Effects of Isometric leg Training on Ambulatory Blood pressure and Morning Blood pressure Surge in Young Normotensive Men and Women

Cardiovascular disease (CVD) is a major cause of death globally with hypertension reported to be a leading modifiable risk factor. Ambulatory blood pressure (BP), in particular diurnal BP variability, is considered to be associated with CVD risk. In addition, the morning BP surge (MBPS) is thought to be associated with increased stroke risk and to be a destabilizing factor for atherosclerotic plaque. Isometric resistance training (IRT) is an effective method of lowering BP and has been recommended by the American Heart Association as an alternative treatment for reducing BP. To date, few studies have investigated the effects of IRT on ambulatory BP and particularly the morning surge in BP. Therefore, the purpose of this study was to determine whether (i) IRT causes reductions in ambulatory BP and the MBPS, in young normotensives and (ii) there are any sex differences in these changes.Ambulatory BP was measured prior to, and after, 10 weeks of bilateral leg IRT using an isokinetic dynamometer (4 x 2 minute contractions at 20% MVC, with 2 minute rest periods on 3 days per week). Twenty normotensive individuals (10 men, age=21 ± 4 years; 10 women, age=23 ± 5 years) were recruited. A two-way repeated measures ANOVA was used to assess the within and between groups ambulatory (mean 24-h, daytime, night time and diurnal variation) BP and MBPS. MBPS was calculated as: mean systolic BP 2 hours after waking minus the lowest sleeping 1 hour mean systolic BP. There were significant reductions in 24-h ambulatory (4 ± 2 mmHg, p=0.0001; 4 ± 2 mmHg, p=0.0001) systolic BP in both men and women following IRT. This comprised significant reductions in day time (5 ± 5 mmHg, p=0.019; 5 ± 4 mmHg, p=0.002) but not night time (1 ± 5 mmHg, p=0.75; 1 ± 3 mmHg, p=0.3) systolic BP. Additionally, there were significant reductions in the MBPS (6 ± 8 mmHg, p=0.044; 6 ± 7 mmHg, p=0.019). There were no significant differences between men and women in these changes (p>0.05).These results support previous research showing that IRT is effective in lowering ambulatory BP. Furthermore, the significant reductions in the MBPS offer the potential for clinically meaningful CVD and stroke risk reduction, provided these effects can be demonstrated in those who are at risk.