Central And Peripheral Mechanisms Of Fatigue Are Not Affected By Ischemic Preconditioning

PURPOSE: Ischemic preconditioning (IPC) may improve exercise performance by attenuating muscular fatigue. The purpose of this investigation was to examine the effects of IPC on indices of central and peripheral fatigue following exercise performed to volitional exhaustion. METHODS: Sixteen (21.5 ± 2.5 years; 170.9 ± 8.8 cm; 72.7 ± 14.5 kg) recreationally active males (n = 10) and females (n = 6) visited the laboratory on three separate occasions. Each participant randomly completed IPC at SHAM (20 mmHg), moderate (80% of total arterial occlusion pressure) and high pressures (220 mmHg). For IPC, a pneumatic cuff was placed most proximal on the dominant limb. Each IPC cycle consisted of the pressure being applied for five minutes followed by five minutes of rest. After completion of IPC, participants completed one-set to volitional failure of unilateral, isotonic leg extension muscle actions at 30% of their one-repetition maximum. To identify mechanisms of fatigue following volitional exhaustion, pre and post maximal voluntary isometric contractions (MVICs) with femoral nerve stimulation were performed to quantify central (superimposed twitch torque [STT]) and peripheral (potentiated twitch torque [PTT]) components of fatigue. Separate two-way, 3 (Condition [low, moderate, and high]) x 2 (Time [pretest, posttest]) repeated measures ANOVAs were performed to assess any mean differences. RESULTS: There was no significant (p = 0.199) interaction or main effects for Condition (p = 0.258) or Time (p = 0.265) for STT. For PTT, there was no significant (p = 0.758) interaction or main effect for Condition (p = 0.082). There was, however, a significant main effect of Time (p < 0.001). Specifically, PTT decreased from pretest (83.5 ± 29.3 Nm) to posttest (65.2 ± 23.9 Nm) (p < 0.001). CONCLUSIONS: Performing IPC prior to an acute bout of fatiguing exercise did not affect the mechanism (central versus peripheral) or magnitude of fatigue. It is possible that additional cycles of IPC are required and/or IPC acts upon mechanisms discrete from central and peripheral fatigue as assessed by femoral nerve stimulation.