Investigating the effect of isometric handgrip training frequency on cardiovascular health in medicated hypertensives
Hypertension (HTN) is expected to affect approximately 50% of the world’s adult population by 2025 and accounts for 10 million deaths worldwide each year. Historically, HTN has been defined as systolic blood pressure (SBP) greater than 140 mmHg and/or diastolic blood pressure (DBP) greater than 90 mmHg. However, it has been recently suggested that the risks of HTN begin at even lower BP levels and in the United States HTN is now defined as ≥130/80 mmHg. HTN increases the presence of many independent risk factors and/or indicators for cardiovascular disease (CVD) such as increased arterial stiffness and reduced cardiovagal baroreflex sensitivity (cvBRS). This study aimed to investigate the minimum training frequency necessary to maintain decreases in BP following an initial 8-week training period by training individuals 0, 1, or 3 times per week for 4 weeks. Sixteen individuals with medicated hypertension (age 65±9 years) were recruited and performed 8 weeks of IHG 3 times per week and were then allocated to one of 3 training frequency groups; 0, 1 or 3 times for a subsequent 4 weeks. Statistically significant decreases in SBP and DBP were observed in all participants following the initial 8-week IHG training program (-9±10mmHg, p=0.004; -5±6mmHg, p=0.006), as well as at 12 weeks (-9±10 p=0.047; -5±7, p=0.051). cvBRS did not demonstrate any significant changes, while carotid-toe pulse wave velocity (ctPWV), a measure of systemic arterial stiffness, demonstrated a significant main effect for time (p=0.002). Post-hoc testing revealed significant decreases in ctPWV at 12 weeks (-1.0±1.1, p=0.002), as well as a significant decrease from 8 to 12 weeks (-0.73±1.1, p=0.017). As for trained limb arterial stiffness, carotid-radial pulse wave velocity (crPWV) demonstrated a significant effect for group (p=0.045) and time (p=0.015). Post-hoc testing revealed that there was no significant difference between groups, however there was a significant decrease in crPWV at 12 weeks (-1.4±1.7, p=0.010). These findings suggest that IHG at a training frequency lower than traditionally prescribed may maintain the decrease in SBP and DBP with the inclusion of improvements in arterial stiffness both systemically and in the trained limb over time. Thus, these results support the prescription of IHG in the treatment of HTN.