The multi-stage 20-m shuttle run fitness test (20mMSFT) is a popular field test which is widely used to measure aerobic fitness by predicting maximum oxygen uptake (VO2 max) and performance. However, the velocity at which VO 2 max occurs (vVO 2 max) is a better indicator of performance than VO 2 max, and can be used to explain inter-individual differences in performance that VO 2 max cannot. It has been reported as a better predictor for running performance and it can be used to monitor athletes’ training for predicting optimal training intensity. This study investigated the validity and suitability of predicting VO2max and vVO2max of adult subjects on the basis of the performance of the 20mMST. Forty eight (25 male and 23 female) physical education students performed, in random order, a laboratory based continuous horizontal treadmill test to determine VO2max, vVO 2 max and a 20mMST, with an interval of 3 days between each test. The results revealed significant correlations between the number of shuttles in the 20mMSFT and directly determined VO 2 max (r = 0.87, p<0.05) and vVO 2 max (r = 0.93, p<0.05). The equation for prediction of VO 2 max was y = 0.0276x + 27.504, whereas for vVO 2 max it was y = 0.0937x + 6.890. It can be concluded that the 20mMSFT can accurately predict VO 2 max and vVO 2 max and this field test can provide useful information regarding aerobic fitness of adults. The predicted vVO 2 max can be used in monitoring athletes, especially in determining optimal training intensity.

The aim of this study was to investigate the acute effects of static (SS) and dynamic stretching (DS) on explosive power, flexibility, and sprinting ability of adolescent boys and girls and to report possible gender interactions. Forty-seven active adolescent boys and girls were randomly tested after SS and DS of 40 seconds on quadriceps, hamstrings, hip extensors, and plantar flexors; no stretching was performed at the control condition. Pretreatment and posttreatment tests examined the effects of stretching on 20-m sprint run (20 m), countermovement jump (CMJ) height, and sit and reach flexibility test. In terms of performance, SS hindered 20 m and CMJ in boys and girls by 2.5 and 6.3%, respectively. Dynamic stretching had no effect on 20 m in boys and girls but impaired CMJ by 2.2%. In terms of flexibility, both SS and DS improved performance with SS being more beneficial (12.1%) compared with DS (6.5%). No gender interaction was found. It can therefore be concluded that SS significantly negates sprinting performance and explosive power in adolescent boys and girls, whereas DS deteriorates explosive power and has no effect on sprinting performance. This diversity of effects denotes that the mode of stretching used in adolescent boys and girls should be task specific.

The main aim of this study was to identify significant relationships between selected anthropometric and kinematic variables and ball release speed. Nine collegiate fast-medium bowlers (mean - s : age 21.0 - 0.9 years, body mass 77.2 - 8.1 kg, height 1.83 - 0.1 m) were filmed and reconstructed three-dimensionally. Ball release speeds were measured by a previously validated Speedchek™ Personal Sports Radar (Tribar Industries, Canada). Relationships between selected anthropometric variablesand ball release speed and between kinematic variables and ball release speed were investigated using Pearson's product-moment correlation coefficients ( r ). A significant relationship was found between the horizontal velocity during the pre-delivery stride ( r = 0.728, P ≪ 0.05) and ball release speed (31.5 - 1.9 m·s -1 ). We believe that the high correlation was due to the bowlers using techniques that allowed them to contribute more of the horizontal velocity created during the run-up to ball release speed. We also found that the angular velocity (40.6 - 3.4 rad·s -1 ) of the right humerus had a low correlation ( r = 0.358, P > 0.05) with ball release speed. Although the action of the wrist was not analysed because of an inadequate frame rate, we found high correlations between ball release speed and shoulder-wrist length (661 - 31 mm; r = 0.626, P ≪ 0.05) and ball release speed and total arm length (860 - 36 mm; r = 0.583, P ≪ 0.05). We conclude that the variance in release speed within this group may be accounted for by the difference in radial length between the axis of rotation at the glenohumeral joint and the release point.

The aim of this study was to identify the kinematic and postural characteristics associated with sprint running on uphill and downhill slopes of 3° and on a horizontal surface. Eight male physical education students were filmed while sprinting maximally on an uphill-downhill platform under each of three conditions: (a) uphill at 3°, (b) downhill at 3° and (c) horizontal. Running speed, step rate, step length, step time, contact time, flight time and selected postural characteristics of the step cycle were analysed. Running speed was 9.2% faster ( P < 0.05) during downhill and 3.0% slower ( P < 0.05) during uphill compared with horizontal sprint running. During downhill and uphill sprint running, step length was the main contributor to the observed changes in running speed. It increased by 7.1% ( P < 0.05) for downhill sprint running and was associated with significant changes in posture at touchdown and take-off. During uphill sprint running, step length decreased by 5.2% ( P < 0.05), which was associated with significant changes in posture and reduced flight distance. Given the interaction between the acute changes in step length and posture when sprinting on a sloping surface, our findings suggest that such changes in posture may detract from the specificity of training on such surfaces. The chronic effects of training on such slopes on the kinematics and posture of horizontal sprint running are currently unclear.

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. 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. 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 (P0.05) in RG athletes. 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.

As the effect of performance level on sprinting mechanics has not been fully studied, we examined mechanical differences at maximal running speed (MRS) over a straight-line 35 m sprint amongst sprinters of different performance levels. Fifty male track and field sprinters, divided in Slow, Medium and Fast groups (MRS: 7.67 ± 0.27 m∙s⁻¹, 8.44 ± 0.22 m∙s⁻¹, and 9.37 ± 0.41 m∙s⁻¹, respectively) were tested. A high-speed camera (250 Hz) recorded a full stride in the sagittal plane at 30–35 m. MRS was higher (p < 0.05) in Fast vs. Medium (+11.0%) and Slow (+22.1%) as well as in Medium vs. Slow (+10.0%). Twelve, eight and seven out of 21 variables significantly distinguished Fast from Slow, Fast from Medium and Medium from Slow sprinters, respectively. Propulsive phase was significantly shorter in Fast vs. Medium (−17.5%) and Slow (−29.4%) as well as in Medium vs. Slow (−14.4%). Fast sprinters had significantly higher vertical and leg stiffness values than Medium (+44.1% and +18.1%, respectively) and Slow (+25.4% and +22.0%, respectively). MRS at 30–35 m increased with performance level during a 35-m sprint and was achieved through shorter contact time, longer step length, faster step rate, and higher vertical and leg stiffness.