Journal of Human Kinetics最新文献

This case study aimed to explore neuromuscular strategies used by a cyclist to control the speed while riding downhill a mountain with a brakeless, fixed-gear bicycle. Accelerations of the pedals and electromyographic activity of four lower limb muscles were registered to determine muscle activation during two decelerating strategies. Eccentric cycling was mostly used to control the bicycle speed with short (536 ± 51 ms) and low-intensity contractions. Isometric pedaling cycles were more efficient for decelerations with long (1,092 ± 281 ms) and intensive contractions. Isometric muscle activation was 122, 31, 25 and 44% greater than eccentric for vastus lateralis, biceps femoris, gastrocnemius lateralis and tibialis anterior muscle, respectively. This study suggests specific activation patterns to help the practitioner for safety rides, but that could have implications for rehabilitation purposes.

The aim of this study was to explore how lower limb strength and push gait asymmetry affected performance of skeleton athletes. Isokinetic strength of the bilateral lower limb was measured in sixteen skeleton athletes. Kinematic and kinetic data were also collected during pushing. The asymmetry of lower limb strength and the push gait were measured using the symmetry angle. Asymmetry existed in the strength of the lower limbs and the push gait of skeleton athletes. The symmetry angle of peak torque of ankle dorsiflexion at 60°/s (r = -0.48, p = 0.06) and contact time (r = -0.48, p = 0.06) was moderately negatively correlated with mean push velocity, but the center of gravity height (r = 0.50, p = 0.05) and the hip joint angle (r = 0.54, p = 0.03) at the touchdown showed a moderate positive correlation with mean push velocity. The asymmetry of lower limb strength and the push gait in skeleton athletes is specialized. Reducing the difference in peak torque of dorsiflexion between both sides, as well as the disparity in contact time during the push phase, may be beneficial in enhancing push velocity.

Early detection of young talent and athlete development programs lack reliable and valid indicators that can predict future success. Therefore, the aim of the present study was to analyse the differences between selected and unselected athletes to define the determinant factors, as well as the influence of gender on the variables that could predict athletic success. The research was carried out using a cross-correlational descriptive design involving 95 athletes, of whom 46 were males (average age = 18.31 ± 2.31 years) and 49 were females (averaged age = 17.27 ± 1.44 years), and whose sociodemographic, psychological, physical and anthropometric variables were analysed. Significant differences were observed in maturity (p < 0.001), anthropometric variables related to bone structure, muscle mass, and body mass (p < 0.001 to 0.044), physical condition variations related to strength, power, sprint ability, flexibility, and balance (p < 0.001 to 0.013), as well as athletic experience and training variants (p = 0.003-0.004). These results should be taken into account for the sporting programming of young athletes and in order to be aware of the modulating effect of biological maturity and its influence on athletic performance.

The elastic band (EB) may be an alternative for restricting the blood flow compared to the Kaatsu and clinical cuffs (KA and CC, respectively). However, the impact of the EB, the KA, and the CC on the blood flow during exercise remains uncertain. This study examined the blood flow (BF), the diameter of the brachial artery (DA), and blood flow velocity (BFV) during elbow flexion exercises using the KA, the CC, and the EB. Twenty-six resistance-trained men (age: 30.7 ± 8.7 years, body mass: 80.7 ± 15.5 kg, body height: 175.7 ± 6.5 cm) completed four sets of 15 repetitions of unilateral elbow flexion exercise at 20% 1RM. All protocols were set to the same perceived tightness (PT) based on Kaatsu optimal pressure (KOP). The BF, BFV and the DA were assessed at baseline, at KOP, and during the exercise sets. The BF and BFV were significantly reduced from baseline to KOP when the KA (67%, ES: 1.4, p = 0.0002; 24%, ES: 1.9, p < 0.0001) and the CC (70%, ES: 1.7, p < 0.0001; 31%, ES: 1.6, p < 0.0001) were applied, yet not the EB (49%, ES: 1.1, p = 0.103; 17%, ES: 0.7, p = 0.123). The BF and BFV increased from KOP to the fourth exercise set in all protocols with the KA (409%, ES: 2.4, p < 0.0001; 37.5 %, ES: 1.7, p = 0.007), the CC (377%, ES: 2.0, p < 0.0001; 55%, ES: 1.3, p < 0.0001) and the EB (411%, ES: 2.9, p < 0.0001; 43%, ES: 1.3, p = 0.002), respectively, with no significant difference between them (p > 0.05). The DA remained unchanged after all protocols (p > 0.05). In conclusion, the EB showed similar blood flow behavior compared to pressure-controlled cuffs.

The main goal of this study was to evaluate the effects of different reperfusion duration following intra-conditioning blood flow restriction (BFR) on bar velocity during the bench press exercise and muscle viscoelastic properties of the triceps brachii. Eleven resistance trained males (age: 24.3 ± 4.9 years; body mass: 85.5 ± 13.2 kg; bench press 1RM: 123.6 ± 25.4 kg; training experience: 6.8 ± 5.1 years) volunteered for the study. During the experimental sessions participants performed 5 sets of 3 repetitions of the bench press exercise with a load of 60% 1RM under four different conditions: two BFR (80% AOP) and two control conditions. For the BFR conditions, cuffs were applied before each set for 4.5 min and released 30 or 60 s before the start of the set as reperfusion. Under the control conditions, BFR was not applied and the total duration of rest intervals amounted to 5 min and 5.5 min. Measurements of viscoelastic properties were conducted at baseline and immediately after completion of each set of the bench press exercise. The two-way ANOVA showed no significant condition × set interaction for mean and peak bar velocity (p = 0.93; p = 0.787; accordingly), and no main effect of condition for mean and peak bar velocity (p = 0.57; p = 0.417; accordingly). The Friedman's test showed no differences in oscillation frequency (p = 0.156), stiffness (p = 0.368), and the logarithmic decrement of tissue oscillation (p = 0.644). The results of this study indicate that BFR during rest intervals does not acutely influence mean and peak bar velocity, as well as mechanical properties of the triceps brachii regardless of the duration of reperfusion.

Futsal warm-ups are crucial pre-match routines designed to enhance players' readiness. However, non-starter players inevitably face longer periods of inactivity. This study aimed to investigate the effects of various post warm-up strategies on physical performance of non-starter players in futsal. Thirteen highly trained male futsal players participated in this study during the in-season period. All players performed three distinct post warm-up strategies over consecutive days: REST, dynamic stretching (DYS), and a combination of plyometrics with change of direction drills (PLY-COD). After performing a standard warm-up, players remained inactive for 10 min, mirroring the traditional time window leading up to the start of the match. Subsequently, post warm-up strategies were implemented. Testing included a countermovement-jump, a reactive strength index, 5- and 10-m sprints, and a 505 COD test. Players were tested 10 min after the conclusion of the warm-up and immediately after the post warm-up strategy. The PLY-COD strategy yielded positive effects across all variables. Running performance improved with small to moderate effect in both sprint (-2.2 ± 1.9%), (-1.6 ± 1.7%), and COD (-2.9 ± 3.5%) tests. Conversely, both DYS and REST strategies had a detrimental impact on running and jumping performances, with this impairment being more pronounced in running following REST strategy, particularly in the 10-m linear sprint (1.4 ± 1.7%). These results suggest that remaining inactive or exerting limited effort after a warm-up may be detrimental to physical performance of futsal non-starter players. On the other hand, PLY-COD drills could be effective strategies to maintain or even enhance physical performance following the warm-up.

Whole-body vibration (WBV), an intervention for enhancing athletes' exercise performance (muscle strength and power), is often used either as a supplement or an alternative to conventional training. The current systematic review and meta-analysis assessed the effects of WBV on exercise performance in athletes. PubMed, Embase, and Cochrane Library databases were searched for relevant randomized controlled trials published from database inception to April 2024. We analyzed three key components of exercise performance: muscle power (measured in terms of countermovement jump (CMJ) and squat jump (SJ) height), strength (measured in terms of isometric and concentric torque of the knee extensors and flexors), and aerobic cardiovascular endurance (measured in terms of maximal oxygen uptake (VO_2max)). This review included 18 randomized controlled trials. WBV significantly improved concentric torque of the knee extensors and flexors, with effect sizes of 8.86 (95% confidence interval: 6.00 to 11.72; I² = 0%; p < 0.00001) and 9.56 (95% confidence interval: 7.40 to 11.72; I² = 0%; p < 0.00001), respectively. However, no significant changes were noted in the indicators of muscle power or cardiovascular endurance. Overall, our findings suggest that WBV interventions can enhance lower-limb strength in athletes. However, the quality of the evidence was low. To provide effective evidence-based guidance for WBV, future studies should consider participants' characteristics as well as intervention frequency, intensity, and duration in their analysis.

The objectives of this study were to compare the external and internal loads of transition games (TGs) without the opposition and TGs with different types of the opposition, and to assess their impact on a series of speed and strength tests. The external and internal loads of 18 young professional players (age: 14.79 ± 0.18 years; body height: 171.9 ± 6.5 cm; body mass: 62.1 ± 7.5 kg) were monitored in three TGs: 1 vs. 0 (no opposition; striker vs. goalkeeper), 1 vs. 1_Front (defender between the goal and the striker), and 1 vs. 1_Behind (defender behind the striker). Peak velocity (PeakV), distance covered (DC) above 24.0 km•h^-1, 21.0-23.9 km•h^-1, 18.0-20.9 km•h^-1, 13.0-17.9 km•h^-1, accelerations and decelerations above 2.5 m•s^-2 and below -2.5 m•s^-2 as well as the rate of perceived exertion (RPE) were obtained. Before and after each TG, vertical jump performance and sprint ability were assessed. PeakV and DC ≥24 km•h^-1 differed among drills, showing superior outcomes in the 1 vs. 1_Behind format. DC 21-23.9 km•h^-1 showed significant differences among drills, with larger distances covered in the 1 vs. 0 format. The number of accelerations-decelerations was significantly different among drills. RPE response differed among drills, with larger values for 1 vs. 1_Behind and 1 vs. 1_Front formats. All post tests showed an effect on time response without significant group interaction. The 1 vs. 1_Behind and 1 vs. 0 formats induce higher values for high speed, sprint and accelerations than the 1 vs. 1_Front format, which shows better performance in decelerations.

This study aimed to compare the impact of varying weekly frequencies of jumping interval training (JIT) on aerobic and anaerobic fitness, as well as jumping abilities of youth female athletes specialized in aerobic gymnastics. A randomized controlled study design was conducted spanning 8-week duration, involving 69 youth female athletes (16.3 ± 1.2 years) specialized in aerobic gymnastics. Participants were allocated into two experimental groups: JITw1 (comprising individuals subjected to JIT once a week), and JITw2 (encompassing individuals undergoing JIT twice a week), alongside a control group. Prior to and post the intervention period, athletes underwent evaluations of their performance through the countermovement jump test (CMJ), a specialized anaerobic assessment personalized for aerobic gymnasts (SAGAT), and a 20-m multistage fitness test. A mixed ANOVA was conducted for statistical analysis. Significant time (baseline and post-intervention) x group (JITw1, JITw2 and control) interactions were found in the SAGAT (p < 0.001), the CMJ (p < 0.001) and the 20-m multistage fitness test (p < 0.001). Post-intervention analysis revealed significantly lower scores in the SAGAT for the control group compared to the JITw2 group (p = 0.003). Significantly higher scores were observed for the JITw2 group in the CMJ test compared to the control group (p = 0.001). Significantly lower scores in the 20-m multistage fitness test were found in the control group compared to the JITw2 and JITw1 groups (both p < 0.001). As conclusion, while additional JIT training once a week may suit for minimal effective training and positive adaptations, training twice a week is advisable when significant improvements are desired.

This study analyzed the transition of Brazilian volleyball athletes from youth national teams to adult national teams, and examined the relative age effect in the selection of athletes for youth categories and their transition to the adult category. In youth categories, 326 athletes participating in the U18 and U20 women's and U19 and U21 men's world championships between 2001 and 2021 were prospectively analyzed. In the adult category, a retrospective analysis was conducted on 55 athletes who participated in the Olympic Games or World Championships between 2004 and 2022. Our results showed that approximately 20% of athletes participating in youth categories advanced to the adult national team. However, around 80% of adult teams comprised athletes who were part of youth categories. An athlete who progressed through both youth categories was 35 times more likely to be selected to the adult national teams compared to an athlete who only participated in the U18/U19 youth team. In youth national teams, there was a higher call-up rate for athletes born earlier. Despite this, athletes born later were more likely to advance to the adult national team.