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The neural drive to the muscle is the primary determinant of the rate of force development (RFD) in the first 50 ms of a rapid contraction. It is still unproven if repetitive rapid contractions specifically impair the net neural drive to the muscles. To isolate the fatiguing effect of contraction rapidity, 17 male adult volunteers performed 100 burst‐like (i.e., brief force pulses) isometric contractions of the knee extensors. The response to electrically‐evoked single and octet femoral nerve stimulation was measured with high‐density surface electromyography (HD‐sEMG) from the vastus lateralis and medialis muscles. Root mean square (RMS) of each channel of HD‐sEMG was normalized to the corresponding M‐wave peak‐to‐peak amplitude, while muscle fiber conduction velocity (MFCV) was normalized to M‐wave conduction velocity to compensate for changes in sarcolemma properties. Voluntary RFD 0–50 ms decreased (d = −0.56, p < 0.001) while time to peak force (d = 0.90, p < 0.001) and time to RFDpeak increased (d = 0.56, p = 0.034). Relative RMS (d = −1.10, p = 0.006) and MFCV (d = −0.53, p = 0.007) also decreased in the first 50 ms of voluntary contractions. Evoked octet RFD 0–50 ms (d = 0.60, p = 0.020), M‐wave amplitude (d = 0.77, p = 0.009) and conduction velocity (d = 1.75, p < 0.001) all increased. Neural efficacy, i.e., voluntary/octet force ratio, largely decreased (d = −1.50, p < 0.001). We isolated the fatiguing impact of contraction rapidity and found that the decrement in RFD, particularly when calculated in the first 50 ms of muscle contraction, can mainly be explained by a decrease in the net neural drive. [ABSTRACT FROM AUTHOR]

Purpose: The primary aim of this study was to evaluate whether the internal (session rating of perceived exertion [sRPE] and Edwards heart-rate-based method) and external training load (jumps) affect the presession well-being perception on the day after (ie, +22 h), according to age and tactical position, in elite (ie, Serie A2) female volleyball training. Methods: Ten female elite volleyball players (age = 23 [4] y, height = 1.82 [0.04] m, body mass = 73.2 [4.9] kg) had their heart rate monitored during 13 team (115 individual) training sessions (duration: 101 [8] min). Mixed-effect models were applied to evaluate whether sRPE, Edwards method, and jumps were correlated (P ≤.05) to Hooper index factors (ie, perceived sleep quality/disorders, stress level, fatigue, and delayed-onset muscle soreness) in relation to age and tactical position (ie, hitters, central blockers, opposites, and setters). Results: The results showed a direct relationship between sRPE (P <.001) and presession well-being perception 22 hours apart, whereas the relationship was the inverse for Edwards method internal training load. Age, as well as the performed jumps, did not affect the well-being perception of the day after. Finally, central blockers experienced a higher delayed-onset muscle soreness than hitters (P =.003). Conclusions: Findings indicated that female volleyball players' internal training load influences the pretraining well-being status on the day after (+ 22 h). Therefore, coaches can benefit from this information to accurately implement periodization in a short-term perspective and to properly adopt recovery strategies in relation to the players' well-being status. [ABSTRACT FROM AUTHOR]

Purpose: The present study aimed to verify if practicing tackles during rugby union training sessions would affect the players' internal training load and acute strength loss. Method: A total of 9 male Italian Serie A rugby union players (age: 21 [2] y) were monitored by means of an integrated approach across 17 sessions, 6 with tackles (WT) and 11 with no tackles (NT). Edwards training load was quantified using heart-rate monitoring. Global positioning system devices were used to quantify the total distance and time at >20 W. Work-to-rest ratio was quantified by means of a video analysis. Before (PRE) and after (POST) the session, the players' well-being and rating of perceived exertion were measured, respectively. The countermovement jump and plyometric push-up jump tests were performed on a force plate to record the players' PRE--POST concentric peak force. Linear mixed models were applied to quantify the differences between WT and NT in terms of training load and PRE--POST force deltas, even controlling for other training factors. Results: The Edwards training load (estimated mean [EM]; standard error [SE]; WT: EM = 214, SE = 11.8; NT: EM = 194, SE = 11.1; P = .01) and session rating of perceived exertion (WT: EM = 379, SE = 21.9; NT: EM = 277, SE = 16.4; P < .001) were higher in WT than in NT. Conversely, no difference between the sessions emerged in the countermovement jump and plyometric push-up concentric peak force deltas. Conclusions: Although elite rugby union players' external and internal training load can be influenced by practicing tackles, upper- and lower-limb strength seem to not be affected. [ABSTRACT FROM AUTHOR]

Purpose: To quantify how many of the top 50 under-18 (U18) sprinters in the world managed to become top 50 ranked as adult competitors. The authors also described the career trajectory of athletes ranked in the top 50 during either U18 or senior category. Methods: A total of 4924 male and female athletes competing in sprint races and ranked in the International Association of Athletics Federations (now World Athletics) lists in any of the seasons between the 2000 and 2018 were included in the study. The athletes ranked in the top 50 positions of all-time lists during U18, senior, or both categories were analyzed. Results: Only 17% of the male and 21% of the female top 50 ranked U18 managed to become top 50 ranked senior athletes. The top 50 ranked senior athletes consistently produced yearly larger improvements during late adolescence and early adulthood compared with those who ranked in the top 50 at U18. Furthermore, top 50 ranked senior athletes reached their peak performance later compared with the top 50 ranked only in U18. Conclusions: This study confirms that early success in track and field is not a good predictor of success at senior level in sprinting events. The yearly performance improvements and their tracking provide the most suitable approach to identify athletes more likely to succeed as elite performers in adulthood. The authors hope that the results of this study can provide useful comparative data and reference criteria for talent-identification and -development programs. [ABSTRACT FROM AUTHOR]

The relative age effect (RAE) is a selection bias resulting from the interaction between the selected dates and birthdates. Nevertheless, the impact of birthdate on the junior-to-senior transition in international track and field is unclear. This study aimed to quantify the RAE's magnitude and test if birthdate affects the junior-to-senior transition rate. The birthdate and performances of 5,766 sprinters (female: 51.0%) and 5,863 jumpers (female: 45.9%) were collected. Elite athletes (operationally defined as the World's all-time Top 200, 100 and 50 athletes) were identified according to Under 18 and Senior categories. Skewed quartile distributions were observed in the Under 18 (effect size ranged = 0.15–0.10) but not in the Senior category. RAE magnitude increased according to performance level (i.e., from Top 200 to Top 50) and was higher in males than females. Relatively younger athletes showed significantly higher transition rates with a higher chance of maintaining top level in the senior category (odds ratio (OR) ~ 1.64). The probability of maintaining success was lower for sprinters than jumpers (OR ~ 0.70), influenced by decade of birth and continental place but similar for male and female athletes. Data corroborate that relatively younger athletes are disadvantaged in the junior category but advantaged when transitioning to the senior category. [ABSTRACT FROM AUTHOR]

The purpose of this study is not only to establish whether the relative age effect (RAE) exists in male international rugby union players, but also to investigate the impact of sociocultural influences (i.e., northern and southern hemispheres) and playing position (i.e., backs, forwards, and scrum-halves). The birth date and the playing position of 7144 senior male professional rugby players included in the rosters of the season 2020–2021 were collected from the top 10 nations of the World Rugby rankings (i.e., Argentina, Australia, England, France, Ireland, Japan, New Zealand, Scotland, South Africa, and Wales). Data were analyzed using a chi-square goodness-of-fit test to compare the observed and expected birth quarter (Q) distributions. Results showed that relatively older players were overrepresented in all the sample (p < 0.001; Q1 = 28.8% vs. Q4 = 20.3%). In players competing in both hemispheres, the RAE was weak despite a more pronounced RAE emerging for southern players. In addition, the RAE was present in backs and forwards, but inconsistent for scrum-halves. In general, the data suggest that relatively older players may be more likely to reach expertise at senior levels than their later-born peers, and that the effect was consistent in different sociocultural contexts as well as in backs and forwards. [ABSTRACT FROM AUTHOR]

Functional aging processes are characterized by a loss of performance capabilities for most physiological systems, such as aerobic endurance and lower body strength, which are important for independent living and active aging. The present study examines the direction of influence between aerobic endurance and lower body strength over time in Italian sedentary older adults. A three-wave longitudinal model was tested using cross-lagged analysis for 202 individuals aged over 65 years (mean = 73.92, SD = 5.84; 140 females). Analysis revealed that aerobic endurance and lower body strength decline over time. In addition, greater aerobic endurance positively affected lower body strength over time; however, the converse was true only during the first period (first 6 months). These findings emphasize the importance of these relationships for the design and implementation of effective physical intervention for older adults. [ABSTRACT FROM AUTHOR]

This study aimed (a) to estimate the transition rate for top 50 ranked track and field jumpers, (b) to compare the performance progression of top 50 ranked senior jumpers (top50 senior) to those who failed to be top 50 ranked in the senior category despite being top 50 ranked in the under 18 category (only U18), and (c) to verify whether relative age effect may at least partially explain the differences in the two above‐mentioned subgroups. The career performance trajectories of 5981 athletes (2837 females) competing in jump events from 2000 to 2019 were extracted from the World Athletics database. The all‐time top 50 ranked athletes for each age from 16 years to senior category were identified. Performance progression characteristics were compared using linear mixed‐effects model. Only 8% of males and 16% of females top 50 ranked at the age of 16 years managed to be included among the top50 senior. Only U18subgroup made the first appearance in the database (at 15‐16 years) and reached the peak performance (at 20 years) earlier than top50 senior (17‐18 and 26‐27 years, respectively). The relative age effect was largely present in Only U18 but not in top50 senior subgroups. Most of the early‐successful U18 world‐class jumpers did not manage to maintain the same level of competitiveness in adulthood since they experienced a plateau in performance from 20 years of age. Conversely, top 50 ranked senior jumpers continued to produce consistent performance improvement up to 26‐27 years of age. [ABSTRACT FROM AUTHOR]

Objectives Dual-task (DT) performance is common to most activities of daily living and difficulties in DT activities may reduce quality of life in older adults. This study investigated the effect of DT training in a sample of older adults. Methods Sixty older adults (mean = 74.4 ± 3.1 years) participated in the study. Twenty-two older adults were included in the control (CG), 19 in the single-task (ST) training and 19 in DT training group. ST group received balance and walking training twice a week for16 weeks, while DT training group performed the same training with additional motor tasks. Data were gathered on 6 m timed walk (6MTW), timed up and go test (TUG) and four square step test (FSST). DT conditions required participants to complete 6MTW, TUG and FSST, either (i) while carrying a glass of water or (ii) while carrying a ball on a round tray. Results A significant Group x Time interaction was found in TUG ( F [2,57] = 29.5; p < 0.01; partial η 2 = 0.51) and in FSST (F [2,57] = 23.2; p < 0.01; partial η 2 = 0.44). After intervention DT showed better scores in overall TUG (mean difference = 1.21 s [95% CI, 0.82–1.60]; p < 0.05) and FSST (mean difference = 2.51 s [95% CI, 1.67–3.35]; p < 0.01), whereas CG and ST did not exhibit significant changes. Conclusion Our results suggested that 16 weeks of motor DT training, using motor additional tasks as manipulation of common objects of everyday life, could improve mobility in older age. [ABSTRACT FROM AUTHOR]