third reviewer (MAH) determined the final eligibility of the selected publications.

Selection criteria An article was eligible for inclusion if it met all of the following criteria: (1) the statistical comparison of at least one intervention with a biomechanical variable of interest was reported; (2) data were

Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393 1

Review BJSM Online First, published on June 23, 2015 as 10.1136/bjsports-2014-094393

Copyright Article author (or their employer) 2015. Produced by BMJ Publishing Group Ltd under licence.

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

derived experimentally from a cohort of skeletally mature able- bodied subjects using a within-subjects design; (3) the outcome of interest was a biomechanical (kinetic, kinematic and/or spatiotemporal) variable; (4) the protocol included straight-line, submaximal running (either on a treadmill or overground); (5) the primary independent variable was a biomechanical interven- tion intended to have a direct result on lower extremity bio- mechanical characteristics during running. Articles were excluded if: (1) the study sample consisted of disabled or chronic disease populations; (2) the protocol only included lateral, cutting, sprinting or other modes of locomotion; (3) the study was designed to investigate the effect of a ‘negative’ inter- vention (eg, fatigue, pain, swelling, delayed onset muscle sore- ness, etc) on running gait biomechanics; (4) the intervention did not include gait modification—studies that only varied the surface (treadmill, overground, trail, road, etc), incline/decline, footwear or velocity were excluded, as were studies where the primary objective was to modify some physiological parameter (eg, muscle strength) that may have had an indirect effect on lower extremity biomechanics during running; or (5) the study did not control for running speed.

Assessment of methodological quality Publications that met all selection criteria were assessed for methodological quality by two independent reviewers (CN and MAH). A modified version of a quality index for randomised and non-randomised trials was used.27 This tool contains 27 items evaluating 5 subscales: reporting, external validity, bias (intervention and outcome measurement), confounding (cohort selection bias) and power. As recommended in the literature,28

the power subscale (question 27) was not used in this study due to item ambiguity. The quality index awards one point for each item. No points are awarded if the answer is negative or is unable to be determined. Thus, the maximum score for the modified index was 26 points. Agreement between reviewers was assessed using a κ statistic, with reference to Landis and Koch’s criteria where κ values >0.81 represent ‘almost perfect’ agreement; >0.61, ‘substantial’ agreement; 0.41–0.60, ‘moder- ate’ agreement; and <0.40, ‘poor to fair’ agreement.29

Data synthesis and analysis A single reviewer (CN) extracted group means, SDs, and sample sizes directly from the selected articles and all reviewers checked extracted data. Statistical pooling of the data was not performed because of the small number of studies that addressed the same outcome measure with the same intervention. However, a best evidence synthesis was performed (see online supplementary table S1). Our inclusion/exclusion criteria limited the studies to repeated measures designs. Studies that only looked at immedi- ate effects (ie, within a single session) and longitudinal effects (ie, multiple training sessions) were not considered to be differ- ent. Rather, the methodological quality of the studies and the consistency of findings across studies were deemed to be import- ant and used to determine level of evidence, as has previously been used.30 Effect sizes (ESs) were also calculated for the primary outcome variables for all studies that provided discrete data (ES=mean difference between normal and intervention measurements/pooled SD). Authors of publications that did not provide data in an extractable form were contacted. Effect sizes were used in this review to provide a means of evaluating success of the intervention because these are not directly affected by sample size but take into account within-group vari- ability. Effect size magnitudes were interpreted based on Cohen (small=0.2, moderate=0.5 and large=0.8).31

RESULTS Selection of studies A search of the MEDLINE, EMBASE, CINAHL, SportDiscus and PSYCINFO databases identified a total of 3558 articles (figure 1). A total of 36 articles met the initial search criteria and their full texts were retrieved. After further review by two reviewers (CN and CKC), 11 of these articles were excluded because they did not meet the inclusion criteria. Ten additional articles were included from one author’s personal collection (CN). As these studies reported on 143 different biomechanical variables, further analysis was conducted only on variables that were reported by three or more papers.32 This reduced the number of biomechanical variables to 14, from 27 articles. Online supplementary table S2 summarises the characteristics of the included studies with regard to participant population, sample sizes, participant ages, intervention protocols, quantita- tive biomechanical variables and the mode of testing.

Methodological quality Two reviewers (CN and MAH) assessed the final 27 studies using the modified quality index instrument. Of the 27 articles assessed, all achieved a score of 14 or above out of a possible 26, with the majority (n=19) scoring between 16 and 19 (see online supplementary table S3), indicating generally low to moderate methodological quality. A study was considered to be of high quality if the methodological quality score was greater than or equal to the mean of all of the quality scores.33 All studies scored zero on items 13 (external validity items), 14, 15 (internal validity: bias items) and 24 (internal validity: con- founding items). While studies scored poorly on blinding items, some (n=13) did use a randomised order of conditions (item 23). In addition, items 8 (reporting item), 10–12 (external valid- ity items), 18 (internal validity: bias item) and 23 (internal valid- ity: confounding item) also scored poorly. Studies generally scored well on items 1–7, 9 (reporting items), 16, 17, 19, 20 (internal validity: bias items), 21, 22, 25 and 26 (internal valid- ity: confounding items). The initial agreement between reviewers was almost perfect (κ=0.923) and reliability for indi- vidual items ranged from substantial (κ=0.609, item 18) to perfect (items 5, 9, 13–15, 17, 20–22, 24 and 26).29 Consensus was reached on all items at the initial discussion between the two reviewers.

Study characteristics The 27 studies that qualified for final inclusion in this review consisted of a mix of gait retraining interventions (see online supplementary table S4). Foot strike manipulation (forefoot/ mid-foot strike vs rearfoot strike) was the most common inter- vention with nine studies using this intervention.20 24 34–40 Step frequency (six studies)37 41–45 and step length (six studies)45–50

modifications were also common interventions, followed by step width (three studies).36 49 51 Four studies provided real-time feedback about peak-positive tibial acceleration. 22 52–54 Finally, two studies provided a combined intervention consisting of a patented technique (Pose method).21 24 In studies with add- itional conditions—such as shoe type or velocity—only out- comes that were compared within the same condition were analysed.

Intervention outcomes Results are grouped by the variable of interest, rather than a spe- cific gait modification. Further, unless specifically stated, all changes described pertain to comparisons with normal,

2 Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

self-selected (ie, not modified) running trials. Studies that only provided a subjective comparison between conditions (eg, ‘more’ or ‘less’) are also detailed below, although these do not contain quantifiable data such as effect sizes or statistical com- parisons. Six studies20–22 24 52 55 employed multiple training sessions and examined longitudinal effects, while the remaining studies were limited to a single session and examined immediate effects.

Kinematics Nine publications looking at kinematic variables were included in this review. Variables examined were: hip angle (sagittal plane) at initial contact, knee angle (sagittal plane) at initial contact, ankle angle (sagittal plane) at initial contact and peak rearfoot eversion/rearfoot eversion at maximum pronation.

Changes in hip kinematics Based on our best evidence synthesis, there was no evidence found to support changing sagittal hip angle at initial contact by modifying stride length or from peak-positive acceleration feed- back. There was conflicting evidence for foot strike manipula- tion. Hip angle at initial contact showed decreased flexion in one study when subjects were asked to run forefoot in shod and barefoot conditions (ES=0.44 and 0.48, respectively).38

However, Williams et al40 found no difference in hip flexion angle at initial contact with a forefoot strike versus rearfoot strike (ES=0.01), and Seay et al47 found no difference when stride length was increased (ES=0.87) or decreased (ES=0.11). Peak-positive acceleration feedback also did not change hip

angle postfeedback protocol (ES=0.17) or at 1 month follow-up (ES=0.18).52

Changes in knee kinematics There was no evidence to support peak-positive acceleration feedback or stride length manipulation in changing sagittal knee angle at initial contact. The evidence for foot strike manipula- tion was conflicting, and limited evidence supported the Pose technique and step frequency manipulation. Contrasting results were reported for knee angle at initial contact, with Shih et al38

reporting increased flexion with a forefoot strike versus rearfoot strike (ES=0.78 and 1.95 for barefoot and shod conditions, respectively), while Williams et al40 found no significant differ- ence (ES=0.02). Arendse et al24 also found increased knee flexion at initial contact with the Pose technique (which employs a forefoot strike and an increased step rate; ES=0.61), but no difference with a mid-foot strike (0.02). Step rate and step length had no significant effect on knee angle at initial contact except when step rate was increased by 10% (ES=0.44).42 47 Peak-positive acceleration feedback had no effect on knee angle postfeedback protocol (ES=0.04) or at 1 month follow-up (ES=0.21).52

Changes in ankle kinematics There was no evidence to support peak-positive acceleration feedback in changing sagittal ankle angle at initial contact, and limited evidence to support the Pose technique and stride length manipulation. Foot strike manipulation, however, was supported by strong evidence. The largest ES from non-pooled data

Figure 1 Flow diagram of the systematic review process. ‘#’ denotes ‘number’.

Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393 3

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

involved the sagittal angle at the ankle at initial contact. Specifically, the ankle tended to be more plantarflexed at initial contact with a mid-foot strike (ES=4.76),24 forefoot strike (ES=3.88 and 5.60 for barefoot and shod, respectively,38 and ES=4.2640) or Pose technique (ES=2.35).24 Peak-positive accel- eration feedback resulted in significantly increased plantarflex- ion both immediately postfeedback protocol (ES=0.76) and at 1 month follow-up (ES=0.90).52 A 20% increase in stride length had the effect of decreasing plantarflexion (ES=0.26).47

No significant difference was reported when stride length was decreased by 20% (ES=0.23).47

Changes in foot kinematics There was no evidence to support step length manipulation in changing rearfoot eversion angle at initial contact. Step width and foot strike manipulation were both supported by limited evidence. Three studies examined peak rearfoot eversion. Two of these studies varied step width, finding that in all but one instance (‘normal’ vs ‘wide step’ (ES=0.37)56) that a crossover gait increased peak rearfoot eversion (compared with ‘normal’ (ES=0.4456 and 0.6649and ‘wide step’ (ES=0.8056) and a wide gait decreased it (ES=1.21)).49 Pohl et al36 also found that peak eversion decreased with a forefoot strike versus rearfoot strike (ES=0.69). This was even more pronounced with a toe foot strike (compared with rearfoot strike (ES=1.81) and forefoot strike (ES=1.03)).36 No significant differences were shown with a change in step length (‘long’ step length (ES=0.03) or ‘short’ step length (ES=0.27)).49

Kinetics Kinetic variables were examined from 17 papers and included: vertical impact peak, average vertical loading rate, instantaneous vertical loading rate, peak-positive tibial acceleration, shock attenuation, vertical stiffness and leg/lower extremity stiffness.

Vertical impact peak There was conflicting evidence for step length and step fre- quency manipulation, as well as peak-positive acceleration feed- back to reduce vertical impact peak. Limited evidence supported hip adduction angle retraining as a means to reduce vertical impact peak, while foot strike manipulation and the Pose tech- nique were backed by moderate evidence. Vertical impact peak was reduced by increasing step frequency (with a 36% increase when compared to a 26% decrease from preferred step fre- quency (ES=NA; not applicable)41) and was increased when step frequency was reduced (with a 30% reduction (ES=NA)43) or when step length was increased (ES=1.54).48 However, con- trasting results from some studies13 37 43 48 suggest that an increase/decrease in step frequency or step length does not con- sistently affect vertical impact peak. Two studies showed a decrease in vertical impact peak with a mid-foot strike (ES=1.39),24 forefoot strike (ES=0.30)21 or Pose technique (ES=1.33),24 but Cheung et al20 did not find a difference between foot strikes (rearfoot strike vs forefoot strike ES=1.06). Peak-positive acceleration feedback did not affect vertical impact peak postfeedback protocol (ES=0.58) or at 1 month follow-up (ES=0.70).52

Average vertical loading rate Evidence was conflicting for the effect of step frequency manipulation on average vertical loading rate. Limited evidence supported the Pose technique and hip adduction angle retrain- ing. Moderate evidence supported foot strike manipulation and peak-positive acceleration feedback for reducing average vertical

loading rate. Average vertical loading rate was consistently reduced with a forefoot strike (ES range from 1.93– 3.32)20 37 38 and mid-foot strike pattern (ES=1.97).37 Average vertical loading rate was not affected by stride frequency unless significantly altered (30% decrease from preferred step fre- quency (ES=NA)).43 A Pose training protocol also decreased average vertical loading rate (ES=0.57).21 The hip adduction angle retraining protocol similarly produced a reduction in average vertical loading rate (ES=1.05).55 Peak-positive acceler- ation feedback training reduced average vertical loading rate by 27.6% (ES=NA)53 and 32% (ES=1.50)22 in two studies and in another, showed a significant decrease immediately postfeedback protocol (ES=0.72), but not at 1 month follow-up (ES=0.26).52

Instantaneous vertical loading rate Reductions in instantaneous vertical loading rate were supported by limited evidence when step frequency was manipulated or with the Pose technique or hip adduction angle retraining. Moderate evidence supported foot strike manipulation and peak-positive acceleration feedback as a means to reduce instant- aneous vertical loading rate. Instantaneous vertical loading rate was reduced with a forefoot strike (ES range from 2.32– 3.74)20 38 and mid-foot strike (ES=1.49),24 and increased with a 30% decrease in preferred step frequency (ES=1.02).43

Peak-positive acceleration feedback training22 53 reduced instant- aneous vertical loading rate (ES=1.70)22 in one study, while in another it showed a reduction immediately postfeedback proto- col (ES=0.70), but not at 1 month follow-up (ES=0.34).52 Hip adduction angle retraining also reduced instantaneous vertical loading rate (ES=1.02),55 as did the Pose technique (ES=1.33).24

Peak-positive tibial acceleration Evidence was limited for the reduction of peak-positive tibial acceleration by manipulating foot strike or step length. Strong evidence supported using real-time direct peak-positive acceler- ation feedback to reduce peak-positive tibial acceleration. Reductions in peak-positive tibial acceleration were seen by altering foot strike (forefoot strike; ES=1.14)35 and decreasing step length.46 An increase in step length produced an increase in peak-positive acceleration.46 This is consistent with the reduc- tions in impact loading noted above (vertical impact peak, average vertical loading rate and average vertical loading rate). Direct feedback about peak-positive acceleration produced a reduction of 32.2% (ES=NA)53 and 48% (ES=1.50)22 post- training in studies by Crowell et al and 30.7% (post-training; ES=1.89) and 22.2% (1 month follow-up; ES=1.25) in Clansey et al52 Another study showed reductions within a single session using audio feedback for peak-positive acceleration (ES=0.31– 1.02).54

Shock attenuation Evidence was conflicting for step length manipulation in decreasing shock attenuation, and limited for foot strike and step frequency manipulation. Derrick et al46 found no differ- ence in shock attenuation when step length was altered by 10– 20%. However, Mercer et al45 found a 10% decrease in step length and corresponding 10% increase in step frequency pro- duced a decrease in shock attenuation (ES=0.41), but the reverse had no significant effect (ES=0.12). Delgado et al35

found that shock attenuation decreased with a forefoot strike versus rearfoot strike (ES=1.18).

4 Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

Vertical and leg/lower extremity stiffness No evidence supported using foot strike manipulation as a means to change vertical or leg stiffness. Evidence was conflict- ing for the effect of step frequency manipulation on leg stiff- ness, but it was limited for its effect on vertical stiffness. Vertical stiffness and leg stiffness followed similar patterns of increasing stiffness with increasing step frequency,37 41 44 but no difference with a change in foot strike pattern.37 38

Spatiotemporal Thirteen papers reporting on three spatiotemporal variables (step frequency, step length and ground contact time) were considered.

Step frequency There was no evidence to support foot strike or step width manipulation to change step frequency.34 38 39 51 Limited evi- dence supported the Pose technique for increasing step fre- quency (ES=1.05).21

Step length Similarly, step length did not respond to alterations in foot strike pattern or step width (no evidence).24 34 49 Step length was decreased by the Pose technique (ES=0.5424 and 0.6621

moderate evidence). One study that held speed constant while manipulating step frequency also showed a corresponding manipulation of step length (limited evidence).42

Ground contact time There was no evidence to support step length manipulation to reduce ground contact time. Evidence was conflicting for foot strike and step frequency manipulation, and limited for the Pose technique. In general, ground contact time decreased with either decreased step length or increased step frequency,41 42 46 50

but these differences did not always reach significance, especially with smaller manipulations.37 42 45 46 Foot strike manipulation did not appear to have a significant impact on ground contact time34 37 39 except in one study by Shih et al,38 which showed a reduction in ground contact time with a forefoot strike (ES=0.19 and 0.31 in barefoot and shod conditions, respect- ively). The training protocol study utilising the Pose technique showed a decrease in ground contact time.21

DISCUSSION We reviewed the effectiveness of biomechanical interventions on modifying aspects of running gait that may be associated with running-related injuries. Foot strike manipulation protocols had the greatest effect on kinematic measures (such as sagittal ankle joint angles); real-time feedback protocols had the greatest effect on kinetic measures (vertical impact peak, average vertical loading rate and instantaneous vertical loading rate); and com- bined training protocols had the greatest effect on spatio- temporal measures (step frequency, step length and ground contact time). Overall, this systematic review shows that many biomechanical parameters can be altered with running modifica- tion training programmes.

Effect of gait modification on kinetic measures Impact loading (the sudden force applied to the skeleton at initial contact) has demonstrated the greatest association with lower extremity overuse injuries from any of the biomechanical variables.10 13–15 57–62 Of the variables used to measure impact loading, average vertical loading rate appears to be the greatest

running-related injury risk factor. A systematic review by Zadpoor et al16 found that while average vertical loading rate was significantly different between populations who had suf- fered a tibial stress fracture and control populations, the overall magnitude of ground reaction force was not. A recent prospect- ive study on the relationship of kinetic variables between injured and non-injured runners showed a higher average vertical loading rate in injured compared to non-injured male runners, but no difference in females.12 Findings from this review show that the most effective strategy for reducing impact loading is through real-time feedback of kinetics and/or kinematics.22 52–55

While the tibial peak-positive acceleration feedback interven- tions had the expected effect of decreasing peak-positive acceler- ation, they also reduced average vertical loading rate and instantaneous vertical loading rate, but not consistently the ver- tical impact peak.22 52–54 Interestingly, the hip adduction angle feedback intervention also produced reductions in vertical impact peak, average vertical loading rate and instantaneous ver- tical loading rate.55 The influence of real-time feedback of kinetic measures to reduce impact forces is logical, but does not explain why the hip adduction angle feedback protocol pro- duced a similar effect on kinetics. While the authors did not explore this relationship in detail, it can be posited that the reduction in impact forces may be due to a compensatory strat- egy for impact load absorption when hip adduction angle is reduced. Unfortunately, individual joint stiffness was not mea- sured in these studies, but might be used in the future to help explain this mechanism.

Average vertical loading rate and instantaneous vertical loading rate were both reduced with a forefoot strike or mid-foot strike versus a rearfoot strike pattern, while instantan- eous vertical loading rate was increased with a pronounced decrease in step frequency. The reduction of the average vertical loading rate and instantaneous vertical loading rate is a result of the smoothing or loss of the vertical impact peak and may be indicative of the ability of the spring mechanism of the Achilles tendon to absorb the impact load from initial contact over a greater period of time. The reduction of the average vertical loading rate with the Pose technique likely occurred via the same mechanism of a forefoot strike.

Multiple kinematic and spatiotemporal variables have been proposed to contribute to the development of running-related injury. These include angles at the ankle, knee and hip;5 9 10

rearfoot eversion/inversion;7 9 10 sagittal and frontal plane movements of the pelvis;63 angle of the tibia at initial contact;42

foot strike index;17 horizontal distance from centre of mass to heel at initial contact;42 vertical excursion of centre of mass;42

percentage of available pronation range of motion used;64 step frequency, step length and ground contact time.42 65 Of these, sagittal angles at the ankle, knee and hip; rearfoot eversion; step frequency, step length and ground contact time were explored in this review.

Effect of gait modification on kinematic measures Sagittal ankle joint kinematics showed the largest ES in this review and were most influenced by foot strike modification. In fact, distal kinematics appeared to be affected to a greater degree than proximal when foot strike was manipulated. This is not surprising given that an individual is most likely to initially focus one’s intentions on this joint specifically to produce the change in foot strike pattern. Interestingly, ankle kinematics also varied the most in a recent study using a peak-positive acceler- ation feedback protocol, suggesting that individuals used an ankle strategy first to minimise impact forces.52 Hip and knee

Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393 5

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

kinematics were minimally changed with this intervention. Effects of stride length and stride frequency manipulations on distal kinematics are most likely due to the fact that a relative increase in stride length tends toward a greater foot strike index (rearfoot strike) at initial contact.

Rearfoot eversion measures were most influenced by a narrow step width. This increased peak value most likely occurs as a direct result of the greater available eversion range of motion at the rearfoot when initial contact occurs closer to (or beyond) the midline as compared to when it occurs more lateral to the vertical projection of the centre of mass. The decreased rearfoot eversion seen with a toefoot strike and forefoot strike indicates that the toefoot strike and forefoot strike may result in a more rigid foot at initial contact than with rearfoot strike running and might account for different shock attenuation strategies employed by rearfoot strike (foot pronation) and toefoot strike/ forefoot strike runners (Achilles spring).

Effect of gait modification on spatiotemporal measures Step frequency, step length and ground contact time are innately linked. Generally, a greater step length and ground contact time has been associated with novice runners and potentially a higher incidence of injury.65 In runner’s terms this is called ‘overstrid- ing.’ Horizontal distance from centre of mass to heel may be considered representative of overstriding, producing a braking effect and a higher impact load at initial contact.42 Step fre- quency and step length did not appear to be sensitive to manip- ulations in foot strike pattern or step width, but did change following a 6-week Pose running programme. This effect was likely due to the specific emphasis given to ‘increasing the running step rate to 3 steps per second’ during the interven- tion.21 The adaptation to a greater step frequency and shorter step length in the Pose technique versus pure manipulation of foot strike pattern could also be attributed to the greater amount of training time (three times/week for 45 min over 6 weeks) given to the Pose technique. Indeed, it is conceivable that foot strike manipulation alone could have produced similar changes had the interventions been over a longer period rather than training and measuring within a single session.

A reduction in ground contact time was generally associated with a decreased step length or increased step frequency, but appeared to depend on the magnitude of these manipulations. This suggests that runners maintain or increase their swing time to increase their step frequency, while reducing the time spent in stance phase. Though not covered under the scope of this review, Stearne et al39 looked at the fraction of the stride spent in contact with the ground (duty factor) in their study on foot strike manipulation. While not reaching significance, there was a trend toward an increased proportion of time spent in the swing phase versus the stance phase in rearfoot strike versus forefoot strike running.39 Further investigation of this concept is war- ranted as it applies to step frequency/length manipulation.

While the Pose technique produced a significant reduction in ground contact time, only one study38 showed a significant change in this variable with foot strike manipulation. Generally, stance time has been shown to be greater in habitual rearfoot strike compared to forefoot strike runners, but when foot strike is imposed—at least within a single session—there is no differ- ence.39 The Pose technique and a forefoot strike pattern both might be expected to decrease ground contact time because of the increased step frequency/decreased stride length associated with these running patterns. Again, the fact that this change only reached significance in the study teaching the Pose tech- nique is likely due to the length of the training programme

given to adapt to the Pose technique as opposed to the single session training and testing in the foot strike manipulation studies.

In general, it can be said that runners tend to employ a distal strategy of gait modification unless specific cues (eg, ‘maintain a flexed knee throughout the gait cycle’) are given. Longer train- ing programmes also likely contribute to global changes that may produce more proximal effects. It is also important to realise that kinetic measures can be influenced by both foot posture at initial contact as well as foot position relative to the centre of mass. Future studies should employ longer gait retrain- ing programmes and test for long-term retention. Including measures of running economy may also help to distinguish between efficient and inefficient patterns of movement.

LIMITATIONS OF THE REVIEW The risk of selection bias was minimised by using a modified version of a quality index for randomised and non-randomised trials.27 Publication bias may bias results toward positive treat- ment effects, but this limitation is difficult to quantify with such a large variation in interventions. Owing to the large variation in interventions, it was impossible to undertake a meta-analysis in this review. Some outcomes were similar in what they attempted to measure, but could not be directly compared because they were measured at different intervals (eg, terminal swing vs initial contact). Some outcomes used different units, which also did not allow for direct comparison (eg, dB vs kg/Nm). All of the studies included in this review were a within- subjects design and as such, none had a control group.

While the inclusion of variables in the analysis that appeared most frequently was necessitated by the large number of vari- ables in the initial search (n=143), it does not necessarily mean that these variables are the most important clinically or bio- mechanically. Instead, these may simply be variables that are easier to manipulate or measure. Further research is required to ascertain the clinical relevance of a range of biomechanical vari- ables to the onset and progression of running-related injury.

Limitations of the actual study methods included the assess- ment of long-term retention and multiple session interventions. Only two studies20 22 had follow-up measurements taken to test for retention of biomechanical changes. As a result, it is unclear what effect some of these interventions might have once they become incorporated into a habitual running pattern as opposed to being tested when the intervention is still novel. Similarly, the only studies that incorporated an intervention beyond one session were those that instructed the Pose method.21 24 These studies showed more significant changes to running biomechan- ics than simple foot strike manipulations, but because of the combined nature of the intervention it is difficult to know whether it was a specific mechanical intervention or the increased time given to incorporate these changes into a habitual pattern that was the main factor that produced these changes.

SUMMARY Gait retraining interventions appear to result in short term small to large effects on kinetic, kinematic and spatiotemporal out- comes during running. Foot strike manipulation had the greatest effect on kinematic measures (conflicting evidence for proximal joint angles, but strong evidence for distal joint angles), real- time feedback had the greatest effect on kinetic measures (ranging from conflicting to strong evidence), and combined training protocols, such as the Pose technique, had the greatest effect on spatiotemporal measures (limited to moderate evidence).

6 Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

This review highlights the need for further research on inter- ventions to modify kinetic, kinematic and spatiotemporal bio- mechanics in running. Future studies should include longer term follow-up measurements to assess retention of these biomechan- ical changes. Studies that include a longitudinal training pro- gramme would also be more useful than the majority of studies that simply investigate immediate changes from a novel inter- vention. Standardisation of the timing of measurements should also be ensured so that comparison between studies can be made.

Contributors CN, MAH devised the study idea, analysed data and contributed to the initial draft of the manuscript as well as the final manuscript. CKC analysed data and contributed to the final manuscript. JET devised the study idea and contributed to the final manuscript.

Competing interests None declared.

Provenance and peer review Not commissioned; externally peer reviewed.

REFERENCES 1 Bovens AM, Janssen GM, Vermeer HG, et al. Occurrence of running injuries in

adults following a supervised training program. Int J Sports Med 1989;10(Suppl 3): S186–90.

2 Buist I, Bredeweg SW, Bessem B, et al. Incidence and risk factors of running-related injuries during preparation for a 4-mile recreational running event. Br J Sports Med 2010;44:598–604.

3 Taunton JE, Ryan MB, Clement DB, et al. A prospective study of running injuries: the Vancouver Sun Run “In Training” clinics. Br J Sports Med 2003;37:239–44.

4 van Gent RN, Siem D, van Middelkoop M, et al. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. Br J Sports Med 2007;41:469–80; discussion 80.

5 Souza RB, Powers CM. Differences in hip kinematics, muscle strength, and muscle activation between subjects with and without patellofemoral pain. J Orthop Sports Phys Ther 2009;39:12–19.

6 Ryan MB, MacLean CL, Taunton JE. A review of anthropometric, biomechanical, neuromuscular and training related factors associated with injury in runners. Int J Sports Med 2006;7:120–37.

7 Ferber R, Hreljac A, Kendall KD. Suspected mechanisms in the cause of overuse running injuries: a clinical review. Sports Health 2009;1:242–6.

8 Krivickas LS. Anatomical factors associated with overuse sports injuries. Sports Med 1997;24:132–46.

9 Miller RH, Lowry JL, Meardon SA, et al. Lower extremity mechanics of iliotibial band syndrome during an exhaustive run. Gait Posture 2007;26:407–13.

10 Milner CE, Ferber R, Pollard CD, et al. Biomechanical factors associated with tibial stress fracture in female runners. Med Sci Sports Exerc 2006;38:323–8.

11 Novacheck TF. The biomechanics of running. Gait Posture 1998;7:77–95. 12 Bredeweg SW, Kluitenberg B, Bessem B, et al. Differences in kinetic variables

between injured and noninjured novice runners: a prospective cohort study. J Sci Med Sport 2013;16:205–10.

13 Gerlach KE, White SC, Burton HW, et al. Kinetic changes with fatigue and relationship to injury in female runners. Med Sci Sports Exerc 2005;37:657–63.

14 Hreljac A, Marshall RN, Hume PA. Evaluation of lower extremity overuse injury potential in runners. Med Sci Sports Exerc 2000;32:1635–41.

15 Messier SP, Davis SE, Curl WW, et al. Etiologic factors associated with patellofemoral pain in runners. Med Sci Sports Exerc 1991;23:1008–15.

16 Zadpoor AA, Nikooyan AA. The relationship between lower-extremity stress fractures and the ground reaction force: a systematic review. Clin Biomech 2011;26:23–8.

17 Daoud AI, Geissler GJ, Wang F, et al. Foot strike and injury rates in endurance runners: a retrospective study. Med Sci Sports Exerc 2012;44:1325–34.

18 Nielsen RO, Buist I, Parner ET, et al. Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: a 1-year prospective cohort study. Br J Sports Med 2014;48:440–7.

19 Bonacci J, Vicenzino B, Spratford W, et al. Take your shoes off to reduce patellofemoral joint stress during running. Br J Sports Med 2014;48:425–8.

20 Cheung RT, Davis IS. Landing pattern modification to improve patellofemoral pain in runners: a case series. J Orthop Sports Phys Ther 2011;41:914–19.

21 Diebal AR, Gregory R, Alitz C, et al. Forefoot running improves pain and disability associated with chronic exertional compartment syndrome. Am J Sports Med 2012;40:1060–7.

22 Crowell HP, Davis IS. Gait retraining to reduce lower extremity loading in runners. Clin Biomech 2011;26:78–83.

23 Willy RW, Scholz JP, Davis IS. Mirror gait retraining for the treatment of patellofemoral pain in female runners. Clin Biomech 2012;27:1045–51.

24 Arendse RE, Noakes TD, Azevedo LB, et al. Reduced eccentric loading of the knee with the pose running method. Med Sci Sports Exerc 2004;36:272–7.

25 Dallam GM, Wilber RL, Jadelis K, et al. Effect of a global alteration of running technique on kinematics and economy. J Sports Sci 2005;23:757–64.

26 Schubert AG, Kempf J, Heiderscheit BC. Influence of stride frequency and length on running mechanics: a systematic review. Sports Health 2014;6:210–17.

27 Downs SH, Black N. The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions. J Epidemiol Community Health 1998;52:377–84.

28 Deeks JJ, Dinnes J, D’Amico R, et al. Evaluating non-randomised intervention studies. Health Technol Assess 2003;7:iii–x, 1–173.

29 Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159–74.

30 Tanamas S, Hanna FS, Cicuttini FM, et al. Does knee malalignment increase the risk of development and progression of knee osteoarthritis? A systematic review. Arthritis Care Res 2009;61:459–67.

31 Cohen J. Statistical power analysis for the behavioural sciences. 2nd edn. Hillsdale, NJ: Lawrence Erlbaum Associates, 1988.

32 Mills K, Hunt MA, Ferber R. Biomechanical deviations during level walking associated with knee osteoarthritis: a systematic review and meta-analysis. Arthritis Care Res 2013;65:1643–65.

33 Chalmers TC, Smith H Jr, Blackburn B, et al. A method for assessing the quality of a randomized control trial. Control Clin Trials 1981;2:31–49.

34 Ardigo LP, Lafortuna C, Minetti AE, et al. Metabolic and mechanical aspects of foot landing type, forefoot and rearfoot strike, in human running. Acta Physiol Scand 1995;155:17–22.

35 Delgado TL, Kubera-Shelton E, Robb RR, et al. Effects of foot strike on low back posture, shock attenuation, and comfort in running. Med Sci Sports Exerc 2013;45:490–6.

36 Pohl MB, Buckley JG. Changes in foot and shank coupling due to alterations in foot strike pattern during running. Clin Biomech 2008;23:334–41.

37 Giandolini M, Arnal P, Millet G, et al. Impact reduction during running: efficiency of simple acute interventions in recreational runners. Eur J Appl Physiol 2013;113:599–609.

38 Shih Y, Lin KL, Shiang TY. Is the foot striking pattern more important than barefoot or shod conditions in running? Gait Posture 2013;38:490–4.

39 Stearne SM, Alderson JA, Green BA, et al. Joint kinetics in rearfoot versus forefoot running: implications of switching technique. Med Sci Sports Exerc 2014;46:1578–87.

40 Williams DSB III, Green DH, Wurzinger B. Changes in lower extremity movement and power absorption during forefoot striking and barefoot running. Int J Sports Phys Ther 2012;7:525–32.

41 Farley CT, Gonzalez O. Leg stiffness and stride frequency in human running. J Biomech 1996;29:181–6.

42 Heiderscheit BC, Chumanov ES, Michalski MP, et al. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc 2011;43:296–302.

43 Hobara H, Sato T, Sakaguchi M, et al. Step frequency and lower extremity loading during running. Int J Sport Med 2012;33:310–13.

44 Hunter I, Smith GA. Preferred and optimal stride frequency, stiffness and economy: changes with fatigue during a 1-h high-intensity run. Eur J Appl Physiol 2007;100:653–61.

45 Mercer JA, Devita P, Derrick TR, et al. Individual effects of stride length and frequency on shock attenuation during running. Med Sci Sports Exerc 2003;35:307–13.

46 Derrick TR, Hamill J, Caldwell GE. Energy absorption of impacts during running at various stride lengths. Med Sci Sports Exerc 1998;30:128–35.

47 Seay J, Selbie WS, Hamill J. In vivo lumbo-sacral forces and moments during constant speed running at different stride lengths. J Sports Sci 2008;26:1519–29.

48 Stergiou N, Bates BT, Kurz MJ. Subtalar and knee joint interaction during running at various stride lengths. J Sports Med Phys Fitness 2003;43:319–26.

49 Williams KR, Ziff JL. Changes in distance running mechanics due to systematic variations in running style. Int J Sport Biomech 1991;7:76–90.

50 Willson JD, Sharpee R, Meardon SA, et al. Effects of step length on patellofemoral joint stress in female runners with and without patellofemoral pain. Clin Biomech 2014;29:243–7.

51 Arellano CJ, Kram R. The effects of step width and arm swing on energetic cost and lateral balance during running. J Biomech 2011;44:1291–5.

52 Clansey AC, Hanlon M, Wallace ES, et al. Influence of tibial shock feedback training on impact loading and running economy. Med Sci Sports Exerc 2014;46:973–81.

53 Crowell HP, Milner CE, Hamill J, et al. Reducing impact loading during running with the use of real-time visual feedback. J Orthop Sports Phys Ther 2010;40:206–13.

54 Wood CM, Kipp K. Use of audio biofeedback to reduce tibial impact accelerations during running. J Biomech 2014;47:1739–41.

55 Noehren B, Scholz J, Davis I. The effect of real-time gait retraining on hip kinematics, pain and function in subjects with patellofemoral pain syndrome. Br J Sport Med 2011;45:691–6.

56 Pohl MB, Messenger N, Buckley JG. Changes in foot and lower limb coupling due to systematic variations in step width. Clin Biomech 2006;21:175–83.

Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393 7

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

57 Bahlsen A. The etiology of running injuries: a longitudinal, prospective study [PhD]. The University of Calgary, 1989.

58 Davis I, Bowser B, Mullineaux D. Do impacts cause running injuries? A prospective investigation. American Society of Biomechanics Meeting; August 2010; Providence, R.I.

59 Davis I, Milner CE, Hamill J. Does increased loading during running lead to tibial stress fractures? A prospective study. Med Sci Sports Exerc 2004;36 (Suppl):S58.

60 Nigg BM, Cole GK, Bruggemann GP. Impact forces during heel-toe running. J Appl Biomech 1995;11:407–32.

61 Pohl MB, Hamill J, Davis IS. Biomechanical and anatomic factors associated with a history of plantar fasciitis in female runners. Clin J Sport Med 2009;19:372–6.

62 Pohl MB, Mullineaux DR, Milner CE, et al. Biomechanical predictors of retrospective tibial stress fractures in runners. J Biomech 2008;41:1160–5.

63 Bazett-Jones DM, Cobb SC, Huddleston WE, et al. Effect of patellofemoral pain on strength and mechanics after an exhaustive run. Med Sci Sports Exerc 2013;45:1331–9.

64 Rodrigues P, TenBroek T, Hamill J. Runners with anterior knee pain use a greater percentage of their available pronation range of motion. J Appl Biomech 2013;29:141–6.

65 Edwards WB, Taylor D, Rudolphi TJ, et al. Effects of stride length and running mileage on a probabilistic stress fracture model. Med Sci Sports Exerc 2009;41:2177–84.

8 Napier C, et al. Br J Sports Med 2015;0:1–8. doi:10.1136/bjsports-2014-094393

Review

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

review gait biomechanics in runners: a systematic Gait modifications to change lower extremity

Michael A Hunt Christopher Napier, Christopher K Cochrane, Jack E Taunton and

published online June 23, 2015Br J Sports Med

http://bjsm.bmj.com/content/early/2015/06/23/bjsports-2014-094393 Updated information and services can be found at:

These include:

Material Supplementary

DC1.html http://bjsm.bmj.com/content/suppl/2015/06/23/bjsports-2014-094393. Supplementary material can be found at:

References

#BIBL http://bjsm.bmj.com/content/early/2015/06/23/bjsports-2014-094393 This article cites 62 articles, 10 of which you can access for free at:

service Email alerting

box at the top right corner of the online article. Receive free email alerts when new articles cite this article. Sign up in the

Collections Topic Articles on similar topics can be found in the following collections

(97)BJSM Reviews with MCQs

Notes

http://group.bmj.com/group/rights-licensing/permissions To request permissions go to:

http://journals.bmj.com/cgi/reprintform To order reprints go to:

http://group.bmj.com/subscribe/ To subscribe to BMJ go to:

group.bmj.com on July 11, 2015 - Published by http://bjsm.bmj.com/Downloaded from

View publication statsView publication stats