The Impact of Isometric Exercise Muscle Mass on Post-Exercise Blood Pressure: 174 Board #12 May 29 9:30 AM - 11:00 AM

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). Like aerobic and resistance exercise, isometric exercise training can reduce resting BP however, considerably less is known regarding the ability of this type of exercise to elicit PEH. PEH may be more robustly stimulated with a larger active muscle mass, therefore, isometric leg exercise (ILX) (large muscle mass) may have greater potential than isometric handgrip exercise (IHGX) (small muscle mass) to evoke PEH. PURPOSE: To determine the impact of a bout of large (ILX) and small (IHGX) muscle mass isometric exercise on post-exercise blood pressure. METHODS: Twelve healthy males (23.7 ± 3.5yrs) completed 3 experimental visits (1 IHGX, 1 ILX, 1 control (rest no exercise)). Blood pressure (systolic and diastolic; SBP and DBP) was assessed at baseline and at 15, 30, 45 and 60 min post-exercise or control with an automated sphygmomanometer. Isometric exercise consisted of 4 alternating 2 min isometric contractions (quadriceps (ILX) or handgrip (IHGX)) at 30% maximum voluntary contraction. Contractions were separated by 1min of rest. Participants completed each condition on a separate day (order counterbalanced). RESULTS: SBP was lower than baseline at 15 and 45 min post (p=0.013 and p=0.014 respectively); but this did not differ between the control, IHGX and ILX conditions (p=0.256, Control: baseline 110 ± 7.3 mmHg, average post 106.7 ± 8.6mmHg; IHGX: baseline 110 ± 10.3mmHg, average post 107.4 ± 8.3mmHg; ILX: baseline 113.25 ± 11.7mmHg, average post 111.8 ± 11.2mmHg). DBP did not differ from baseline (Baseline DBP: control 69.17 ± 7.4mmHg, IHGX 68.6 ± 7.9mmHg, ILX 72.3 ± 7.4mmHg) at any time point in any condition (P>0.05). However, DBP 15 min post was higher in the ILX (73.4 ± 8.9mmHg) vs. the IHGX (68.3 ± 7.9mmHg) and Control (68.3 ± 8.6mmHg) conditions. CONCLUSION: PEH did not occur following a single session of either IHGX or ILX suggesting that this type of exercise may not be a potent stimulus for PEH in this population, even when engaging the larger quadriceps muscle mass. Further research is required to identify the importance of the duration and intensity of isometric exercise on post-exercise blood pressure. Funded by NSERC