The acute effects of different training loads of whole body vibration on flexibility and explosive strength of lower limbs in divers.

The purpose of this study was to examine the acute effects of different vibration loads (frequency and amplitude) of whole-body vibration (WBV) on flexibility and explosive strength of lower limbs in springboard divers. Eighteen male and female divers, aged 19 ± 2 years, volunteered to perform 3 different WBV protocols in the present study. To assess the vibration effect, flexibility and explosive strength of lower limbs were measured before (Pre), immediately after (Post 1) and 15 min after the end of vibration exposure (Post 15). Three protocols with different frequencies and amplitudes were used in the present study: a) low vibration frequency and amplitude (30 Hz/2 mm); b) high vibration frequency and amplitude (50 Hz/4 mm); c) a control protocol (no vibration). WBV protocols were performed on a Power Plate platform, whereas the no vibration divers performed the same protocol but with the vibration platform turned off. A two-way ANOVA 3 x 3 (protocol × time) with repeated measures on both factors was used. The level of significance was set at p < 0.05. Univariate analyses with simple contrasts across time were selected as post hoc tests. Intraclass coefficients (ICC) were used to assess the reliability across time. The results indicated that flexibility and explosive strength of lower limbs were significantly higher in both WBV protocols compared to the no vibration group (NVG). The greatest improvement in flexibility and explosive strength, which occurred immediately after vibration treatment, was maintained 15 min later in both WBV protocols, whereas NVG revealed a significant decrease 15 min later, in all examined strength parameters. In conclusion, a bout of WBV significantly increased flexibility and explosive strength in competitive divers compared with the NVG. Therefore, it is recommended to incorporate WBV as a method to increase flexibility and vertical jump height in sports where these parameters play an important role in the success outcome of these sports.

Acute effect of different stretching methods on flexibility and jumping performance in competitive artistic gymnasts.

AIM: The purpose of this study was to investigate the acute effects of 3 different warm up methods of stretching (static, proprioceptive neuromuscular facilitation, and stretching exercises on a Vibration platform) on flexibility and legs power-jumping performance in competitive artistic gymnasts. METHODS: Eighteen competitive artistic gymnasts were recruited to participate in this study. Subjects were exposed to each of 3 experimental stretching conditions: static stretching (SS), proprioceptive neuromuscular facilitation stretching (PNF), and stretching exercises on a Vibration platform (S+V). Flexibility assessed with sit and reach test (S & R) and jumping performance with squat jump (SJ) and counter movement jump (CMJ) and were measured before, immediately after and 15 min after the interventions. RESULTS: Significant differences were observed for flexibility after all stretching conditions for S+V (+1.1%), SS (+5.7%) and PNF (+6.8%) (P=0.000), which remained higher 15 min after interventions (S+V (1.1%), SS (5.3%) and PNF (5.5%), respectively (P=0.000). CONCLUSION: PNF stretching increased flexibility in competitive gymnasts, while S+V maintained jumping performance when both methods were used as part of a warm-up procedure.

Strength-power parameters as predictors of sprinting performance.

AIM: The purpose of this study was to determine the relationship between strength - power parameters and sprint performance and to predict sprint times from strength - power parameters. METHODS: Twenty-five male young sprinters participated in this study. Squat Jump(SJ), counter-movement jump (CMJ), drop jump height (DJH), repeated jump(RJ) and 100m sprint time from block start, including reaction time (RT) and times at 10m, 30m and 60m were measured. Reactive strength index (RSI), the difference between counter-movement and squat jump (CMJ-SJ) and the mean velocities of the intermediate sections 0-10m, 10-30m, 30-60m, 60-100 m (V0-10, V10-30, V30-60 and V60-100) were also calculated. RESULTS: The canonical correlation analysis with strength - power parameters as predictors and reaction time and mean velocities as dependent variables revealed two canonical variables that explained 89.6% of the total variance. The first canonical variable (R=0.840) explained the association between SJ, RJ, DJH, RSI and all mean velocities. The second canonical variable (R=0.707) had only one predictor, CMJ-SJ, and loaded only on RT. Stepwise multiple regression analysis confirmed that RT depends only on CMJ-SJ. V0-10 depends on both DJ and SJ, while V10-30 depends only on SJ. Finally, V30-60 and V60-100 are primarily dependent on RSI. Multiple regression analysis of the 100m sprint time revealed that 46.5% of the variability could be explained by the variability of the strength- power predictors. CONCLUSION: Performance at 100m sprint is strongly associated with strength-power parameters. The best predictor of the overall performance is probably SJ (or CMJ).