Injury-reduction effectiveness of prescribing running shoes on the basis of foot arch height: summary of military investigations.

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Journal of Orthopaedic & Sports Physical Therapy® Downloaded from www.jospt.org at MUSC Library on October 1, 2014. For personal use only. No other uses without permission. Copyright © 2014 Journal of Orthopaedic & Sports Physical Therapy®. All rights reserved.

JOSEPH J. KNAPIK, ScD1 • DANIEL W. TRONE, PhD2 • JUSTE TCHANDJA, MPH3 • BRUCE H. JONES, MD1

Injury-Reduction Effectiveness of Prescribing Running Shoes on the Basis of Foot Arch Height: Summary of Military Investigations

T

he first clinical use of footprints (plantar shapes) may be attributed to Colonel R. I. Harris and Major T. Beath, who used them to evaluate foot problems in Canadian soldiers. Recruits and soldiers stepped on a rubber mat that provided

a visualization of their footprint and the amount of static weight-bearing pressure exerted on different parts of the foot.19,35 TTSTUDY DESIGN: Secondary analysis of 3 randomized controlled trials.

TTOBJECTIVE: Analysis of studies that examined whether prescribing running shoes on the basis of foot arch height influenced injury risk during military basic training.

TTBACKGROUND: Prior to 2007, running maga-

zines and running-shoe companies suggested that imprints of the bottom of the feet (plantar shape) could be used as an indication of foot arch height and that this could be used to select individually appropriate types of running shoes.

TTMETHODS: Similar studies were conducted in

US Army (2168 men, 951 women), Air Force (1955 men, 718 women), and Marine Corps (840 men, 571 women) basic training. After foot examinations, recruits were randomized to either an experimental or a control group. Recruits in the experimental group selected or were assigned motion-control, stability, or cushioned shoes to match their plantar shape, which represented a low, medium, or high

Subsequently, these footprints were used to determine a number of clinical indices, which included plantar shapes classified foot arch, respectively. The control group received a stability shoe regardless of plantar shape. Injuries during basic training were assessed from outpatient medical records.

TTRESULTS: Meta-analyses that pooled results

of the 3 investigations showed little difference between the experimental and control groups in the injury rate (injuries per 1000 person-days) for either men (summary rate ratio = 0.97; 95% confidence interval [CI]: 0.88, 1.06) or women (summary rate ratio = 0.97; 95% CI: 0.85, 1.08). When injury rates for specific types of running shoes were compared, there were no differences.

TTCONCLUSION: Selecting running shoes based

on arch height had little influence on injury risk in military basic training.

TTLEVEL OF EVIDENCE: Prevention, level 1b.

J Orthop Sports Phys Ther 2014;44(10):805-812. Epub 25 August 2014. doi:10.2519/jospt.2014.5342

TTKEY WORDS: footprints, foot type, pronation

as high arched, broad (low arched), and normal,34,36 as shown in FIGURE 1. Perhaps the first to apply plantar shapes to running shoes was Dr Peter Cavanagh, who recommended that static footprints, in conjunction with dynamic foot flexibility measurements, could be used as part of a 10-point plan to find the most appropriate running shoe.8,10 Subsequently, several running-shoe authorities in the popular running magazine Runner’s World suggested that plantar shapes could assist in determining if individuals overpronated, underpronated, or had normal pronation during running.9,12,13 Beginning in the late 1980s and into the 2000s, running shoes were largely classified based on their intended purpose and related to plantar shapes. It was assumed that plantar shapes were reflective of foot arch height and could assist in selecting individually appropriate types of running shoes, with the goal of reducing the likelihood of injury.2-5,14,30,39 Individuals with a foot shape reflecting a low arch were presumed to have greater rearfoot and midfoot mobility that allowed the foot to pronate excessively during the stance phase of running. For these individuals, “motion-control” shoes were rec-

US Army Institute of Public Health, Portfolio of Epidemiology and Disease Surveillance, Aberdeen Proving Ground, MD. 2Naval Health Research Center, San Diego, CA. 3559th Medical Group, Joint Base San Antonio, Lackland, TX. This study was funded by the Defense Safety Oversight Council. The authors certify that they have no affiliations with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the article. The views expressed herein are the views of the authors and do not reflect the official policy of the Department of the Army, the Department of Defense, or the US government. Address correspondence to Dr Joseph Knapik, US Army Institute of Public Health, Portfolio of Epidemiology and Disease Surveillance, ATTN: MCHB-IP-DI, Aberdeen Proving Ground, MD 21010. E-mail: joseph.j.knapik. [email protected] t Copyright ©2014 Journal of Orthopaedic & Sports Physical Therapy® 1

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[ ommended, because it was assumed that these shoes could control excessive foot motion. Individuals with a plantar shape reflecting a high arch were assumed to have rigid or inflexible feet that impacted the ground with greater force and did not pronate sufficiently. These individuals were directed toward “cushioned” shoes, which presumably increased shock absorption by providing for more pronation and cushioning to soften ground impact. Individuals with a foot shape reflecting a normal arch height were assumed to impact the ground with less force and to have an appropriate amount of foot pronation. A “stability” shoe, which was presumed to have moderate cushioning and motion-control characteristics, was recommended for these individuals.32 Prior to 2007, the military services had generally followed the recommendations of the shoe companies. In fact, many military post exchanges had wall displays advertising various types of running shoes categorized by foot shape (FIGURE 2). During basic training inprocessing, new recruits could select or were assigned a running shoe based on the plantar shape of their foot. However, whether shoes based on foot arch height reduced injuries had not been tested in a randomized controlled trial. Consequently, the Military Training Task Force of the US Department of Defense Safety Oversight Council requested that this be examined in the military services, and studies were subsequently conducted in the Army, Air Force, and Marine Corps basic training.22,26,27 The purpose of this paper was to analyze and summarize the data from previously published basic training studies that examined the effectiveness of assigning running shoes on the basis of plantar shape, assumed to reflect foot arch height, in reducing injury. For this purpose, we performed a secondary analysis of the data from 3 randomized controlled trials.22,26,27 Our goal was to fully synopsize the results of the investigations and to provide evidence-based conclusions.

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FIGURE 1. Plantar shapes showing high (A), low (B), and normal (C) arch heights.

FIGURE 2. A typical display of running shoes in a military post exchange, showing the shoes based on their purpose and plantar shapes.

METHODS

I

n 2007, independent studies were conducted in Army, Air Force, and Marine Corps basic training. The design of the 3 studies was identical. Recruits were randomized into either an experimental or control group and trained side by side in the same military units. The recruits in the experimental group were assigned motion-control, stability, or cushioned running shoes, based on their plantar shape, which represented a low, medium, or high foot arch, respectively. The recruits in the control group were provided with a stability shoe regardless of plantar shape. In the Air Force and Marine Corps

studies, 3 models of New Balance shoes were used, 1 matching each foot type. The Army study included 19 different models of shoes from 5 different shoe companies, but shoes for the recruits in the experimental group were still assigned based on plantar shapes. The shoe brands and models used in each study are shown in TABLE 1. All recruits’ plantar shapes were evaluated by having them step onto the acrylic surface of a device shown in FIGURE 3. Recruits were instructed to stand with equal weight on each foot. The device contained a mirror that reflected the underside of the foot, thus providing a visual image of the footprint

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Running Shoes Used in the Military Footwear Studies

TABLE 1

Control Group


Experimental Group Service

Motion-Control Shoe

Stability Shoe

Cushioned Shoe

Stability Shoe

Army26

Asics Gel Foundation 7 Brooks Addiction 7 Saucony Grid Stabil 6 New Balance 857*

Asics Gel 1120 Asics Gel 2120 Brooks Adrenaline GTS6 Brooks Adrenaline GTS7 Nike Structure Triax Nike Air Max Moto* Saucony Grid Omni 5 New Balance 717 New Balance 767

Asics Gel Cumulus Brooks Radius 6 Nike Air Pegasus Saucony Grid Trigon 4 New Balance 644 New Balance 755

New Balance 767

Air Force22

New Balance 587

New Balance 498

New Balance 755

New Balance 498

Marine Corps27

New Balance 587

New Balance 767

New Balance 881

New Balance 767

*For 2 shoes, the Army classification differed from those of Runner’s World and the manufacturer. One shoe was the New Balance 857, which the Army classification listed as a motion-control shoe but Runner’s World and the manufacturer listed as a stability shoe; the other was the Nike Air Max Moto, listed in the Army classification as a stability shoe but by Runner’s World and the manufacturer as a cushioned shoe.

FIGURE 3. Device used to evaluate plantar shape: individual standing on device (A) and reflective surface showing high-arched individual (B).

and the proportion of the plantar surface coming into contact with the acrylic surface. Two testers independently classified each recruit’s arch height as high, medium, or low, based on a template (FIGURE 1). Disagreements were discussed between raters and a final decision was made. The between-rater reliability of the plantar-shape evaluations (n = 66) was formally determined using kappa statistics and was found to be 0.91 for both feet.27 Basic training in the Army, Air Force, and Marine Corps was conducted for 9, 6, and 12 weeks, respectively, during which the assigned running shoes were worn throughout physical training. Some re-

cruits did not complete training and were either discharged because of unsuitability for military service or transferred to another unit because they needed additional time to successfully complete required training activities. For these recruits, the amount of time they were in training in their initial unit was obtained from administrative training records. Individuals were followed for injuries until graduation, discharge, or assignment to another unit. In all 3 military services, information on injuries that occurred during training was obtained from the Defense Medical Surveillance System. The Defense Medical Surveillance System

regularly incorporates data on all ambulatory (outpatient) encounters that occur within military treatment facilities and those outside military treatment facilities that are paid for by the Department of Defense. The Defense Medical Surveillance System provided visit dates and ICD-9 codes for all outpatient medical visits within the recruit training time frame for each recruit volunteer. An injury case was defined as a recruit who had at least 1 specific ICD-9 code included in 1 of 3 injury indices: the comprehensive injury index, overuse injury index, and training-related injury index. These indices and the ICD-9 codes used in each have been previously defined.23 The comprehensive injury index captures all ICD-9 codes related to injuries, classically defined as physical damage to the body as a result of energy exchanges.15,16 The overuse injury index captures the subset of musculoskeletal injuries presumably resulting from cumulative microtrauma (overuse), such as stress fractures, stress reactions, tendinitis, bursitis, fasciitis, arthralgia, neuropathy, radiculopathy, shin splints, synovitis, sprains, strains, and musculoskeletal pain (not otherwise specified). The training-related injury index is a subset of the overuse injury index that is limited to lower extremity overuse injuries and is routinely used to compare injury rates among Army basic training locations. The Comprehensive Meta-Analysis statistical package Version 2 (Biostat, Inc, Englewood, NJ) was used to perform a secondary analysis of the data from the 3 studies using meta-analysis. For each injury index in each of the 3 studies, the person-time injury incidence rate (IIR) was calculated as the sum of recruits with 1 or more injuries divided by the sum of total recruit time in training, multiplied by 1000 to obtain injuries per 1000 person-days. A fixed meta-analysis model was used that employed the IIR ratios of the control and experimental groups (control IIR/experimental IIR) and their 95% confidence intervals (CIs) to pro-



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Injury Incidence Rates and Meta-analyses of Experimental and Control Groups in 3 Military Studies

TABLE 2

Men Injury Index/ Service/Group

n

Injury Incidence Rate*

Rate Ratio (CG/EG)†


Comprehensive injury index Army

Women Summary Rate Ratio†‡

P Value§

I2

0.97 (0.88, 1.06)

.63

0%

n


0.99 (0.86, 1.13)

CG

1079

5.95

EG

1089

6.04

Air Force 913

6.43

EG

1042

7.04

Marine Corps

10.87

468

11.37

345

10.89

432

5.72

EG

408

5.76

Overuse injury index

373

12.96

257

6.00

.77

314

4.96

0%

0.96 (0.82, 1.13) 1079

4.37

483

8.87

EG

1089

4.55

468

9.16

345

8.50

373

10.55

257

3.29

314

2.80

0.89 (0.74, 1.08)

CG

913

5.25

EG

1042

5.86

Marine Corps 432

4.14

EG

408

4.06

Training-related injury index

.71

0%

0.91 (0.77, 1.08) 1079

3.99

483

8.80

EG

1089

4.38

468

8.59

345

6.68

373

8.41

0.85 (0.69, 1.05)

CG

913

3.94

EG

1042

4.62

Marine Corps

0.93 (0.82, 1.06)

.21

35%

0.95 (0.83, 1.09)

.21

37%

0.99 (0.83, 1.18)

CG Air Force

57%

1.18 (0.83, 1.66)

0.90 (0.80, 1.02)

Army

.10

0.81 (0.63, 1.02)

1.02 (0.79, 1.31)

CG

0.97 (0.85, 1.08)

0.94 (0.79, 1.11)

CG Air Force

I2

1.21 (0.94, 1.57)

0.95 (0.85, 1.06)

Army

P Value§

0.84 (0.68, 1.04)

0.99 (0.80, 1.22)

CG

Summary Rate Ratio†‡

0.96 (0.82, 1.12) 483

0.91 (0.77, 1.09)

CG

Rate Ratio (CG/EG)†

0.79 (0.61, 1.04)

0.98 (0.75, 1.28)

1.18 (0.79, 1.77)

CG

432

3.56

257

2.03

EG

408

3.63

314

1.72

Abbreviations: CG, control group; EG, experimental group. *Injuries per 1000 person-days. † Values in parentheses are 95% confidence interval. ‡ From meta-analyses. § Q-statistic.

duce a summary IIR ratio and summary 95% CI that reflected the pooled results from all 3 studies. The homogeneity of the IIR ratios from the individual studies was assessed using the Q-statistic and the I2 statistic. The I2 statistic indicated the percent of heterogeneity among studies, with larger values indicating more het-

erogeneity and smaller values less. In calculating I2, negative values were equal to zero,20 indicating very little heterogeneity. Men and women were analyzed separately in all calculations, due to large differences in IIRs. Because the Army study utilized a number of different running shoes, it

was possible to examine IIRs between different shoe makes and models using a chi-square test for person-time.1 Each shoe was compared to each other shoe (2-by-2 analysis). The comprehensive injury index was used for this analysis, and shoes that were used by at least 40 recruits were included.



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TABLE 3

Injury Incidence Rates and Meta-analyses (Comprehensive Injury Index) of Low- and High-Arched Individuals Wearing Different Types of Running Shoes Men

Plantar Shape/ Service/Shoe Type

n


Rate Ratio†


Low Army

Women Summary Rate Ratio†‡

P Value§

I2

0.91 (0.68, 1.23)

.70

0%

n


0.95 (0.63, 1.43) 137

5.88

38

8.91

MCS

119

6.21

43

12.32

79

6.83

23

13.61

134

8.67

37

14.52

20

6.44

37

5.02

SS MCS

0.79 (0.48, 1.30)

Marine Corps 27

5.44

MCS

35

4.67

High

.57

0%

0.81 (0.57, 1.16) 162

5.78

81

11.93

CS

176

7.13

81

11.76

41

9.73

64

12.48

0.99 (0.64, 1.51)

SS

119

6.93

CS

181

7.03

Marine Corps

0.90 (0.60, 1.35)

.55

0%

0.94 (0.71, 1.24)

.78

0%

1.01 (0.70, 1.48)

SS Air Force

I2

1.28 (0.56, 2.96)

0.89 (0.69, 1.15)

Army

P Value§

0.94 (0.46, 1.90)

1.17 (0.51, 2.66)

SS

Summary Rate Ratio†‡

0.72 (0.39, 1.34)

SS Air Force

Rate Ratio †

0.78 (0.42, 1.43)

0.97 (0.48, 1.93)

0.92 (0.51, 1.64)

SS

34

5.46

48

5.64

CS

45

5.66

57

6.17

Abbreviations: CS, cushioned shoe; MCS, motion-control shoe; SS, stability shoe. *Injuries per 1000 person-days. † Values in parentheses are 95% confidence interval. Ratio: SS/MCS (low) or SS/CS (high). ‡ From meta-analyses. § Q-statistic.

RESULTS

T

ABLE 2 shows the IIRs, the IIR ra-

tios, and the meta-analysis summary IIR ratios with the summary 95% CIs. Results from the independent studies, as well as the pooled results, indicated that there was little difference between the experimental and control groups, regardless of the injury index employed. The Q-statistic indicated that the results of the 3 studies were relatively homogeneous for both men and women. The I2 statistic indicated virtually no heterogeneity among studies for any injury index among the men. Among the women, the I2 statistic indicated somewhat more heterogeneity, but this was still relatively low for the 2 overuse injury indices.

TABLE 3 shows a comparison of injury rates among individuals with high and low arches who wore different types of running shoes. Recruits with plantar shapes indicative of low arches who wore stability shoes had injury rates that were similar to those who wore motion-control shoes. Recruits with plantar shapes indicative of high arches who wore stability shoes had injury rates similar to those who wore cushioned shoes. The Q-statistic and I2 statistic indicated that the data from the 3 studies were relatively homogeneous for both men and women. FIGURE 4 shows the IIRs (comprehensive injury index) for shoes that were worn by at least 40 recruits in the Army study. There was little difference in the injury rates based on the shoes worn for

both men (P = .14-.99) and women (P = .44-.99).

DISCUSSION

T

he results of this analysis indicated that there was little difference in injury rates between military recruits who wore a running shoe assigned on the basis of plantar-shape foot arch height compared to those who were assigned a stability shoe regardless of plantar shape. The 3 studies used a randomized prospective design, the same injury definitions, and examined individuals who trained side by side in the same units in the well-standardized basic training environment. The results were relatively homogeneous for the 3 studies



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Injury Incidence Rate, Injuries per 1000 Person-Days


14

12.16 12

11.62

10.78

10.76

10

8

6

5.94

6.49

5.83

5.90

4.66

4.58

4

n= 1390

n= 124

n= 118

n= 108

n= 69

n= 42

n= 604

Brooks GTS7

Nike Air Pegasus

Brooks GTS6

n= 64

n= 42

n= 41

2

0 NB 767

Nike Asics 2120 Structure

NB 767 Asics 2120 Nike Air Max Moto

Brooks GTS7

Shoe Make and Model Men

Women

FIGURE 4. Comparison of injury incidence rates (comprehensive injury index) between different running-shoe makes and models. Abbreviation: NB, New Balance.

in the meta-analyses. Three different injury definitions were examined, and the results were similar in all 3 studies and in the meta-analyses, indicating little effect on injury rates in those who were or were not assigned shoes on the basis of plantar shape. In addition, similar injury rates occurred with the use of several different models of running shoes in Army basic training. If injury risk could be reduced by assigning shoes on the basis of plantar shape, the largest risk reduction might be expected between those wearing shoes specifically designed for that plantar shape and those wearing shoes not designed for that plantar shape. Thus, recruits with low-arch feet who wore motion-control shoes (presumably designed to control for excessive pronation) were compared to those with low-arch feet who wore stability shoes. Likewise, recruits with high-arch feet who wore cushioned shoes (presumably designed to provide cushioning and allow more foot pronation) were compared to

those with high-arch feet who wore stability shoes. Injury rates were found to be similar, even for those comparisons looking at match versus mismatch foot and shoe types. Overall, the results of the meta-analysis suggested a tendency for recruits with low- and high-arch feet wearing stability shoes to have slightly lower injury rates than those wearing shoes presumably designed specifically for their foot type (ie, motion-control or cushioned shoes). A comprehensive literature search was performed up to January 2014 to find other studies that addressed injuries among individuals using running shoes that were assigned based on foot arch height. Only 1 review33 and 1 observational study24 were found. The review33 was conducted before the studies reported here had been published and merely noted that no investigations on this topic existed. The observational investigation24 showed a decrease in serious injuries at Fort Drum, NY after initiation of a running-shoe prescription program. There

] were a number of methodological differences between the Fort Drum project and the basic training studies reported here. The basic training studies involved a prescription based only on plantar shape, whereas the observational study involved a prescription based on foot arch height and foot flexibility. In the basic training studies of a population of recruits, it was ensured that the recruits were given the correct shoe and the shoe was worn during training. The Fort Drum investigation involved soldiers who were given the shoe prescription, but there was no follow-up to determine whether they had actually purchased and/or worn the recommended shoe. In fact, a survey involving a convenience sample of 122 Fort Drum soldiers (out of an average of 9752 estimated to be on post) found that only 11% self-reported that they had followed the shoe-prescription advice. The basic training studies involved a prospective shoe prescription involving 2 randomly assigned groups (control and experimental) training side by side in a standardized program, with follow-up for any injury occurring during the period of training. The Fort Drum investigation involved a retrospective examination of medical visits to a physical therapy clinic before and after the shoe program was initiated. A number of temporal factors were potential confounders in the Fort Drum project, and these were discussed at length in the report.24 The major potential bias was a change in the medical surveillance system used to track injuries, which was discovered after investigating the time point when injuries dramatically decreased. In summary, the advantages of the basic training studies were that they (1) used a randomized prospective design, (2) provided considerably better knowledge about the shoes worn, and (3) involved a more controlled training environment. The development of motion-control and cushioned shoes appears to have been based on 2 assumptions: (1) that individuals with high and low foot arch heights have particular gait mechanics, and (2) that particular shoe characteris-



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tics can adjust or compensate for these gait differences such that they more closely conform to those of individuals with more average arch heights. With regard to the first assumption, individuals with low foot arches were presumed to have disproportionate foot flexibility that allowed the foot to pronate excessively during the stance phase of running. Individuals with high foot arch were presumed to have rigid or inflexible feet that underpronate and impact the ground with higher forces. However, studies have shown that when nonsymptomatic runners and walkers with highand low-arch feet were tested using the same shoes, there were few arch-related differences in rearfoot motion or impact forces.18,21,28,31 Conversely, when previously injured or symptomatic runners with low and high arches were tested using the same shoes, there were differences in running kinematics. Injured or symptomatic runners with low arches tended to demonstrate more inversion/ eversion and less internal tibial rotation on the talus during the stance phase of running. Injured or symptomatic runners with high arches had less inversion/ eversion, more internal tibial rotation on the talus, more leg stiffness, higher initial ground impact forces, and a higher rate of initial force development on ground impact.29,37,38 Thus, gait differences associated with foot type may be more applicable to symptomatic and previously injured individuals than to those who are not experiencing symptoms or who have not been previously injured. With regard to the second assumption, when individuals with high- or low-arch feet ran in motion-control or cushioned shoes, there was little difference in kinematics between these 2 foot types, including during prolonged running.6,7 The only variable to differ was the instantaneous loading rate (maximal instantaneous slope of initial force development on ground impact), which was actually higher in the cushioned shoe (compared with the motion-control shoe) when worn by individuals with low-arch

feet. This occurred despite the fact that, regardless of arch type, motion-control shoes attenuated rearfoot motion better than cushioned shoes and that cushioned shoes generally attenuated shock better and allowed more pronation than the motion-control shoes.6,7,11,17 Thus, while the shoes performed as expected, there was little difference in mechanics between individuals with low- and higharch feet running in these shoes. The military training studies analyzed here additionally show that injury rates appear to be the same regardless of the type of shoe worn by individuals with high- or low-arch feet. One major advantage of the basic training studies was that all recruits were evaluated under very similar living and activity conditions. Recruits lived in the same barracks, consumed meals in similar dining halls, and performed physical training and other activities together. Specific operational training activities differed in the various military services (Army, Air Force, Marine Corps), but the physical training in which the running shoes were used was similar and generally consisted of calisthenics, various movement drills, and running in groups of those with similar fitness levels. The findings were similar in all 3 services, showing no difference between the experimental and the control groups in terms of injury outcomes. Although we did not consider covariates in the present summary, several were considered in the individually reported investigations.22,26,27 These covariates included age, physical characteristics, physical fitness, and lifestyle characteristics (cigarette smoking, prior physical activity level, prior injuries, and menstrual history). Many of these characteristics had been shown to be associated with injuries in past investigations.25 To see if these factors might have made a difference in injury rates, a fixed-model metaanalysis was performed on the adjusted hazard ratios from the Cox regressions reported in the articles. The pooled adjusted hazard ratios from the 3 studies

were 1.04 (95% CI: 0.94, 1.16; Q-statistic, P = .54) for men and 1.07 (95% CI: 0.95, 1.20; Q-statistic, P = .64) for women. This analysis supports the earlier ones reported here, showing no difference in injury rates among the control and experimental groups when the significant covariates were considered.

CONCLUSION

T

he results of the present investigation indicated that selecting or assigning running shoes on the basis of foot arch type did not reduce injuries in military basic training compared to assigning a stability shoe regardless of plantar shape. In addition, injury rates for several brands of running shoes were similar during Army basic training. It should be noted that these studies examined the effect of selecting or assigning running shoes only on the basis of the static weight-bearing plantar shape. This was the practice in basic training when the studies were conducted and the method recommended by popular running magazines and shoe companies to presumably reduce the risk of injury. Anecdotal observations during the studies indicated that there was a great amount of variety of recruit foot sizes and shapes. A single running shoe is not likely to accommodate the variety of foot types encountered in basic training. Consideration should be given to providing recruits with a selection of running shoes that at least provide a wide range of lengths and widths, although shoe selection based on plantar shape is not necessary. t

KEY POINTS FINDINGS: Assigning running shoes on the

basis of the height of the longitudinal foot arch did not influence injury rates in military basic combat training. Injury rates in military basic training were also similar regardless of the type of running shoe worn. IMPLICATIONS: Selecting the type of running shoes based on foot arch height does not appear to be beneficial in



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[ reducing injury risk in military basic training. CAUTION: These studies only examined shoe assignments and injuries in US military basic training, and shoe selection or assignment was based exclusively on the shape of the footprint.


ACKNOWLEDGEMENTS: We would like to thank

Claudia Coleman and Ryan Steelman for assistance with obtaining references, and Ryan Steelman for editorial review.

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