Transitioning to Minimal Footwear: a Systematic Review of Methods and Future Clinical Recommendations

The "impacts cause injury" hypothesis: Running in circles or making new strides?

Some of the earliest biomechanics research focused on running and the ground reaction forces generated with each step. Research in running gait accelerated in the 1970's as the growing popularity in running increased attention to the musculoskeletal injuries sustained by runners. Despite decades of high-quality research, running remains the most common cause of exercise-related musculoskeletal injuries and rates of overuse running-related injuries (RRI) have not appreciably declined since the research began. One leading area of running gait research focuses on discrete variables derived from the vertical ground reaction force, such as the vertical loading rate. Across sub-disciplines of running gait research, vertical loading rate is often discussed as the primary and undisputed variable associated with RRI despite only low to moderate evidence that retrospectively or prospectively injured runners generate greater vertical loading rates than uninjured counterparts. The central thesis of this review is that relying on vertical loading rate is insufficient to establish causal mechanisms for RRI etiology. To present this argument, this review examines the history of the 'impacts cause injury' hypothesis, including a historical look at ground reaction forces in human running and the research from which this hypothesis was generated. Additionally, a synthesis of studies that have tested the hypothesis is provided and recommendations for future research are discussed. Although it is premature to reject or support the 'impacts cause injury' hypothesis, new knowledge of biomechanical risk factors for RRI will remain concealed until research departs from the current path or adopts new approaches to previous paradigms.

Transitioning to Barefoot Running Using a Minimalist Shoe Intermediary: A Prospective Cohort Study

OBJECTIVES

The objectives of this study are, first, to investigate the probability of runners successfully transitioning from running in a traditional shoe to barefoot. Second, to identify prognostic indicators of failure of transition to barefoot running.

METHODS

Over 20 wk, 76 healthy runners (female, 40; age, 35.04 yr [SD, 8.9 yr]; body weight, 69.9 kg [SD 13.4 kg]) attempted to transition from running in traditional shoes to running barefoot. A minimalist shoe was used as an intermediary. Participants ran for 4 wk exclusively in provided traditional shoes followed by 4 wk of transitioning to minimalist shoes. This process was repeated to transition to barefoot running. Participants were followed up until they withdrew from the study or successfully transitioned to running barefoot. A survival analysis examined the weeks of successful transition. Along with sex and age, baseline measures of traditional shoe overall comfort, footstrike pattern, midfoot width mobility and plantar foot pressure pain threshold were examined as prognostic variables for failure to transition using Cox regression.

RESULTS

The cumulative probability of successful transition to running barefoot was 70.8% (95% confidence interval [CI], 61%-83%). The primary footwear-related reason for withdrawal was pain, primarily in the foot ( n = 7), two runners had confirmed injuries. Runners exhibiting a rearfoot strike pattern and higher midfoot width mobility were more likely to fail to transition (hazard ratios [HR], 4.02; 95% CI, 1.33-12.16 and HR, 1.22; 95% CI, 1.05-1.42).

CONCLUSIONS

Most runners who wish to run barefoot will be able to transition. Our study indicates that there may be biomechanical and anatomical characteristics that are prognostic of failing to transition when using a 20-wk transition period and an intermediary minimalist shoe. Whether a different transition process increases the probability of a success remains to be seen.

Time course of muscle activation, energetics and mechanics of running in minimalist and traditional cushioned shoes during level running

The study aimed to compare the ankle muscles activation, biomechanics and energetics of running in male runners during submaximal level run using minimalist (MinRS) and traditional cushioned (TrdRS) running shoes. During 45-min running in MinRS and TrdRS, the ankle muscles pre- and co-activation, biomechanics, and energetics of running of 16 male endurance runners (25.5 ± 3.5 yr) were assessed using surface electromyography (tibialis anterior and gastrocnemius lateralis), instrumented treadmill and indirect calorimetry, respectively. The net energy cost of running (C_r) was similar for both conditions (P = 0.25) with a significant increase over time (P < 0.0001). Step frequency (P < 0.001), and total mechanical work (P = 0.001) were significantly higher in MinRS than in TrdRS with no evolution over time (P = 0.28 and P = 0.85, respectively). The ankle muscles pre- and co-activation during the contact phase did not differ between the two shoe conditions (P ≥ 0.33) or over time (P ≥ 0.15). In conclusion, during 45-min running, Cr and muscle pre- and co-activation were not significantly different between MinRS and TrdRS with significantly higher step frequency and total mechanical work noted in the former than in the latter. Moreover, C_r significantly increased during the 45-min trial in both shoe conditions along with no significant change over time in muscle activation and biomechanical variables.

The effects of footwear on dynamic stability and impact loading in jump landing

Research into the effect of footwear on dynamic stability and impact loading is still in its infancy. The aim of this study was to determine whether cushioned footwear influenced dynamic stability (dynamic postural stability index (DPSI) and time to stabilisation (TTS)) or impact loading (peak ground reaction force (pGRF) and loading rate (LR)) through a series of single-leg jump landings when compared to barefoot and minimalist shoes. Fourteen healthy, active participants (9 males, 5 females, Age: 21 ± 1 years; height: 174 ± 9.87 cm; weight: 75 ± 15.40 kg) were recruited to undergo a series of single-leg jump landings. Each participant randomly performed three jumps in each footwear condition. Repeated measures ANOVA was conducted to determine whether any differences occurred between condition. No statistically significant difference was observed for DPSI (p = 0.300, pη2 = 0.083) between footwear types. A statistically significant difference was determined between footwear condition for TTS (p = 0.001, pη2 = 0.52), and also for pGRF (p = 0.003, pη2 = 0.39), and LR (p ≤ 0.001, pη2 = 0.53). For TTS, pGRF, and LR, no differences were noted between minimalist and barefoot, but were worse in the cushioned shoe vs. both other conditions. Overall, this study determined that cushioned footwear can negatively influence both TTS and impact loading, but not DPSI.

Immediate Effects of Manipulating Footwear or Cadence on the Lower Limb Biomechanics of Female Masters Runners

The objective of this study was to compare the immediate effects of modifications to footwear or cadence on lower limb biomechanics of female Masters runners. After analyzing habitual treadmill running biomechanics in 20 female runners (52.4 [8.3] y), we assessed the effects of 5 conditions: (1) barefoot running, (2) Merrell Vapor Glove, (3) Merrell Bare Access, (4) Brooks Pure Flow, and (5) increasing cadence by 10%. In comparison with habitual biomechanics, greater vertical loading rates of the ground reaction force were observed during running barefoot or with a Merrell Vapor Glove or Bare Access. There was high variability among participants as to changes in foot kinematics during the conditions. Running barefoot (-26.0%) and with a Merrell Vapor Glove (-12.5%) reduced sagittal plane knee moments, but increased sagittal plane ankle moments (both 6.1%). Increasing cadence by 10% resulted in a more modest decrease in knee flexion moments (-7.7%) without increasing peak external ankle dorsiflexion moments. When asked if they would prefer minimalist shoes or increasing cadence, 11 participants (55%) chose cadence and 9 (45%) chose footwear. Minimalist footwear decreased sagittal knee moments, but increased vertical loading rate and sagittal ankle moments. Increasing cadence may be useful to lower sagittal knee moments without increasing ankle moments.

Kinematics of recreational male runners in "super", minimalist and habitual shoes

We conducted an exploratory analysis to compare running kinematics of 16 male recreational runners wearing Nike Vaporfly 4% (VP4), Saucony Endorphin racing flat (FLAT), and their habitual (OWN) footwear. We also explored potential relationships between kinematic and physiological changes. Runners (age: 33 ± 12 y, V˙ O_2peak: 55.2 ± 4.3 ml · kg^-1·min^-1) attended 3 sessions after completing an V˙ O_2peak test in which sagittal plane 3D kinematics at submaximal running speeds (60%, 70% and 80% ʋ V˙ O_2peak) were collected alongside economy measures. Kinematics were compared using notched boxplots, and between-shoe kinematic differences were plotted against between-shoe economy differences. Across intensities, VP4 involved longer flight times (6.7 to 10.0 ms) and lower stance hip range of motion (~3°), and greater vertical pelvis displacement than FLAT (~0.4 cm). Peak dorsiflexion angles (~2°), ankle range of motion (1.0° to 3.9°), and plantarflexion velocities (11.3 to 89.0 deg · sec^-1) were greatest in FLAT and lowest in VP4. Foot-ground angles were smaller in FLAT (2.5° to 3.6°). Select kinematic variables were moderately related to economy, with higher step frequencies and shorter step lengths in VP4 and FLAT associated with improved economy versus OWN. Footwear changes from OWN altered running kinematics. The most pronounced differences were observed in ankle, spatiotemporal, and foot-ground angle variables.

Gait Retraining With Visual Biofeedback Reduces Rearfoot Pressure and Foot Pronation in Recreational Runners

CONTEXT

Running is a popular sport globally. Previous studies have used a gait retraining program to successfully lower impact loading, which has been associated with lower injury rates in recreational runners. However, there is an absence of studies on the effect of this training program on the plantar pressure distribution pattern during running.

OBJECTIVE

To investigate the short-term effect of a gait retraining strategy that uses visual biofeedback on the plantar pressure distribution pattern and foot posture in recreational runners.

DESIGN

Randomized controlled trial.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Twenty-four recreational runners were evaluated (n = 12 gait retraining group and n = 12 control group).

INTERVENTION

Those in the gait retraining group underwent a 2-week program (4 sessions/wk, 30 min/session, and 8 sessions). The participants in the control group were also invited to the laboratory (8 times in 2 wk), but no feedback on their running biomechanics was provided.

MAIN OUTCOME MEASURES

The primary outcome measures were plantar pressure distribution and plantar arch index using a pressure platform. The secondary outcome measure was the foot posture index.

RESULTS

The gait retraining program with visual biofeedback was effective in reducing medial and lateral rearfoot plantar pressure after intervention and when compared with the control group. In the static condition, the pressure peak and maximum force on the forefoot and midfoot were reduced, and arch index was increased after intervention. After static training intervention, the foot posture index showed a decrease in the foot pronation.

CONCLUSIONS

A 2-week gait retraining program with visual biofeedback was effective in lowering rearfoot plantar pressure, favoring better support of the arch index in recreational runners. In addition, static training was effective in reducing foot pronation. Most importantly, these observations will help healthcare professionals understand the importance of a gait retraining program with visual biofeedback to improve plantar loading and pronation during rehabilitation.

Training Load Capacity, Cumulative Risk, and Bone Stress Injuries: A Narrative Review of a Holistic Approach

Bone stress injuries (BSIs) are a common orthopedic injury with short-term, and potentially long-term, effects. Training load capacity, influenced by risk factors, plays a critical role in the occurrence of BSIs. Many factors determine how one's body responds to repetitive loads that have the potential to increase the risk of a BSI. As a scientific community, we have identified numerous isolated BSI risk factors. However, we have not adequately analyzed the integrative, holistic, and cumulative nature of the risk factors, which is essential to determine an individual's specific capacity. In this narrative review, we advocate for a personalized approach to monitor training load so that individuals can optimize their health and performance. We define “cumulative risk profile” as a subjective clinical determination of the number of risk factors with thoughtful consideration of their interaction and propose that athletes have their own cumulative risk profile that influences their capacity to withstand specific training loads. In our narrative review, we outline BSI risk factors, discuss the relationship between BSIs and training load, highlight the importance of individualizing training load, and emphasize the use of a holistic assessment as a training load guide.

What are the Benefits and Risks Associated with Changing Foot Strike Pattern During Running? A Systematic Review and Meta-analysis of Injury, Running Economy, and Biomechanics

BACKGROUND

Running participation continues to increase. The ideal strike pattern during running is a controversial topic. Many coaches and therapists promote non-rearfoot strike (NRFS) running with a belief that it can treat and prevent injury, and improve running economy.

OBJECTIVE

The aims of this review were to synthesise the evidence comparing NRFS with rearfoot strike (RFS) running patterns in relation to injury and running economy (primary aim), and biomechanics (secondary aim).

DESIGN

Systematic review and meta-analysis. Consideration was given to within participant, between participant, retrospective, and prospective study designs.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, and SPORTDiscus.

RESULTS

Fifty-three studies were included. Limited evidence indicated that NRFS running is retrospectively associated with lower reported rates of mild (standard mean difference (SMD), 95% CI 3.25, 2.37-4.12), moderate (3.65, 2.71-4.59) and severe (0.93, 0.32-1.55) repetitive stress injury. Studies prospectively comparing injury risk between strike patterns are lacking. Limited evidence indicated that running economy did not differ between habitual RFS and habitual NRFS runners at slow (10.8-11.0 km/h), moderate (12.6-13.5 km/h), and fast (14.0-15.0 km/h) speeds, and was reduced in the immediate term when an NRFS-running pattern was imposed on habitual RFS runners at slow (10.8 km/h; SMD = - 1.67, - 2.82 to - 0.52) and moderate (12.6 km/h; - 1.26, - 2.42 to - 0.10) speeds. Key biomechanical findings, consistently including both comparison between habitual strike patterns and following immediate transition from RFS to NRFS running, indicated that NRFS running was associated with lower average and peak vertical loading rate (limited-moderate evidence; SMDs = 0.72-2.15); lower knee flexion range of motion (moderate-strong evidence; SMDs = 0.76-0.88); reduced patellofemoral joint stress (limited evidence; SMDs = 0.63-0.68); and greater peak internal ankle plantar flexor moment (limited evidence; SMDs = 0.73-1.33).

CONCLUSION

The relationship between strike pattern and injury risk could not be determined, as current evidence is limited to retrospective findings. Considering the lack of evidence to support any improvements in running economy, combined with the associated shift in loading profile (i.e., greater ankle and plantarflexor loading) found in this review, changing strike pattern cannot be recommended for an uninjured RFS runner.

PROSPERO REGISTRATION

CRD42015024523.

Running barefoot leads to lower running stability compared to shod running - results from a randomized controlled study

Local dynamic running stability is the ability of a dynamic system to compensate for small perturbations during running. While the immediate effects of footwear on running biomechanics are frequently investigated, no research has studied the long-term effects of barefoot vs. shod running on local dynamic running stability. In this randomized single-blinded controlled trial, young adults novice to barefoot running were randomly allocated to a barefoot or a cushioned footwear running group. Over an 8-week-period, both groups performed a weekly 15-min treadmill running intervention in the allocated condition at 70% of their VO2 max velocity. During each session, an inertial measurement unit on the tibia recorded kinematic data (angular velocity) which was used to determine the short-time largest Lyapunov exponents as a measure of local dynamic running stability. One hundred running gait cycles at the beginning, middle, and end of each running session were analysed using one mixed linear multilevel random intercept model. Of the 41 included participants (48.8% females), 37 completed the study (drop-out = 9.7%). Participants in the barefoot running group exhibited lower running stability than in the shod running group (p = 0.037) with no changes during the intervention period (p = 0.997). Within a single session, running stability decreased over the course of the 15-min run (p = 0.012) without differences between both groups (p = 0.060). Changing from shod to barefoot running reduces running stability not only in the acute phase but also in the longer term. While running stability is a relatively new concept, it enables further insight into the biomechanical influence of footwear.

Training and technique choices predict self-reported running injuries: An international study

OBJECTIVES

The aim of this study was to describe the self-reported injury, training, and running technique choices of regular runners in four international regions.

DESIGN AND SETTING

756 participants began an expert derived self-report online survey in Ireland, USA, Hong Kong and Australia.

PARTICIPANTS

325 participants completed the survey (age = 38 ± 10 years; weight = 68.0 ± 13.1 kg; height = 1.70 ± 0.10 m).

MAIN OUTCOME MEASURES

Descriptive statistics are reported examining injury incidence and location; shoe and orthosis choices; and training and technique practices. A backwards logistic regression was implemented to examine associations between injury and training choices.

RESULTS

68.3% reported having an injury in the last year. 81.45% of these injuries were believed to be running related. A large variation in training and footwear choices were observed for respondents. The regression (P ≤ 0.001) explained 20% of the variance in injury selection (Nagelkerke R²) and was able to identify 73% of cases accurately. Associated injury factors included competitive running, running on more than one surface, younger age, having a lower running age, and a higher proportion of running at an easy intensity.

CONCLUSIONS

The high amount of variability in runner's choices highlights the lack of consistent information being presented to them and may be the reason for the high injury incidence.

A Contemporary Approach to Patellofemoral Pain in Runners

Patellofemoral pain (PFP) is among the most common injuries in recreational runners. Current evidence does not identify alignment, muscle weakness, and patellar maltracking or a combination of these as causes of PFP. Rather than solely investigating biomechanics, we suggest a holistic approach to address the causes of PFP. Both external loads, such as changes in training parameters and biomechanics, and internal loads, such as sleep and psychological stress, should be considered. As for the management of runners with PFP, recent research suggested that various interventions can be considered to help symptoms, even if these interventions target biomechanical factors that may not have caused the injury in the first place. In this Current Concepts article, we describe how the latest evidence on education about training modifications, strengthening exercises, gait and footwear modifications, and psychosocial factors can be applied when treating runners with PFP. The importance of maintaining relative homeostasis between load and capacity will be emphasized. Recommendations for temporary or longer-term interventions will be discussed. A holistic, evidence-based approach should consist of a graded exposure to load, including movement, exercise, and running, while considering the capacity of the individual, including sleep and psychosocial factors. Cost, accessibility, and the personal preferences of patients should also be considered.

Minimalist style boot improves running but not walking economy in trained men

This study examined movement economy under load with 1000 g minimalist (MIN) vs. 1600 g traditional (TRD) style boots. Fourteen trained, male participants completed a VO_2peak test (46.6 ± 7.3 ml/kg/min) while wearing a 16 kg external load. Treadmill speeds for the running economy (RE) trials were determined by the slowest pace in which participants completed a full stage with a running gait pattern during the VO_2peak test. Walking economy (WE) pace was 1.6 km/h slower than RE pace. During the second session, participants completed 5-min exercise bouts at WE and RE pace under load wearing MIN and TRD. There were no differences for any measured variables during WE trials. In contrast, RE (MIN = 2.95 ± 0.28 vs. TRD = 3.04 ± 0.30 L/min; p = .003: Cohen's d = 0.32), respiratory exchange ratio (p < .001), and perceptual measures (p < .05) were all improved while wearing MIN. Practitioner summary: In trained men, 1000 g/pair minimalist style boots (MIN) resulted in improvements of approximately 3% and 5% for running economy and respiratory exchange ratio versus 1600 g/pair traditional boots while wearing a 16 kg kit. Perceptual responses, including comfort, also favoured MIN. These effects were not found at walking pace. Abbreviations: MIN: minimalist style boots; TRD: traditional style boots; RE: running economy; WE: walking economy; ES: effect size; RER: respiratory exchange ratio; HR: heart rate.

What are the perceptions of runners and healthcare professionals on footwear and running injury risk?

Objectives

There is a gap in research exploring perceptions of runners and healthcare professionals (HCPs) about running footwear and injury risk. The objectives of this study were: (1) to document factors considered by runners when selecting footwear; (2) to compare perceptions on footwear and injury risk in runners and HCPs; and (3) to evaluate the perceived usefulness of an online educational module.

Methods

Using an online survey, we collected information on demographics and perceptions about footwear and injury risk. Runners reported their footwear selection strategy, and HCPs their typical recommendations. An evidence-based educational module was presented, and participants rated its usefulness.

Results

The survey was completed by 2442 participants, of which 1035 completed the optional postmodule questions. Runners reported relying mostly on comfort and advice from retailers when selecting shoes. Perceptions regarding the effects of specific footwear types (minimalist, maximalist), characteristics (softness, drop) and selection strategy (foot type, transition) on biomechanics and injury risk were different between HCPs and runners. Overall, runners perceived footwear as more important to prevent injury than did HCPs (7.6/10, 99% CI 7.4 to 7.7 vs 6.2/10, 99% CI 6.0 to 6.5; p<0.001). Both runners (8.1/10, 99% CI 7.9 to 8.3) and HCPs (8.7/10, 99% CI 8.6 to 8.9) found the educational module useful. A majority of respondents indicated the module changed their perceptions.

Conclusion

Footwear is perceived as important in reducing running injury risk. This online module was deemed useful in educating about footwear evidence. Future studies should evaluate if changes in perceptions can translate to behaviour change and, ultimately, reduced injury risk.

Transition to forefoot strike reduces load rates more effectively than altered cadence

BACKGROUND

Excessive vertical impacts at landing are associated with common running injuries. Two primary gait-retraining interventions aimed at reducing impact forces are transition to forefoot strike and increasing cadence. The objective of this study was to compare the short- and long-term effects of 2 gait-retraining interventions aimed at reducing landing impacts.

METHODS

A total of 39 healthy recreational runners using a rearfoot strike and a cadence of ≤170 steps/min were randomized into cadence (CAD) or forefoot strike (FFS) groups. All participants performed 4 weeks of strengthening followed by 8 sessions of gait-retraining using auditory feedback. Vertical average load rates (VALR) and vertical instantaneous load rates (VILR) were calculated from the vertical ground reaction force curve. Both cadence and foot strike angle were measured using 3D motion analysis and an instrumented treadmill at baseline and at 1 week, 1 month, and 6 months post retraining.

RESULTS

ANOVA revealed that the FFS group had significant reductions in VALR (49.7%) and VILR (41.7%), and changes were maintained long term. Foot strike angle in the FFS group changed from 14.2° dorsiflexion at baseline to 3.4° plantarflexion, with changes maintained long term. The CAD group exhibited significant reduction only in VALR (16%) and only at 6 months. Both groups had significant and similar increases in cadence at all follow-ups (CAD, +7.2% to 173 steps/min; and FFS, +6.1% to 172 steps/min).

CONCLUSION

Forefoot strike gait-retraining resulted in significantly greater reductions in VALR and similar increases in cadence compared to cadence gait-retraining in the short and long term. Cadence gait-retraining resulted in small reductions in VALR at only the 6-month follow-up.

Young Adults Performance of Unipedal Dynamic Balance with Various Footwear Conditions

Wearing barefoot-style (minimalist) shoes is suggested as a transition between wearing shoes and barefoot running. Some sources equate wearing Vibram FiveFingers™(VFFs), a brand of barefoot shoes, with running/walking barefoot. Static and dynamic balance exercises are recommended. Little information is available on the effects barefoot shoes may have on dynamic balance. This study's purpose was to examine dynamic balance when participants wore VFFs, athletic shoes, or went barefoot (BF). To test dynamic balance, participants used a modified version of the Star Excursion Balance Test (SEBT), in which the reaching leg followed only three spokes of the test: the anterior, posteromedial and posterolateral. For the timed test, participants touched down as quickly as possible in both directions using all 8 spokes. Thirty participants (ages 24.1+/-3.71 years) without lower extremity injury or experience wearing minimalist shoes were tested using the modified SEBT and a timed test wearing VFFs™, athletic shoes, or BF. Three trials for each footwear were completed for three reaching positions: anterior, posterolateral, posteromedial. The timed test measured (seconds) one counterclockwise and one clockwise direction of the 8-spoke figure. A repeated measures analysis of variance determined if any differences existed between footwear type and studied variables. Anterior reach was significantly greater when wearing shoes than with VFF or BF. Posteromedial reach was greater with shoes than BF. Time trials were not significantly different. Because no difference was found in any measured variables between VFF and BF, the results suggest wearing VFFS™ provided similar dynamic balance as going barefoot.

Adaptation of Running Biomechanics to Repeated Barefoot Running: A Randomized Controlled Study

BACKGROUND

Previous studies have shown that changing acutely from shod to barefoot running induces several changes to running biomechanics, such as altered ankle kinematics, reduced ground-reaction forces, and reduced loading rates. However, uncertainty exists whether these effects still exist after a short period of barefoot running habituation.

PURPOSE/HYPOTHESIS

The purpose was to investigate the effects of a habituation to barefoot versus shod running on running biomechanics. It was hypothesized that a habituation to barefoot running would induce different adaptations of running kinetics and kinematics as compared with a habituation to cushioned footwear running or no habituation.

STUDY DESIGN

Controlled laboratory study.

METHODS

Young, physically active adults without experience in barefoot running were randomly allocated to a barefoot habituation group, a cushioned footwear group, or a passive control group. The 8-week intervention in the barefoot and footwear groups consisted of 15 minutes of treadmill running at 70% of VO₂ max (maximal oxygen consumption) velocity per weekly session in the allocated footwear. Before and after the intervention period, a 3-dimensional biomechanical analysis for barefoot and shod running was conducted on an instrumented treadmill. The passive control group did not receive any intervention but was also tested prior to and after 8 weeks. Pre- to posttest changes in kinematics, kinetics, and spatiotemporal parameters were then analyzed with a mixed effects model.

RESULTS

Of the 60 included participants (51.7% female; mean ± SD age, 25.4 ± 3.3 years; body mass index, 22.6 ± 2.1 kg·m^-2), 53 completed the study (19 in the barefoot habituation group, 18 in the shod habituation group, and 16 in the passive control group). Acutely, running barefoot versus shod influenced foot strike index and ankle, foot, and knee angles at ground contact (P < .001), as well as vertical average loading rate (P = .003), peak force (P < .001), contact time (P < .001), flight time (P < .001), step length (P < .001), and cadence (P < .001). No differences were found for average force (P = .391). After the barefoot habituation period, participants exhibited more anterior foot placement (P = .006) when running barefoot, while no changes were observed in the footwear condition. Furthermore, barefoot habituation increased the vertical average loading rates in both conditions (barefoot, P = .01; shod, P = .003) and average vertical ground-reaction forces for shod running (P = .039). All other outcomes (ankle, foot, and knee angles at ground contact and flight time, contact time, cadence, and peak forces) did not change significantly after the 8-week habituation.

CONCLUSION

Changing acutely from shod to barefoot running in a habitually shod population increased the foot strike index and reduced ground-reaction force and loading rates. After the habituation to barefoot running, the foot strike index was further increased, while the force and average loading rates also increased as compared with the acute barefoot running situation. The increased average loading rate is contradictory to other studies on acute adaptations of barefoot running.

CLINICAL RELEVANCE

A habituation to barefoot running led to increased vertical average loading rates. This finding was unexpected and questions the generalizability of acute adaptations to long-term barefoot running. Sports medicine professionals should consider these adaptations in their recommendations regarding barefoot running as a possible measure for running injury prevention.

REGISTRATION

DRKS00011073 (German Clinical Trial Register).

Effects of footwear midsole thickness on running biomechanics

Shoe manufacturers launch running shoes with increased (e.g., maximalists) or decreased (e.g., minimalists) midsole thickness and claim that they may prevent running injury. Previous studies tested footwear models with different midsole thicknesses on the market but the shoe construct was not strictly comparable. Therefore, in the present study, we examined the effect of midsole thickness, from 1-mm to 29-mm, in a standard test shoe prototype on the vertical loading rates, footstrike angle and temporal spatial parameters in distance runners. Fifteen male habitual rearfoot strikers were recruited from local running clubs. They were asked to run on an instrumented treadmill in shoes with different midsole thicknesses. We found significant interactions between midsole thickness with vertical loading rates (p < 0.001), footstrike angle (p = 0.013), contact time (p < 0.001), cadence (p = 0.003), and stride length (p = 0.004). Specifically, shoes with thinner midsole (1- and 5-mm) significantly increased the vertical loading rates and shortened the contact time, when compared with thicker midsole shoes (25- and 29-mm). However, we did not observe any substantial differences in the footstrike angle, cadence and stride length between other shod conditions. The present study provides biomechanical data regarding the relationship between full spectrum midsole thicknesses and running biomechanics in a group of rearfoot strikers.

Improving Running Economy by Transitioning to Minimalist Footwear: A Randomised Controlled Trial

OBJECTIVES

Ongoing debates about benefits and risks of barefoot- and minimally-shod running have, to date, revealed no conclusive findings for long-term effects on physical performance. The purpose of this study was to examine the effects of an 8-week transition to minimalist footwear (MFW) on running economy (RE).

DESIGN

Randomised controlled trial.

METHODS

Thirty-two male, habitually-shod runners were assigned randomly to an 8-week training intervention either in minimalist (=intervention group) or conventional running shoes (=control group). The intervention consisted of a gradual increase in use of the new footwear by 5% of the individual weekly distance. Before and after the intervention, a VO₂max test was followed by a submaximal RE test at 70% and 80% of vVO₂max in both shoe conditions 7days later. RE was measured at the submaximal tests and expressed as caloric unit cost (kcalkg^-1km^-1) and oxygen consumption (mlkg^-1km^-1).

RESULTS

RE improved in the intervention group over time compared to the control group with small to moderate effect sizes (ES) in both shoe conditions: Effects on RE (kcalkg^-1km^-1) in conventional running shoes: ES vVO₂70%: 0.68 (95% CI: -0.14 to 1.51), ES vVO₂80%: 0.78 (95% CI: 0-1.56). In minimalist footwear: ES vVO₂70%: 0.3 (95% CI: -0.54 to 1.14), ES vVO₂80%: 0.42 (95% CI: -0.41 to 1.25). These effects were not statistically significant (p>0.05). The repeated-measures ANOVA also showed no group by time interactions for all submaximal RE testing conditions (p>0.05).

CONCLUSIONS

Although not reaching statistical significance, training in MFW compared to CRS resulted in small to moderate improvements in RE.