Cardiovascular response to sustained maximal voluntary static muscle contraction

The cardiovascular response to maximal, voluntary, sustained 2-min static contraction by three different muscle groups (right hand finger flexors [RHF], right leg extensors [RLE], and both leg extensors [BLE]) was studied in young adult males (N = 13) and females (n = 14). Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were recorded at 30 s intervals prior to, during, and after exercise. Mean arterial blood pressure (MABP) and pulse pressure (PP) were computed from SBP and DBP. The force of muscle contraction was monitored continuously throughout the 2-min task. Data were analyzed by MANOVA. The results showed that impulse (force x time) declined significantly throughout exercise, and there were significant differences in impulse among muscle groups. SBP, DBP, PP, and MABP increased significantly throughout the 2-min contraction period, while heart rate increased initially and then leveled off. The magnitudes of the blood pressure and HR responses were related to the muscles involved: BLE > RLE > RHF. Blood pressures during rest and exercise were significantly lower for females than for males, but there was no sex effect for heart rate. These findings suggest that blood pressure increases throughout sustained static muscular contractions despite significant reductions in force production. Heart rate, on the other hand, does not increase throughout exercise under these conditions. It appears that heart rate and blood pressure responses to sustained static contraction are mediated by different mechanisms, but these mechanisms are similar for males and females.