Purpose: Neuromuscular fatigue is considered to be important in the etiology of hamstring strain injuries in football. Fatigue is assumed to lead to decreases in hamstring contractile strength and changes in sprinting kinematics, which would increase hamstring strain injury risk. Therefore, the aim was to examine the effects of football-specific fatigue on hamstring maximal voluntary torque (MVT) and rate of torque development (RTD), in relation to alterations in sprinting kinematics. Methods: Ten amateur football players executed a 90-min running-based football match simulation. Before and after every 15 min of simulated play, MVT and RTD of the hamstrings were obtained in addition to the performance and lower body kinematics during a 20-m maximal sprint. Linear mixed models and repeated measurement correlations were used to assess changes over time and common within participant associations between hamstring contractile properties and peak knee extension during the final part of the swing phase, peak hip flexion, peak combined knee extension and hip flexion, and peak joint angular velocities, respectively. Results: Hamstring MVT and sprint performance were significantly reduced by 7.5% and 14.3% at the end of the football match simulation. Unexpectedly, there were no indications for reductions in RTD when MVT decrease was considered. Decreases in hamstring MVT were significantly correlated to decreases in peak knee angle (R = 0.342) and to increases in the peak combined angle (R = −0.251). Conclusions: During a football match simulation, maximal voluntary isometric hamstring torque declines. This decline is related to greater peak knee extension and peak combined angle during sprint running, which indicates a reduced capacity of the hamstrings to decelerate the lower leg during sprint running with fatigue.

Equations predicting age at peak height velocity (APHV) are often used to assess somatic maturity and to adjust training load accordingly. However, information on the intra-individual accuracy of A...

We investigated the effects of anxiety on the execution of police officers' arrest and self-defense skills. Police officers (n=13) performed three tasks in which they kicked, blocked, or restrained an opponent who attacked them with a rubber knife (low anxiety, LA) or a shock knife (high anxiety, HA) in a within-subject design. We analyzed performance (on a 5-point Likert scale), movement times, posture, and movement velocity and acceleration. Results revealed that performance was worse in the HA compared to the LA condition. Furthermore, analysis of full-body movement showed that under increased anxiety, police officers' performance contained characteristics of avoidance behavior, such as faster reactions (to reduce the time being exposed to the threat), leaning further backward (kick), and ducking down (block). In line with recent theoretical developments, it appears that under increased anxiety, police officers were less able to inhibit stimulus-driven processing (fear of getting hit) and enforce goal-directed processing (perform the skill as well as possible) leading to avoidance behavior and a decrease in performance.