The Acute Impact of Large and Small Muscle Mass Isometric Exercise and Post-Exercise Blood Pressure

Abstract

A single bout of aerobic or resistance exercise can lead to a temporary drop in blood pressure (BP) following exercise; a phenomenon referred to as post-exercise hypotension (PEH). PEH has been well-documented in individuals with normal and high BP. Like aerobic and resistance exercise, isometric exercise (IEX) training chronically reduces resting BP in both populations; however, considerably less attention has been given regarding the ability of this type of exercise to elicit PEH. IEX involves static contractions against an immovable load where no or minimal change in length occurs within the engaged muscle group; it is often performed in the arm and leg, with protocols being completed in as little as 11-min. While PEH has been reported in older subjects with normal resting BP following a single session of isometric handgrip exercise (IHGX), it has yet to be examined beyond 5-min following an acute bout of isometric leg exercise (ILX). There is some evidence to suggest that the magnitude and/or duration of PEH is proportional to the exercising muscle mass; therefore, ILX (i.e. large muscle mass IEX) may have greater potential than IHGX (i.e. small muscle mass IEX) to evoke PEH. The purpose of this study was twofold: 1) to determine whether an acute bout of IHGX would elicit PEH in a sample of young, normotensive males and 2) if the magnitude of PEH, following IEX, was influenced by muscle mass. A total of 21 healthy males (24.1 ± 3.5yrs) completed 2 experimental visits (1 IHGX, 1 control), wherein cardiovascular reactivity and recovery responses (heart rate and BP) were assessed. In a subset of 12, an additional ILX visit was conducted, for a total of 3 experimental visits. PEH did not occur following a single session of either IHGX or ILX. The absence of PEH following either IEX protocol suggests that this type of exercise may be a less potent stimulus for PEH in this population. The findings from this study extend current knowledge with respect to PEH in healthy, young individuals and provide novel insight into the dependence, or lack thereof, of muscle mass on PEH.