PURPOSE: The purpose of this study was to investigate whether the decrease in pulse wave reflection and central systoloc blood pressure (SBP) as a result of isometric handgrip (IHG) training improves cognitive function in older adults.
METHODS: Twenty-two men and women (age 75±7 years, mean±standard deviation) who were not actively involved in regular resistance or endurance training were randomly assigned to either the group that performed IHG training (IHG group, n=11) or the sedentary control group (CON group, n=11). The IHG exercise comprised four unilateral 2-min isometric contractions at 30% of maximal voluntary contraction using a programmed handgrip dynamometer with 1-min rest periods for 5 days per week for 8 weeks. Carotid augmentation index (AIx), an index of the magnitude of pulse wave reflections, and carotid SBP were non-invasively measured after resting in the supine position for at least 5 min in both groups before (baseline) and after 8 weeks of training using an arterial applanation tonometry system. Trail making test (TMT) Part A, which measures processing speed, and Part B, which assesses task shifting, were used to determine processing speed and flexibility in task switching and cognition.
RESULTS: Carotid AIx and carotid SBP in the IHG group after training were significantly lower than baseline values, decreasing from 52±4 to 39±3 mmHg and from 148±5 to 137±5 mmHg, respectively (p<0.05 for both). TMT-A and TMT-B in the IHG group after training were significantly lower than baseline values, decreasing from 34.73±3.04 to 26.41±2.33 and from 60.52±5.25 to 49.39±4.51 s, respectively (p<0.05 for both). The carotid AIx, carotid SBP, TMT-A and TMT-B did not significantly change before and after training in the CON group. A significant positive correlation was observed between the amount of change in carotid AIx and the amount of change in TMT-A (r=0.603, p<0.05) and TMT-B (r=0.591, p<0.05). In addition, a significant positive correlation was observed between the amount of change in carotid SBP and the amount of change in TMT-A (r=0.736, p<0.01) and TMT-B (r=0.582, p<0.05).
CONCLUSIONS: These results demonstrate that isometric handgrip exercises reduce carotid AIx and carotid SBP, which is associated with improving cognitive function.