RESUMO
Most research concerning the effects of music on physical performance was conducted using endurance parameters. This study investigated the effects of relaxing (RLX) vs. self-selected stimulating music (SM) vs. no music (NM) on jump height (JH), jump power (PWR), and average rest period between jumps (RP) in 13 athletes (age: 25.5 ± 2.6 years). After a warm-up and listening to music (1 min) or NM, participants completed five squat jumps on a force plate. Psychological ratings of mood were assessed using a questionnaire before warm-up and after jumping. A one-way ANOVA was conducted to compare effects of music on JH, PWR, and RP. A Friedman test with Wilcoxon signed-rank test was used to detect changes in mood. There were no significant effects of music on JH (p = 0.162) and PWR (p = 0.162). A trend towards longer RP in RLX when compared to SM was detected (+2.72 s, +22%, p = 0.059, d = 0.35). Participants felt more "relaxed" (+3 ranks) and more "powerful" after listening to SM (+2 ranks). Following NM and RLX, athletes felt more "energetic" (each +3 ranks) but less energetic (-3 ranks) after SM. In conclusion, this study did not find any performance-enhancing effects of self-selected SM on jump performance. The influences of music on psychological ratings were inconclusive. For this reason, no evidence-based guidelines for the practical application of music in elite jumping athletes can be made, and more studies are warranted.
RESUMO
The Nordic Hamstring Exercise (NHE) is effective for selective hamstring strengthening to improve muscle balance between knee flexors and extensors. The purpose of this study (within subject design of repeated measures) was to determine the effects of a standardized 4-week NHE training on thigh strength and muscle balance with concomitant kinetic and kinematic monitoring. Sixteen male sprinters (22 years, 181 cm, 76 kg) performed a standardized 4-week NHE training consisting of three sessions per week (each 3×3 repetitions). Six rope-assisted and six unassisted sessions were performed targeting at a constant knee extension angular velocity of ~15°/s across a ~90-100° knee joint range of motion. Kinetic (peak and mean moment, impulse) and kinematic parameters (eg, ROM to downward acceleration, ROMDWA ) were recorded during selected sessions. Unilateral isokinetic tests of concentric and eccentric knee flexors and extensors quantified muscle group-, contraction mode-, and velocity-specific training adaptations. Peak moments and contractional work demonstrated strong interactions of time with muscle group, contraction modes, and angular velocities (η²>.150). NHE training increased eccentric hamstring strength by 6%-14% as well as thigh muscle balance with biggest adaptations at 150°/s 2 weeks after NHE training. Throughout the training period significant increases (P<.001) of peak (η²=.828) and mean moments (η²=.611) became apparent, whereas the impulse and the ROMDWA of unassisted NHE repetitions remained unchanged (P>.05). A 4-week NHE training significantly strengthened the hamstrings and improved muscle balance between knee flexors and extensors. Despite the slow training velocity, biggest adaptations emerged at the highest velocity 2 weeks after training ended.
