Short-term isometric exercise reduces systolic blood pressure in hypertensive adults: possible role of reactive oxygen species.

OBJECTIVE: A short-term isometric exercise protocol was tested in ten hypertensive individuals to determine its efficacy as a high blood pressure-reducing intervention. DESIGN: The study was a prospective case study of 10 hypertensive individuals (8 men, 2 woman, mean age = 52 + 5 years) who underwent six weeks of isometric exercise training (three sessions/week). METHODS: Blood pressure, blood lipids and markers of oxidative stress were monitored before, during and following the isometric intervention. Electron spin resonance spectroscopy was used to directly measure radicals in the blood samples. RESULTS: After six weeks, systolic blood pressure decreased an average 13 mm Hg (p < 0.05) from a mean blood pressure of 146 to 133 mm Hg, a level that is below the usual 140 mm Hg hypertension threshold. Blood lipids were unchanged, but markers of oxidative stress were affected, with a dramatic decrease in exercise-induced oxygen centered radicals (-266%), (p < 0.05) and an increased resting whole blood glutathione:oxidized glutathione (+61%) in hypertensive adults following six weeks of isometric exercise. CONCLUSION: Six weeks of isometric exercise training was effective in lowering systolic but not diastolic blood pressure in pre-hypertensive and hypertensive individuals, and enhanced antioxidant protection is a likely underlying mechanism.

Access to exercise and its relation to cardiovascular health and gene expression in laboratory animals.

The interaction between genes and environment can influence cardiovascular disease (CVD). This 16 month study investigated if genes associated with cardiovascular (CV) regulation were expressed differently in animals having: 1) no access to physical activity or exercise (SED), 2) access to hour-long, twice weekly activity (PA), and 3) access every-other-day to a running wheel (EX). Out of 31,000 genes, a CV subset comprising 44 genes was investigated. Ten genes from this subset were expressed differently in EX compared with SED, and 34 genes were expressed differently in PA compared with SED (p<0.05). Total cholesterol (70+/-8 vs. 101+/-9 mg dl(-1)), triglycerides (104+/-8 vs. 127+/-4 mg dl(-1)), resting systolic blood pressure (130+/-3 vs. 141+/-3 mmHg), mean arterial pressure (110+/-2 vs. 120+/-2 mmHg) and heart rate (380+/-6 vs. 405+/-9 beats min(-1)) were lower in EX compared with SED (p<0.05), but intracellular adhesion molecule levels did not differ among groups. Mean gene expressions for Gja1, Fdft1, Edn1, Cd36, and Hmgb2 differed in animals according to access to physical activity. These genes play roles in heart rate, cholesterol biosynthesis, blood pressure, cell adhesion, and transcription and neurogenesis regulation, respectively. In conclusion, a total of 44 CV genes were expressed differently in SED compared to PA and EX; and SED showed more physiological evidence of CVD.

Exercise improves biomarkers of health and stress in animals fed ad libitum.

Voluntary and forced exercise decrease morbidity and mortality in laboratory animals. Caloric restriction has similar effects on health and unique benefits on life span. Nonetheless, in most experiments, animals do not have access to physical activity and are fed ad libitum (AL). We hypothesized that with regular access to either unlimited running wheel exercise (EX) or limited physical activity (PA), key biomarkers of health would be enhanced enough to counter some consequences of a sedentary AL lifestyle. This 16-month study compared body weight, tumor number and size, tissue lesions, oxidative stress, and reactive stress in (1) sedentary animals with no access to physical activity (SED); (2) animals with access to hour-long, twice weekly activity in a large box (PA); and (3) animals with access every other day to a running wheel (EX). At the end of the study, EX body weight was 8-9% lower than PA and SED. In addition, EX had no kidney lesions versus 50% in PA and SED, and had smaller tumor size (10+/-2 vs. 14+/-4 and 30+/-4 mm). Exhaustive exercise lowered glutathione/oxidized glutathione ratio in EX and PA, but in SED, the ratio was depressed even in resting animals. In all treatments, prolactin (PRL) levels were lower in resting animals than in acutely exercised animals. In conclusion, EX had the most favorable health biomarkers while SED had the least. PA did not confer gross health benefits different than the SED group, but was biochemically more similar to EX animals.

Isometric training lowers resting blood pressure and modulates autonomic control.

PURPOSE: This study examined the effects of isometric handgrip training on resting arterial blood pressure, heart rate variability, and blood pressure variability in older adults with hypertension. METHODS: Nine subjects performed four 2-min isometric handgrip contractions at 30% of the maximum voluntary contraction force, 3 d.wk(-1) for 10 wk, and eight subjects served as controls. RESULTS: After training, there was a significant reduction in resting systolic pressure and mean arterial pressure. In addition, power spectral analysis of heart rate variability demonstrated that the low frequency: high frequency area ratio tended to decrease. CONCLUSIONS: It is concluded that isometric training at a moderate intensity elicits a hypotensive response and a simultaneous increase in vagal modulation in older adults with hypertension.