349 research outputs found
Relative Age Effect is Modulated by Playing Position but is Not Related to Competitive Success in Elite Under-19 Handball Athletes
No full textThis study aimed to verify the occurrence of the relative age effect (RAE) in male elite young handball athletes according to the playing position and its association with team performance in a World Championship. Data from 383 handball athletes from 24 countries who participated in the 7th World Men’s Championship in the under-19 category were analyzed. RAE was investigated from the birth trimester of the athletes, their playing position, and final ranking in the Championship. The results showed an overrepresentation of athletes born in the first two trimesters (Q1 and Q2) (χ2(3) = 32.97; p < 0.001, ω = 0.29). The analysis of the athlete’s position showed that most wings (χ2(3) = 18.37; p < 0.001, ω = 0.32) and backs (χ2(3) = 12.51; p = 0.006, ω = 0.34) were born in the first trimesters (Q1 and Q2). The ranking in the Championship presented no significant association with the date of the birth (p > 0.05). The results showed the existence of the RAE in youth handball elite athletes, especially for the back and wing positions. However, the strategy of selecting is questionable once the presence of RAE was not associated with competitive success
Performing Repetitions to Failure in Lower-Limb Single-Joint Exercise Does Not Reduce Countermovement Jump Performance in Trained Male Adults
No full textPerforming repetitions to failure (RF) is a strategy that might acutely reduce neuromuscular performance, as well as increase the rating of perceived exertion (RPE) and the internal training load (ITL) during and after a resistance training (RT) session. Thus, this study aimed to analyze the acute effects of RF or repetitions not to failure (RNF) on countermovement jump (CMJ) performance and the ITL in trained male adults. Eleven men performed two experimental protocols in randomized order (RF vs. RNF). Under the RF condition, participants performed three sets of the leg extension exercise using 100% of the 10RM load and rest intervals of 180-s between sets. Under the RNF condition, participants were submitted to six sets of five repetitions with the same intensity and an 80-s rest interval between sets in the same exercise. The CMJ test was analyzed before and following (15-s and 30-min, respectively) each experimental session. The ITL was evaluated by multiplying the RPE and the total session time, 30-min after the protocol. No main effect or interaction time vs. condition was found for CMJ performance (p > 0.05). In contrast, the ITL showed higher values under the RF condition (p = 0.003). Therefore, even though RF-induced a greater ITL, our results suggest that adopting this strategy in one single-joint exercise for the lower limbs does not seem sufficient to reduce CMJ height
Does Social Media Use on Smartphones Influence Endurance, Power, and Swimming Performance in High-Level Swimmers?
No full textObjective: This study aimed to investigate the repeated effect of social media on smartphones immediately before training sessions on inhibitory control (Stroop task), endurance (tethered swimming), countermovement jump (CMJ), and swimming performance (50, 100, and 400-m freestyle) in high-level female swimmers.Methods: It is a randomized and experimental investigation with parallel groups. Twenty-two participants underwent the eight weeks of the experiment. The swimmers (eight to twelve sessions per week with 15.9 +/- 1.6 hours/week, and training experience of similar to 5.6 years) were randomized in two groups: control (CON,n= 11) and smartphone (SMA,n= 11). Immediately before each training session, the CON group watched videos about Olympic Games for 30-min. The SMA group used social network smartphone apps during 30-min. The inhibitory control, endurance, CMJ, and swimming performance were measured before and after the eight weeks of intervention.Results: No group x time interaction for 50-m freestyle (F-(4,F- 18) = 1.04;p= .33;eta(2) = 0.09) and CMJ performance (F-(4,F- 18) = 0.31;p= .58;eta(2) = 0.03) was found. Both experimental groups improved CMJ (F-(2,F- 20) = 8.71;p= .01;eta(2) = 0.46). Only the CON group improved the 100-m (p= .02), 400-m freestyle (p= .01), and endurance performance (p= .01). The CON group improved the inhibitory control response (p= .01).Conclusion: It is concluded that the repeated effect of social media on smartphones immediately before swimming training sessions might reduce or nullify training gains on swimming and endurance performance
Prolonged cognitive effort impairs inhibitory control and causes significant mental fatigue after an endurance session with an auditive distractor in professional soccer players
No full textBackground
Throughout official soccer matches, the presence of cheer by the crowd could be considered a critical auditive distraction that could further impair the cognitive interference control system, multiple object tracking (MOT) skill, heart rate variability (HRV), and increase mental fatigue. As the resource is not immediately replenished, the impairment of the cognitive interference control system may be delayed following a soccer game. Then, evaluating the recovery time course of the cognitive interference control system, MOT skill, HRV, and mental fatigue after prolonged tasks combining physical, endurance, and cognitive effort are essential.
Purpose
We aimed to analyze the acute effect of cognitive effort and auditive distractor with 24-h follow-up throughout a prolonged endurance session on inhibitory control, subjective mental fatigue, MOT skill, and HRV in professional soccer players.
Methods
Twenty professional male soccer players were recruited (23.56 ± 3.8 years, 78.1 ± 6.9 kg, 1.77 ± 0.06 m, and 12.5 ± 5.3% body fat). The sessions were performed in a randomized and counterbalanced crossover design, divided into four experimental conditions: endurance, endurance + MOT, endurance + MOT + AD, and endurance + AD. The soccer players completed the incongruent Stroop task utilizing an eye-tracker to assess cognitive effort. MOT task, subjective mental fatigue, and HRV were evaluated before the endurance training (60%Δ of maximal aerobic velocity during 40-min) and after 30-min and 24-h of recovery. These sessions were designed to investigate the acute effect of prolonged cognitive effort (repeated MOT throughout the endurance task) and AD (constant crowd noise and coach's voice each 15–40 s, totalizing = 80 voices) on inhibitory control, MOT skills, HRV, and subjective mental fatigue after a fixed endurance training session.
Results
There was no condition × time interaction for accuracy of inhibitory control (p > 0.05, ηp2 = 0.001). There was a significant condition × time interaction for inhibitory control response time (p < 0.05, ηp2 = 0.16). A higher response time of inhibitory control was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was a significant condition × time interaction for subjective mental fatigue (p < 0.05, ηp2 = 0.46). A higher subjective mental fatigue was found for the endurance + MOT + AD and endurance + MOT experimental sessions (p < 0.05). There was no condition × time interaction for HRV (p > 0.05, ηp2 = 0.02).
Conclusion
We concluded that cognitive effort throughout a prolonged endurance session impaired inhibitory control and increased mental fatigue without promoting greater MOT skill and HRV changes in professional soccer players
Repeated stroboscopic vision training improves anticipation skill without changing perceptual-cognitive skills in soccer players
No full textIn this study we aimed to analyze the repeated effect of stroboscopic vision training on perceptual-cognitive skills in soccer players. A total of 28 male soccer players participated in this experimental and randomized study with parallel groups. The soccer players were pair-matched according to perceptual-cognitive skills and randomized into two groups: Stroboscopic vision training and Control. Multiple object tracking, anticipation, and decision-making skills were measured before and after the 8-week intervention. An increase in multiple object tracking (p < 0.05) and decision-making skills (p < 0.05) from baseline to post-experiment was found in both groups without main group effect (p > 0.05). The findings showed an increase in anticipation skill from baseline to post-experiment in both groups (p < 0.05), with higher anticipation skill for the stroboscopic group than in the control group post-experiment (p < 0.05). Thus, we conclude that repeated stroboscopic vision training could improve anticipation skill in soccer athletes
Smartphone Use Among High Level Swimmers Is Associated With Mental Fatigue and Slower 100- and 200- but Not 50-Meter Freestyle Racing
No full textDiscovering any performance degradation effect of racing swimmers' use of social media smartphone apps might lead to new training and race preparation protocols, including pre-meet smartphone avoidance. This study's objective was to analyze the performance effects of using smartphone social media apps on the 50, 100, and 200-m freestyle among 25 high-level swimmers. Each participant performed the three race distances in two conditions: with smartphone app exposure (50-MF, 100-MF, and 200-MF) and without (50-CON, 100-CON, and 200-CON). We randomized the order of these two conditions across participants. While smartphone app use was not associated with statistically significant performance differences on the shortest race (50CON versus 50MF), a repeated measures ANOVA showed a significant condition x time interaction for the swimmers'100-m freestyle performance (p = 0.01), with a significantly slower performance following smartphone app use evident in the last half of this race (p = 0.02) but not in the first half (p = 0.41). We also found a condition x time interaction in the same direction (slower for swimmers who used the smartphone app) for the 200-m freestyle performance (p = 0.01), with the slower performance occurring in the second (p = 0.01) but not the first (p = 0.91), third (p = 0.07) or fourth (p = 0.06)quarters of this race. Thus, prolonged smartphone social media app use was associated with reduced performance from elite swimmers on the 100- and 200- but not the 50-m freestyle
Acute effects of equated volume-load resistance training leading to muscular failure versus non-failure on neuromuscular performance
No full textBackground/objective: The aim of this study was to compare the acute effects of resistance training to failure (TF) and non-failure (TNF) with volume-load equalization on neuromuscular performance in recreationally resistance-trained adults. Methods: Twenty-two trained men (age 21.4 +/- 2.3 years) were included in a controlled, randomized, and design cross-over investigation with two experimental conditions and one-week of washout interval between them. The participants performed parallel back-squat adopting TF or TNF with volume, in- tensity, and rest between sets equalized. Countermovement jump (CMJ) height and peak power (PP) were used as mechanical indicators of neuromuscular performance. The mechanical variables were assessed in five moments (pre-experiment, post 15-s, 10-min, 20-min, and 30-min). Results: When compared with the TNF condition, TF presented greater decrement on CMJ height (P < 0.001) and PP (P 0.001) performance. The CMJ height and PP performance in parallel back-squat exercise following the TNF condition returned to the pre-experiment values 10-min after (P 0.05). On the other hand, the TF condition promoted greater decrement in CMJ and PP performance compared with the pre-experiment and TNF protocol even 20-30 min later (P < 0.05). Conclusion: These findings suggest that TF promotes greater acute impairment on neuromuscular per- formance even when volume-load is equalized
A discrete-time system with uncertainty information
No full textThis paper considers a discrete-time queueing system with uncertainty information, that is, an arriving customer may opt, with a certain probability, to be served under a Last Come First Served (LCFS) discipline or, with complementary probability, becomes a negative customer. The arrival of a negative customer to the system removes the customer that is currently being served, if any, and has no effect on the system if the server is free. The input stream of the arriving customers is described by means of
a Bernoulli process, and the service times are geometrically distributed. Breakdowns can occur, that is, the possibility of a server failure during the service time of a customer is considered, and the customer that was receiving its service in the moment of a failure of the server goes to the first place of the queue. The server has a general life time distribution, and the repair times are ruled by an arbitrary distribution. A thorough study of the model is carried out, and, using a generating function approach, the steady-state distributions of the
number of customers in the queue and in the system are obtained.We also give a necessary and sufficient condition for the stability of the system. Characteristics measures of the model are also given. Finally, some numerical examples to illustrate the effect of the parameters on several performances measures of the system are presented.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Effect of Dehydration on Passing Decision Making in Soccer Athletes
No full textIt seems that dehydration may impair decision-making performance in athletes. Purpose: This study aimed to investigate the influence of dehydration on passing decision-making performance in soccer players. Method: Participants were 40 male soccer players (M-age = 22.3 +/- 2.3years) who agreed to participate in the study and were randomly assigned to the following conditions: control (CON), dehydration (DEH), and euhydration (EUH). The players played in 2 games of 90min in duration (2 45-min halves) followed by 2 15-min halves (overtime) with and without proper hydration. The Game Performance Assessment Instrument (GPAI) was considered for the analysis of passing decision making. Results: The GPAI analysis indicated effective reduction in the decision-making index in the DEH condition compared with the EUH and CON conditions, F(2, 38)=31.4, p<.05, ES=0.8. Conclusions: In conclusion, dehydration may be considered a mediating factor in the passing decision-making performance of male soccer athletes
Acute Effects of Parallel Back Squat Performed in Different Set Configurations on Neuromuscular Performance
No full textWe compared the acute effects of parallel back squat performed from different resistance training configurations on neuromuscular performance. Twenty-eight young adults underwent 4 experimental conditions: inter-repetition rest, traditional, traditional to failure, and rest-pause in the parallel back squat in a randomized, counterbalanced, and cross-over design. The neuromuscular performance was assessed through peak torque of knee extensors and flexors at two angular velocities (90 and 120o/s) in three moments (before, post, and post-30 min). The peak torque of the knee extensors and flexors at 90 and 120o/s decreased immediately after training for traditional, traditional to failure, and rest-pause (-8.1% to -17.7%, P <0.001). A greater reduction in the extensor peak torque was found at 120o/s ( P <0.05) in the rest-pause (-17.7%) when compared to traditional (-10.8%). The peak torque returned to baseline values only at post-30 min for the traditional configuration for the knee flexion action at 120o/s. The peak torque remained similar for the muscular actions and angular velocities for the inter-repetition rest ( P >0.05). Our results suggest the inter-repetition rest configuration seems to be a more appropriate strategy for maintaining the lower limb neuromuscular performance after a resistance training session
- …
