Effects of training in minimalist shoes on the intrinsic and extrinsic foot muscle volume

Sticking the landing: A comparison of shod vs barefoot landing kinetics and foot muscle characteristics in gymnasts, cheerleaders, and non-athletes

OBJECTIVES

The ability to control landings and stabilize quickly is essential in sports like gymnastics and cheerleading, where landing quality impacts scores. The similarities and contrasts between these sports, where one trains primarily barefoot and the other shod, may increase understanding of the kinetic role of the foot during landings.

DESIGN

Sixteen gymnasts (GYM), sixteen cheerleaders (CHR), and sixteen non-athletes (NAT) performed single-foot shod and barefoot drop landings onto a force plate.

METHOD

Foot muscle strength was assessed using a custom test and ultrasound imaging was used to measure six foot muscles. Group differences in muscle sizes and strength measurements were compared using one-way ANOVAs (α = 0.05). Landing mechanics metrics were evaluated using 3 x 2 between-within ANOVAs (α = 0.05). Pairwise comparisons were made using Tukey post-hoc tests.

RESULTS

Barefoot landings resulted in greater peak vertical ground reaction force (pVGRF) and lower time to pVGRF (TTpVGRF). Significant group main effect differences were found between GYM and NAT for all kinetic measures (GYM: shorter time to stability (TTS) and TTpVGRF, and greater pVGRF), while no significant differences in landing kinetics were found between CHR and either GYM or NAT. No interactions were found between group and condition. GYM and CHR had significantly greater summed foot muscle size than NAT, however, only CHR displayed significantly greater toe flexion force than NAT.

CONCLUSIONS

Our data suggests that while wearing shoes does not affect groups differently, footwear reduces initial peak VGRFs but does not influence later stabilization times.

Figure Skating Musculoskeletal Injury: Evidence across Disciplines, Mechanisms, and Future Directions

ABSTRACT

This review provides a synopsis of current injury patterns, potential mechanisms, and off-ice exercise prevention considerations as the sport of figure skating evolves. The lifetime prevalence of injury for all skaters is estimated to be 79.5%, with the most common sites being spine and lower extremity. Singles skaters more often develop chronic injuries compared to acute (68.9% vs 31.1%), whereas non-singles skaters more often experience acute injuries. Lower limb stress fracture prevalence ranges from 10% to 21.4% across disciplines. Emerging contributors include training volume, technical difficulty and repetition of complex elements (multirotational jumps, lifts, holds), extreme ranges of movement about the spine and hip, age and experience level, and functional capacity (dynamic strength, flexibility, balance, and neuromotor control). Prevention programs in competitive figure skaters may include monitoring of training volumes, emphasis on technique, appropriate boot fit, and strength and conditioning content to prepare for increasing neuromotor, balance, and power demands of the sport.

Effects of technological running shoes versus barefoot running on the intrinsic foot muscles, ankle mobility, and dynamic control: a novel cross-sectional research

BACKGROUND

Technological running shoes have become increasingly popular, leading to improvements in performance. However, their long-term effects on foot musculature and joint mobility have not been thoroughly studied.

OBJECTIVE

To compare the activation of the intrinsic foot muscles between runners wearing technological footwear and barefoot runners. Secondary objectives included assessing ankle dorsiflexion (DF) range of motion (ROM) and dynamic postural control in both groups.

METHODS

A cross-sectional study was conducted involving 22 technological footwear runners and 22 barefoot runners. Ultrasonography was used to measure the thickness of the plantar fascia (PF) and the quadratus plantae (QP), abductor digiti minimus (ADM), abductor hallucis (AH), and flexor hallucis longus (FHL) muscles. Ankle mobility and dynamic postural control were also recorded.

RESULTS

Ultrasonography measurements showed statistically significant differences for PF thickness (mean difference [MD]: -0.10 cm; 95% CI: -0.13, -0.05 cm), QP cross-sectional area (CSA) (MD: -0.45 cm2; 95% CI: -0.77, -0.12 cm2), ADM CSA (MD: -0.49 cm2; 95% CI: -0.70, -0.17 cm2), and FHL thickness (MD: 0.82 cm; 95% CI: 0.53, 1.09 cm), with all measurements being lower in the group wearing technological footwear compared to the barefoot runners. Ankle DF ROM was also significantly greater for the barefoot runners (MD: -5.1°; 95% CI: -8.6, -1.7°).

CONCLUSIONS

These findings suggest potential implications for the foot musculature and ankle mobility in runners using technological footwear.

A four-week minimalist shoe walking intervention influences foot posture and balance in young adults-a randomized controlled trial

INTRODUCTION

Minimalist shoes (MS) are beneficial for foot health. The foot is a part of the posterior chain. It is suggested that interventions on the plantar foot sole also affect the upper segments of the body. This study aimed to investigate the local and remote effects along the posterior chain of four weeks of MS walking in recreationally active young adults.

METHODS

28 healthy participants (15 female, 13 male; 25.3 ± 5.3 years; 70.2 ± 11.9 kg; 175.0 ± 7.8 cm) were randomly assigned to a control- or intervention group. The intervention group undertook a four-week incremental MS walking program, which included 3,000 steps/day in the first week, increasing to 5,000 steps/day for the remaining three weeks. The control group walked in their preferred shoe (no MS). We assessed the following parameters in a laboratory at baseline [M1], after the four-week intervention [M2], and after a four-week wash-out period [M3]: Foot parameters (i.e., Foot Posture Index-6, Arch Rigidity Index), static single-leg stance balance, foot-, ankle-, and posterior chain range of motion, and muscle strength of the posterior chain. We fitted multiple hierarchically built mixed models to the data.

RESULTS

In the MS group, the Foot Posture Index (b = -3.72, t(51) = -6.05, p < .001, [-4.94, 2.51]) and balance (b = -17.96, t(49) = -2.56, p = .01, [-31.54, 4.37]) significantly improved from M1 to M2, but not all other parameters (all p >.05). The improvements remained at M3 (Foot Posture Index: b = -1.71, t(51) = -2.73, p = .009, [-4,94,0.48]; balance: b = -15.97, t(49) = -2.25, p = .03, [-29.72, 2.21]).

DISCUSSION

Walking in MS for four weeks might be advantageous for foot health of recreationally active young adults but no chronic remote effects should be expected.

Fatigue of the intrinsic foot core muscles had a greater effect on gait than extrinsic foot core muscles: A time-series based analyze

BACKGROUND

The Heel Rise endurance (HRE) which indicates the extrinsic foot core (ECO) muscle's performance and the paper grip endurance (PGE) which indicates the intrinsic foot core (ICO) muscle's performance are essential components of a healthy foot function. However, the foot core muscles' fatigue response on spatial and temporal gait parameters after the HRE and the PGE tests were not adequately investigated. The purpose of this study was to determine whether the fatigue of the ICO and the ECO muscles affect gait parameters.

MATERIAL AND METHODS

A prospective, cross-sectional study was conducted on 22 sedentary individuals (44 feet). Gait was investigated pre and after the Heel Rise (HR) endurance test and the paper grip (PG) endurance test by inertial sensors. At least 500 consecutive steps were collected for each individual. Spatial-temporal gait parameters were used as outcome measures.

RESULTS

ECO fatigue and ICO fatigue led to increases in the step length (p < 0.05) and the stride lengths (p < 0.05), the single support (p < 0.05), and the terminal stance durations (p < 0.05). It was also seen that ICO fatigue had a greater effect on gait than ECO fatigue. The ECO fatigue had a medium to large effect on the gait parameters (d=0.313-0.646). The ICO fatigue affected gait with a large effect (d=0.524-2.048).

CONCLUSION

The ECO fatigue and the ICO fatigue led to clinically important changes in long-range gait parameters and the ICO fatigue had a greater effect on gait than ECO fatigue. It was suggested that clinicians add ICO muscle endurance training to improve the physical performance of individuals.

Minimalist school shoes improve intrinsic foot muscle size, strength, and arch integrity among primary school students

Minimalist walking shoes have been shown to improve foot muscle size and strength in active adults, but not in our previous study involving children, which could relate to the more structured footwear used in our study. Hence, this study examined the effects of true minimalists on intrinsic foot muscle size and strength, foot arch integrity, and physical function among primary school children. After a baseline assessment, 30 primary school students aged between 9 and 12 were given a pair of minimalist shoes (minimalist index = 92%) as their regular school shoes for two school terms, followed by a re-assessment. Seventeen of the 30 participants in the minimalist group completed the study. Compared to the control group, the minimalist group showed significantly increased cross-sectional area of abductor hallucis (p = 0.047, Cohen's d = 0.57) and flexor digitorum brevis (p = 0.037, Cohen's d = 0.80), increased strength of the hallux (p = 0.015, Cohen's d = 0.76) and lesser toes (p = 0.014, Cohen's d = 0.66), greater arch height (p = 0.020, Cohen's d = 0.52) and standing long jump distance (p = 0.001, Cohen's d = 9.79). The control group exhibited improved standing long jump performance only (p = 0.020, Cohen's d = 10.70). Minimalist shoes worn daily to school promote intrinsic foot muscle size and strength, and improve foot arch integrity among primary school students.

Predictive factors for foot pain in the adult population

BACKGROUND

Foot pain has been associated to factors like: fat, body mass index, age increased, female gender and the presence of pathologies. Although evidence is limited. The purpose is to determine the predictive factors for foot pain in the adult population.

METHODS

From January to December 2021, 457 patients were > 18 years, gave signed informed consent to take part to this cross sectional study. All completed demographic data and various questionnaires related to pain: Foot Function Index, EuroQoL-5D and Visual Analogue Scale (foot pain). Anthropometric measurements were obtained using McPoil platform and foot posture was assessed by the Foot Posture Index (FPI). To determine whether a volume change is a predictive factor for foot pain, a parameter was established: the volumetric index for footwear (VIF). Factors linked to the presence of pain, including the considered VIF variables, were analyzed through multivariable logistic regression.

RESULTS

Among the study population, 40.7% were male and 59.3% female. The mean age of 39.06 years and a body mass index of 25.58 Kg/cm2. The logistic regression model had a classification capability of 72.4%, a sensitivity of 72.3% and a specificity of 73%, in which, the predictors considered were the variables found to have a significant association with FFI-pain > 45 points,, showed that younger women, with a higher BMI, higher values of right FPI (pronation), poorer overall perceived health and with problems in walking were more likely to experience foot pain.

CONCLUSION

Predictive factors for foot pain in the adult population include gender, age, Body Mass Index, FPI on the right foot, perceived health and mobility. Clinical implication, the presented measure aids physicians in assessing their patients´ foot pain likelihood.

Foot and Ankle Muscle Isometric Strength in Nonrearfoot Compared With Rearfoot Endurance Runners

Background

Transitioning to a forefoot strike pattern can be used to manage running-related knee injuries. However, adopting a nonrearfoot strike induces a higher load on foot and ankle structures than rearfoot strike. Sufficient foot muscle strength is also necessary to prevent excessive longitudinal arch (LA) deformation when running with nonrearfoot strike. The aim of this study was to investigate the potential differences in foot-ankle muscle strength between RF and NRF runners.

Methods

A cross-sectional study including 40 RF and 40 NRF runners was conducted. The foot posture and the maximal voluntary isometric strength (MVIS) of 6 foot-ankle muscles were measured. The footstrike pattern was determined using a 2-D camera during a self-paced run on a treadmill.

Results

NRF had higher MVIS for ankle plantar flexor (+12.5%, P = .015), ankle dorsiflexor (+17.7%, P = .01), hallux flexor (+11%, P = .04), and lesser toe flexor (+20.8%, P = .0031). We found a small positive correlation between MVIS of ankle plantar flexor with MVIS of hallux flexor (r = 0.26; P = .01) and lesser toe flexor (r = 0.28; P = .01).

Conclusion

In this cross-sectional study, we found that NRF runners on average have a higher MVIS of hallux and lesser toe flexor compared with RF runners. NRF runners also have a higher MVIS of ankle plantar flexor and dorsiflexor than RF runners. We found only a small correlation between ankle plantar flexor and foot muscle strength.

Level of Evidence

Level III, case-control study.

Biomechanical Tradeoffs in Foot Function From Variations in Shoe Design

There is debate and confusion over how to evaluate the biomechanical effects of running shoe design. Here, we use an evolutionary perspective to analyze how key design features of running shoes alter the evolved biomechanics of the foot, creating a range of tradeoffs in force production and transmission that may affect performance and vulnerability to injury.

Effects of tDCS on Foot Biomechanics: A Narrative Review and Clinical Applications

In recent years, neuro-biomechanical enhancement techniques, such as transcranial direct current stimulation (tDCS), have been widely used to improve human physical performance, including foot biomechanical characteristics. This review aims to summarize research on the effects of tDCS on foot biomechanics and its clinical applications, and further analyze the underlying ergogenic mechanisms of tDCS. This review was performed for relevant papers until July 2023 in the following databases: Web of Science, PubMed, and EBSCO. The findings demonstrated that tDCS can improve foot biomechanical characteristics in healthy adults, including proprioception, muscle strength, reaction time, and joint range of motion. Additionally, tDCS can be effectively applied in the field of foot sports medicine; in particular, it can be combined with functional training to effectively improve foot biomechanical performance in individuals with chronic ankle instability (CAI). The possible mechanism is that tDCS may excite specific task-related neurons and regulate multiple neurons within the system, ultimately affecting foot biomechanical characteristics. However, the efficacy of tDCS applied to rehabilitate common musculoskeletal injuries (e.g., CAI and plantar fasciitis) still needs to be confirmed using a larger sample size. Future research should use multimodal neuroimaging technology to explore the intrinsic ergogenic mechanism of tDCS.

A Novel Intrinsic Foot Muscle Strength Dynamometer Demonstrates Moderate-To-Excellent Reliability and Validity

Background

Intrinsic foot muscle (IFM) weakness can result in reduced foot function, making it crucial for clinicians to track IFM strength changes accurately. However, assessing IFM strength can be challenging for clinicians, as there is no clinically applicable direct measure of IFM strength that has been shown to be reliable and valid with the foot on the ground.

Purpose

The purpose was to investigate the intra-rater and inter-rater reliability of a novel, budget-friendly IFM dynamometer and determine its agreement with a handheld dynamometer (HHD). The researchers also examined correlations of foot morphology and activity level to IFM strength.

Study design

Descriptive Laboratory Study.

Methods

Two assessors measured IFM strength of 34 healthy volunteers (4 male, 30 female; age=21.14±2.57, height=164.66 ±7.62 cm, mass=64.45±11.93 kg) on two occasions 6.62±0.78 days apart with the novel dynamometer to assess intra- and inter-rater reliability. The HHD was used to measure IFM in the first session in order to assess validity.

Results

For the novel dynamometer, intra- and inter-rater reliability was moderate-to-excellent (ICC = 0.73 - 0.95), and the majority of the strength tests were within the 95% limits of agreement with the HHD. Wider foot morphology and a higher number of days walking over the prior seven days had small but significant correlations with IFM strength (dominant foot r = 0.34, non-dominant foot r = 0.39; r = -0.33, -0.39 respectively).

Conclusion

This novel IFM dynamometer is a budget-friendly ($75) tool that was shown to be reliable and valid in a healthy population.

Levels of evidence

Level 3©The Author(s).

Effect of Footwear Type on Biomechanical Risk Factors for Knee Osteoarthritis

BACKGROUND

Regular walking in different types of footwear may increase the mediolateral shear force, knee adduction moment, or vertical ground-reaction forces that could increase the risk of early development of knee osteoarthritis (OA).

PURPOSE

To compare kinematic and kinetic parameters that could affect the development of knee OA in 3 footwear conditions.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 40 asymptomatic participants performed walking trials in the laboratory at self-selected walking speeds under barefoot (BF), minimalistic (MF), and neutral (NF) footwear conditions. Knee joint parameters were described using discrete point values, and continuous curves were evaluated using statistical parametric mapping. A 3 × 1 repeated-measures analysis of variance was used to determine the main effect of footwear for both discrete and continuous data. To compare differences between footwear conditions, a post hoc paired t test was used.

RESULTS

Discrete point analyses showed a significantly greater knee power in NF compared with MF and BF in the weight absorption phase (P < .001 for both). Statistical parametric mapping analysis indicated a significantly greater knee angle in the sagittal plane at the end of the propulsive phase in BF compared with NF and MF (P = .043). Knee joint moment was significantly greater in the propulsive phase for the sagittal (P = .038) and frontal planes (P = .035) in BF compared with NF and MF and in the absorption phase in the sagittal plane (P = .034) in BF compared with MF and NF. A significant main effect of footwear was found for anteroposterior (propulsion, ↑MF, NF, ↓BF [P = .008]; absorption, ↑BF, MF, ↓NF [P = .001]), mediolateral (propulsion, ↑MF, NF, ↓BF [P = .005]; absorption, ↑NF, MF, ↓BF [P = .044]), and vertical (propulsion, ↑NF, BF, ↓MF [P = .001]; absorption, ↑MF, BF, ↓NF [P < .001]) ground-reaction forces. Knee power showed a significant main effect of footwear (absorption, ↑NF, MF, ↓BF [P = .015]; propulsion, ↑MF, NF, ↓BF [P = .039]).

CONCLUSION

Walking in MF without sufficient accommodation affected kinetic and kinematic parameters and could increase the risk of early development of knee OA.

Adolescent Marathon Training: Prospective Evaluation of Musculotendinous Changes During a 6-Month Endurance Running Program

OBJECTIVES

Assess changes in lower extremity musculotendinous thickness, tissue echogenicity, and muscle pennation angles among adolescent runners enrolled in a 6-month distance running program.

METHODS

We conducted prospective evaluations of adolescent runners' lower extremity musculotendinous changes at three timepoints (baseline, 3 months, and 6 months) throughout a progressive marathon training program. Two experienced researchers used an established protocol to obtain short- and long-axis ultrasound images of the medial gastrocnemius, tibialis anterior, flexor digitorum brevis, abductor hallicus, and Achilles and patellar tendons. ImageJ software was used to calculate musculotendinous thickness and echogenicity for all structures, and fiber pennation angles for the ankle extrinsic muscles. Repeated measures within-subject analyses of variance were conducted to assess the effect of endurance training on ultrasound-derived measures.

RESULTS

We assessed 11 runners (40.7% of eligible runners; 6F, 5M; age: 16 ± 1 years; running experience: 3 ± 2 years) who remained injury-free and completed all ultrasound evaluation timepoints. Medial gastrocnemius muscle (F_2,20  = 3.48, P = .05), tibialis anterior muscle (F_2,20  = 7.36, P = .004), and Achilles tendon (F_2,20  = 3.58, P = .05) thickness significantly increased over time. Echogenicity measures significantly decreased in all muscles (P-range: <.001-.004), and increased for the patellar tendon (P < .001) during training. Muscle fiber pennation angles significantly increased for ankle extrinsic muscles (P < .001).

CONCLUSIONS

Adolescent runners' extrinsic foot and ankle muscles increased in volume and decreased in echogenicity, attributed to favorable distance training adaptations across the 6-month timeframe. We noted tendon thickening without concomitantly increased echogenicity, signaling intrasubstance tendon remodeling in response to escalating distance.

Impact of biomechanics on therapeutic interventions and rehabilitation for major chronic musculoskeletal conditions: A 50-year perspective

The pivotal role of biomechanics in the past 50 years in consolidating the basic knowledge that underpins prevention and rehabilitation measures has made this area a great spotlight for health practitioners. In clinical practice, biomechanics analysis of spatiotemporal, kinematic, kinetic, and electromyographic data in various chronic conditions serves to directly enhance deeper understanding of locomotion and the consequences of musculoskeletal dysfunctions in terms of motion and motor control. It also serves to propose straightforward and tailored interventions. The importance of this approach is supported by myriad biomechanical outcomes in clinical trials and by the development of new interventions clearly grounded on biomechanical principles. Over the past five decades, therapeutic interventions have been transformed from fundamentally passive in essence, such as orthoses and footwear, to emphasizing active prevention, including exercise approaches, such as bottom-up and top-down strengthening programs for runners and people with osteoarthritis. These approaches may be far more effective inreducing pain, dysfunction, and, ideally, incidence if they are based on the biomechanical status of the affected person. In this review, we demonstrate evidence of the impact of biomechanics and motion analysis as a foundation for physical therapy/rehabilitation and preventive strategies for three chronic conditions of high worldwide prevalence: diabetes and peripheral neuropathy, knee osteoarthritis, and running-related injuries. We conclude with a summary of recommendations for future studies needed to address current research gaps.

Seven-Weeks Gait-Retraining in Minimalist Footwear Has No Effect on Dynamic Stability Compared With Conventional Footwear

Purpose: To investigate the effects of two different running footwear conditions (transition to minimalist footwear and conventional running footwear) on dynamic postural stability before and after 7 weeks of gait retraining program, and to evaluate the effect of fatigue on dynamic stability. Method: This randomized controlled clinical trial was carried out by 42 recreational male runners, who were randomly divided into two groups; Conventional Footwear Group (CFG) (n = 22) and Minimalist Footwear Group (MFG) (n = 20). Dynamic Postural Stability Index (DPSI), in a fatigued and non-fatigued state, were assessed before and after a gait retraining program. The gait retraining program consisted of three guided training sessions per week for 7 weeks. Training program was mainly focused on running technique and submaximal aerobic training with step-frequency exercises. Minimalist footwear was progressively introduced in the MFG. The CFG and MFG performed the same training exercises and a full body conditioning program. Fatigue was induced using a 30-minute running test at individual 85% of the maximal aerobic speed. Results: No differences in dynamic stability variables were found between MFG and CFG in any of the study condition. MFG and CFG showed better dynamic stability after the intervention program (CFG: 13.1% of change, DPSIpre = 0.3221 ± 0.04, DPSIpost = 0.2799 ± 0.04; p < .05; MFG: 6.7% of change, DPSIpre = 0.3117 ± 0.04, DPSIpost = 0.2907 ± 0.05). Finally, dynamic stability was significatively lower in both groups after fatigue protocol (p < .05). Conclusions: Following a 7-week gait retraining program, footwear did not affect the results, being the gait retraining program more relevant on improving dynamic stability.

Effects of Barefoot and Shod on the In Vivo Kinematics of Medial Longitudinal Arch During Running Based on a High-Speed Dual Fluoroscopic Imaging System

Shoes affect the biomechanical properties of the medial longitudinal arch (MLA) and further influence the foot’s overall function. Most previous studies on the MLA were based on traditional skin-marker motion capture, and the observation of real foot motion inside the shoes is difficult. Thus, the effect of shoe parameters on the natural MLA movement during running remains in question. Therefore, this study aimed to investigate the differences in the MLA’s kinematics between shod and barefoot running by using a high-speed dual fluoroscopic imaging system (DFIS). Fifteen healthy habitual rearfoot runners were recruited. All participants ran at a speed of 3 m/s ± 5% along with an elevated runway in barefoot and shod conditions. High-speed DFIS was used to acquire the radiographic images of MLA movements in the whole stance phase, and the kinematics of the MLA were calculated. Paired sample t-tests were used to compare the kinematic characteristics of the MLA during the stance phase between shod and barefoot conditions. Compared with barefoot, shoe-wearing showed significant changes (p < 0.05) as follows: 1) the first metatarsal moved with less lateral direction at 80%, less anterior translation at 20%, and less superiority at 10–70% of the stance phase; 2) the first metatarsal moved with less inversion amounting to 20–60%, less dorsiflexion at 0–10% of the stance phase; 3) the inversion/eversion range of motion (ROM) of the first metatarsal relative to calcaneus was reduced; 4) the MLA angles at 0–70% of the stance phase were reduced; 5) the maximum MLA angle and MLA angle ROM were reduced in the shod condition. Based on high-speed DFIS, the above results indicated that shoe-wearing limited the movement of MLA, especially reducing the MLA angles, suggesting that shoes restricted the compression and recoil of the MLA, which further affected the spring-like function of the MLA.

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.

Measurement of the Developing Foot in Shod and Barefoot Paediatric Populations: A Narrative Review

The theory that footwear may change foot shape dates back 100 years. Since this period, research has revealed the anatomical and functional consequences that footwear can cause to the foot. Children’s feet remain malleable as they undergo developmental changes until adolescence, which is why childhood is arguably a crucial period to understand how footwear can affect natural foot development. This review explored the development of the foot in children and adolescents and the methods used to measure the different foot structures; it comments on the key issues with some of these methods and gives direction for future research. Various internal and external factors can affect foot development; the main factors are age, gender, ethnicity, body mass index (BMI) and footwear habits. Research on how footwear can affect foot development has increased over the years and the final section of this review aimed to unpick the findings. Studies investigating the influence of footwear habits on foot length and width have established inconsistent findings. Many of the studies in the review did not control for internal and external factors that can affect foot development. There was also a limited number of studies that investigated hallux valgus angle and muscle strength differences in those with different footwear habits. Moreover, multiple studies in the final section of this review did not successfully examine the footwear habits of the participants and instead used observations or self-assessments, which is a major limitation. Future research should examine footwear behaviors and other confounding factors when investigating the development of the foot in children and adolescents. Moreover, researchers should critically evaluate the methods used to quantify the different structures of the foot to ensure valid and reliable parameters are being used.

Reversing the Mismatch With Forefoot Striking to Reduce Running Injuries

Recent studies have suggested that 95% of modern runners land with a rearfoot strike (RFS) pattern. However, we hypothesize that running with an RFS pattern is indicative of an evolutionary mismatch that can lead to musculoskeletal injury. This perspective is predicated on the notion that our ancestors evolved to run barefoot and primarily with a forefoot strike (FFS) pattern. We contend that structures of the foot and ankle are optimized for forefoot striking which likely led to this pattern in our barefoot state. We propose that the evolutionary mismatch today has been driven by modern footwear that has altered our footstrike pattern. In this paper, we review the differences in foot and ankle function during both a RFS and FFS running pattern. This is followed by a discussion of the interaction of footstrike and footwear on running mechanics. We present evidence supporting the benefits of forefoot striking with respect to common running injuries such as anterior compartment syndrome and patellofemoral pain syndrome. We review the importance of a gradual shift to FFS running to reduce transition-related injuries. In sum, we will make an evidence-based argument for the use of minimal footwear with a FFS pattern to optimize foot strength and function, minimize ground reaction force impacts and reduce injury risk.

The long-term effects of wearing moderate minimalist shoes on a child's foot strength, muscle structure and balance: A randomised controlled trial

BACKGROUND

From retrospective research, it is believed that children who predominantly spend their time shod have poorer foot strength and performance than those who are predominantly barefoot. Children's foot motion has been shown to be adversely affected by standard school shoes; however, the long-term effect of moderate minimalist shoes on foot strength, muscle structure and balance in children is unknown.

RESEARCH QUESTION

Does wearing moderate minimalist shoes, compared to stiff shoes, benefit a child's foot strength, muscle structure and performance over time?

METHODS

Seventy healthy children (9-12 yr) were randomly assigned to wear standard (control), or minimalist shoes (experimental) at school, for nine months. Cross-sectional areas (CSA) of Abductor Hallucis (AH) and Flexor Digitorum Brevis (FDB) muscles, and toe flexor strength (TFS) of hallux and lesser toes separately, were primary outcome measures. Single leg balance (SLB), Y-balance test (YBT) and standing long jump (SLJ) were secondary outcome measures. Pre- and post-intervention measurements were analysed for between group differences with ANCOVA.

RESULTS

Minimalist shoes resulted in moderate but statistically non-significant increases in muscle CSA (AH η²_p =.04, FDB η²_p =.05) and TFS (hallux η²_p =.05, lesser toes η²_p =.04). Significant moderate to large improvements in YBT in the experimental group were found in the postero-medial (P = .04, η²_p =.07) and postero-lateral (P = .01, η²_p =.10) directions. YBT (anterior, postero-medial and postero-lateral) was correlated with hallux TFS (R =.29,.27 and.33 respectively), lesser toes TFS (R =.28,.35 and.38 respectively) and SLJ (R =.30,.39 and.57 respectively). CSA of FDB was correlated with SLJ (R =.34) and SLB (R =.42).

SIGNIFICANCE

Wearing moderate minimalist shoes long-term improves balance in children. TFS is correlated with better balance and SLJ. Moderate minimalist school shoes are recommended for children.

Effects of Minimalist Footwear and Foot Strike Pattern on Plantar Pressure during a Prolonged Running

The use of minimalist shoes (MS) in running involves changes in running mechanics compared to conventional shoes (CS), but there is still little research analysing the effects of this footwear on plantar pressure, which could help to understand some risk injury factors. Moreover, there are no studies examining the effects of a prolonged running and foot strike patterns on baropodometric variables in MS. Therefore, the aim of this study was to analyse the changes produced using MS on plantar pressure during a prolonged running, as well as its interaction with the time and foot strike pattern. Twenty-one experienced minimalist runners (age 38 ± 10 years, MS running experience 2 ± 1 years) ran with MS and CS for 30 min at 80% of their maximal aerobic speed, and mean pressure, peak pressure, contact time, centre of pressure velocity, relative force and contact area were analysed using a pressure platform. Foot strike pattern and time were also considered as factors. The multivariable linear regression mixed models showed that the use of MS induced, at the end of a prolonged running, higher peak pressure (p = 0.008), lower contact time (p = 0.004) and lower contact area (p < 0.001) than using CS. Also, runners with forefoot strike pattern using MS, compared to midfoot and rearfoot patterns, showed higher mean and peak pressure (p < 0.001) and lower contact time and area (p < 0.05). These results should be considered when planning training for runners using MS, as higher peak pressure values when using this type of footwear could be a risk factor for the development of some foot injuries.

Effect of training volume on footstrike patterns over an exhaustive run

BACKGROUND

Although footstrike pattern (FP) may not be a factor influencing running performance, 11-75% of world-class distance runners use a non-rearfoot FP. However, little attention has been paid to describe the effect of running volume on FP changes when a runner is fatigued.

RESEARCH QUESTION

Does the training volume provide an adequate stimulus to mitigate FP changes during an exhaustive run in non-rearfoot, habitual minimalist footwear runners?

METHODS

The objective of this study was to compare FP between non-rearfoot, habitual minimalist footwear runners with a moderate training volume (MT) and a high training volume (HT) during an exhaustive run on a motorized treadmill. Based on their weekly training volume (distance), twenty-eight runners were arranged into two groups paired by height and age. At the first visit, runners underwent a VO2max test to acquire their velocity for the exhaustive run. During the second visit, biomechanical and physiological analysis of the beginning and the end phase of the exhaustive run was done.

RESULTS

The frontal plane foot angle, the sagittal plane ankle angle at the initial contact (IC), and the foot eversion ROM showed a significant interaction effect (P < 0.05). Additionally, the sagittal plane footstrike angle, the frontal plane foot angle, the sagittal plane ankle angle, knee flexion angle at IC and foot eversion ROM showed a significant effect of fatigue (P < 0.05). Finally, the frontal plane foot angle, the sagittal plane footstrike angle, the sagittal plane ankle angle, and the knee flexion angle showed significant group effects (P < 0.05).

SIGNIFICANCE

The training volume affects the footstrike pattern of non-rearfoot, habitual minimalist footwear runners when they are fatigued. The highly trained runners maintained their ankle angle throughout the exhaustive running protocol, whereas the moderately trained group changed the frontal and sagittal plane characteristics of their footstrike pattern.

Surface Stiffness and Footwear Affect the Loading Stimulus for Lower Extremity Muscles When Running

ABSTRACT

Willwacher, S, Fischer, KM, Rohr, E, Trudeau, MB, Hamill, J, and Brüggemann, G-P. Surface stiffness and footwear affect the loading stimulus for lower extremity muscles when running. J Strength Cond Res 36(1): 82-89, 2022-Running in minimal footwear or barefoot can improve foot muscle strength. Muscles spanning the foot and ankle joints have the potential to improve performance and to reduce overuse injury risk. Surface stiffness or footwear use could modify the intensity of training stimuli acting on lower extremity joints during running. The purpose of this study was to systematically investigate external ankle, knee, and hip joint moments during shod and barefoot running while considering the stiffness of the running surface. Two footwear conditions (barefoot and neutral running shoe) and 4 surface conditions (Tartan, Tartan + Ethylene Vinyl Acetate [EVA] foam, Tartan + artificial turf, Tartan + EVA foam + artificial turf) were tested at 3.5 m·s-1. Repeated measures analysis of variance revealed that barefoot running in general and running barefoot on harder surfaces increased and decreased ankle (between +5 and +26%) and knee (between 0 and -11%) joint moments, respectively. Averaged over all surfaces, running barefoot was characterized by a 6.8° more plantarflexed foot strike pattern compared with running shod. Foot strike patterns were more plantarflexed on harder surfaces; the effects, however, were less than 3°. Most surface effects were stronger in barefoot compared with shod running. Surface stiffness may be used to modulate the loading intensity of lower extremity muscles (in particular extrinsic and intrinsic foot muscles) during running. These results need to be considered when coaches advise barefoot running as a method to improve the strength of extrinsic and intrinsic foot muscles or when trying to reduce knee joint loading.

Stepping Back to Minimal Footwear: Applications Across the Lifespan

Minimal footwear has existed for tens of thousands of years and was originally designed to protect the sole of the foot. Over the past 50 yr, most footwear has become increasingly more cushioned and supportive. Here, we review evidence that minimal shoes are a better match to our feet, which may result in a lower risk of musculoskeletal injury.

Daily activity in minimal footwear increases foot strength

The human foot is uniquely adapted to bipedal locomotion and has a deformable arch of variable stiffness. Intrinsic foot muscles regulate arch deformation, making them important for foot function. In this study we explore the hypothesis that normal daily activity in minimal footwear, which provides little or no support, increases foot muscle strength. Western adults wore minimal footwear for a six-month period (the “intervention” group). Foot strength, i.e., maximum isometric plantarflexion strength at the metatarsophalangeal joints, and foot biometrics were measured before and after the intervention. An additional group was investigated to add further insight on the long-term effects of footwear, consisting of Western adults with an average 2.5 years of experience in minimal footwear (the “experienced” group). This study shows that foot strength increases by, on average, 57.4% (p < 0.001) after six months of daily activity in minimal footwear. The experienced group had similar foot strength as the post intervention group, suggesting that six months of regular minimal footwear use is sufficient to gain full strength, which may aid healthy balance and gait.

Evolution of distance running shoes: performance, injuries, and rules

Over the last 50 years, the development of running shoes has been mainly focused on improving the protection and comfort of the runner and her/his foot. Although there have been tentative attempts by companies to make shoes a tool for improving athletic performance, this goal has only recently been achieved. Indeed, the year 2016 was a real turning point when Nike launched its first shoe benefiting from the advanced footwear technology. Advanced footwear technology (AFT) mostly consists of an increased sole thickness, a curved and stiff plate embedded or below the shoe midsole, and an outsole with a marked concave shape. This innovation turned to a game changer in the world of distances running performance. Indeed, between 2016 and 2019, many male and female runners broke personal best times, national records, area, and world records in distance from 5 km to the marathon. The present article aimed at describing the magnitude of these performance enhancements in distance running as well as and the possible underlying performance-enhancement mechanisms associated with the advanced footwear technology. It also reviewed the existing literature on the safety aspects of "classical" construction shoes and AFT shoes. It concluded on a possible shoe mechanical tests-based protocol to maintain fair distance running competitions while not totally preventing manufacturers to innovate, and some thoughts on the nature and goals of further studies to be conducted to assess the safety (macro- and micro-traumatic) AFT in both elite and recreational runner populations.

New insights into intrinsic foot muscle morphology and composition using ultra-high-field (7-Tesla) magnetic resonance imaging

Background

The intrinsic muscles of the foot are key contributors to foot function and are important to evaluate in lower limb disorders. Magnetic resonance imaging (MRI), provides a non-invasive option to measure muscle morphology and composition, which are primary determinants of muscle function. Ultra-high-field (7-T) magnetic resonance imaging provides sufficient signal to evaluate the morphology of the intrinsic foot muscles, and, when combined with chemical-shift sequences, measures of muscle composition can be obtained. Here we aim to provide a proof-of-concept method for measuring intrinsic foot muscle morphology and composition with high-field MRI.

Methods

One healthy female (age 39 years, mass 65 kg, height 1.73 m) underwent MRI. A T1-weighted VIBE – radio-frequency spoiled 3D steady state GRE – sequence of the whole foot was acquired on a Siemens 7T MAGNETOM scanner, as well as a 3T MAGNETOM Prisma scanner for comparison. A high-resolution fat/water separation image was also acquired using a 3D 2-point DIXON sequence at 7T. Coronal plane images from 3T and 7T scanners were compared. Using 3D Slicer software, regions of interest were manually contoured for each muscle on 7T images. Muscle volumes and percentage of muscle fat infiltration were calculated (muscle fat infiltration % = Fat/(Fat + Water) x100) for each muscle.

Results

Compared to the 3T images, the 7T images provided superior resolution, particularly at the forefoot, to facilitate segmentation of individual muscles. Muscle volumes ranged from 1.5 cm³ and 19.8 cm³, and percentage muscle fat infiltration ranged from 9.2–15.0%.

Conclusions

This proof-of-concept study demonstrates a feasible method of quantifying muscle morphology and composition for individual intrinsic foot muscles using advanced high-field MRI techniques. This method can be used in future studies to better understand intrinsic foot muscle morphology and composition in healthy individuals, as well as those with lower disorders.

Effect of footwear on intramuscular EMG activity of plantar flexor muscles in walking

One of the purposes of footwear is to assist locomotion, but some footwear types seem to restrict natural foot motion, which may affect the contribution of ankle plantar flexor muscles to propulsion. This study examined the effects of different footwear conditions on the activity of ankle plantar flexors during walking. Ten healthy habitually shod individuals walked overground in shoes, barefoot and in flip-flops while fine-wire electromyography (EMG) activity was recorded from flexor hallucis longus (FHL), soleus (SOL), and medial and lateral gastrocnemius (MG and LG) muscles. EMG signals were peak-normalised and analysed in the stance phase using Statistical Parametric Mapping (SPM). We found highly individual EMG patterns. Although walking with shoes required higher muscle activity for propulsion than walking barefoot or with flip-flops in most participants, this did not result in statistically significant differences in EMG amplitude between footwear conditions in any muscle (p > 0.05). Time to peak activity showed the lowest coefficient of variation in shod walking (3.5, 7.0, 8.0 and 3.4 for FHL, SOL, MG and LG, respectively). Future studies should clarify the sources and consequences of individual EMG responses to different footwear.

Effect of the upward curvature of toe springs on walking biomechanics in humans

Although most features of modern footwear have been intensively studied, there has been almost no research on the effects of toe springs. This nearly ubiquitous upward curvature of the sole at the front of the shoe elevates the toe box dorsally above the ground and thereby holds the toes in a constantly dorsiflexed position. While it is generally recognized that toe springs facilitate the forefoot’s ability to roll forward at the end of stance, toe springs may also have some effect on natural foot function. This study investigated the effects of toe springs on foot biomechanics in a controlled experiment in which participants walked in specially-designed sandals with varying curvature in the toe region to simulate toe springs ranging from 10 to 40 degrees of curvature. Using inverse dynamics techniques, we found that toe springs alter the joint moments and work at the toes such that greater degrees of toe spring curvature resulted in lower work requirements during walking. Our results help explain why toe springs have been a pervasive feature in shoes for centuries but also suggest that toe springs may contribute to weakening of the foot muscles and possibly to increased susceptibility to common pathological conditions such as plantar fasciitis.

Effects of the weight of shoes on calf muscle simulation

The current study investigated the effects of shoes of different weights on calf individual muscle contributions during a running cycle. Twenty male runners ran on a force platform with shoes of four different weights (175 g, 255 g, 335 g, and 415 g). The study evaluated runners’ lower extremity muscle forces under the four shoe weight conditions using a musculoskeletal modeling system. The system generates equality and inequality constraint equations to simulate muscle forces. The individual muscle contributions in each calf were determined using these muscle forces. Data were compared using one-way repeated-measure ANOVA. The results revealed significant differences in the contributions of the gastrocnemius lateralis. Post hoc comparisons revealed that running in the 175 g shoes resulted in a larger contribution of the gastrocnemius lateralis than running in the 415 g shoes during the braking phase. Therefore, wearing lightweight shoes while running may promote fatigue in the gastrocnemius muscle during the braking phase. The calf muscle activation results may indicate that an adaptation period is warranted when changing from heavy to lightweight shoes.

Recognition of Foot-Ankle Movement Patterns in Long-Distance Runners With Different Experience Levels Using Support Vector Machines

Running practice could generate musculoskeletal adaptations that modify the body mechanics and generate different biomechanical patterns for individuals with distinct levels of experience. Therefore, the aim of this study was to investigate whether foot-ankle kinetic and kinematic patterns can be used to discriminate different levels of experience in running practice of recreational runners using a machine learning approach. Seventy-eight long-distance runners (40.7 ± 7.0 years) were classified into less experienced (n = 24), moderately experienced (n = 23), or experienced (n = 31) runners using a fuzzy classification system, based on training frequency, volume, competitions and practice time. Three-dimensional kinematics of the foot-ankle and ground reaction forces (GRF) were acquired while the subjects ran on an instrumented treadmill at a self-selected speed (9.5–10.5 km/h). The foot-ankle kinematic and kinetic time series underwent a principal component analysis for data reduction, and combined with the discrete GRF variables to serve as inputs in a support vector machine (SVM), to determine if the groups could be distinguished between them in a one-vs.-all approach. The SVM models successfully classified all experience groups with significant crossvalidated accuracy rates and strong to very strong Matthew’s correlation coefficients, based on features from the input data. Overall, foot mechanics was different according to running experience level. The main distinguishing kinematic factors for the less experienced group were a greater dorsiflexion of the first metatarsophalangeal joint and a larger plantarflexion angles between the calcaneus and metatarsals, whereas the experienced runners displayed the opposite pattern for the same joints. As for the moderately experienced runners, although they were successfully classified, they did not present a visually identifiable running pattern, and seem to be an intermediate group between the less and more experienced runners. The results of this study have the potential to assist the development of training programs targeting improvement in performance and rehabilitation protocols for preventing injuries.

Multi-Segmental Motion in Foot during Counter-Movement Jump with Toe Manipulation

Human toes are crucial for vertical jumping performance. The purpose of this study is to investigate the acute effect of hallux abduction manipulation on foot inter-segment kinematic alterations and plantar loading redistribution during the countermovement jump (CMJ). Thirteen participants were recruited to join in this experiment, for the collection of the foot inter-segment kinematics and plantar pressure data. During the take-off phase, the contact area presented a significant increase while the pressure-time integral decreased in the second metatarsal (M2), whilst the third metatarsal (M3) and fourth metatarsal (M4) decreased significantly in pressure-time integral with Toe-Manipulation (TM). During the landing phase, maximum force and peak pressure were smaller in the big toe (BT) after hallux abduction manipulation. HXFFA (hallux-forefoot angle) showed a greater pronation after manipulation in the frontal plane (0%–26% and 50%–100%) with p = 0.002 and p < 0.001. In the transverse plane, the smaller adductions were found during 62%–82% in take-off and 62%–91% in landing (p = 0.003 and p < 0.001). There was a redistributed plantar loading during the landing phase from the medial to lateral forefoot. However, a reduced hallux range of motion in the TM session was exhibited, compared to Non-Toe-Manipulation (NTM).

Fatigue matters: An intense 10 km run alters frontal and transverse plane joint kinematics in competitive and recreational adult runners

BACKGROUND

Fatigue is an essential component of distance running. Still, little is known about the effects of running induced fatigue on three-dimensional lower extremity joint movement, in particular in the frontal and transverse planes of motion.

RESEARCH QUESTION

How are non-sagittal plane lower extremity joint kinematics of runners altered during a 10 km treadmill run with near-maximum effort?

METHODS

In a cross-sectional study design, we captured three-dimensional kinematics and kinetics at regular intervals throughout a 10 km treadmill run in 24 male participants (subdivided into a competitive and recreational runner group) at a speed corresponding to 105 % of their season-best time. We calculated average and peak joint angles at the hip, knee and ankle during the stance phase.

RESULTS

We observed peak deviations of 3.5°, 3° and 5° for the hip (more adduction), knee (more abduction) and ankle (more eversion) in the frontal plane when comparing the final (10 km) with the first (0 km) measurement. At the end of the run peak knee internal rotation angles increased significantly (up to 3° difference). Running with a more abducted knee joint and with a higher demand for hip abductor muscles in the unfatigued state was related to greater fatigue-induced changes of joint kinematics at the knee and hip.

SIGNIFICANCE

The fatigue related change of non-sagittal joint kinematics needs to be considered when addressing risk factors for running-related injuries, when designing shoe interventions as well as strengthening and gait retraining protocols for runners. We speculate that strengthening ankle invertors and hip abductors and monitoring the dynamic leg axis during running appear to be promising in preventing fatigue induced alterations of non-sagittal joint kinematics.

A biomechanical assessment of the acute hallux abduction manipulation intervention

BACKGROUND

Naturally aligned toes, particularly hallux, have reported with gripping functions during locomotion, thus expanding the forefoot loading area.

RESEARCH QUESTION

The purpose of this study was aimed to investigate the influence of hallux abduction manipulation on the foot plantar pressure distribution and inter-segment kinematic alterations.

METHODS

Thirteen subjects participated in this toe manipulation study. A Footscan® pressure plate and Vicon motion capture system were utilized for the measurement of plantar pressure distribution and lower extremity and foot inter-segment kinematics during walking and running. Paired-sample t-test from statistical parametric mapping 1d was used to check the kinematic significance.

RESULTS

Peak pressure in third metatarsal (M3) increased significantly during walking under manipulation. Contact area increased in second metatarsal (M2) with manipulation during running. Peak pressure and pressure-time integral illustrated significant increases in M3, and the maximum force and impulse in fourth metatarsal (M4) increased significantly. Arch height index increased while walking with toe manipulation. The foot progression angle in the frontal plane showed significant decrease in mid-swing phase during walking and significant increase in mid-stance phase during running. The hallux relative to forefoot angles presented higher axial rotation in the frontal plane.

SIGNIFICANCE

Findings form this study showed centrally and laterally redistributed foot loadings and increased forefoot inter-segment flexibility with manipulation, which may be used as baseline to evaluate toe-manipulation interventions in foot disorders, specifically hallux valgus deformity.

How to Evaluate and Improve Foot Strength in Athletes: An Update

The foot is a complex system with multiple degrees of freedom that play an essential role in running or sprinting. The intrinsic foot muscles (IFM) are the main local stabilizers of the foot and are part of the active and neural subsystems that constitute the foot core. These muscles lengthen eccentrically during the stance phase of running before shortening at the propulsion phase, as the arch recoils in parallel to the plantar fascia. They play a key role in supporting the medial longitudinal arch, providing flexibility, stability and shock absorption to the foot, whilst partially controlling pronation. Much of the foot rigidity in late stance has been attributed to the windlass mechanism – the dorsiflexion of the toes building tension up in the plantar aponeurosis and stiffening the foot. In addition, recent studies have shown that the IFM provide a necessary active contribution in late stance, in order to develop sufficient impedance in the metatarsal-phalangeal joints. This in turn facilitates the propulsive forces at push-off. These factors support the critical role of the foot in providing rigidity and an efficient lever at push-off. During running or sprinting, athletes need to generate and maintain the highest (linear) running velocity during a single effort in a sprinting lane. Acceleration and sprinting performance requires forces to be transmitted efficiently to the ground. It may be of particular interest to strengthen foot muscles to maintain and improve an optimal capacity to generate and absorb these forces. The current evidence supports multiple exercises to achieve higher strength in the foot, such as the “short foot exercise,” doming, toes curl, towing exercises or the more dynamic hopping exercises, or even barefoot running. Their real impact on foot muscle strength remains unclear and data related to its assessment remains scarce, despite a recognized need for this, especially before and after a strengthening intervention. It would be optimal to be able to assess it. In this article, we aim to provide the track and field community with an updated review on the current modalities available for foot strength assessment and training. We present recommendations for the incorporation of foot muscles training for performance and injury prevention in track and field.

Youth Distance Running: Strategies for Training and Injury Reduction

Running is a popular sport for children in the United States. However, review of available literature on health effects and safety recommendations for youth running has not been previously conducted. Unique factors for injury include periods of growth during puberty and potential for growth plate injury. Youth runners may benefit from activities that incorporate high-impact loading and multidirectional movement for optimal bone maturation, exercises to strengthen tendons and muscles, and strategies aimed at improving running biomechanics to reduce risk of injury. In addition, addressing lifestyle factors, including nutrition and sleep is essential for a runner's general health. Similar to other sports, sports specialization should not be encouraged in youth runners. Reducing running-related injury in growing children and assessing readiness for running should be based on a combination of physical, emotional, psychological, social, and cognitive factors. Youth runners require individualized training and competition to safely participate in the sport.

The effect of running on foot muscles and bones: A systematic review

Despite the widespread evidence of running as a health-preserving exercise, little is known concerning its effect on the foot musculature and bones. While running may influence anatomical foot adaptation, it remains unclear to what extent these adaptations occur. The aim of this paper is to provide a systematic review of the studies that investigated the effects of running and the adaptations that occur in foot muscles and bones. The search was performed following the PRISMA guidelines. Relevant keywords were used for the search through PubMed/MEDLINE, Scopus and SPORTDiscus. The methodological quality of intervention studies was assessed using the Downs and Black checklist. For cross-sectional studies, the Newcastle-Ottawa scale was used. Sixteen studies were found meeting the inclusion criteria. In general, the included studies were deemed to be of moderate methodological quality. Although results of relevant literature are limited and somewhat contradictory, the outcome suggests that running may increase foot muscle volume, muscle cross-sectional area and bone density, but this seems to depend on training volume and experience. Future studies conducted in this area should aim for a standard way of reporting foot muscle/bone characteristics. Also, herein, suggestions for future research are provided.

Foot internal stress distribution during impact in barefoot running as function of the strike pattern

The aim of the present study is to examine the impact absorption mechanism of the foot for different strike patterns (rearfoot, midfoot and forefoot) using a continuum mechanics approach. A three-dimensional finite element model of the foot was employed to estimate the stress distribution in the foot at the moment of impact during barefoot running. The effects of stress attenuating factors such as the landing angle and the surface stiffness were also analyzed. We characterized rear and forefoot plantar sole behavior in an experimental test, which allowed for refined modeling of plantar pressures for the different strike patterns. Modeling results on the internal stress distributions allow predictions of the susceptibility to injury for particular anatomical structures in the foot.

Does neuromuscular electrostimulation have the potential to increase intrinsic foot muscle strength?

PURPOSE

The purpose of this study was to investigate the effect of an eight-week neuromuscular electrostimulation program on the intrinsic foot muscle strength. The results were compared with those from a passive and an active control group.

METHODS

74 healthy participants were recruited and divided into three groups: a neuromuscular electrostimulation group (n=19), a passive control group (n=15) with no further intervention, and an active control group following a running protocol with minimal shoes (n=40). The electrostimulation and running groups followed a training protocol consisting of two sessions per week over a period of eight weeks. Three characteristics of intrinsic foot muscle strength were investigated: cross sectional area of the abductor hallucis muscle, longitudinal arch stability, and intrinsic foot muscle fatigue.

RESULTS

After eight weeks of intervention, the cross sectional area increased by 16.3% for the running group with a large effect size (0.801) according to Cohen's d. The electrostimulation group showed no such effect. The increase in the cross sectional area had no impact on longitudinal arch stability or intrinsic foot muscle fatigue results.

CONCLUSION

This study investigated neuromuscular electrostimulation as a prevention and rehabilitation strategy. The results indicate that, compared to minimally shod running, the effects of electrostimulation on healthy participants might be too small to be detected. Further, the results provide evidence that the static navicular drop test is not sensitive enough to indicate intrinsic foot muscle strength. This appears clinically relevant, as this test is often used by therapists to evaluate patients' longitudinal arch function.

Heel impact forces during barefoot versus minimally shod walking among Tarahumara subsistence farmers and urban Americans

Despite substantial recent interest in walking barefoot and in minimal footwear, little is known about potential differences in walking biomechanics when unshod versus minimally shod. To test the hypothesis that heel impact forces are similar during barefoot and minimally shod walking, we analysed ground reaction forces recorded in both conditions with a pedography platform among indigenous subsistence farmers, the Tarahumara of Mexico, who habitually wear minimal sandals, as well as among urban Americans wearing commercially available minimal sandals. Among both the Tarahumara (n = 35) and Americans (n = 30), impact peaks generated in sandals had significantly (p < 0.05) higher force magnitudes, slower loading rates and larger vertical impulses than during barefoot walking. These kinetic differences were partly due to individuals' significantly greater effective mass when walking in sandals. Our results indicate that, in general, people tread more lightly when walking barefoot than in minimal footwear. Further research is needed to test if the variations in impact peaks generated by walking barefoot or in minimal shoes have consequences for musculoskeletal health.

Foot strength and stiffness are related to footwear use in a comparison of minimally- vs. conventionally-shod populations

The longitudinal arch (LA) helps stiffen the foot during walking, but many people in developed countries suffer from flat foot, a condition characterized by reduced LA stiffness that can impair gait. Studies have found this condition is rare in people who are habitually barefoot or wear minimal shoes compared to people who wear conventional modern shoes, but the basis for this difference remains unknown. Here we test the hypothesis that the use of shoes with features that restrict foot motion (e.g. arch supports, toe boxes) is associated with weaker foot muscles and reduced foot stiffness. We collected data from minimally-shod men from northwestern Mexico and men from urban/suburban areas in the United States who wear ‘conventional’ shoes. We measured dynamic LA stiffness during walking using kinematic and kinetic data, and the cross-sectional areas of three intrinsic foot muscles using ultrasound. Compared to conventionally-shod individuals, minimally-shod individuals had higher and stiffer LAs, and larger abductor hallucis and abductor digiti minimi muscles. Additionally, abductor hallucis size was positively associated with LA stiffness during walking. Our results suggest that use of conventional modern shoes is associated with weaker intrinsic foot muscles that may predispose individuals to reduced foot stiffness and potentially flat foot.

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

BACKGROUND

Recent interest in barefoot running has led to the development of minimalist running shoes that are popular in distance runners. A careful transition to these shoes has been suggested and examined in the literature. However, no guidelines based on systematic evidence have been presented. The purpose of this review is to systematically examine the methods employed in the literature to transition to minimal footwear (MFW), as well as the outcomes to these studies in distance runners. In addition, MFW transition guidelines for future clinical practice will be presented based on observations from this review.

METHODS

A systematic database search was employed using PubMed online as the primary database. Twenty papers were included in the final review.

RESULTS

All studies implemented a prospective transition design to MFW with a detail of this transition provided, which increased MFW exposure up to an average of 60% (30-100%) at completion. Only 8/20 studies included injury prevention exercises, and 9/20 included gait retraining. The main outcomes of this transition included limited positive evidence of transitioning into MFW for running economy (n = 4 studies) and muscle development (n = 5). The injury incidence comparing running during the MFW transition (17.9 injuries per 100 participants) to matched participants in conventional running shoes (13.4 injuries per 100) appears equivocal (p = 0.219; effect size phi (φ) = 0.06 [very small]). Finally, several important recommendations for clinical practice and future research have been presented.

CONCLUSIONS

It is hoped that this paper will present important first steps in unifying the process of transitioning to MFW, both for academic and clinical use.

Preventing running-related injuries using evidence-based online advice: the design of a randomised-controlled trial

Introduction

Running-related injuries (RRIs) are frequent and can lead to cessation of health promoting activities. Several risk factors for RRIs have been identified. However, no successful injury prevention programme has been developed so far. Therefore, the aim of the present study is to investigate the effect of an evidence-based online injury prevention programme on the number of RRIs.

Methods and analysis

The INSPIRE trial is a randomised-controlled trial with a 3-month follow-up. Both novice and more experienced runners, aged 18 years and older, who register for a running event (distances 5 km up to 42.195 km) will be asked to participate in this study. After completing the baseline questionnaire, participants will be randomised into either the intervention group or control group. Participants in the intervention group will get access to the online injury prevention programme. This prevention programme consists of information on evidence-based risk factors and advices to reduce the injury risk. The primary outcome measure is the number of self-reported RRIs in the time frame between registration for a running event and 1 month after the running event. Secondary outcome measures include the running days missed due to injuries, absence of work or school due to injuries, and the injury location.

Ethics and dissemination

An exemption for a comprehensive application is obtained by the Medical Ethical Committee of the Erasmus University Medical Centre Rotterdam, Netherlands. The results of the study will be published in peer-reviewed journals and presented on international congresses.

Trial registration number

NTR5998. Pre-results

Immediate and short-term biomechanical adaptation of habitual barefoot runners who start shod running

This study investigated the immediate and short-term effects of minimalist shoes (MS) and traditional running shoes (TRS) on vertical loading rates, foot strike pattern and lower limb kinematics in a group of habitual barefoot runners. Twelve habitual barefoot runners were randomly given a pair of MS or TRS and were asked to run with the prescribed shoes for 1 month. Outcome variables were obtained before, immediate after and 1 month after shoe prescription. Average and instantaneous vertical loading rates at the 1-month follow-up were significantly higher than that at the pre-shod session (P < 0.034, η²_p > 0.474). Foot strike angle in the TRS group was significantly lower than that in the MS group (P = 0.045, η²_p = 0.585). However, there was no significant time nor shoe effect on overstride, knee and ankle excursion (P > 0.061). Habitual barefoot runners appeared to land with a greater impact during shod running and they tended to have a more rearfoot strike pattern while wearing TRS. Lower limb kinematics were comparable before and after shoe prescription. Longer period of follow-up is suggested to further investigate the footwear effect on the running biomechanics in habitual barefoot runners.