Post Activation Potentiation and Concentric Contraction Performance: Effects on Rate of Torque Development, Neuromuscular Efficiency, and Tensile Properties.

Gago, P, Zoellner, A, Cezar, J, and Ekblom, MM. Post activation potentiation and concentric contraction performance: effects on rate of torque development, neuromuscular efficiency and tensile properties. J Strength Cond Res 34(6): 1600-1608, 2020-This study investigated how a 6-second maximal voluntary isometric contraction (MVIC) conditioning affected plantar flexor twitch rate of torque development (RTDTW), as well as peak torque (PTCC) and rate of torque development (RTDCC) of maximal voluntary concentric contractions (MVCC) performed at 60°·s. RTDCC and normalized triceps surae electromyography signals (EMGTS) were measured during different phases of contraction. In addition, muscle tendon unit passive stiffness index (SI) calculated from the torque-angle relation was measured after each MVCC. Enhancements were found in the RTDTW immediately (by 59.7%) and up to 480 seconds (by 6.0%) after MVIC (p < 0.05). RTDCC during the 100-200 ms, 50-200 ms, and 0-200 ms phases and PTCC were enhanced (by 5.7-9.5%) from 90 to 300 seconds after conditioning (p < 0.05). Neuromuscular efficiency increased (decreased EMGTS/RTDCC) in the 50-200 ms and 0-200 ms phases by 8.8-12.4%, from 90 to 480 seconds after MVIC (p < 0.05). No significant changes were found in the SI or in RTDCC during the 50-100 ms phase, suggesting that the enhancements reported reflect mainly contractile rather than neural or tensile mechanisms. PAP effects on PTCC and RTDCC were significant and more durable at a lower velocity than previously reported. Enhancement in RTDCC and neuromuscular efficiency were found to be more prominent in later phases (>100 ms) of the MVCC. This suggests that enhanced contractile properties, attained through MVIC, benefit concentric contraction performance.

Prevalence of sport specialisation and association with injury history in youth football.

OBJECTIVES: The aims of this study were to determine the prevalence of sport specialisation in youth football, and to investigate the associations of sport specialisation and volume of sport participation with injury history. DESIGN: Cross-sectional questionnaire. SETTING: New Zealand youth football teams. PARTICIPANTS: 414 youth football players aged 10-15 years. MAIN OUTCOME MEASURES: The level of specialisation, average weekly sport participation and free-play volume were recorded. 12-month injury history was captured and grouped by injury type. Associations between level of specialisation and demographic variables were analysed using chi square tests. Logistic regression was used to investigate associations between injury history, level of specialisation, and volume of participation. RESULTS: Participants were classified as high (43%), moderate (38%), or low (19%) specialised (n = 399 complete). High specialisation was more likely in boys, older participants, and those from large schools. Highly specialised participants were more likely to report a history of gradual onset injury than those who were low specialised (n = 340 with complete injury data). Odds of reporting a gradual onset injury also increased with greater weekly and annual sport participation volume. CONCLUSIONS: There is a high prevalence of sport specialisation in youth football, and it is associated with increased incidence of gradual onset injury.

The Importance of Fundamental Motor Skills in Identifying Differences in Performance Levels of U10 Soccer Players.

This study examined the differences in fundamental motor skills (FMSs) and specific conditioning capacities (SCCs) between a coach's classification of first team (FT) and second team (ST) U10 soccer players and examined the most important qualities based on how the coach differentiates them. The FT (n = 12; Mage = 9.72 ± 0.41) and ST (n = 11; Mage = 9.57 ± 0.41) soccer players were assessed using the Test of Gross Motor Development-2, standing long jump, sit and reach, diverse sprints, and the 20 m multistage fitness test (MSFT). The coach's subjective evaluation of players was obtained using a questionnaire. No significant differences existed between the FT and ST in any variables (p > 0.05). However, large and moderate effect sizes were present in favour of the FT group in locomotor skills (d = 0.82 (0.08, 1.51)), gross motor quotient (d = 0.73 (0.00, 1.41)), height (d = 0.61 (-0.12, 1.29)), MSFT (d = 0.58 (-0.14, 1.25)), and maximum oxygen uptake (VO2max) (d = 0.55 (-0.17, 1.22)). Furthermore, the coach perceived the FT group as having greater technical and tactical qualities relative to ST players. This suggests that it might be more relevant for players of this age to develop good FMS connected to technical skills, before focusing on SCC. Therefore, it might be beneficial for soccer coaches to emphasize the development of FMSs due to their potential to identify talented young soccer players and because they underpin the technical soccer skills that are required for future soccer success.