Sports Biomechanics最新文献

Traditional sidestepping experiment often relies on simplified visual stimuli that lack ecological validity. This study aimed to develop a fully immersive, football-specific virtual reality (VR) system to examine knee biomechanics during sidestepping in response to realistic visual stimuli. Twelve male collegiate footballers performed unanticipated sidestepping in response to a virtual footballer avatar executing either non-deceptive (VF-ND) or deceptive (VF-D) dribbling. Despite similar approach velocity and stance time, participants exhibited greater knee flexion angles and abduction and internal rotation moments in VF-D trials. Secondary analyses compared the results with previously reported arrow-preplanned (A-PP) and arrow-unplanned (A-UP) trials from the same participants. Approaching velocity decreased, and stance time increased in the following order: A-PP, VF-ND, VF-D and A-UP. Knee flexion angles and abduction moments increased, while peak internal rotation moments decreased in the same order. These findings suggested that the VR-based approach imposed more realistic visuospatial and temporal constraints than traditional methods, enhancing ecological validity. As in real environment, players in VR can perceive subtle cues, distinguish deceptive from non-deceptive actions and adapt their movements accordingly. Practitioners should design their protocols to resemble real-world scenarios as closely as possible and interpret the biomechanical outcomes cautiously when comparing across different visual stimuli.

The goal of this study was to investigate whole-body kinematic adaptations when running on an unstable, irregular, and compliant surface in comparison to running on asphalt. We hypothesised that the gait pattern (H1) and its stride-to-stride variability (H2) would be affected by the unstable surface but that variability related to some movement features would be reduced over multiple testing days indicative of gait optimisation (H3). Fifteen runners ran on a woodchip and asphalt track on five testing days while their whole-body movements were captured using inertial motion capture and examined using joint angle and principal component analysis. Joint angles and stride-to-stride variability in eight principal running movements were subjected to surface by day analyses of variance. The woodchip track compared to asphalt resulted in (H1) a more crouched gait pattern including more leg flexion and forward trunk lean and (H2) higher stride-to-stride variability in most investigated principal running movements. However, (H3) stride-to-stride variability did not systematically change over testing days. Running on an unstable, irregular, and more compliant surface leads to the adoption a gait pattern and control strategy that are more robust against disturbances caused by the surface but may pose certain risks for overuse injury in trail runners.

Shortly after beginning the upward phase of a free-weight barbell back squat there is often a deacceleration phase (sticking region) that may lead to repetition failure. The cause for this region is not well understood. Therefore, this study investigated the effects of 90%, 100%, and 102% of 1-RM barbell loads on kinematics, kinetics, and myoelectric activity in back squats. Twelve resistance-trained healthy males (body mass: 83.5 ± 7.8 kg, age: 27.3 ± 3.8 years, height: 180.3 ± 6.7 cm) participated in the study and lifted 134 ± 17 kg at 90% and 149 ± 19 kg at 100%, while they failed at 153 ± 19 kg with 102% load. The main findings were that barbell displacement and barbell velocity in the sticking region decreased with increasing loads. Moreover, the external hip extensor moment increased with heavier loads, whereas the knee extension and ankle plantarflexion moments were similar during the concentric phase. Also, reduced hip and knee extension together with lower myoelectric activity for all hip extensors and vastus lateralis were found for the 102% load compared to the others. Our finding suggests that the increased external hip extensor moment together with lower hip extensor myoelectric activity due to a reduced hip extension and thereby are responsible for lifting failure among resistance-trained males.

Static measurements are clinically useful in characterising foot morphology, but it remains unclear to what extent it can influence dynamic lower limb performance. Therefore, the purpose of this study was to investigate if foot posture or foot morphology deformation relates to ankle plantarflexion isokinetic strength and specific kinetics variables during jumping using principal component analysis (PCA). Thirty-eight physically active participants performed drop vertical jump (DVJ) onto force platforms and ankle plantarflexion contractions in different modalities on an isokinetic dynamometer. Foot posture was assessed using the Foot Posture Index-6 item, whereas foot one-, two- and three-dimensional morphological deformation was calculated using the Arch Height Index Measurement System. A PCA was applied to the ankle plantarflexion and kinetics performance data and correlations between PCs and foot parameters measured. The analysis revealed 3 PCs within the ankle plantarflexion and DVJ kinetics variables that captured more than 80% of the variability within the data, but none of them showed significant correlations (r ≤ 0.27) with any foot variables. While foot posture and foot morphological deformation remain of interest in characterising foot morphology across individuals, these findings highlight the lack of clinical relevance of these static evaluations at characterising lower limb and ankle performance.

The modularisation of sports science curricula allows students to individualise degrees to fit their interests and aspirations via elective modules. The aim of this study was to explore the factors which influence sports science students' elective biomechanics enrolment decisions. A total of 45 students completed an online survey focussing on personal and academic characteristics which may influence enrolment decisions. Significant differences were found for three personal characteristics. Biomechanics module enrolees were more positive in their self-concept of subject ability, had a greater like for their previous subject experience, and displayed a higher agreement in requiring the knowledge for future career aspirations. Although, statistical power was reduced when respondents were categorised into demographic sub-groups, exploratory analysis highlighted self-concept of subject ability may differentiate female students' enrolment, while previous subject experience may distinguish male students' enrolment and academic entry route students' enrolment. Undergraduate sports science core biomechanics modules should consider adopting learning pedagogies which help to increase individual students' self-concept of ability and inspires them to recognise the value of biomechanics in their potential career aspirations.

Despite squatting being important in strength training and rehabilitation, few studies have investigated motor unit (MU) behaviour. This study explored the MU behaviour of vastus medialis (VM) and vastus lateralis (VL) during the concentric and eccentric phases of a squat exercise performed at two speeds. Twenty-two participants had surface dEMG sensors attached over VM and VL, and IMUs recorded thigh and shank angular velocities. Participants performed squats at 15 and 25 repetitions per minute in a randomised order, and EMG signals were decomposed into their MU action potential trains. A four factor (muscle × speed × contraction phase × sexes) mixed methods ANOVA revealed significant main effects for MU firing rates between speeds, between muscles and between sexes, but not contraction phases. Post hoc analysis showed significantly greater MU firing rates and amplitudes in VM. A significant interaction was seen between speed and the contraction phases. Further analysis revealed significantly greater firing rates during the concentric compared to the eccentric phases, and between speeds during the eccentric phase only. VM and VL respond differently during squatting depending on speed and contraction phase. These new insights in VM and VL MU behvaviour may be useful when designing training and rehabilitation protocols.

Peak tibial acceleration (PTA) is a widely used indicator of tibial bone loading. Indirect bone loading measures are of interest to reduce the risk of stress fractures during running. However, tibial compressive forces are caused by both internal muscle forces and external ground reaction forces. PTA might reflect forces from outside the body, but likely not the compressive force from muscles on the tibial bone. Hence, the strength of the relationship between PTA and maximum tibial compression forces in rearfoot-striking runners was investigated. Twelve runners ran on an instrumented treadmill while tibial acceleration was captured with accelerometers. Force plate and inertial measurement unit data were spatially aligned with a novel method based on the centre of pressure crossing a virtual toe marker. The correlation coefficient between maximum tibial compression forces and PTA was 0.04 ± 0.14 with a range of -0.15 to +0.28. This study showed a very weak and non-significant correlation between PTA and maximum tibial compression forces while running on a level treadmill at a single speed. Hence, PTA as an indicator for tibial bone loading should be reconsidered, as PTA does not provide a complete picture of both internal and external compressive forces on the tibial bone.  .

This paper summarises recent advancement in applications of machine learning in sports biomechanics to bridge the lab-to-field gap as presented in the Hans Gros Emerging Researcher Award lecture at the annual conference of the International Society of Biomechanics in Sports 2022. One major challenge in machine learning applications is the need for large, high-quality datasets. Currently, most datasets, which contain kinematic and kinetic information, were collected using traditional laboratory-based motion capture despite wearable inertial sensors or standard video cameras being the hardware capable of on-field analysis. For both technologies, no high-quality large-scale databases exist. A second challenge is the lack of guidelines on how to use machine learning in biomechanics, where mostly small datasets collected on a particular population are available. This paper will summarise methods to re-purpose motion capture data for machine learning applications towards on-field motion analysis and give an overview of current applications in an attempt to derive guidelines on the most appropriate algorithm to use, an appropriate dataset size, suitable input data to estimate motion kinematics or kinetics, and how much variability should be in the dataset. This information will allow research to progress towards bridging the lab-to-field gap.

Shoulder pain is common in team handball; however, many continue playing. The purpose was to investigate whether a functional fatigue protocol (FFP) containing repeated sub and maximal standing throws affects throwing performance, upper body kinematics, muscle peak activation (MPA) and whether the effect was different between the players playing with or with no pain. Thirty female elite handball players performed five maximal standing throws before and after the FFP. Throwing velocity, throwing kinematics, and MPA were measured before and after the FFP. An increased ball velocity (p = .02) was found, but only the total throwing time increased significantly in pain group (p = .05). Fatigue also resulted in a larger maximal pelvis (p = .03) and trunk rotation (p = .03) in addition to an increased shoulder flexion at ball release in both groups (p = .03), but only the maximal external (p = .03) and internal shoulder rotation (p = .05) increased in the pain group. Furthermore, fatigue also affected MPA in the latissimus dorsi (p = .02) and infraspinatus (p = .01). It was concluded that fatigue influenced throwing performance, kinematics, MPA and timing, which may increase the risk of developing non-traumatic shoulder injuries in team handball. The information may help to understand how fatigue influences throwing kinematics and MPA in players playing with pain.

We compared the effects of two 8-week concurrent strength and endurance trainings (CSETs) on running economy (RE) and running biomechanics, and we explored whether the effects on running biomechanics were mediated by responder status [high vs low responder based on -2.6% change in RE]. Thirty-one male recreational runners were randomly assigned to a standard endurance running training combined with either plyometric (CSET-PLY) or dynamic body-weight (CSET-DYN) training. RE and running biomechanics [contact (t_c) and flight (t_f) time, step frequency (SF), duty factor (DF), and leg stiffness (k_leg)] were measured pre- and post-intervention. RE significantly improved following CSET (RE = -2.1 ± 3.9%; p = 0.005) and no changes in t_c, DF, SF, and k_leg (p ≥ 0.10) but a shorter t_f (p ≥ 0.03) from pre- to post-intervention were seen. The prevalence of high responders was 42% (RE = -5.7 ± 2.4%). Among high responders, there were no changes in running biomechanics except participants following CSET-DYN who increased their SF (+3%). These results indicate that improvements in RE obtained through CSET-PLY and CSET-DYN involve minimal to no changes in running biomechanics and that there was not a training modality, which was better than the other. More detailed biomechanical assessments involving kinematics, kinetics, and electromyography could shed light on the underlying mechanisms of RE improvement.