Can the recent sex-specific evolutions in elite running performances be attributed to advanced footwear technology?

Recent improvements in elite running performances across all distances have been largely attributed to the introduction of advanced footwear technology (AFT), which features a curved and stiff plate working synergistically with a new generation of midsole foams demonstrating enhanced resilience and compliance. These recent improvements appear to be considerably more pronounced in women's events, highlighted by improvements in road racing world records by an average of 3.7% (range: 2.6%-5.2%) compared to mean progressions of 1.5% (range: 1.3%-1.9%) in the same men's events. Although there is a growing body of research investigating the mechanisms underpinning running performance enhancements derived from AFT, there remains no explanation for potential sex-based differences in their benefits. We overview the currently available evidence and highlight why the recent direction of AFT research provides a barrier to progress by focusing primarily on male athletes. We subsequently provide our perspective on why women may be benefiting from the new generation of shoes more than men, suggest potential mechanisms leading to hypotheses that need to be further investigated in upcoming studies, and finally propose that factors outside of footwear innovation may have concurrently driven the recently observed performance evolutions.

Foam rolling and stretching do not provide superior acute flexibility and stiffness improvements compared to any other warm-up intervention: A systematic review with meta-analysis.

BACKGROUND: Acute improvement in range of motion (ROM) is a widely reported effect of stretching and foam rolling, which is commonly explained by changes in pain threshold and/or musculotendinous stiffness. Interestingly, these effects were also reported in response to various other active and passive interventions that induce responses such as enhanced muscle temperature. Therefore, we hypothesized that acute ROM enhancements could be induced by a wide variety of interventions other than stretching or foam rolling that promote an increase in muscle temperature. METHODS: After a systematic search in PubMed, Web of Science, and SPORTDiscus databases, 38 studies comparing the effects of stretching and foam rolling with several other interventions on ROM and passive properties were included. These studies had 1134 participants in total, and the data analysis resulted in 140 effect sizes (ESs). ES calculations were performed using robust variance estimation model with R-package. RESULTS: Study quality of the included studies was classified as fair (PEDro score = 4.58) with low to moderate certainty of evidence. Results showed no significant differences in ROM (ES = 0.01, p = 0.88), stiffness (ES = 0.09, p = 0.67), or passive peak torque (ES = -0.30, p = 0.14) between stretching or foam rolling and the other identified activities. Funnel plots revealed no publication bias. CONCLUSION: Based on current literature, our results challenge the established view on stretching and foam rolling as a recommended component of warm-up programs. The lack of significant difference between interventions suggests there is no need to emphasize stretching or foam rolling to induce acute ROM, passive peak torque increases, or stiffness reductions.

The potential impact of advanced footwear technology on the recent evolution of elite sprint performances.

Background: Elite track and field sprint performances have reached a point of stability as we near the limits of human physiology, and further significant improvements may require technological intervention. Following the widely reported performance benefits of new advanced footwear technology (AFT) in road-running events, similar innovations have since been applied to sprint spikes in hope of providing similar performance enhancing benefits. However, it is not yet clear based on current evidence whether there have been subsequent improvements in sprint performance. Therefore, the aims of this study were to establish if there have been recent year-to-year improvements in the times of the annual top 100 and top 20 athletes in the men's and women's sprint events, and to establish if there is an association between the extensive use of AFT and potential recent improvements in sprint performances. Methods: For the years 2016-19 and 2021-2022, the season best performances of the top 100 athletes in each sprint event were extracted from the World Athletics Top lists. Independent t-tests with Holm corrections were performed using the season's best performance of the top 100 and top 20 athletes in each year to identify significant differences between years for each sprint discipline. Following the classification of shoes worn by the top 20 athletes in each event during their annual best race (AFT or non-AFT), separate linear mixed-model regressions were performed to determine the influence of AFT on performance times. Results: For the top 100 and top 20 athletes, there were no significant differences year-to-year in any sprint event prior to the release of AFT (2016-2019). There were significant differences between AFT years (2021 or 2022) and pre-AFT years (2016-2019) in eight out of 10 events. These differences ranged from a 0.40% improvement (men's 100 m) to a 1.52% improvement (women's 400 m hurdles). In the second analysis, multiple linear mixed model regressions revealed that the use of AFT was associated with improved performance in six out of ten events, including the men's and women's 100 m, women's 200 m, men's 110 m hurdles, women's 100 m hurdles and women's 400 m hurdles (estimate range: -0.037 - 0.521, p = <0.001 - 0.021). Across both analyses, improvements were more pronounced in women's sprint events than men's sprint events. Conclusion: Following a period of stability, there were significant improvements in most sprint events which may be partly explained by advances in footwear technology. These improvements appear to be mediated by event, sex and potentially level of athlete.

Which trunk muscle parameter is the best predictor for physical function in older adults?

Background: Despite preliminary evidence demonstrating the relevance of trunk muscle strength for physical function in older adults, it is not clear which muscle-related trunk parameter is the best predictor for physical functions. Therefore, this study aimed to compare trunk muscle morphology or strength parameters regarding their predictive ability for physical functions. Methods: Seventy-four older adults (38 men, 36 women, mean age 76.85 years) were tested for maximum absolute and relative isokinetic trunk flexion and extension strength, trunk lean mass, and trunk muscle quality. Functional assessment included normal and fast walking speed, repeated sit-to-stand transfer, timed up and go, and postural sway during a closed-feet and a semi-tandem stance adjusted for body height. Pearson's correlations were used to compare relationship between trunk strength adjusted and unadjusted for body weight to physical functions. Linear regression analysis including sex and age as co-variables was performed between trunk muscle and functional test parameters. Results: Relative back extension strength was the most consistent significant predictor for all physical function tests (p = 0.004-0.04) except for postural sway. Relative trunk flexion strength was related to normal walking speed (p = 0.024). Trunk lean mass was related to timed up and go performance (p = 0.024). Conclusion: Relative back extension strength is associated with better performance in nearly all standard tests for physical function in older adults, while trunk flexion strength and lean mass seem to play a minor role. Our findings emphasize the importance of trunk muscle strength, especially the back extensor muscles, for physical function in older adults.

Physiology of Stretch-Mediated Hypertrophy and Strength Increases: A Narrative Review.

Increasing muscle strength and cross-sectional area is of crucial importance to improve or maintain physical function in musculoskeletal rehabilitation and sports performance. Decreases in muscular performance are experienced in phases of reduced physical activity or immobilization. These decrements highlight the need for alternative, easily accessible training regimens for a sedentary population to improve rehabilitation and injury prevention routines. Commonly, muscle hypertrophy and strength increases are associated with resistance training, typically performed in a training facility. Mechanical tension, which is usually induced with resistance machines and devices, is known to be an important factor that stimulates the underlying signaling pathways to enhance protein synthesis. Findings from animal studies suggest an alternative means to induce mechanical tension to enhance protein synthesis, and therefore muscle hypertrophy by inducing high-volume stretching. Thus, this narrative review discusses mechanical tension-induced physiological adaptations and their impact on muscle hypertrophy and strength gains. Furthermore, research addressing stretch-induced hypertrophy is critically analyzed. Derived from animal research, the stretching literature exploring the impact of static stretching on morphological and functional adaptations was reviewed and critically discussed. No studies have investigated the underlying physiological mechanisms in humans yet, and thus the underlying mechanisms remain speculative and must be discussed in the light of animal research. However, studies that reported functional and morphological increases in humans commonly used stretching durations of > 30 min per session of the plantar flexors, indicating the importance of high stretching volume, if the aim is to increase muscle mass and maximum strength. Therefore, the practical applicability seems limited to settings without access to resistance training (e.g., in an immobilized state at the start of rehabilitation), as resistance training seems to be more time efficient. Nevertheless, further research is needed to generate evidence in different human populations (athletes, sedentary individuals, and rehabilitation patients) and to quantify stretching intensity.

Asymmetries of foot strike patterns during running in high-level female and male soccer players.

BACKROUND: Foot strike pattern (FSP) is defined by the way the foot makes initial ground contact and is influenced by intrinsic and extrinsic factors. This study investigated the effect of running speed on asymmetries of FSP. METHODS: Seventeen female and nineteen male soccer players performed an incremental running test on an instrumented treadmill starting at 2.0 m/s until complete exhaustion. Force plate data were used to categorize foot strikes into rearfoot (RFS) and non-rearfoot strikes. Additionally, peak vertical ground reaction force (peakGRF) and stride time were calculated. The symmetry index (SI) was used to quantify lateral asymmetries between legs. RESULTS: The SI indicated asymmetries of the rate of RFS (%RFS) of approximately 30% at slow running speed which decreased to 4.4% during faster running speed (p = 0.001). There were minor asymmetries in peakGRF and stride time at each running stage. Running speed influenced %RFS (p < 0.001), peakGRF (p < 0.001) and stride time (p < 0.001). Significant interaction effects between running speed and sex were shown for %RFS (p = 0.033), peakGRF (p < 0.001) and stride time (p = 0.041). CONCLUSION: FSP of soccer players are asymmetric at slower running speed, but symmetry increases with increasing speed. Future studies should consider that FSP are non-stationary and influenced by running speed but also differ between legs.

Prevalence of symptoms of depression and generalized anxiety disorder in field hockey players of German first and lower leagues.

BACKGROUND: While several studies on mental health of elite athletes were published in recent years, few compared the prevalence with the general population and none included field hockey players. AIMS: To analyze the prevalence of symptoms of depression and generalized anxiety disorder in field hockey players of different skill levels and to compare it to the general population. METHODS: Male and female hockey players from different leagues were asked to answer questions on player characteristics, the Centre of Epidemiologic Studies Depression Scale (CES-D) and the Generalized Anxiety Disorder-7 (GAD-7). RESULTS: One hundred and eighty-seven players (incl. 54 first and 28 second league players) participated in the study (response rate 97.4%). More than a third (n = 64; 35.0%) reported to be affected by an injury/health complaint, but 157 (86.3%) were able to train and play without limitations. The CES-D score indicated depression symptoms in more female (n = 15; 18.3%) than male (n = 5; 4.8%) players (χ2=8.8; p < 0.01). No male and one female player had symptoms of generalized anxiety disorder. Players who played 60 or more matches in the previous 12 months had on average significantly higher depression (t = 2.3; p < 0.05) and generalized anxiety scores (t = 4.2; p < 0.001) than players who played fewer matches. The prevalence of depression and of generalized anxiety symptoms was similar to or lower than in the general population. Although 20 (10.7%) players had depression symptoms, only 4 (2.2%) received psychological counseling or psychotherapy. CONCLUSION: It is recommended to provide routine screening of mental health problems and low-threshold access to adequate treatment for elite athletes.

[The influence of footwear on the human gait]. / Beinflussbarkeit des Gang- und Laufverhaltens durch Schuhbedingungen.

The development of individual gait and running patterns is influenced by internal (anatomical, anthropometric) and external (activity-related, environmental) factors. The predominantly used rearfoot running style is mainly attributed to the use of cushioned shoes, although from an anthropological perspective running barefoot, and thus running forefoot, is considered to be more natural. Numerous studies have shown a long-term influence of habitual footwear use on foot morphology, running biomechanics and basic motor skills. It has further been shown that an acute change in footwear, e.g. by running barefoot, immediately changes kinematics and vertical load parameters. However, to date, there is no strong evidence for an influence of habitual footwear use or footstrike patterns on the prevalence of injuries or physical complaints.

Relationship between Muscle Strength and Gait Parameters in Healthy Older Women and Men.

Maintaining sufficient muscle strength is fundamental to prevent a decline in basic physical functions such as gait, and is therefore a prerequisite for a healthy independent life in older people. However, the relationship between gait parameters and the strength of single muscle groups is reported with inconclusive results. The objective of this study was to analyze the relationship of strength of nine single muscle groups of lower and upper leg muscles as well as handgrip strength for gait parameters in older adults. Sixty-nine independently living older adults participated in the study. Maximum ankle plantar- and dorsiflexion, knee flexion and extension, as well as hip abduction, adduction, flexion, and extension strength, were measured using an isokinetic dynamometer. Additionally, hand grip strength measured via a hand dynamometer was obtained. Walking gait parameters were recorded with a 3D motion capture system on an instrumented treadmill. The relationships between multiple strength and gait variables were analyzed by Pearson's correlation coefficient. Linear regression analyses were performed to identify the predictive ability of muscle strength (normalized to body weight) for gait speed, stride time, stance time, stride length and step width. Multiple significant weak to moderate positive ([r = 0.343, p = 0.047]-[r = 0.538, p = 0.002]) and negative ([r = -0.340, p = 0.046]-[r = 0.593, p = 0.001]) correlations that were unequally distributed between both sexes were detected. Significant regression models explained ([r2 = 16.6%, p = 0.015]-[r2 = 44.3 %, p = 0.003]) and ([r2 = 21.8%, p = 0.022]-[r2 = 36.1%, p = 0.044]) of the gait parameter variations for men and women, respectively. The results suggest a sex-specific relevance of single muscle groups for all gait parameters. This may be attributed to anatomical differences and it is important to prevent strength-related changes in gait parameters.

Using Daily Stretching to Counteract Performance Decreases as a Result of Reduced Physical Activity-A Controlled Trial.

There are many reasons for reduced physical activity leading to reduced maximal strength and sport-specific performance, such as jumping performance. These include pandemic lockdowns, serious injury, or prolonged sitting in daily work life. Consequently, such circumstances can contribute to increased morbidity and reduced physical performance. Therefore, a demand for space-saving and home-based training routines to counteract decreases in physical performance is suggested in the literature. This study aimed to investigate the possibility of using daily static stretching using a stretching board to counteract inactivity-related decreases in performance. Thirty-five (35) participants were either allocated to an intervention group (IG), performing a daily ten-minute stretch training combined with reduced physical activity or a reduced physical activity-only group (rPA). The effects on maximal voluntary contraction, range of motion using the knee-to-wall test, countermovement jump height (CMJheight), squat jump height (SJheight), drop jump height (DJheight), contact time (DJct) and the reactive strength index (DJRSI) were evaluated using a pre-test-post-test design. The rPA group reported reduced physical activity because of lockdown. Results showed significant decreases in flexibility and jump performance (d = -0.11--0.36, p = 0.004-0.046) within the six weeks intervention period with the rPA group. In contrast, the IG showed significant increases in MVC90 (d = 0.3, p < 0.001) and ROM (d = 0.44, p < 0.001) with significant improvements in SJheight (d = 0.14, p = 0.002), while no change was measured for CMJheight and DJ performance. Hence, 10 min of daily stretching seems to be sufficient to counteract inactivity-related performance decreases in young and healthy participants.

Intrinsic Risk Factors for Ankle Sprain Differ Between Male and Female Athletes: A Systematic Review and Meta-Analysis.

BACKGROUND: Ankle sprains remain prevalent across most team sports. However, despite divergent ankle sprain injury rates in male and female athletes, little is known about potential sex-specific risk factors for ankle sprain. OBJECTIVE: To systematically investigate the sex-specific risk factors for ankle sprain. METHODS: Combinations of the key terms were entered into PubMed, Web of Science, Embase and Cochrane Library databases, and prospective studies reporting ankle sprain risk factors in males or females were included for meta-analysis. RESULTS: Sixteen studies were eligible for inclusion, for a total of 3636 athletes (735 female) and 576 ankle sprains (117 female). Out of 21 prognostic factors, previous ankle sprain injury (odds ratio = 2.74, P < .001), higher body mass index (SMD = 0.50, P < 0.001), higher weight (SMD = 0.24, P = 0.02), lower isometric hip abduction strength (SMD = - 0.52, P < 0.0001) and lower dynamic balance performance (SMD = - 0.48 to - 0.22, P < 0.001-0.04) were identified as risk factors in male athletes. In female athletes, out of 18 factors eligible for meta-analysis, only lower concentric dorsiflexion strength was identified as a risk factor (SMD = - 0.48, P = 0.005). CONCLUSION: This meta-analysis provides novel evidence for different risk factor profiles for ankle sprain injuries between female and male athletes. Further studies, particularly in female athletes, are needed to strengthen the evidence.

Using Long-Duration Static Stretch Training to Counteract Strength and Flexibility Deficits in Moderately Trained Participants.

Many sports injuries result in surgery and prolonged periods of immobilization, which may lead to significant atrophy accompanied by loss of maximal strength and range of motion and, therefore, a weak-leg/strong-leg ratio (as an imbalance index ∆ ) lower than 1. Consequently, there are common rehabilitation programs that aim to enhance maximal strength, muscle thickness and flexibility; however, the literature demonstrates existing strength imbalances after weeks of rehabilitation. Since no study has previously been conducted to investigate the effects of long-duration static stretch training to treat muscular imbalances, the present research aims to determine the possibility of counteracting imbalances in maximal strength and range of motion. Thirty-nine athletic participants with significant calf muscle imbalances in maximal strength and range of motion were divided into an intervention group (one-hour daily plantar flexors static stretching of the weaker leg for six weeks) and a control group to evaluate the effects on maximal strength and range of motion with extended and bent knee joint. Results show significant increases in maximal strength (d = 0.84-1.61, p < 0.001-0.005) and range of motion (d = 0.92-1.49, p < 0.001-0.002) following six weeks of static stretching. Group * time effects (p < 0.001-0.004, η² = 0.22-0.55) revealed ∆ changes in the intervention group from 0.87 to 1.03 for maximal strength and from 0.92 to 1.11 in range of motion. The results provide evidence for the use of six weeks of daily, one hour stretching to counteract muscular imbalances. Related research in clinical settings after surgery is suggested.

Chronic and Residual Effects of a Two-Week Foam Rolling Intervention on Ankle Flexibility and Dynamic Balance.

BACKGROUND: Foam rolling has been shown to acutely improve joint range of motion (ROM). However, limited knowledge exists on the chronic and residual effects. The primary purpose of this study was to examine the chronic and residual effects of a 2-week roller-massager intervention on ankle dorsiflexion ROM and dynamic balance. METHODS: Forty-two participants (24.3 ± 2.5 years, 33 males, 9 females) were randomly assigned to either roller-massage (RM) or control group (= no intervention). Ankle ROM was assessed with the weight-bearing lunge test (WBLT) and dynamic balance with the Y-Balance test for both limbs. The RM group was instructed to roll their calf muscles for three sets of 60 s per leg on 6 days a week over 2 weeks. Acute effects were measured during baseline testing for dorsiflexion ROM and dynamic balance immediately after foam rolling. Chronic and residual effects were measured 1 day and 7 days after the intervention period. Multivariate ANOVA was performed for post-hoc comparisons to determine acute, chronic, and residual effects. RESULTS: Significant acute and chronic foam rolling effects (p <0.05) were found for ankle dorsiflexion ROM. The chronic increase in ROM slightly decreased 7 days post-intervention but remained significantly above baseline (p < 0.05). Regarding dynamic balance, there were no acute but chronic (p < 0.05) and residual (p < 0.05) effects. CONCLUSION: Using a roller-massager for a 2-week period chronically increases ROM and dynamic balance. These increases are still significant 7 days post-intervention emphasizing the sustainability of foam rolling effects.

Maximum isometric torque at individually-adjusted joint angles exceeds eccentric and concentric torque in lower extremity joint actions.

BACKGROUND: Previous research indicates the high relevance of optimal joint angles for individual isometric strength assessment. The objective was to compare lower limb peak isometric muscle strength abilities at the strongest joint angles with those of dynamic contractions in healthy young adults. METHODS: Eighteen young male adults performed maximum concentric, isometric, and eccentric contractions of the ankle, knee, and hip flexors and extensors, and hip adductors and abductors in a randomized sequence on an isokinetic dynamometer (ISOMED 2000). Angular velocity was set at 60°/s. The peak of concentric contraction torque curves was used to define optimal joint angles best suited to generate maximum torque during isometric contractions. Maximum voluntary contraction torque of all contraction conditions was adjusted for limb weight and analyzed via a generalized linear mixed gamma regression model (GLMM). RESULTS: The gamma GLMM revealed strongly significant effects for all three categorical covariates (contraction types, muscle group, and test order) ([Formula: see text]). Eccentric contraction increases the muscle torque ([Formula: see text]) compared to concentric contraction, and isometric contraction even more ([Formula: see text]). A moderate individual-specific variation was found (random effects standard deviation [Formula: see text]). CONCLUSION: The results support the importance of optimal joint angles for isometric maximum strength assessment. When such conditions are given, isometric contractions can produce higher muscle torques than eccentric contractions in the lower body.

Tracking sleep in the field: sleep quality and sleep behaviours of elite track and field athletes during preparation and competition.

Elite athletes are susceptible to inadequate sleep, which may peak during competition and be exacerbated by poor sleep behaviours. This study sought to characterise and compare the sleep quality and sleep behaviours of elite track and field athletes during preparation and major competitions. Forty elite international track and field athletes (50% female, aged 25.1 ± 3.9 years) completed the Athlete Sleep Screening Questionnaire and the Athlete Sleep Behaviour Questionnaire on three separate occasions: during habitual training, during a pre-meet training camp and during a major international competition. Overall, 62.5% of athletes reported at least mild sleep difficulty during competition. Athletes reported higher sleep difficulty and poorer sleep behaviour during major competitions and the pre-meet training camp compared to habitual training (P = .001-.025). No significant differences were observed between the training camp and major competition. Global sleep behaviour scores were underpinned by unique characteristics at each timepoint. Sleep behaviour (R2 = .330, P = .017), injury status (R2 = .253, P = .003) and major championship experience (R2 = .113, P = .034) were associated with sleep difficulty during competition. Sleep quality and behaviours vary according to stage of the track and field season, providing a foundation for targeted intervention.

The Interval Between Matches Significantly Influences Injury Risk in Field Hockey.

Fixture congestion increases injury risk in football, but how it impacts other sports is unclear. The aim of this study was to identify associations between match density and injury incidence in field hockey players. Injury data from a prospective cohort study of professional and youth players was analysed in two ways. Inter-match intervals were clustered into<2424-hours, 3-7-days, and 13 + days, and injury rate ratios (IRR) were calculated to identify differences between clusters in match injuries. Separately, a Lasso-penalised Poisson regression model was used to determine the association between match load across the previous 24-hours, 3-days, 7-days and 14-days, and match and training injuries. Injury rates in matches within 24-hours of the previous match were mostly significantly higher when compared to matches after 3-7-days (IRRs: 3.78; 6.77, P = 0.003; 0.005). While a higher match exposure in the preceding 24-hour and 3-day periods was associated with higher combined match and training injury rates (ß̂ = 0.0001; 0.0018), a higher match exposure in the previous 7-and 14-day periods was associated with a reduced injury rate (ß̂ = -0.0001; -0.0005). Due to the increased injury risk in matches 3-days and especially 24-hours following the previous fixture, match distribution should be cautiously planned.

Sex differences in injury rates in team-sport athletes: A systematic review and meta-regression analysis.

BACKGROUND: Team-sport players have a particularly high injury risk. Although female sex is considered a risk factor, it is still unknown whether female and male team-sport players, in fact, differ in their injury rates. We aimed to compare injury rates between female and male players by systematically reviewing and meta-analyzing injury surveillance studies of both sexes in order to evaluate sex-specific differences in team-sport injuries. METHODS: Studies that prospectively collected injury data for high-level female and male players (age ≥16 years) in basketball, field hockey, football (soccer), handball, rugby (union and sevens), and volleyball were included. Two reviewers (AZ and ALR) independently assessed study quality and extracted data for overall, match, training, and severe injuries (>28 days' time loss) as well as data regarding injury locations and types. Incidence rate ratios (IRRs) were pooled in a meta-analysis, and meta-regression analysis was performed when 10 or more studies were available. RESULTS: Of 20 studies, 9 studies reported injury data from football, 3 studies from rugby, 3 studies from handball, 1 study from basketball, 1 study from field hockey, 2 studies from volleyball, and 1 study from basketball and field hockey. For overall injuries, the pooled IRR = 0.86 (95% confidence interval (95%CI): 0.76-0.98) indicated significantly more injuries in male than in female players. For injury location, the pooled IRR showed higher injury rates in male athletes than in female athletes for upper extremity, hip/groin, thigh, and foot injuries. Female players had a significantly higher rate of anterior cruciate ligament injuries (IRR = 2.15, 95%CI: 1.27-3.62) than male players. No significant sex-specific differences in IRR were found for match, training, severe injuries, concussions, or ankle sprains. CONCLUSION: Our meta-analysis provides evidence for sex-specific differences in the injury rates in team sports. Further epidemiological studies including both sexes in sports other than football are needed in order to strengthen the evidence.

Effects of barefoot vs. shod walking during indoor and outdoor conditions in younger and older adults.

BACKGROUND: Gait stability and variability measures in barefoot and shod locomotion are frequently investigated in younger but rarely in older adults. Moreover, most studies examine gait measures in laboratory settings instead of real-life settings. RESEARCH QUESTIONS: How are gait stability and variability parameters affected by footwear compared to barefoot walking in younger and older adults as well as under indoor vs. outdoor conditions? METHODS: Healthy younger (<35 years) and older adults (>65 years) participated in the randomised within-subject study design. Participants conducted consecutive 25 m walking trials barefoot and with standardised footwear inside and outside. Inertial measurement units were mounted on the participant's foot and used to calculate local dynamic stability (LDS), velocity and minimal toe clearance (MTC), stride length and stride time, including variabilities for these parameters. Linear mixed models were calculated. RESULTS: Data of 32 younger (17 female, 15 male, age: 30 ± 4 years) and 42 older participants (24 female, 18 male, age: 71 ± 4 years) were analysed. MTC variability was higher in shod conditions compared to barefoot (p = 0.048) and in outdoor conditions (p < 0.001). LDS was different between age groups (p < 0.001). Gait velocity and MTC were higher in shod and outdoor conditions (both p < 0.001). Stride length and time were higher in shod conditions (both p < 0.001) and different between outdoor vs. indoor (longer stride length and shorter stride time outdoor, both (p < 0.001) as well as age groups (shorter stride length (p < 0.021) and stride time in older adults (p < 0.001). SIGNIFICANCE: Results suggest that gait stability and variability in older and younger adults are acutely affected by footwear vs. barefoot and indoor vs. outdoor walking conditions, indicating a high adaptiveness of these parameters to different experimental conditions. Consequently, future studies should be careful with generalising results obtained under certain conditions. Findings stress the clinical potential of barefoot walking.

Sex differences in stretch-induced hypertrophy, maximal strength and flexibility gains.

Introduction: If the aim is to increase maximal strength (MSt) and muscle mass, resistance training (RT) is primarily used to achieve these outcomes. However, research indicates that long-duration stretching sessions of up to 2 h per day can also provide sufficient stimuli to induce muscle growth. In RT literature, sex-related differences in adaptations are widely discussed, however, there is a lack of evidence addressing the sex-related effects on MSt and muscle thickness (MTh) of longer duration stretch training. Therefore, this study aimed to investigate the effects of 6 weeks of daily (1 h) unilateral static stretch training of the plantar flexors using a calf-muscle stretching device. Methods: Fifty-five healthy (m = 28, f = 27), active participants joined the study. MSt and range of motion (ROM) were measured with extended and flexed knee joint, and MTh was investigated in the medial and lateral heads of the gastrocnemius. Results: Statistically significant increases in MSt of 6%-15% (p < .001-.049, d = 0.45-1.09), ROM of 6%-21% (p < .001-.037, d = 0.47-1.38) and MTh of 4%-14% (p < .001-.005, d = 0.46-0.72) from pre-to post-test were observed, considering both sexes and both legs. Furthermore, there was a significant higher increase in MSt, MTh and ROM in male participants. In both groups, participants showed more pronounced adaptations in MSt and ROM with an extended knee joint as well as MTh in the medial head of the gastrocnemius (p < .001-.047). Results for relative MSt increases showed a similar result (p < .001-.036, d = 0.48-1.03). Discussion: Results are in accordance with previous studies pointing out significant increases of MSt, MTh and ROM due to long duration static stretch training. Both sexes showed significant increases in listed parameters however, male participants showed superior increases.