The effect of lower limb strengthening exercise on orthostatic blood pressure and the skeletal muscle pump in older people with orthostatic hypotension.

Abstract

Activation of muscles during standing is recommended to activate the skeletal muscle pump, increasing venous return and increasing blood pressure (BP) in people with orthostatic hypotension (OH). The aim of this study is to determine if increasing the strength of the lower limb muscles can improve the effectiveness of the venous pump and postural BP in older people with OH. Ten older people with OH underwent an 8-week lower limb strengthening intervention. Repeated measurements of orthostatic BP, calf venous ejection fraction (EF) and muscle strength took place before, during and after intervention. The intervention increased calf muscle strength by 21% (interquartile range: 18-28), p = 0.018, from a median baseline of 38 (34-45) kg. Participants had normal levels of venous EF 64% (51-75) at baseline, with little to no venous reflux. The median ejection volume at baseline was 44 (36-58) mL per calf. Despite increasing muscle strength, venous EF did not increase (percentage change -10% (-16 to 24), p = 0.8) and systolic BP drop did not improve (percentage change 0% (-17 to 16), p = 1.0). Similarly, visual analysis of individual case-series trends revealed increasing muscle strength with no clinically meaningful change in EF or orthostatic BP. Muscle strengthening exercise does not increase the effectiveness of the skeletal muscle pump and is not an efficacious intervention for OH. As there is little to no venous pooling in the calf during standing in older people with OH, below knee compression is unlikely to be clinically effective.