Background: caffeine is an ergogenic aid that still needs to be investigated in women’s sports performance. Methods: Eight semi-professional women’s volleyball players (height = 1.63 ± 0.08 m; weight = 66.67 ± 4.74 kg) voluntarily participated in this study. A randomized crossover design was implemented where players underwent caffeine and placebo conditions. In the caffeine condition, participants consumed 5 mg/kg of caffeine based on their body weight before acute training. The evaluations were performed over two weeks of training. In both conditions, the countermovement jump, repeated jumps for 15 s, and handgrip tests were performed. The change of direction was assessed using the 505 test. Well-being was also assessed with a wellness questionnaire. A repeated measures ANOVA and correlation analysis were performed. Results: The repeated measures ANOVA revealed a main effect of supplementation (F (1.7) = 8.41, p = 0.02, η2 = 0.54) across the training week on physical performance. Additionally, there was a positive effect on perceived fatigue (F (1.7) = 7.29, p = 0.03, η2 = 0.51). Conclusions: Caffeine improved performance and fatigue parameters over one week of training. Further research is needed on women, focusing on physical performance and wellbeing, especially during intense periods.

Background: Caffeine is an ergogenic aid that still needs to be investigated in female sports per-formance. Methods: Eight semi-professional female volleyball (Heigth=1.63±0.08 m; Weigth= 66.67 ± 4,.74 kg) players voluntarily participated in this study. A randomised crossover design was carried out. Players went through the caffeine and placebo condition. In the caffeine condi-tion, participants consumed 5 mg/kg of caffeine. The evaluations were performed over two weeks of training. In both conditions, the countermovement jump test, repeated jumps for 15s and hand-grip were performed. Change of direction was assessed using the 505 test. Well-being was also assessed by a wellness questionnaire. A repeated measures Anova and correlation analysis were performed. Results: The repeated-measures ANOVA revealed a main effect of supplementation (F (1.7) = 8.41, p = 0.02, η2 = 0.54) across the training week on physical performance. Besides, there was a positive effect on perceived fatigue (F (1.7) = 7.29, p = 0.03, η2 = 0.51). Conclusions: Caf-feine improved performance and fatigue parameters over one week of training.

Running-induced fatigue affects several biomechanical parameters, and yet few studies are focused on the acceleration spikes’ asymmetries. This study aimed to evaluate the effects of a 30 min run on lower limbs spikes’ asymmetries. Eighteen recreational runners (35.6 ± 7.5 years; seven women) performed a treadmill running protocol at a moderate speed and acceleration spikes’ asymmetries and kinematic (temporal) parameters were measured via accelerometers—on the tibias and sacrum—and photogrammetry. Acceleration spikes’ parameters were continuously measured and averaged per minute to assess the relationship between fatigue and acceleration spike asymmetries via a linear regression model. Right tibial acceleration spikes increased over time (r = 0.9; p < 0.001) and left tibia spikes decreased (r = 0.78; p < 0.001), with a rise in tibial load asymmetry from 9% to 25% at the end (r = 0.98; p < 0.001). This study suggest that fatigue affects the acceleration spikes of the two legs differently, with increasingly greater acceleration spikes in the right (dominant) leg. These findings should be considered, as greater asymmetries are related to overuse injuries and lower efficiency. Also, in studies focusing on running mechanics with fatigue, it is recommended that researchers collect data from both limbs, and not only from the right (dominant) leg.

Running-induced fatigue affects several biomechanical parameters, yet few studies are focused on the acceleration spikes asymmetries. This study aims to evaluate the effects of a 30-minute run on lower limbs spikes’ asymmetries. Eighteen recreational runners per-formed the test at a moderate speed and acceleration spikes asymmetries and kinematic (temporal) parameters were measured via accelerometers -on tibias and sacrum- and 2D photogrammetry. Acceleration spikes parameters were continuously measured and aver-aged per minute to assess the relationship between fatigue and acceleration spike asym-metries via a linear regression model. Right tibial acceleration spikes increased over time (r = 0.9; p < 0.001) and left tibia spikes decreased (r = 0.78; p < 0.001), with a rise in tibial load asymmetry index from 9% at the start of the test to a 25% at the end (r = 0.98; P < 0.001). The study suggest that fatigue affects acceleration spike of both limbs differently, with increasingly greater acceleration spikes in the right-dominant leg. The findings should be considered, as greater asymmetries are related to overuse injuries and lower ef-ficiency. Also, in studies focusing on running mechanics with fatigue, it is recommended to collect data from both limbs, and not only from the right-dominant.