The effect of four weeks of plyometric training on reactive strength index and leg stiffness is sport dependent.

BACKGROUND: Plyometric exercises are often used to develop lower limb strength and performance-related biomechanics such as leg stiffness. However, the effectiveness of plyometric training may depend on participants' own training and performance demands. The purpose of this study was to examine the effect of plyometric training on Reactive Strength Index (RSI) and leg stiffness (Kleg) on young athletes of different sports. METHODS: Forty eight female athletes (25 Taekwondo (TKD) and 23 rhythmic gymnastics (RG), mean±SD: age: 8.94±2.50 years; mass: 29.73±7.69 kg; height: 138.84±11.90 cm; training experience: 4.62±2.37 years) participated in this study. Participants were randomly assigned to experimental (PT, N.=24) and control (CG, N.=24) groups. The PT group followed a twice-weekly plyometric training program for 4 weeks. Plyometric drills lasted approximately 5-10 s, and at least 90 s rest was allowed after each set. To examine RSI, participants performed trials of five maximal CMJs. Submaximal hopping (20 hops) was performed in order to examine leg stiffness. RESULTS: Significant interaction effect was found for RSI and the post hoc analysis showed that RSI significantly increased by 35% (P=0.017) in RG athletes, whereas a significantly reduction by 28% (P=0.004) was revealed in TKD athletes. The interaction effect between time and group was statistically significant for Kleg (P<0.05) with Kleg significantly increasing by 31% (P=0.008) in TKD athletes, but remaining unchanged (P>0.05) in RG athletes. CONCLUSIONS: The results showed that the effect of a 4-week plyometric training program on RSI and leg stiffness is sport dependent. Further, the applied plyometric program was effective in reducing ground contact time and therefore increasing leg stiffness.

Effect of acupuncture in physiological parameters and endurance running performance.

BACKGROUND: Few studies have examined the effect of acupuncture (AC) treatment in aerobic capacity and endurance performance in healthy adults. Thus, the aim of the present study was to evaluate the effects of AC on selected physiological parameters and 3 km running performance. METHODS: Twenty-four healthy subjects with low to moderate aerobic capacity participated in the study and randomly assigned in two groups: AC group (ACG - N.=14) and control group (CG - N.=10). The subjects completed an incremental test to exhaustion and a 3 km race on a treadmill to evaluate their physiological responses and endurance running performance respectively, prior and after 4 weeks (8 sessions, twice a week) of acupuncture treatment. RESULTS: AC treatment had a significant main effect in T3km [F(1, 21)=7.173, P=0.014, partial η2=0.255], as well as in VT [F(1, 21)=8.476, P=0.008, partial η2=0.288] and HRmax@3km [F(1, 21)=4.930, P=0.038, partial η2=0.190], after controlling for the effect of the pre-test, while no other significant main effects were detected. CONCLUSIONS: Healthy physically active adults significantly improved their endurance running performance after 4 weeks of AC treatment. This is mainly due to the enhancement of the speed corresponding with VT, comparing with their baseline values.