Ischemic Preconditioning Does Not Affect Neuromuscular Function During Fatiguing Exercise

PURPOSE: Ischemic preconditioning (IPC) applied at high pressures has been proposed to increase neuromuscular function by augmenting muscle excitation through the attenuation of central fatigue, but less is known regarding IPC applied at a moderate pressure. The purpose of this investigation was to examine the acute effects of three different IPC protocols on neuromuscular function during fatiguing exercise. METHODS: Eleven recreationally active (21.1 ± 1.9 years; 169.8 ± 6.7 cm; 73.3 ± 11.3 kg) males (n = 5) and females (n = 6) visited the laboratory on three separate occasions. Participants randomly completed three cycles of IPC at low (SHAM [20 mmHg]), moderate (80% of total arterial occlusion pressure) and high (220 mmHg) pressures. Each cycle of IPC consisted of pressures applied for five-minutes followed by five-minutes of rest. Following IPC, surface electromyographic (sEMG) sensors were placed on the vastus lateralis muscle and participants completed one-set of unilateral, isotonic leg extension muscle actions to volitional failure at 30% of their one-repetition maximum. sEMG amplitude (AMP) and mean power frequency (MPF) were determined as the root mean square and MPF of the power density spectrum, respectively. For analyses, the average of the first 5 (F5) and last 5 (L5) repetitions were normalized to a pretest maximal voluntary isometric contraction (MVIC) and are expressed as a percentage of it. Separate 3 (Pressure [low, moderate, and high]) x 2 (Time [F5, L5]) repeated measures ANOVA were used to assess mean differences. RESULTS: There was no significant (p = 0.765; p = 0.076) interaction or main effect for Pressure (p = 0.603; p = 0.283) for sEMG AMP and sEMG MPF, respectively. There was, however, a significant main effect of Time for sEMG AMP (p < 0.001) and sEMG MPF (p < 0.001). Specifically, collapsed across Pressure, sEMG AMP increased from the F5 repetitions (76.9 ± 27.6%) to the L5 repetitions (178.7 ± 85.5%) (p < 0.001). sEMG MPF, collapsed across Pressure, decreased from the F5 repetitions (83.3 ± 11.2%) to the L5 repetitions (68.9 ± 8.9%) (p < 0.001). CONCLUSIONS: IPC at various pressures did not affect neuromuscular function as inferred by sEMG AMP and sEMG MPF. Thus, altering the implementation of IPC, such as number and/or duration of cycles, may be warranted to positively affect neuromuscular function.