Effects of neuromuscular fatigue induced by various modes of isometric handgrip exercise on post-exercise blood pressure responses

BACKGROUND: Isometric handgrip exercise (IHE) is recommended as a non-pharmacological treatment for managing blood pressure. However, the effect of various modes of IHE on neuromuscular fatigue and post-exercise blood pressure responses have not been explored. The purpose of this study was to investigate the effects of the duration and muscle mass factors of IHE on post-exercise blood pressure responses. METHODS: Twenty healthy participants were recruited for this repeated-measures study. Three isometric protocols with similar exercise load were conducted on 3 different days including: 1) unilateral IHE at 30% of maximal voluntary contraction (MVC) for 2 minutes; 2) bilateral IHE at 30% MVC for 1 minute; and 3) unilateral IHE at 20% MVC for 3 minutes. Each exercise had four bouts of IHE with two minutes of rest between bouts. The median frequency (MDF) and root mean square (RMS) of surface electromyography was used to assess the level of neuromuscular fatigue in the flexor digitorum superficialis (FDS), extensor carpi radialis longus (ECR), flexor carpi ulnaris (FCU), and extensor carpi ulnaris (ECU). RESULTS: Correlation analysis revealed that FDS MDF fatigue during the bilateral IHE was moderately correlated with the immediate post-exercise systolic blood pressure change (SBP, r=0.456, P<0.05) and diastolic blood pressure change (DBP, r=0.682, P<0.01) and ten-minute post-exercise SBP change (r=0.510, P<0.05) and DBP change (r=0.569, P<0.01) during bilateral IHE at 30% MVC for 1 min. The RMS results indicate a significant correlation between ECR and DBP immediate post-exercise (r=-0.634, P<0.01) and DBP 10-minute post exercise (r=-0.484, P<0.05). CONCLUSIONS: This study suggests that neuromuscular fatigue of FDS and ECR of IHE are related to post-exercise blood pressure changes.