Publication

Effects of systemic versus local hypoxia on post-activation potentiation in elite field hockey players

Date
2023-11-20
Type
Conference Contribution - published
Keywords
Abstract
Introduction. Post-activation potentiation (PAP) is based on the idea that a maximum/near-maximum muscle contraction (called conditioning activity, CA) stimulates the body to produce even greater strength/power production in subsequent exercise. Traditionally, CA is plyometric exercise however, recently blood flow restriction and systemic hypoxia have also been used. It is thought hypoxia either from breathing hypoxic gas or from reduction in blood flow to the muscle in BFR may result in fatigue to oxidative slow-twitch-fibres, thus triggering recruitment of fast-twitch-glycolytic-fibres and therefore improved muscular force and power. Since both plyometric exercise and systemic or local hypoxia may result in a PAP effect we wanted to investigate whether combining these stimuli would enhance PAP effect. Also, how long the PAP effect lasts is controversial so a secondary aim was to examine the change in PAP over time. Methods. Fourteen elite field hockey players (19.1±1.2years;75.4±9.3kg;177.2±7.4cm) (4females and 10males), voluntarily participated in this cross-over study and randomly applied each of 5 conditions. HYP:hypoxia, NORM:normoxia, BFR:blood flow restriction, PLCHYP:placebo for hypoxia, PLCBFR:placebo for BFR. The exercise program consisted of 1x5 drop-jumps (DJ), 1x5 countermovement-jumps and, 1x5 single-leg horizontal-jumps. Hypoxia was applied under normobaric conditions at SpO2of 87% with a face mask attached to a hypoxic generator. BFR was applied with a cuff positioned around the upper thigh with a pressure set to 50% of predicted individual arterial occlusion pressure. The placebo conditions were the same set-up but without hypoxia and with 15-20%cuff pressure. To test for the PAP effect we had subjects complete a DJ at baseline and at 3, 6, 9, 12, 15 and 18min after the CA exercise. Results. We found a significant interaction between time and condition on DJ height(p=0.029) and flight time(p=0.031). Jump height and flight time increased significantly at 18min (32.3±5.9cm;511.5±46.8ms) compared to 3min (29.5±4.2cm;489.6±34.2ms) and 6min (29.9±5.2cm;491.8±42.2ms) for HYP; at 18min (31.9±5.5cm;508.0±44.8ms) compared to 15min (30.5±5.2cm;496.8±42.6ms) for PLCBFR; and at 3min (31.9±4.9cm;508.6±39.2ms) compared to 12min (29.9±4.5cm;492.8±37.9ms) and 15min (29.8±5.8cm;490.6±48.3ms) for BFR(p<0.05). Conclusions. While the same plyometric protocol in normoxia conditions has no PAP effect, we found jump performance improvement after a CA, early with only BFR and late with systemic hypoxia and low-pressure-BFR. These are preliminary data, and we would require more testing on further subjects to substantiate these findings.
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