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  • Author: Andreas Zafeiridis x
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Fotini Arabatzi, Dimitrios Patikas, Andreas Zafeiridis, Konstantinos Giavroudis, Theodoros Kannas, Vassilios Gourgoulis and Christos M. Kotzamanidis

This study examined the post-activation potentiation (PAP) effects on squat jump (SJ) performance and on peak rate of force development (RFDpeak) in preadolescent (10–12 y), adolescents (14–15 y) and adults (20–25 y) males and females. All participants performed a SJ with and without prior conditioning stimulus (PAP and control protocol, respectively), consisting of 3 × 3-second maximal isometric squats. Jump height and RFDpeak of the vertical ground reaction force during SJ were assessed before, and at 20 seconds and at 4 minutes following the conditioning stimulus. The results revealed a different pattern of age-effect on SJ performance within males and females. The RFDpeak significantly increased as a factor of age in both males and females (P < .05). Increase in SJ performance after conditioning stimulus occurred only in men (P < .05), with no effects in teen-males, boys, and female groups. There was a significant PAP effect on RFDpeak in both adult groups (P < .05) and teen-males, with no effects in children. In conclusion, the PAP effects on SJ performance and RFDpeak are age- and sex-dependent; that is PAP appears as a viable method for acutely enhancing SJ performance in men but not in pediatric population.

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Vassilis Gerodimos, Andreas Zafeiridis, Stefanos Perkos, Konstantina Dipla, Vassiliki Manou and Spiros Kellis

This study examined from childhood to adulthood: (1) the effects of countermovement (use of stretch-shortening cycle-SSC) and arm-swing (AS) on vertical jumping (VJ) performance and (2) the ability to use the SSC and AS during VJ. Male basketball players (n = 106) were divided according to their age into: children (12.0 ± 0.23), young adolescents (14.5 ± 0.41), old adolescents (16.9 ± 0.27), and adults (21.9 ± 0.32). Each participant executed three maximal squat jumps (SJ), countermovement jumps without arms (CMJ) and with arms (CMJA). The contribution of SSC and AS was calculated by the augmentation (difference and percent change) in performance between CMJ and SJ, and CMJA and CMJ, respectively. CMJA performance was significantly (p < .05) higher than CMJ and SJ, and CMJ was higher than SJ within all age-groups. There were no significant differences (p > .05) among children, young and old adolescents, and adults in the percent contribution of SSC and AS to VJ performance. The variability in the contribution of SSC and AS to VJ performance was about twofold higher in children vs. adults. It appears that the ability to use the SSC and AS is not affected by the maturation process in males, trained in basketball.

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Vassilis Tsiaras, Andreas Zafeiridis, Konstantina Dipla, Kostas Patras, Anastasios Georgoulis and Spiros Kellis

The aims were to develop and validate a VO2peak prediction equation from a treadmill running test in active male adolescents. Eighty-eight athletes (12–18 yrs.) performed a maximal exercise test on a treadmill to assess the actual VO2peak and a 20m Shuttle-Run-Test (20mST). A step-wise linear regression analysis was used and the following equation for estimation of VO2peak (mL·kg−1·min−1) = 35.477 + 1.832 × duration in min - 0.010 × duration × body mass in kg was developed. The cross-validation statistics were: R = .54, CE = 0.1 mL·kg−1·min−1, SEE = 2.5 mL·kg−1·min−1 (4.6%), and TE = 2.6 mL·kg−1·min−1 (4.9%). The cross-validation values (CE, SEE, and TE) were lower compared with those of previously published equations in adolescents that estimated VO2peak using anthropometric data, performance in 20mST, and energy cost at submaximal speeds.