Isolated injury to the long head of biceps femoris is the most common type of acute hamstring strain injury (HSI). However, the precise hamstring injury mechanism (i.e., sprint-type) is still not well understood, and research is inconclusive as to which phase in the running cycle HSI risk is the greatest. Since detailed information relating to hamstring muscle function during sprint running cannot be obtained in vivo in humans, the findings of studies investigating HSI mechanisms are based on modeling that requires assumptions to be made based on extrapolations from anatomical and biomechanical investigations. As it is extremely difficult to account for all aspects of muscle-tendon tissues that influence function during high-intensity running actions, much of this complexity is not included in these models. Furthermore, the majority of analyses do not consider the influence of prior activity or muscular fatigue on kinematics, kinetics and muscle activation during sprinting. Yet, it has been shown that fatigue can lead to alterations in neuromuscular coordination patterns that could potentially increase injury risk. The present critical review will evaluate the current evidence on hamstring injury mechanism(s) during high-intensity running and discuss the interactions between fatigue and hamstring muscle activation and function.
The brain is a plastic entity that can undergo dynamic changes throughout the lifespan as a result of training. Attention-deficit/hyperactivity disorder (ADHD) is commonly treated with psychostimulant medication, and the prevalence of ADHD medication prescription is a topic of heated scientific debate. In addition, cognitive training is frequently provided to patients with ADHD. Although psychostimulant effects have been thoroughly investigated, no previous studies have assessed the neural effects of cognitive training in ADHD. We applied fMRI-paradigms of response inhibition and selective attention to chart the effects of a 10-day cognitive training program in 19 unmedicated ADHD children receiving either cognitive or control training. The two resulting longitudinal datasets were analyzed using whole-brain random-effects general linear models. Although we observed no increases of activity in the control group, both fMRI-datasets revealed enhanced activity after cognitive training in neural structures closely related to ADHD pathophysiology. On the inhibition paradigm, our results indicated increases in orbitofrontal, superior frontal, middle temporal, and inferior frontal cortex. The attentional task was characterized by increased activity in the cerebellum, which correlated with improvement on in-scanner measures of attention. Our findings provide preliminary evidence that cognitive training enhances activity in neural structures typically affected by the disorder. Similar results have been obtained following methylphenidate administration, suggesting that training of cognitive functions may mimic the effects of psychostimulant medication on the brain. These findings postulate a neural account for the potency of cognitive training in ADHD, and hold clinical implications, supporting the inclusion of training programs in standard ADHD-treatment.
The aim of the present study was to evaluate the consequence of implementing a Nordic Hamstring exercise (NHE) protocol during the first 15 to 17 weeks of the season to assess the effect on sprinting and NHE strength (NHEs) in professional football players. The study examined 50 healthy male professional football players (age 18.8±0.8yr; height 176.8±6.9cm; weight 71.3±5.7kg) belonging to 3 of the reserve squads of three Spanish La-Liga clubs divided in 2 intervention teams [Nordic-Group1 (NG-1) and Nordic-Group2 (NG-2, extensive experience in NHE)] and 1 team as a control-group (CG). NHEs and linear sprint (T5, T10, T20-m) were evaluated at the beginning of the season and at the end of an intervention period of conditioning and football training, supplemented with a NHE protocol (24 sessions for NG-1 and 22 sessions for NG-2) or without using the NHE at all (CG). Sprint times were substantially improved in all groups (ES from -2.24±0.75 to -0.60±0.37). NHEs was enhanced absolute and relative to body-mass only in NG-1 after the training period (ES from 0.84±0.32 to 0.74±0.26), while in the NG-2 there were only improvements in average NHEs relative to body-mass (ES = 0.39±0.36). The improvements in T20-m were substantially greater in NG-2 vs. NG-1, and there were no differences in sprint performance changes between NG-1 and CG. Changes in sprinting performance and NHEs were unrelated. NHEs was largely correlated with the body-mass of the players. Results indicate that the improvements in sprint are not dependent on the NHEs changes, with no relationships between NHEs and sprint performance, and between sprint changes and changes in NHEs.
Despite approval of the use of electronic performance-tracking systems (EPTSs) during competition by the International Football Association Board, other team-sport organizations and leagues have banned their use due to "safety concerns," with no evidence to support this assertion. The aim of the current brief report was to provide empirical evidence to support the widespread use of EPTSs across all sports by examining safety issues concerning their use in a multi-team-sport club. Five outdoor football teams (1st team, 2nd team, under 19 [U-19], under 18 [U-18], and 1st team female) and 3 indoor-sport (basketball, futsal, and handball) teams were monitored, accounting for a total of 63,734 h of training and 12,748 h of game time. A questionnaire was sent to all fitness coaches involved, and the clinical history was reviewed for every medical issue reported. Six minor chest contusions were recorded in female football goalkeepers wearing the frontal chest strap (3.17 episodes per 1000 training h). During training, 3 episodes of minor skin abrasion affecting the thoracic area due to wearing vests too tight were recorded in the U-19 football team (0.21 per 1000 h) and 2 episodes in U-18 (0.39 per 1000 h). It must be noted that none of these episodes resulted in lost days of training or games, and none required medical assistance. In conclusion, empirical evidence confirms that EPTSs are safe to use across team sports.
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