Abstract
PURPOSE: To compare the effect of ischemic preconditioning (IPC) and incremental warm-up (IW) before graded exercise test (GXT) on maximal oxygen consumption (VO2max), blood indicators of oxidative stress and activities of antioxidative enzymes. METHODS: Nineteen recreational endurance athletes (eleven males and eight females; age: 26.5 ± 5.1 yrs, height: 169.2 ± 8.9 cm, weight: 62.8 ± 11.3 kg) randomly undertook 3 separate episodes (IPC, IW and CON) and followed by GXT on a cycle ergometer with an interval of 3-5 days. IPC was performed in both upper thighs in turn for 3 cycles of 5-min arterial occlusion using a cuff inflated to 220 mmHg and 5-min relaxation in between. IW was composed of staged cycling at 50 W, 80 W, 110 W in 60 rpm with an interval of 5-min rest). CON only took a rest for 30 min. Repeated measures of ANOVA was used to analyze expiratory gas during GXT and blood parameters at each end of cycles/stages in IPC/ IW respectively. Statistical significance was set at p <.05. Data were presented as mean ± SEM. RESULTS: IPC significantly enhanced VO2max in GXT by 5.8% (p <.05) and 3.6% (p >.05) than levels of CON and IW, respectively. Time to exhaustion was highest in IPC than that in CON and GW, though no difference of peak power, respiratory quotient among trials. TBARS levels (5.23 ± 1.11 v.s. 3.72 ± 0.29 µM, p <.05) were increased and levels of glutathione peroxide (GPx) activity (58.46 ± 6.29 v.s 75.10 ± 7.57 KU/gHb, p <.05) and superoxide dismutase (SOD) activity (6653.30 ± 394.43 v.s. 7572.19 ± 479.54 U/gHb, p <.05) were reduced after IPC trial as compared to resting level. Immediately after GXT, similar changes were found in IPC and CON with significant higher levels of catalase (CAT) activity (358.49 ± 69.78, 322.12 ± 107.48 v.s. 169.93 ± 20.88 KU/gHb, p <.05), SOD activity (7534.98 ± 424.36, 7531.18 ± 456.08 v.s. 6456.90 ± 263.17 U/gHb, p <.05) and GPx (68.29 ± 6.58, 71.47 ± 6.77 v.s. 61.73 ± 6.54 KU/gHb, p <.05) than levels in IW and no difference of TBARS levels among trials. All blood parameters had no difference among trials at 60 min in recovery period. CONCLUSIONS: In contrast to incremental warm-up, repetitive ischemic preconditioning in legs prior to graded cycling may transiently induce oxidative stress, which can be attenuated in later exercise, and improve maximal oxygen consumption and time to exhaustion.
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