The effect of slow breathing on cardiovascular and electromyographic responses during standing perturbations in older adults.

A bi-directional interaction between the cardiovascular and postural control systems has been previously reported in young adults; however, limited data exist in older populations where physiological alternations in these systems are well known. The purpose of this study was to determine: (1) the effect of slow breathing on heart rate (HR) and systolic blood pressure (SBP) responses following surface support postural perturbations in older adults and (2) the effect of slow breathing on lower limb muscle burst onset and burst amplitude during postural perturbations of the support surface in older adults. Twenty community-dwelling older adults experienced posteriorly directed accelerations of treadmill belts during quiet standing while breathing spontaneously (SPON) or breathing at 6 breaths per minute (SLOW). SBP, HR, and muscle burst onset and burst amplitude were analyzed for 7 s from each perturbation's onset. Post-perturbation comparison of SLOW and SPON showed that SBP was significantly higher during SPON over the entire analyzed time period (0-7 s) (p < 0.001), while there was no difference in HR throughout the same analysis window (0-7 s) (p > 0.05). The muscle burst onset was shortened in the SLOW compared to SPON task (p < 0.001), while muscle burst amplitude was not significantly different between SPON and SLOW (p = 0.353). Although slow breathing affected cardiovascular and muscle activation onset responses during postural perturbations in older adults, they differed from the responses in younger adults reported previously. The findings highlight the physiological adaptations that may occur to maintain postural stability in older adults.