The Hypotensive Effects of Isometric Training are Associated with Decreasing Daytime Sleepiness in Young Women

Abstract

Isometric exercise training (IET) has been conducted to reduce resting blood pressure; however, the underlying mechanisms are not fully understood. Sleep and sleepiness have been shown to be associated with cardiac risk factors including hypertension. In addition, although some studies indicate that exercise can improve sleep and sleepiness, it remains unknown whether IET can influence sleep, sleepiness, and their relationship with hypotensive effects. PURPOSE: To investigate whether IET influences sleep, sleepiness, and to determine their relationship with reduced resting blood pressure (BP). METHODS: Twenty-two normotensive young women were assigned to either control (n=11) or training (n=11) group. The training group performed unilateral isometric handgrip (IHG) sessions three times per week for 8 weeks (wks). The training protocol consisted of four 2-min bouts of IHG exercise at 25 % of maximal voluntary contraction, separated by 3-min rest periods. Sleep and sleepiness were assessed using the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS). Resting blood pressure was measured pre and post 8 wks of training. PSQI and ESS were measured at pre (0 wk), middle (4 wk), and post (8 wk) training. BP was compared between pre and post training, using paired T-test in each group. PSQI and ESS were analyzed by two-way analysis of variance (time x group), using post hoc Tukey HSD test. A Pearson correlation was determined between resting BP change ratio and change ratio for PSQI and ESS from pre to post training period. RESULTS: Following 8 wks, IHG training significantly reduced systolic BP (-4.5±6.3 mmHg, p<0.05) and mean BP (-3.8±4.6 mmHg, p<0.05), but not diastolic BP (-3.4±5.3 mmHg, p=0.058); no BP changes were noted in the control group. The PSQI scores were not significantly different among groups. A significant interaction effect was observed in ESS, which indicated that ESS significantly decreased from pre to post training period in the training group (10.3±3.7 to 8.4±4.6, p<0.05). ESS change ratio was significantly associated with the resting mean BP change ratio (r=0.732, p=0.01). CONCLUSION: This study indicates that isometric exercise training could reduce resting blood pressure and was associated with daytime sleepiness in young women.