Gender differences in lower extremity mechanics during running

The effects of core muscle fatigue on lower limbs and trunk during single-leg drop landing: A comparison between recreational runners with and without dynamic knee valgus

BACKGROUND

A deficit in neuromuscular trunk control can impact the lower limb motion, predisposing runners to injuries. This deficit may show a greater impact on runners with dynamic knee valgus. This study aimed to compare the effect of core fatigue on kinetic, kinematic, and electromyographic parameters of the trunk and lower limbs during single-leg drop landing between runners with and without dynamic knee valgus.

METHODS

Twenty-seven recreational runners were allocated to the valgus (n = 14) and non-valgus groups (n = 13). They performed the test before and after a fatigue protocol, taking a step forward and landing on the force platform while maintaining balance. The fatigue protocol included isometric and dynamic exercises performed consecutively until voluntary exhaustion. The vertical ground reaction force, the sagittal and frontal plane angles, and the electromyographic activity were evaluated. The integral of electromyographic activity was calculated into three movement phases. ANOVA with repeated measures was used to verify the group, time, and interaction effects.

RESULTS

After fatigue, both groups showed a significant reduction in the minimum (p = 0.01) and maximum (p = 0.02) knee angles in the frontal plane (more dynamic knee valgus) and greater gluteus medius activity (p = 0.05) from the peak of knee flexion to the end of the movement. The valgus group had a greater hip excursion (p = 0.01) and vertical linear shoulder displacement (p = 0.02) than the non-valgus.

CONCLUSION

Our results suggest that core fatigue can impact the local muscle and the distal joint and that the groups presented different strategies to deal with the demand during landing.

Running Shoes of the Postmodern Footwear Era: A Narrative Overview of Advanced Footwear Technology

The modern era of running shoes began in the 1960s with the introduction of simple polymer midsole foams, and it ended in the late 2010s with the introduction of advanced footwear technology (AFT). AFT is characterized by highly compliant, resilient, and lightweight foams with embedded, rigid, longitudinal architecture. This footwear complex improves a runner's efficiency, and it introduced a step change in running performance. Purpose: This review serves to examine the current state of knowledge around AFT-what it is and what we know about its ingredients, what benefits it confers to runners, and what may or may not mediate that benefit. We also discuss the emerging science around AFT being introduced to track-racing spikes and how it is currently regulated in sporting contexts. Conclusions: AFT has changed running as a sport. The construction of AFT is grossly understood, but the nature of the interacting elements is not. The magnitude of the enhancement of a runner's economy and performance has been characterized and modeled, but the nuanced factors that mediate those responses have not. With these knowns and unknowns, we conclude the review by providing a collection of best practices for footwear researchers, advice for runners interested in AFT, and a list of pertinent items for further investigation.

Transgender competition in combat sports: Position statement of the Association of ringside physicians

The Association of Ringside Physicians (ARP) is committed to the concept of fair competition. It advocates for two equally skilled and matched athletes to keep bouts fair, competitive, entertaining, and, most importantly, safe for all combatants. Numerous studies have proven that transgender women may have a competitive athletic advantage against otherwise matched cis-gender women. Likewise, transgender men may suffer a competitive disadvantage against cis-gender men. These differences - both anatomic and physiologic - persist despite normalization of sex hormone levels and create disparities in competitive abilities that are not compatible with the spirit of fair competition. More importantly, allowing transgender athletes to compete against cisgender athletes in combat sports, which already involve significant risk of serious injury, unnecessarily raises the risk of injury due to these differences. Hence the ARP does not support transgender athlete competition against cisgender athletes in combat sports.

Sex differences in body composition and shock attenuation during running

Running-related impact shock is absorbed via biological tissue deformation. Given known sex differences in body composition, shock attenuation may also differ between sexes thereby influencing sex-specific running-related injury risk. This study examined sex differences in body composition and shock attenuation during running. Seventeen female (mean ± 1SD age: 34.7 ± 16.1) and twenty-one male runners (age: 29.0 ± 13.8) ran overground as inertial measurement units with triaxial accelerometers measured impact shock at the distal tibia and low-back. Frequency-domain axial and resultant shock attenuation were calculated between the low-back relative to the tibia using a transfer function of the power spectral density within 9-20, 21-35, and 36-50 Hz. Bone mineral density and content, fat and lean mass were measured in the lower extremity and pelvis/gynoid regions using dual x-ray absorptiometry. The association between sex and shock attenuation was tested using age-adjusted linear regression models, adjusted and unadjusted for body composition as a post-hoc analysis (α = 0.05). Body composition variables normalized to body mass were compared between sexes using independent samples t-tests (α = 0.05). Body composition differed between sexes (p-range: <0.001-0.01, Cohen's d range: 0.17-2.41). Before adjusting for body composition, sex was not significantly associated with axial or resultant shock attenuation (p > 0.05), but adjusting for select body composition variables like lower extremity lean and bone mass revealed greater attenuation in females than males (β-range: -124.76 to -46.42, negative indicates greater attenuation; p-range = 0.004-0.04). Sex may not influence shock attenuation during running, but body composition must be accounted for to better understand this association and consequently sex-specific tissue capacities relative to applied loads.

Effects of prosthetic stiffness and added mass on metabolic power and asymmetry in female runners with a leg amputation

Similar to nonamputees, female athletes with unilateral transtibial amputation (TTA) using running-specific leg prostheses (RSPs) may have worse running economy and higher rates of running-related injury than male athletes. Optimizing RSP configuration for female athletes could improve running economy and minimize biomechanical asymmetry, which has been associated with running-related injury. Nine females with a TTA ran at 2.5 m/s while we measured metabolic rates and ground reaction forces. Subjects used an RSP with a manufacturer-recommended stiffness category, one category less stiff and two categories less stiff than recommended. Use of an RSP two categories less stiff resulted in 3.0% lower net metabolic power (P = 0.04), 7.8% lower affected leg stiffness (P = 6.01 × 10-4), increased contact time asymmetry (P = 0.04), and decreased stance average vertical ground reaction force asymmetry (P = 0.04) compared with a recommended stiffness category RSP. Lower RSP stiffness (kN/m) values were associated with lower net metabolic power (P = 0.02), lower affected leg stiffness (P = 1.36 × 10-4), longer affected leg contact time (P = 1.46 × 10-4), and similar affected leg peak and stance-average vertical ground reaction force compared with higher RSP stiffness values. Subjects then used the RSP stiffness category that elicited the lowest net metabolic power with 100 g, 200 g, and 300 g added distally. We found no significant effects of added mass on net metabolic power, biomechanics, or asymmetry. These results suggest that female runners with a TTA could decrease metabolic power during running while minimizing biomechanical asymmetries, which have been associated with running-related injury, by using an RSP two categories less stiff than manufacturer recommended.NEW & NOTEWORTHY Females with unilateral transtibial amputation can improve running performance through reductions in net metabolic power by using a running-specific prosthesis (RSP) that is less stiff than manufacturer-recommended. Lower RSP stiffness values are associated with greater leg stiffness and contact time asymmetry, and lower stance-average vertical ground reaction force asymmetry. However, we found that adding mass to the RSP did not affect net metabolic power and stance-phase biomechanical asymmetries during running.

Investigation of the functional and biomechanical effect of instrument-assisted soft tissue mobilization technique in individuals with asymptomatic dynamic knee valgus - Randomized controlled trial

Although there are studies showing that myofascial release will increase muscle force production, the contribution of its application alone to muscle force production has not been examined. Aim of the study is to investigate the effect of instrument-assisted soft tissue mobilization (IASTM) on eccentric strength, frontal plane projection angle (FPPA), dynamic (DPS), and static postural stability (SPS), femoral internal rotation (FIR) angle in females with dynamic knee valgus (DKV). A total of 44 recreationally active females with asymptomatic DKV (age: 21,39 ± 1,79, body mass index: 20,09 ± 2,45) participated and were randomly assigned to either control group (CG) or IASTM group (IASTMG). Participants' eccentric contraction strength, FPPA, DPS, SPS, and FIR on the involved leg were measured pre- and post. IASTM application was applied to IASTMG for 6 weeks, twice a week, for 5 min, using Graston Technique® instruments on gluteus medius. CG received no intervention. In comparison of ECS difference values, change in IASTMG was found to be statistically significantly higher than CG (p = .004; p < .01). There was no statistical difference in comparison of FIR and FPPA values (respectively p = .213, p = .360; p < .05). In SPS and DPS evaluation, a statistically significant improvement was observed in favor of IASTMG in comparison of both intergroup and difference values (p < .05 for all). Strength gain without exercise can increase postural stability, but it isn't sufficient to correct faulty movement patterns. We recommend adding IASTM to injury prevention programs, but there is a need to investigate the effect of IASTM with technique correction feedback.

The Influence of "Super-Shoes" and Foot Strike Pattern on Metabolic Cost and Joint Mechanics in Competitive Female Runners

PURPOSE

The objective of this study is to assess the influence of "super-shoes" on metabolic cost and joint mechanics in competitive female runners and to understand how foot strike pattern may influence the footwear effects.

METHODS

Eighteen competitive female runners ran four 5-min bouts on a force instrumented treadmill at 12.9 km·h -1 in 1) Nike Vaporfly Next% 2™ (SUPER) and 2) Nike Pegasus 38™ (CON) in a randomized and mirrored order.

RESULTS

Metabolic power was improved by 4.2% ( P < 0.001; d = 0.43) and metatarsophalangeal (MTP) negative work ( P < 0.001; d = 1.22), ankle negative work ( P = 0.001; d = 0.67), and ankle positive work ( P < 0.001; d = 0.97) were all smaller when running in SUPER compared with CON. There was no correlation between foot strike pattern and the between-shoe (CON to SUPER) percentage change for metabolic power ( r = 0.093, P = 0.715).

CONCLUSIONS

Metabolic power improved by 4.2% in "super-shoes" (but only by ~3.2% if controlling for shoe mass differences) in this cohort of competitive female runners, which is a smaller improvement than previously observed in men. The reduced mechanical demand at the MTP and ankle in "super-shoes" are consistent with previous literature and may explain or contribute to the metabolic improvements observed in "super-shoes"; however, foot strike pattern was not a moderating factor for the metabolic improvements of "super-shoes." Future studies should directly compare the metabolic response among different types of "super-shoes" between men and women.

Consistency of sex-based differences between treadmill and overground running using an inertial measurement unit (IMU)

Differences in running gait between treadmill and overground running has been subject of study, while consistency of group differences between running surfaces has not been previously analysed. This study examined both the differences between running surfaces and the consistency of sex-based differences between surfaces in some spatiotemporal and kinematic variables measured by an inertial measurement unit fastened over the lumbar spine. Thirty-two (sixteen females) endurance runners firstly performed overground and then treadmill (1 % inclination) runs at speeds between 9-21 km∙h-1. Males showed lower flight time (FT) [moderate effect size (ES)] during treadmill running compared to overground, while females showed greater stride frequency (SF) (moderate ES), lower stride length (SL) (moderate ES), FT (moderate ES), and vertical (VT) trunk displacement (moderate ES), as well as greater medio-lateral (ML) trunk displacement (moderate ES). No differences in CT between surfaces were found (trivial to small). Furthermore, all the sex-differences were consistent between treadmill and overground running: Males showed lower SF (large and moderate ES, respectively), greater SL (large and moderate ES) and CT (moderate and large ES), lower FT (large ES), greater VT displacement (moderate to large ES), and lower ML displacement (moderate ES) than females. These results may be of interest to carefully transfer the running gait analyses between surfaces depending on sex.

Effect of Strength and Plyometric Training on Kinematics in Female Novice Runners

ABSTRACT

Harrison, K, Williams, DSB III, Darter, BJ, Zernicke, RF, Shall, M, and Finucane, S. Effect of strength and plyometric training on kinematics in female novice runners. J Strength Cond Res 38(6): 1048-1055, 2024-Both running performance and injury have been associated with running kinematics. Plyometric training improves run performance and reduces injury risk in court-sport and field-sport athletes. The aim of this study was to assess longitudinal changes in kinematics in novice runners before and after a typical beginners' running program, compared with those who perform a plyometric intervention before running. Fifty-seven novice female runners were assigned to the control group (8 weeks walking +8 weeks running) or the intervention group (8 weeks strength or plyometric training +8 weeks running). Kinematics were assessed at baseline, 8 weeks, and 16 weeks. Joint angles throughout the stride of those who completed the training ( n = 21) were compared between groups and assessment time points using a statistical parametric mapping 2-way analysis of variance, with group and study time point as independent variables. There was no interaction effect of group and study time point ( p > 0.05), indicating that both training programs had similar effects on running kinematics. There was a main effect of time for sagittal plane knee and hip kinematics ( p < 0.001); after training, subjects ran with a more extended leg, particularly during swing. Programs of 8 weeks of preparatory training, followed by 8 weeks of running, resulted in altered sagittal plane biomechanics, which have previously been related to improved running economy. A greater volume of plyometric, run training or concurrent plyometric and run training may be required to elicit changes in running form associated with lower injury risk.

Incidence and Predictors of Subsidence Using Modular, Tapered, Fluted Titanium Femoral Stems in Aseptic Revision Total Hip Arthroplasty

BACKGROUND

Tapered, fluted titanium (TFT) femoral stems have become the gold standard in revision total hip arthroplasty (rTHA). However, there is a paucity of data on TFT stem subsidence rates following aseptic rTHA. Subsidence can lead to instability, mechanical failure, leg-length discrepancy, and may require revision surgery. This study evaluated the incidences and predictors of TFT subsidence in aseptic rTHA.

METHODS

A total of 102 TFT femoral stems of 4 designs were retrospectively reviewed. Stem subsidence was measured on digital radiographs taken immediately after surgery and at standard clinical follow-up. Patient characteristics, risk factors for subsidence, revision etiologies, and implant characteristics were recorded. Patient-reported outcome measures were also evaluated for a subset of cases.

RESULTS

Overall, 12% of stems subsided >1 cm, and subsidence was minimal (<3 mm) in ≥64% of cases. From immediate postoperative to 1-month radiographic follow-up, 79% of stems subsided a mean of 2.9 mm (range, 0.1 to 12 mm). Beyond 1 month, subsidence was minimal for ≥77% of cases. In multivariate analyses, women and less femoral implant canal fill were associated with greater subsidence (P ≤ .034). The TFT stem design was not associated with early subsidence (P = .816). There were no modular junction fractures. There were 2 fractures and 2 subsidence-related revisions for aseptic loosening that occurred postoperatively.

CONCLUSIONS

The amount of subsidence in TFT stems was low and was detectable in the early (less than 1 year) postoperative period. Maximizing TFT stem fill within the femoral canal appears to reduce the risk of subsidence without increasing femoral fracture rates and should be the goal with implantation of these devices.

LEVEL OF EVIDENCE

IV-Case Series, No Control Group.

Running-Related Injury Incidence: Does It Correlate with Kinematic Sub-groups of Runners? A Scoping Review

BACKGROUND

Historically, kinematic measures have been compared across injured and non-injured groups of runners, failing to take into account variability in kinematic patterns that exist independent of injury, and resulting in false positives. Research led by gait patterns and not pre-defined injury status is called for, to better understand running-related injury (RRI) aetiology and within- and between-group variability.

OBJECTIVES

Synthesise evidence for the existence of distinct kinematic sub-groups across a population of injured and healthy runners and assess between-group variability in kinematics, demographics and injury incidence.

DATA SOURCES

Electronic database search: PubMed, Web of Science, Cochrane Central Register of Controlled Trials (Wiley), Embase, OVID, Scopus.

ELIGIBILITY CRITERIA

Original, peer-reviewed, research articles, published from database start to August 2022 and limited to English language were searched for quantitative and mixed-methods full-text studies that clustered injured runners according to kinematic variables.

RESULTS

Five studies (n = 690) were included in the review. All studies detected the presence of distinct kinematic sub-groups of runners through cluster analysis. Sub-groups were defined by multiple differences in hip, knee and foot kinematics. Sex, step rate and running speed also varied significantly between groups. Random injury dispersal across sub-groups suggests no strong evidence for an association between kinematic sub-groups and injury type or location.

CONCLUSION

Sub-groups containing homogeneous gait patterns exist across healthy and injured populations of runners. It is likely that a single injury may be represented by multiple movement patterns, and therefore kinematics may not predict injury risk. Research to better understand the underlying causes of kinematic variability, and their associations with RRI, is warranted.

Load carriage changes tibiofemoral arthrokinematics during ambulatory tasks in recruit-aged women

The introduction of women into U.S. military ground close combat roles requires research into sex-specific effects of military training and operational activities. Knee osteoarthritis is prevalent among military service members; its progression has been linked to occupational tasks such as load carriage. Analyzing tibiofemoral arthrokinematics during load carriage is important to understand potentially injurious motion and osteoarthritis progression. The study purpose was to identify effects of load carriage on knee arthrokinematics during walking and running in recruit-aged women. Twelve healthy recruit-aged women walked and ran while unloaded (bodyweight [BW]) and carrying additional + 25%BW and + 45%BW. Using dynamic biplane radiography and subject-specific bone models, tibiofemoral arthrokinematics, subchondral joint space and center of closest contact location between subchondral bone surfaces were analyzed over 0-30% stance (separate one-way repeated measures analysis of variance, load by locomotion). While walking, medial compartment contact location was 5% (~ 1.6 mm) more medial for BW than + 45%BW at foot strike (p = 0.03). While running, medial compartment contact location was 4% (~ 1.3 mm) more lateral during BW than + 25%BW at 30% stance (p = 0.04). Internal rotation was greater at + 45%BW compared to + 25%BW (p < 0.01) at 30% stance. Carried load affects tibiofemoral arthrokinematics in recruit-aged women. Prolonged load carriage could increase the risk of degenerative joint injury in physically active women.

Effect of thoracolumbosacral braces on running ground reaction force components in male individuals with kyphosis

BACKGROUND & AIMS

Braces are one of the methods for kyphosis treatment, but they can relocate the center of gravity of the trunk, affecting the ground reaction force (GRF) during running. Therefore, this study aimed to investigate the effects of two types of thoracolumbosacral braces on running GRF components in individuals with kyphosis.

MATERIALS & METHODS

Participants were 15 males diagnosed with kyphosis who volunteered in this quasi-experimental study. Each subject performed the barefoot running trials on the force plate with one simple brace, with a sensor brace, and without the brace condition. The ground reaction forces components were calculated in the stance phase. Statistical analysis was done with repeated measures test with a significant level of 0.05.

RESULTS

Peak medial ground reaction force when running with a sensor brace was lower than running with a simple brace (p = 0.017). Free moments were similar during three running conditions (p > 0.05).

CONCLUSION

Lower maximum medial ground reaction force while using a sensor brace may possibly demonstrate the beneficial effects of a sensor brace in individuals with kyphosis.

Influence of running on femoroacetabular joint bone-to-bone distances

There is limited data quantifying the influence of running on hip cartilage mechanics. The goal of this investigation was to quantify changes in hip joint bone-to-bone distance in response to a 3-mile treadmill run. We acquired magnetic resonance (MR) images of the dominant hip of eight young, asymptomatic runners (five males, three females) before and immediately after they ran 3 miles at a self-selected pace on a level treadmill. The femoral heads and acetabula were semiautomatically segmented from the pre- and post-exercise MR images to generate three-dimensional models of each participant's hip that were used to compute changes in the bone-to-bone distances incurred by the running exercise. We observed a significant 3% decrease in bone-to-bone distance from 3.47 ± 0.20 to 3.36 ± 0.22 mm between the femoral head and acetabulum after a 3-mile treadmill run (mean ± 95% confidence interval; p = 0.03). These findings provide new baseline data describing how running impacts the hip joint in young, asymptomatic runners.

Kinematic variations in the barbell back squat under different footwear conditions in female college athletes

BACKGROUND

The barbell back squat is one of the most performed exercises, being important for the strengthening of lower limbs and trunk. Recently, it has become popular to train under different conditions of footwear or without it, and some investigations have analyzed the changes that this brings, with some contradictions in this regard. The purpose of this study was to analyze the kinematic variations under different shoe conditions (running shoes, barefoot and barefoot with heel raised) in the back squat in female university athletes.

METHODS

Fifteen athletes in the three conditions with a load equal to 70% of their one-maximum repetition (1RM), were recorded and analyzed to determine the angles of the ankle, knee, hip and trunk by five movements in each condition.

RESULTS

The use of enhancement significantly increased (P<0.05) the dorsal flexion angle of the ankle, against the footwear condition and barefoot without enhancement (109.6±11.1° vs. 99.1±9.0° vs. 101.3±11.5°). No significant differences were observed in any of the other variables.

CONCLUSIONS

An optimal squat technique is important for preventing injuries, optimal rehabilitation and for improving sports performance. Increased dorsal ankle flexion angle may protect distal tibiofibular joint.

Three-dimensional kinematics of the trunk, pelvis, hip, and knee during the single-leg squat and hip torque in subjects with isolated patellofemoral osteoarthritis compared to individually matched controls: Preliminary results

Objectives: This study aimed to compare three-dimensional kinematic of the trunk, pelvis, hip, and knee during the single-leg squat and hip torque in individuals with and without isolated patellofemoral osteoarthritis (PFOA). Patients and methods: This cross-sectional study evaluated trunk, pelvis, hip, and knee kinematics at 30°, 45°, and 60° knee flexion during the single-leg squat using the Vicon motion capture and analysis system, the Nexus System 2.1.1, and 3D Motion Monitor software. Sixteen individuals (8 males, 8 females; mean age: 49.3±6.2 years; range 40 to 61 years) participated in the study, of which eight were PFOA patients and eight were healthy controls. Isometric hip abductor, extensor, and external rotator torques were evaluated using a handheld dynamometer. Results: The PFOA group exhibited greater hip adduction at 30° (p=0.008), 45° (p=0.005), and 60° (p=0.008) knee flexion in the descending phase of the single-leg squat, as well as at 60° (p=0.009) and 45° (p=0.03) knee flexion in the ascending phase. No significant differences were found between groups for other kinematic variables (p>0.05). The PFOA group exhibited lower isometric hip abductor (p=0.02), extensor (p <0.001), and external rotator (p=0.007) torques. Conclusion: Individuals with PFOA exhibited excessive hip adduction that could increase stress on the lateral patellofemoral joint at 30°, 45°, and 60° knee flexion during the single-leg squat and exhibited weakness of the hip abductors, extensors, and external rotators in comparison to healthy controls.

The interaction effect of different footwear types and static navicular drop or dynamic ankle pronation on the joint stiffness of the lower limb during running

BACKGROUND

Although the effects of footwear type on joint stiffness have previously been investigated, researchers did not consider foot flexibility. Thus, the present investigation aimed to determine the interaction effects of footwear type, static navicular drop and dynamic ankle pronation on dynamic joint stiffness in running.

RESEARCH QUESTION

Does the footwear types in interaction with the foot posture affect the stiffness of the joints of the lower limb?

METHODS

Forty-seven male individuals participated in this study. Firstly, they were divided into the high navicular, low navicular, and normal navicular drop. Secondly, they were divided into the high dynamic ankle pronation, low dynamic ankle pronation, and normal dynamic ankle pronation groups. Participants performed three running trials at 3 ± 0.2 m/s at minimalist footwear, conventional footwear, and barefoot conditions. We collected the ground reaction forces and three-dimensional kinematic data and calculated joint stiffness over the stance phase.

RESULTS

There was no significant main effect of navicular drop or dynamic ankle pronation on dynamic joint stiffness for the ankle, knee, and hip (p > 0.05). However, footwear type significantly affected dynamic joint stiffness. The pairwise comparison revealed that the ankle and hip dynamic joint stiffness magnitudes in the conventional footwear condition were greater than in the barefoot and minimalist footwear conditions (p 0.001). In contrast, the knee dynamic joint stiffness magnitude in the conventional footwear condition was lesser than in barefoot and minimalist footwear conditions (p 0.001).

SIGNIFICANCE

The navicular drop or dynamic ankle pronation did not influence lower limb joint stiffness, and there was no significant interaction between navicular drop or dynamic ankle pronation and footwear on lower limb dynamic joint stiffness. However, conventional footwear increased the ankle and hip dynamic joint stiffness while reducing knee dynamic joint stiffness, leading to changes in transfer energy, which could have implications for relative injury risk.

Effect of gender and running experience on lower limb biomechanics following 5 km barefoot running

Barefoot running has been increasing in popularity, yet there is a gap in understanding concerning the biomechanics of mid-distance barefoot running, especially between genders and runners of different running-experience levels. This study examines the effects of running-experience, gender, and their interaction on running biomechanics following 5 km barefoot running. Before and after a 5 km run, three-dimensional kinematics and kinetics of the lower limb joints and plantar pressure during barefoot running were collected from 20 participants. Participants were stratified by their running-experience levels (novice and marathon-experienced) and gender. This study revealed significant gender effects on lower limb biomechanics following a 5 km barefoot run. Increased plantar pressure under the lateral aspect of the foot was observed in the female cohort, while the male cohort exhibited reduced plantar pressure under the lateral heel. This study suggests that modified lower limb running biomechanics and modified lateral foot loading after 5 km barefoot running may create a different foot loading environment for female and male runners that should be accommodated in barefoot runningand minimalist shoe design.

Gender differences on the age-related distal-to-proximal shift in joint kinetics during running

The increased running participation in women and men over 40 years has contributed to scientific interest on the age-related and gender differences in running performance and biomechanics over the last decade. Gender differences in running biomechanics have been studied extensively in young runners, with inconsistent results. Understanding how gender influences the age-related differences in running mechanics could help develop population-specific training interventions or footwear to address any potential different mechanical demands. The purpose of this study was to assess gender and age effects on lower limb joint mechanics while running. Middle-aged men (57 ± 5 years) and women (57 ± 8 years) and young men (28 ± 6 years) and women (30 ± 6 years) completed five overground running trials at a set speed of 2.7 m/s while lower limb kinematics and ground reaction forces were collected. Lower limb joint kinetics were computed, normalized to body mass and compared between age and gender groups using two-factor analyses of variance. Women reported slower average running paces than men and middle-aged runners reported slower running paces than young runners. We confirmed that young runners run with more ankle, but less hip positive work and peak positive power compared to middle-aged runners (i.e., age-related distal-to-proximal shift in joint kinetics). We also present a novel finding that women run with more ankle, but less hip peak positive power compared to men suggesting an ankle dominant strategy in women at a preferred and comfortable running pace. However, the age-related distal-to-proximal shift in joint kinetics was not different between genders.

The knee kinematic patterns and associated factors in healthy Thai adults

BACKGROUND

Reference values for normal knee kinematics were limited in Asian population and were influenced by race and other factors. This study was aimed to establish the reference values and identify the factors associated with knee kinematics in healthy Thai adults, aged 18-40 years.

METHODS

A retrospective cohort study was conducted between 2016 and 2020. Healthy Thai adults aged 18-40 years old with body mass index (BMI) between 18.5 and 24.9 kg/m2 were included. All eligible participants were attached with reflective markers. Their walking was captured by 8-digital cameras, and assessed by motion analysis software. The primary outcomes were average knee kinematic data (degrees) in three dimensional planes as valgus-varus, flexion-extension, and internal-external rotation. Paired t-test and multiple linear regression were applied to compare the outcomes and to determine their associated factors.

RESULTS

Ninety-eight participants (60 females and 38 males) were included with mean age 28.5 ± 5.4 years, and BMI 21.1 ± 2.0 kg/m2. Knee kinematics showed slight adduction during the swing phase, flexion during the stance phase, and obvious external rotation throughout the gait cycle, with a peak of 30-31 degrees during mid-swing. Right knee was significantly more adducted, flexed and externally rotated than the left side, particularly at mid-stance (P = 0.047, 0.017, and < 0.001, respectively). Females had more knee abduction, flexion and external rotation than males. Age, sex, and BMI were significantly correlated with knee abduction at terminal stance (correlation coefficient - 0.12, 95% confidence interval (CI) -0.23, -0.01; -1.37, 95%CI -2.54, -0.20; and - 0.32, 95%CI -0.61, -0.39, respectively), and rotation at mid-swing (correlation coefficient - 0.36, 95%CI -0.69, -0.02; -7.37, 95%CI -10.82, -3.92; and 0.89, 95%CI 0.01, 1.78, respectively).

CONCLUSION

Knee kinematics demonstrates external tibial rotation throughout the gait cycle, significant side differences, and are associated with age, sex, and BMI. Reference values from this study will be useful for functional gait assessment in healthy Thais. However, further comprehensive knee kinetic study including spatio-temporal parameter is recommended.

The Influence of Footwear Longitudinal Bending Stiffness on Running Economy and Biomechanics in Older Runners

Purpose: This study assessed the effects of footwear longitudinal bending stiffness on running economy and biomechanics of rearfoot striking older runners. Methods: Nine runners over 60 years of age completed two running bouts at their preferred running pace in each of three footwear conditions: low (4.4 ± 1.8 N·m-1), moderate (5.7 ± 1.7 N·m-1), and high (6.4 ± 1.6 N·m-1) bending stiffness. Testing order was randomized and a mirror protocol was used (i.e., A,B,C,C,B,A). Expired gases, lower limb kinematics, and ground reaction forces were collected simultaneously and lower limb joint kinetics, running economy (i.e., VO2), leg stiffness, and spatio-temporal variables were calculated. Results: Running economy was not different among stiffness conditions (p = 0.60, p = 0.53 [mass adjusted]). Greater footwear stiffness reduced step length (p = 0.046) and increased peak vertical ground reaction force (p = 0.019) but did not change peak ankle plantarflexor torque (p = 0.65), peak positive ankle power (p = 0.48), ankle positive work (p = 0.86), propulsive force (p = 0.081), and leg stiffness (p = 0.46). Moderate footwear stiffness yielded greater peak negative knee power compared to low (p = 0.04) and high (p = 0.03) stiffness. Conclusions: These novel findings demonstrate that increasing footwear longitudinal bending stiffness using flat carbon fiber inserts does not improve running economy and generally does not alter lower limb joint mechanics of rearfoot strike runners over 60 years. Future studies should investigate how other footwear characteristics (e.g., midsole material, plate location, and sole curvature) influence economy and biomechanics in this population.

Frontal plane pelvic kinematics during high velocity running: Association with hamstring injury history

INTRODUCTION

Hamstring injuries are the most prevalent non-contact soft tissue injury in sports, with a larger portion of injuries being recurrent. The sagittal plane running kinematics correlated to hamstring injury history has been well documented. However, analysis of frontal plane kinematics allows for observation of stability and symmetry. This study aimed to examine the frontal plane running kinematics of elite collegiate level sprinters, with and without previous hamstring injury, compared to healthy counterparts.

METHODS

Thirty-nine participants performed three 50-m sprints, with three inertial measurement unit sensors placed on the pelvis: one on each iliac crest and one on the sacrum. Participants were classified based on sex, competitive status, and injury history. To investigate differences based on group classification, the data were used to analyze mediolateral motion (relative magnitude of mediolateral acceleration) and asymmetry (difference in acceleration between right and left iliac crests) during each stance phase throughout the run.

RESULTS

Injured sprinters displayed significantly greater mediolateral motion and asymmetry during stances than healthy counterparts.

CONCLUSIONS

This study demonstrates that frontal plane running stance dynamics are different in athletes with previous hamstring injury than healthy athletes. These athletes may benefit from rehabilitation strategies targeting postural control and stability during dynamic tasks.

Differences in running biomechanics between young, healthy men and women carrying external loads

During U.S. Army basic combat training (BCT), women are more prone to lower-extremity musculoskeletal injuries, including stress fracture (SF) of the tibia, with injury rates two to four times higher than those in men. There is evidence to suggest that the different injury rates are, in part, due to sex-specific differences in running biomechanics, including lower-extremity joint kinematics and kinetics, which are not fully understood, particularly when running with external load. To address this knowledge gap, we collected computed tomography images and motion-capture data from 41 young, healthy adults (20 women and 21 men) running on an instrumented treadmill at 3.0 m/s with loads of 0.0 kg, 11.3 kg, or 22.7 kg. Using individualized computational models, we quantified the running biomechanics and estimated tibial SF risk over 10 weeks of BCT, for each load condition. Across all load conditions, compared to men, women had a significantly smaller flexion angle at the trunk (16.9%-24.6%) but larger flexion angles at the ankle (14.0%-14.7%). Under load-carriage conditions, women had a larger flexion angle at the hip (17.7%-23.5%). In addition, women had a significantly smaller hip extension moment (11.8%-20.0%) and ankle plantarflexion moment (10.2%-14.3%), but larger joint reaction forces (JRFs) at the hip (16.1%-22.0%), knee (9.1%-14.2%), and ankle (8.2%-12.9%). Consequently, we found that women had a greater increase in tibial strain and SF risk than men as load increases, indicating higher susceptibility to injuries. When load carriage increased from 0.0 kg to 22.7 kg, SF risk increased by about 250% in women but only 133% in men. These results provide quantitative evidence to support the Army's new training and testing doctrine, as it shifts to a more personalized approach that shall account for sex and individual differences.

Anterior cruciate ligament injuries in female athletes

The anterior cruciate ligament (ACL) is frequently injured in elite athletes, with females up to eight times more likely to suffer an ACL tear than males. Biomechanical and hormonal factors have been thoroughly investigated; however, there remain unknown factors that need investigation. The mechanism of injury differs between males and females, and anatomical differences contribute significantly to the increased risk in females. Hormonal factors, both endogenous and exogenous, play a role in ACL laxity and may modify the risk of injury. However, data are still limited, and research involving oral contraceptives is potentially associated with methodological and ethical problems. Such characteristics can also influence the outcome after ACL reconstruction, with higher failure rates in females linked to a smaller diameter of the graft, especially in athletes aged < 21 years. The addition of a lateral extra-articular tenodesis can improve the outcomes after ACL reconstruction and reduce the risk of failure, and it should be routinely considered in young elite athletes. Sex-specific environmental differences can also contribute to the increased risk of injury, with more limited access to and availablility of advanced training facilities for female athletes. In addition, football kits are designed for male players, and increased attention should be focused on improving the quality of pitches, as female leagues usually play the day after male leagues. The kit, including boots, the length of studs, and the footballs themselves, should be tailored to the needs and body shapes of female athletes. Specific physiotherapy programmes and training protocols have yielded remarkable results in reducing the risk of injury, and these should be extended to school-age athletes. Finally, psychological factors should not be overlooked, with females' greater fear of re-injury and lack of confidence in their knee compromising their return to sport after ACL injury. Both intrinsic and extrinsic factors should be recognized and addressed to optimize the training programmes which are designed to prevent injury, and improve our understanding of these injuries.

Thoughts and perspectives on biomechanical numerical models under impacts: Are women forgotten from research?

The present paper explores a series of articles in the literature which deal with impact biomechanics of the head and thorax/abdomen segments, investigating the "sex specific properties/data" used in the studies. Statements in these studies are analyzed and point out, the use of male or female subjects for the developments of finite element models and their validation against experimental data. The present analysis raises the question about "androcentrism," and how biomechanical engineering findings and the design of the derived protecting devices are focused on male subjects.

Muscle Activation and Ground Reaction Force between Single-Leg Drop Landing and Jump Landing among Young Females during Weight-Acceptance Phase

Single-leg drop landing (SLDL) and jump landing (SLJL) are frequently used as assessment tools for identifying potential high-risk movement patterns; thus, understanding differences in neuromuscular responses between these types of landings is essential. This study aimed to compare lower extremity neuromuscular responses between the SLDL and SLJL. Thirteen female participants performed an SLDL and SLJL from a 30-cm box height. Vertical ground reaction force (vGRF), time to peak vGRF, and surface electromyography (sEMG) data were collected. Continuous neuromuscular responses, peak vGRF, and time to peak vGRF were compared between the tasks. Statistical parametric mapping (SPM) analysis demonstrated that the SLJL had a significantly higher sEMG activity in the rectus femoris (RF), vastus lateralis (VL) and vastus medialis (VM) within the first 10% of the landing phase compared with SLDL. At 20-30% of the landing phase, sEMGs in the RF and VL during the SLDL were significantly higher compared with SLJL (p < 0.05). A higher peak vGRF and shorter time to peak vGRF was observed during SLJL (p < 0.05). In conclusion, our findings highlight that SLJL exhibited greater RF, VL, and VM activities than SLDL at initial impact (10% landing), coinciding with a higher peak vGRF and shorter time to attain peak vGRF. Our findings support the role of the quadriceps as the primary energy dissipator during the SLJL.

The Effect of Bicycle Saddle Widths on Saddle Pressure in Female Cyclists

Choosing an unsuitable bicycle saddle increases the saddle pressure and discomfort during cycling. Women contract sports injuries more easily than men during cycling owing to their anatomy. To investigate the effect of saddle widths on the saddle pressure in female cyclists. Ten healthy women with an average age of 20.7 ± 1.3 years, height of 162 ± and 5.9 cm, weight of 56.1 ± 7.5 kg, and a sciatic bone width of 15.5 ± 1.4 cm were recruited for this study. The distributions of saddle pressure for four different saddle widths (i.e., narrow, moderate, wide, and self-chosen) were recorded using a saddle pressure mat. Participants were instructed to pedal steadily with a frequency of 90 RPM and a load of 150 watts. Thirty seconds of riding data was randomly retrieved for analysis. The trials were conducted with a counter-balanced design to minimize random errors. One-way repeated measures ANOVA was used to compare the saddle pressure of different saddle widths, and the significance level was set at α = 0.05. When wide saddles were used, the maximum and average pressure on the right surface of the posterior ischium were lower than those with narrow (p = 0.001, p = 0.012) and moderate (p = 0.016, p = 0.019) saddles. The area of pressure on the pubic bone was smaller when using a wide saddle than when using narrow (p = 0.005) and moderate (p = 0.018) saddles, and the area of pressure on the right posterior sciatic bone was larger under the wide saddle than under the narrow (p = 0.017) and moderate (p = 0.036) saddles. The average force was greater with the moderate saddle than with the wide (p = 0.008) and self-chosen (p = 0.025) saddles. Using a saddle with a width that is longer than the width of the cyclist's ischium by 1 cm can effectively improve the distribution of saddle pressure during riding, while providing better comfort.

An Analysis of Running Impact on Different Surfaces for Injury Prevention

The impact that occurs on the runner's foot when it lands on the ground depends on numerous factors: footwear, running technique, foot strike and landing pattern, among others. However, the surface is a decisive factor that can be selected by the runner to improve their sports practice, thereby avoiding injuries. This study aimed to assess the number and magnitude of accelerations in impact (produced by the runner when their foot strikes the ground) on three different surfaces (grass, synthetic track, and concrete) in order to know how to prevent injuries. Thirty amateur runners (age 22.6 ± 2.43 years) participated in the study. They had to run consecutively on three different surfaces at the same speed, with a three axis-accelerometer placed on the sacrum and wearing their own shoes. The results showed that the running impacts differed based on the type of surface. Higher mean acceleration (MA) and mean peak acceleration (PA) in the impacts were observed on concrete compared to the other two surfaces. There were small differences for MA: 1.35 ± 0.1 g (concrete) vs. 1.30 ± 0.1 g (synthetic track) SD: 0.43 (0.33, 0.54) and 1.30 ± 0.1 g (grass) SD: 0.36 (0.25, 0.46), and small differences for PA: 3.90 ± 0.55 g (concrete) vs. 3.68 ± 0.45 g (synthetic track) SD 0.42 (0.21, 0.64) and 3.76 ± 0.48 g (grass) SD 0.27 (0.05, 0.48), implying that greater impacts were produced on concrete compared to synthetic track and grass. The number of peaks of 4 to 5 g of total acceleration was greater for concrete, showing small differences from synthetic track: SD 0.23 (-0.45, 0.9). Additionally, the number of steps was higher on synthetic track (34.90 ± 2.67), and small differences were shown compared with concrete (33.37 ± 2.95) SD 0.30 (-0.25, 0.85) and with grass (35.60 ± 3.94) SD 0.36 (-0.19, 0.91). These results may indicate a change in technique based on the terrain. Given the increasing popularity of running, participants must be trained to withstand the accelerations in impact that occur on different surfaces in order to prevent injuries.

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.

Effects of pubertal growth variation on knee mechanics during walking in female and male adolescents

INTRODUCTION

Puberty substantially alters the body's mechanical properties, neuromuscular control, and sex differences therein, likely contributing to increased, sex-biased knee injury risk during adolescence. Female adolescents have higher risk for knee injuries than male adolescents of similar age engaging in similar physical activities, and much research has investigated sex differences in mechanical risk factors. However, few studies address the considerable variation in pubertal growth (timing, pace), knee mechanics, and injury susceptibility within sexes, or the impact of such growth variation on mechanical injury risk.

OBJECTIVES

The present study tested for effects of variation in pubertal growth on established mechanical knee injury risk factors, examining relationships between and within sexes.

METHODS

Pubertal growth indices describing variation in the timing and rate of pubertal growth were developed using principal component analysis and auxological data from serial stature measurements. Linear mixed models were applied to evaluate relationships between these indices and knee mechanics during walking in a sample of adolescents.

RESULTS

Later developing female adolescents with slower pubertal growth had higher extension moments throughout stance, whereas earlier developers had higher valgus knee angles and moments. In male adolescents, faster and later growth were related to higher extension moments throughout gait. In both sexes, faster growers had higher internal rotation moments at foot-strike.

CONCLUSIONS

Pubertal growth variation has important effects on mechanical knee injury risk in adolescence, affecting females and males differently. Earlier developing females exhibit greater injury risk via frontal plane factors, whereas later/faster developing males have elevated risk via sagittal plane mechanisms.

Biomechanics associated with tibial stress fracture in runners: A systematic review and meta-analysis

BACKGROUND

Tibial stress fracture (TSF) is an overuse running injury with a long recovery period. While many running studies refer to biomechanical risk factors for TSF, only a few have compared biomechanics in runners with TSF to controls. The aim of this systematic review and meta-analysis was to evaluate biomechanics in runners with TSF compared to controls.

METHODS

Electronic databases PubMed, Web of Science, SPORTDiscus, Scopus, Cochrane, and CINAHL were searched. Risk of bias was assessed and meta-analysis conducted for variables reported in 3 or more studies.

RESULTS

The search retrieved 359 unique records, but only the 14 that compared runners with TSF to controls were included in the review. Most studies were retrospective, 2 were prospective, and most had a small sample size (5-30 per group). Many variables were not significantly different between groups. Meta-analysis of peak impact, active, and braking ground reaction forces found no significant differences between groups. Individual studies found larger tibial peak anterior tensile stress, peak posterior compressive stress, peak axial acceleration, peak rearfoot eversion, and hip adduction in the TSF group.

CONCLUSION

Meta-analysis indicated that discrete ground reaction force variables were not statistically significantly different in runners with TSF compared to controls. In individual included studies, many biomechanical variables were not statistically significantly different between groups. However, many were reported by only a single study, and sample sizes were small. We encourage additional studies with larger sample sizes of runners with TSF and controls and adequate statistical power to confirm or refute these findings.

Using Arterial Pulse and Laser Doppler Analyses to Discriminate between the Cardiovascular Effects of Different Running Levels

BACKGROUND AND AIMS

Running can induce advantageous cardiovascular effects such as improved arterial stiffness and blood-supply perfusion. However, the differences between the vascular and blood-flow perfusion conditions under different levels of endurance-running performance remains unclear. The present study aimed to assess the vascular and blood-flow perfusion conditions among 3 groups (44 male volunteers) according to the time taken to run 3 km: Level 1, Level 2, and Level 3.

METHODS

The radial blood pressure waveform (BPW), finger photoplethygraphy (PPG), and skin-surface laser-Doppler flowmetry (LDF) signals of the subjects were measured. Frequency-domain analysis was applied to BPW and PPG signals; time- and frequency-domain analyses were applied to LDF signals.

RESULTS

Pulse waveform and LDF indices differed significantly among the three groups. These could be used to evaluate the advantageous cardiovascular effects provided by long-term endurance-running training, such as vessel relaxation (pulse waveform indices), improvement in blood supply perfusion (LDF indices), and changes in cardiovascular regulation activities (pulse and LDF variability indices). Using the relative changes in pulse-effect indices, we achieved almost perfect discrimination between Level 3 and Level 2 (AUC = 0.878). Furthermore, the present pulse waveform analysis could also be used to discriminate between the Level-1 and Level-2 groups.

CONCLUSIONS

The present findings contribute to the development of a noninvasive, easy-to-use, and objective evaluation technique for the cardiovascular benefits of prolonged endurance-running training.

Which Factors Influence Running Gait in Children and Adolescents? A Narrative Review

In recent years, running has dramatically increased in children and adolescents, creating a need for a better understanding of running gait in this population; however, research on this topic is still limited. During childhood and adolescence multiple factors exist that likely influence and shape a child's running mechanics and contribute to the high variability in running patterns. The aim of this narrative review was to gather together and assess the current evidence on the different factors that influence running gait throughout youth development. Factors were classified as organismic, environmental, or task-related. Age, body mass and composition, and leg length were the most researched factors, and all evidence was in favour of an impact on running gait. Sex, training, and footwear were also extensively researched; however, whereas the findings concerning footwear were all in support of an impact on running gait, those concerning sex and training were inconsistent. The remaining factors were moderately researched with the exception of strength, perceived exertion, and running history for which evidence was particularly limited. Nevertheless, all were in support of an impact on running gait. Running gait is multifactorial and many of the factors discussed are likely interdependent. Caution should therefore be taken when interpreting the effects of different factors in isolation.

Measurement and reporting of footwear characteristics in running biomechanics: A systematic search and narrative synthesis of contemporary research methods

This review aimed to synthesise the methods for assessing and reporting footwear characteristics among studies evaluating the effect of footwear on running biomechanics. Electronic searches of Scopus®, EBSCO, PubMed®, ScienceDirect®, and Web of Science® were performed to identify original research articles of the effect of running footwear on running biomechanics published from 1^st January 2015 to 7^th October 2020. Risk of bias among included studies was not assessed. Results were presented via narrative synthesis. Eligible studies compared the effect of two or more footwear conditions in adult runners on a biomechanical parameter. Eighty-seven articles were included and data from 242 individual footwear were extracted. Predominantly, studies reported footwear taxonomy (i.e., classification) and manufacturer information, however omitted detail regarding the technical specifications of running footwear and did not use validated footwear reporting tools. There is inconsistency among contemporary studies in the methods by which footwear characteristics are assessed and reported. These findings point towards a need for consensus regarding the reporting of these characteristics within biomechanical studies to facilitate the conduct of systematic reviews and meta-analyses pertaining to the effect of running footwear on running biomechanics.

Lower extremity kinematics during running and hip abductor strength in iliotibial band syndrome: A systematic review and meta-analysis

BACKGROUND

Iliotibial band syndrome is a common overuse injury that is twice as likely to affect female runners compared to male runners. It is unclear if there is a consistent running pattern and strength profile exhibited by female and male runners with iliotibial band syndrome.

RESEARCH QUESTION

The purpose of this systematic review and meta-analysis was to determine if any differences existed in lower-extremity kinematics and hip strength between runners who retrospectively, currently, or prospectively had iliotibial band syndrome.

METHODS

Papers included must have reported three-dimensional kinematic running data and/or hip strength data that were statistically analyzed between runners that never developed iliotibial band syndrome and runners with iliotibial band syndrome. Meta-analysis was performed for each kinematic or strength variable reported in at least three studies. Female and male runners were analyzed separately and grouped into three cohorts (retrospective, current, prospective).

RESULTS

Seventeen articles were included in this systematic review. Data from 10 cross-sectional studies were included for meta-analysis. Female runners with current iliotibial band syndrome exhibited smaller peak hip internal rotation angles and lower isometric hip abductor strength compared to controls.

SIGNIFICANCE

Although limited biomechanical evidence exists, risk factors for ITBS are different between female and male runners and may vary according to injury status. Specifically, transverse plane hip motion and hip abductor strength weakness may be biomechanical risk factors in female runners with current iliotibial band syndrome only.

The influence of midsole shear on running economy and smoothness with a 3D-printed midsole

The objectives of this study were to first determine whether a newly designed 3D-printed midsole, configured with a mechanism to increase anterior-posterior deformation, could increase anterior midsole shear during the stance phase of running. We then wanted to determine whether these shoes could affect running economy and smoothness. Two footwear conditions, differing in midsole technology, were used in this study. The control condition consisted of a thermoplastic polyurethane midsole (TPU-Control), whereas the prototype shoes (3D-Shear) were constructed with a 3D-printed lattice midsole designed for greater anterior foot displacement during early to mid-stance. Twenty male participants ran on a treadmill for 6 min in each condition, and data were collected during the final 2 min. Midsole shear was measured using 3D kinematic data; running smoothness was quantified with peak acceleration and jerk magnitudes from the foot, sacrum, and head; and running economy was determined with oxygen consumption data. As hypothesised, the anterior midsole shear was greater in the 3D-Shear condition compared to the TPU-Control. The 3D-Shear did not improve running economy. Runners exhibited significantly lower peak accelerations at the sacrum, along with lower magnitudes of jerk at the foot, sacrum, and head in the 3D-Shear condition, indicating smoother running patterns.

Differences between Sexes and Speed Levels in Pelvic 3D Kinematic Patterns during Running Using an Inertial Measurement Unit (IMU)

This study aimed to assess the 3D kinematic pattern of the pelvis during running and establish differences between sexes using the IMU sensor for spatiotemporal outcomes, vertical acceleration symmetry index, and ranges of motion of the pelvis in the sagittal, coronal, and transverse planes of movement. The kinematic range in males was 5.92°-6.50°, according to tilt. The range of obliquity was between 7.84° and 9.27° and between 9.69° and 13.60°, according to pelvic rotation. In females, the results were 6.26°-7.36°, 7.81°-9.64°, and 13.2°-16.13°, respectively. Stride length increased proportionally to speed in males and females. The reliability of the inertial sensor according to tilt and gait symmetry showed good results, and the reliability levels were excellent for cadence parameters, stride length, stride time, obliquity, and pelvic rotation. The amplitude of pelvic tilt did not change at different speed levels between sexes. The range of pelvic obliquity increased in females at a medium speed level, and the pelvic rotation range increased during running, according to speed and sex. The inertial sensor has been proven to be a reliable tool for kinematic analysis during running.

A Scoping Review of Transgender Policies in the 15 Most Commonly Played UK Professional Sports

INTRODUCTION

There has been much debate recently on the participation of transgender and gender-diverse (TGD) athletes in sport, particularly in relation to fairness, safety and inclusion. The 2021 IOC Framework on Fairness, Inclusion and Non-discrimination acknowledges the central role that eligibility criteria play in ensuring fairness, particularly in the female category, and states that athletes should not be excluded solely on the basis of their TGD identity.

AIMS

To identify policies that address TGD athlete participation in the 15 major United Kingdom (UK) sporting organisations and to summarise the evidence for each of these policies.

METHODS

A scoping review of TGD policies from the 15 major UK sporting organisations.

RESULTS

Eleven of the governing bodies had publicly available TGD policies. Most of the sporting associations drew guidance from the official 2015 IOC Consensus Meeting on Sex Reassignment and Hyperandrogenism, particularly with regard to physiological testosterone levels. Many organisations referenced their policies as a guide for decision making but stated that they ultimately made case-by-case decisions on an athlete's eligibility. Relevant considerations not addressed in most policies included pre- versus post-pubertal athletes, justification for testosterone thresholds, the length of time out of competitive action (if any) for transitioning athletes, the irreversible advantage from male puberty (if any), the responsibility for and frequency of follow up for hormonal testing and the consequences for athletes outside set testosterone limits.

CONCLUSIONS

There is a lack of consensus among the top 15 UK sporting organizations relating to elite sport participation for TGD athletes. It would be useful for sport organizations to work together to develop greater standardization/consensus for TGD athlete policies, taking into consideration fairness, safety and inclusion in each sport.

The association between hip strength, physical function and dynamic balance in people with unilateral knee osteoarthritis: A cross-sectional study

BACKGROUND

In people with knee osteoarthritis, the association between multidirectional hip strength and physical function or balance is unknown.

OBJECTIVE

To determine the relationship between hip flexion, extension, abduction, adduction, external and internal rotation strength and (1) physical function and (2) dynamic balance.

DESIGN

Cross-sectional.

METHODS

Forty-seven participants (20 men and 27 women, age 66.2 ± 8.2 years) with unilateral knee osteoarthritis were included. Hip strength was assessed with hand-held dynamometry; physical function was assessed with the 40m fast-paced walk test (40mFPWT), 30-s chair-stand test (30sCST), and stair-climb test (SCT); and dynamic balance was assessed in 3 directions using the Star Excursion Balance Test. Multivariable linear regression analysis was used to determine the strength of relationships between measures.

RESULTS

Hip strength, in all directions except for internal rotation, was positively associated with better physical function (40mFPWT: R2 = 0.48 to 0.65; SCT: R2 = 0.5 to 0.54; 30sCST: R2 = 0.39 to 0.42), and dynamic balance (anterior: R2 = 0.33 to 0.45; posteromedial: R2 = 0.32 to 0.45; posterolateral: R2 = 0.27 to 0.35). Hip strength, after adjusting for knee extension strength, explained an additional 8%-12% (p < 0.05) and 5%-12% (p < 0.05) reach in the anterior and posteromedial directions of the Star Excursion Balance Test, respectively.

CONCLUSIONS

Hip strength in multiple directions is associated with measures of physical function and dynamic balance in people with unilateral knee osteoarthritis. Clinicians are encouraged to consider hip strength in multiple directions in the context of the patients' functional and/or balance goals when developing exercise programs for people with knee osteoarthritis.

Sex Difference in Lower-limb Electromyography and Kinematics when Using Resistance Bands during a Barbell Back Squat

The aim of this study was to compare the muscle activity of the gluteus medius (GMe), gluteus maximus (GMa), biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM) and erector spinae (ES) as well as medial knee displacement (MKD) while using varying stiffness resistance bands (red: 1.68 kg; black: 3.31 kg; gold: 6.44 kg) during a barbell back squat (BBS) among males and females. A total of 23 (females: 11) resistance trained people were recruited for this study. Muscle activity was measured using electromyography, and motion capture cameras tracked lower-limb kinematics and MKD. Three resistance bands were placed at the distal end of the femur while performing a BBS at their 85% repetition maximum (RM). Parametric and non-parametric statistical analyses were conducted with the alpha level of 0.05. The gold resistance band resulted in a smaller knee-width-index value (i.e., greater MKD) compared to other bands (p < 0.01). Males exhibited less MKD compared to females during the BBS for each resistance band (p = 0.04). Males produced greater VL activity when using the black and gold resistance bands during the BBS (p = 0.03). When using a gold resistance band, the GMe muscle activation was higher compared to other resistance bands (p < 0.01). VM muscle activity was reduced when using a gold resistance band compared to no band condition (p < 0.01). BF (p = 0.39) and ES (p = 0.88) muscle activity did not change when using different resistance bands. As a result, females may be at a biomechanical disadvantage when using resistance bands compared to males while performing the BBS hindering them from optimal performance.

Do Repeated Sprints Affect the Biceps Femoris Long Head Architecture in Football Players with and without an Injury History?-A Retrospective Study

The aim of this study was to compare the biceps femoris long head (BFlh) architecture between football players with (twelve) and without (twenty) history of BFlh injury before and after a repeated sprint task. Fascicle length (FL), pennation angle (PA) and muscle thickness (MT) were assessed at rest and in the active condition before and after the repeated sprint protocol. Athletes with previous BFlh injury showed shorter FL at rest (p = 0.014; η2p = 0.196) and active state (p < 0.001; η2p = 0.413), and greater PA at rest (p = 0.002; η2p = 0.307) and active state (p < 0.001; η2p = 0.368) before and after the task. Intra-individual comparisons showed that injured limbs have shorter FL at rest (p = 0.012; η2p = 0.519) and in the active state (p = 0.039; η2p = 0.332), and greater PA in passive (p < 0.001; η2p = 0.732) and active conditions (p = 0.018; η2p = 0.412), when compared with contralateral limbs. Injured players, at rest and in the active condition, display shorter BFlh FL and greater PA than contralateral and healthy controls after repeated sprints. Moreover, the BFlh of injured players presented a different architectural response to the protocol compared with the healthy controls.

Modifications to head-trunk coordination dynamics during running and sidestepping

The purpose of this study was to determine how the intrinsic head-trunk coordination dynamics that exist during forward running are modified during a dynamic sidestepping task. Fourteen athletes performed both forward running and sidestepping tasks. Head-trunk coordination and range of motion were assessed during the flight and stance phases in the transverse and sagittal planes. The sidestepping task resulted in greater in-phase head-trunk coordination during stance in the transverse plane (p < .001, ES = -1.71) and in reduced anti-phase coordination between head and trunk in the sagittal plane (p < .001, ES = 1.52). Statistical non-parametric mapping revealed that during sidestepping the sagittal plane coupling angle shifted away from anti-phase earlier during midstance. The sidestepping task resulted in greater transverse and sagittal plane head and trunk range of motion and greater vertical trunk centre of mass displacement. Sidestepping modified the intrinsic coordination dynamics that are present during forward running, with greater transverse plane head contributions and reductions in compensatory sagittal plane head motion, which may occur during the transition from weight acceptance to propulsion during the stance phase. These changes in the intrinsic coordination dynamics of the upper body during sidestepping tasks may impact visual perception and readiness compared to forward running during complex sports tasks.

Selected Spatiotemporal and Joint Angle Parameters in Normal Gait and Nordic Walking with Classical and Mechatronic Poles in Aspects of Sex Differences

Introduction

The aim of this study was to compare selected spatiotemporal parameters and changes in the range of motion in the joints of lower and upper limbs during normal gait and during Nordic walking performed with classical and mechatronic poles of females and males.

Methods

The study involved 19 physical education students (11 males and 8 females). The MyoMotion research motion analysis system was used to collect gait kinematic variables. The subject task was to cover a 100 m distance in a straight line with three types of gait: gait without poles, gait with classical poles, and gait with mechatronic poles at preferred velocity. Parameters were measured both on the right (RT) and on the left side (LT) of the body. The data was analyzed using two-way repeated measures ANOVA with the between-subject factor "sex." Friedman's test was used when necessary.

Results

The most significant differences in spatiotemporal parameters between males and females were revealed in gait with the classical and mechatronic pole (stance phase LT and RT, load response LT and RT, single support LT and RT, preswing LT and RT, swing phase LT and RT, double stance LT and RT, and step length LT), the least in gait without a pole (stance phase RT, load response LT, single support LT, preswing RT, and swing phase RT); whereas, the most significant differences in kinematic parameters were revealed in gait without poles (shoulder rotation RT, wrist radial-ulnar LT, hip flexion-extension LT and RT, knee flexion-extension LT and RT, ankle inversion-eversion LT, and ankle abduction-adduction LT and RT), the least in gait with mechatronic poles (knee flexion-extension LT and RT, ankle dorsiflexion-plantarflexion LT, ankle inversion-eversion LT, and ankle abduction-adduction LT and RT).

Conclusion

Statistical analysis revealed many differences in spatiotemporal and kinematic parameters in normal gait, as well as in gait with the classical and mechatronic poles, which allows the conclusion that the gait of females and males should be analyzed separately.

An Updated Model Does Not Reveal Sex Differences in Patellofemoral Joint Stress during Running

Background

Structure-specific loading may have implications in understanding the mechanisms of running related injury. As females demonstrate a prevalence of patellofemoral pain twice that of males, this may indicate differences in patellofemoral loads between males and females. Previous works investigating differences in patellofemoral joint stress have shown conflicting results, but the models employed have not used estimates of muscle forces or sex specific contact areas.

Hypothesis/Purpose

The aim of this study was to examine sex differences in patellofemoral joint stress using an updated model to include estimates of quadriceps muscle force and sex-specific patellofemoral contact area.

Study Design

Descriptive Laboratory Study.

Methods

Forty-five healthy recreational runners ran at a controlled speed down a 20-meter runway. Kinetic and kinematic data were utilized to estimate muscle forces using static optimization. Quadriceps muscle force was utilized with sex-specific patellofemoral joint contact area in a two-dimensional patellofemoral joint model to estimate patellofemoral joint stress. Multivariate tests were utilized to detect sex differences in patellofemoral loading and hip and knee kinematics.

Results

No differences were found between sexes in measures of patellofemoral loading or quadriceps force. Females displayed a reduced knee extension moment and greater hip adduction and internal rotation than males.

Conclusion

The inclusion of static optimization to estimate quadriceps muscle force and sex-specific contact area of the patellofemoral joint did not reveal sex differences in patellofemoral joint stress, but differences in non-sagittal plane hip motion were detected. Therefore, two-dimensional patellofemoral models may not fully characterize differences in patellofemoral joint stress between males and females. Three-dimensional patellofemoral models may be necessary to determine if sex differences in patellofemoral joint stress exist.

Level of Evidence

3b.

The Effect of Two Types of Foot Orthoses on the Knee Valgus Angle Within Single-Leg Landing: Implications for ACL Damage Hazard Decrease

Background: Non-contact anterior cruciate ligament (ACL) injuries commonly occur when athletes land in high risk positions such as knee valgus. The impact of foot orthoses during exercises that recreate a non-contact ACL harm system (i.e., landing) in any case will be obscured. Objectives: The purpose of the current study research was to evaluate the effect of two foot orthoses (semi-hard foot orthoses and hard foot orthoses) on knee valgus angle during single-leg drop landing. Methods: Twenty male leisure volleyball gamers performed landing in one-leg step from 30 cm height in 3 conditions (without foot orthoses, mid-hard foot orthoses, and hard foot orthoses). A motion capture system was used to measure lower extremity kinematics. Two risk factors of ACL injury, maximum knee valgus angle (KVA), and maximum knee flexion was measured. ANOVA was used for statistical analysis (P < 0.05). Results: With mid-hard foot, orthoses provide the maximum level of knee flexion and the minimum level of knee valgus during single-leg drop landing. Conclusions: It may be concluded showed that foot orthoses affect knee kinematics. More knee flexion and less knee valgus brought about by mid-hard foot orthoses can reduce injuries of the anterior cruciate ligament (ACL).

Identification of Gait and Personal Factors Associated with Shoe Abrasion Patterns

Shoe abrasion data can be used as major evidence to distinguish suspects, but their actual application in the field is limited due to a lack of associated empirical studies. This study analyzed the significant factors of shoe abrasion by identifying significant differences between gait, personal characteristics, and shoe abrasion patterns. Experiments were conducted on 291 Korean subjects, and data were analyzed using cluster analysis and cross-tabulation analysis with data collected to identify significant factors. As a result, overall, medial abrasion was very rare and would be useful for human identification. The greater the gait characteristics of the knee valgus, the greater the inner abrasion characteristics shown. In the case of knee varus, outer abrasion characteristics occurred more often. Additionally, in the double support phase while walking, the greater the tilt to the left or right, the more the outer parts of the shoes tend to wear out. Men have the characteristic of wearing out the outer side of their shoes more compared to women. Regarding human body dimensions, there were significant differences between the abrasion patterns of the shoes with some body dimensions. The results of this study could be used effectively in the identification of suspects using shoe abrasion patterns.

Sex-specific differences in biomechanics among runners: A systematic review with meta-analysis

Patellofemoral disorders are more common in female runners compared to their male counterparts. Differences in biomechanical characteristics between groups of runners could provide insight into the causes of higher rates of injury in female versus male runners, which would be useful to physical therapists and athletic trainers in development of individualized injury prevention programs. This review compares the differences in biomechanical characteristics between female and male runners. Electronic databases, including PubMed, Scopus, Web of Science, and Embase were searched in December 2021 for studies evaluating sex-specific differences in lower limb mechanics of healthy participants during running. Two independent reviewers determined the inclusion and quality of each research paper. Meta-analyses were used where possible. A total of 13 studies were selected. Means and standard deviations of reported data were retrieved from each selected paper for comparison of results. Three biomechanical variables, including dynamics, muscle activation, and kinematics, were compared between female and male runners. However, no differences were found in kinetic variables or muscle activation between groups due to insufficient data available from the selected studies. Meta-analyses of kinematic variables revealed that female runners exhibited significantly greater hip flexion angle, hip adduction angle, and hip internal rotation angle, but smaller knee flexion angle compared to male runners during running. We found significant differences in kinematic variables between female and male runners, which could influence the training advice of physical therapists and athletic trainers who work with runners, and inform the development of injury prevention programs.