Acute effects of plyometric warm-up with different box heights on sprint and agility performance in national-level field hockey athletes

BACKGROUND: Postactivation potentiation (PAP) is an acute and temporary enhancement of muscular performance resulting from previous muscular contraction. Extensive research exists examining the PAP effect after a heavy resistance exercise but there is limited research examining the PAP effect after a plyometric stimulus to the pre-competition practices (e.g., warm-up) of well-trained athletes. OBJECTIVE: The purpose of this study was to investigate the acute effects of plyometric warm-up with different box heights on sprint and agility performance in national-level field hockey athletes at recovery time of immediately, 5 minutes and 10 minutes. METHODS: In a randomized crossover design, ten male national-level field hockey athletes performed 30-m sprint (with 10-m split) and agility test at baseline, immediately (∼ 15 sec), 5 minutes and 10 minutes after a high-intensity plyometric warm-up (HIPW), a low-intensity plyometric warm-up (LIPW) and a control trial (CT). RESULTS: Mean 10-m sprint times, 30-m sprint times and agility times were similar between trials at baseline (p> 0.05). Significant trial x time interactions (p⩽ 0.05) were observed for 10-m sprint time, 30-m sprint time and agility time. 10-m sprint times were significantly decreased after HIPW at all time-points and LIPW at immediately time-point, relative to baseline (p⩽ 0.05). HIPW 10-m sprint times were faster at all time-points and LIPW sprint time was faster at 10 minutes when compared with CT (p⩽ 0.05). Thirty-meter sprint times were significantly decreased after HIPW and LIPW at all time-points, relative to baseline (p⩽ 0.05). HIPW 30-m sprint times at all time-points and LIPW at both the 5 and 10 minute time-points were faster than CT (p⩽ 0.05). Agility times were significantly decreased after HIPW at all time-points and LIPW at both the immediately and 5 minutes time-points, relative to baseline (p⩽ 0.05). HIPW and LIPW agility times were faster than CT, at all time-points (p⩽ 0.05). CONCLUSIONS: Both HIPW and LIPW may be effective in enhancing the pre-training or pre-competition practices in off-season for national-level field hockey athletes. However, the individualization of HIPW is highly recommended in order to maintain PAP effects for 10-m sprint times, 30-m sprint times and agility times throughout the 10 minutes when compared to LIPW.

Acute Effects of Resistance Exercise and the Use of GH or IGF-1 Hormones on Oxidative Stress and Antioxidant Markers in Bodybuilders

The aim of this study was to examine the influence of peptide hormone use on oxidative stress and antioxidant responses to a single session of resistance exercise in male bodybuilders. Forty-five male bodybuilders were divided into three groups: bodybuilders using growth hormone for at least 1 year (i.e., 3 to 4 times in the year) (GH-user, n = 15), bodybuilders using insulin-like growth factor-1 for at least 1 year (i.e., 3 to 4 times in the year) (IGF-1-user, n = 15), and peptide hormone-free bodybuilders (Non-user, n = 15). The heavy resistance exercise protocol consisted of five sets with 80% of one repetition maximum for six exercises. Blood samples were obtained pre and post heavy resistance exercise (HRE) in order to evaluate changes in oxidative stress (8-hydroxy-2-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and nitric oxide (NO)) and antioxidant biomarkers (glutathione peroxidase (GPx), catalase (CAT) and glutamate (GLU)) level. All the experimental groups showed increases in MDA (p = 0.038), NO (p = 0.028), GPx (p = 0.012), and GLU (p = 0.003) concentrations after resistance exercise. For 8-OHdG, the Non-user and IGF-1-user groups indicated increases at post-exercise (p = 0.001), without any significant changes in the GH-user group (p = 0.87). In addition, the changes in serum GPx and GLU levels were greater for the GH-user group than the Non-user and IGF-1-user groups (p = 0.001). In conclusion, HRE induced significant increases in 8-OHdG (except to GH-user group), MDA, NO, GPx, and GLU levels with greater changes in GPx and GLU for the GH-user group.

Effects of Post-Activation Potentiation induced by a plyometric protocol on deceleration performance

Post-Activation Potentiation is a phenomenon by which muscular performance characteristics are acutely enhanced as a result of their previous contractile actions. It has been shown how Post-Activation Potentiation, which is usually evoked through heavy resistance exercise, has the potential to improve many different power performances, such as sprinting and jumping. Due to an easier applicability, some studies explored the potential of plyometric muscular actions to evoke the effects of Post-Activation Potentiation. Despite some findings on acceleration running performance, to the authors’ best knowledge, no studies investigated the effects of Post-Activation Potentiation on deceleration performance, which is a key factor in sports involving change of directions. Therefore, the aim of this study is to investigate the influence of a plyometric exercise protocol to a subsequent deceleration running performance. University soccer players (n = 18) performed 7 deceleration trials: at baseline and after ∼ 15 seconds, 2, 4, 8, 12 and 16 minutes a walking control condition (C) or 3 sets of 10 repetitions of alternate-leg bounding (plyometric, P). Results show that no significant differences were found at any of the trials of the control condition (C) in comparison to the relative baseline. In the plyometric condition (P), the deceleration performance executed 2 minutes after the plyometric activity resulted significantly faster compared to the relative baseline (p = 0.042; ES = 0.86, large effect; % of improvement = 4.13 %). Therefore, the main findings of this study showed that a plyometric exercise has the potential to improve a subsequent running deceleration performance in soccer players, if an adequate recovery between these activities is provided to the players. These findings encourage further future investigations about the possible potentiating effects of plyometric activities on more complex actions like changes of direction and agility.