Author(s): TREMBLAY, R., ASSELIN, W., LEBEL, K., LANDRY, C., PAGEAUX, B., MAMPUYA, W.M., O’BRIEN, M.W., RIESCO, E., Institution: UNIVERSITÉ DE SHERBROOKE, Country: CANADA, Abstract-ID: 2169

INTRODUCTION:
Evidence suggests a dose-response relationship between reductions in systolic blood pressure (BP) and resistance exercise intensity. However, some inconsistencies remain. These discrepancies may partly stem from the inadequate control of physiological stimulus. In resistance exercise, intensity is typically defined by external load (i.e., percentage of one-repetition maximum [%1-RM]), while proximity to muscular failure (i.e., effort intensity), and thus physiological stimulus, is frequently not controlled. To enable a valid comparison of the effects of different external load, effort intensity should be standardized while performing resistance exercise. Although this nuance is well documented in the hypertrophy and strength literature, it remains poorly characterized in the context of BP management.
METHODS:
Thirty-six post-menopausal females (50-70 years) with elevated resting BP (≥ 120/80 mmHg) are enrolled in a randomized controlled crossover study including three experimental conditions: 1) Seated control (REST); 2) High-load resistance exercise (80% 1-RM; HL-RE) performed at a standardized high effort intensity (2 repetitions in reserve; [RIR]); and 3) Low-load resistance exercise (50% 1-RM; LL-RE) performed at the same effort (2 RIR). BP was measured in the seated position every 5 min for 30 min, and at 45 and 60 min post-exercise. Following each experimental condition, 24-hour ambulatory BP monitoring was conducted while participants maintained their habitual daily activities. Post-exercise BP changes were calculated as the difference between each time point and pre‑exercise values.
RESULTS:
Interim analyses (n = 7) indicate greater reductions in systolic BP following HL-RE compared with REST at 15 min (-11 [-21–5] vs. 7 [0–11] mmHg), 20 min (-8 [-21–5] vs. 12 [6–16] mmHg), 25 min (-9 [-19–4] vs. 5 [3–13] mmHg), 30 min (-7 [-13–15] vs. 9 [1–13] mmHg), and 45 min (-4 [-9–5] vs. 12 [7–21] mmHg) post-exercise (all p ≤ 0.05). In contrast, LL-RE induced smaller systolic BP reductions, which were significantly different from REST only at 20 min ((-4 [-6–8] vs. 12 [6–16] mmHg) and 45 min (4 [-7–14] vs. 12 [7 – 21]) mmHg) post-exercise (all p ≤ 0.05). Diastolic BP reductions following HL-RE were significantly greater than REST at 0, 5, 15, 20, 45 and 60 min post-exercise (all p ≤ 0.05). For LL-RE, diastolic BP reductions were significantly greater than REST only at 20 and 45 min post-exercise (all p ≤ 0.05). No significant differences were observed between conditions for 24-hour ambulatory, diurnal, and nocturnal BP (p ≥ 0.28).
CONCLUSION:
These preliminary findings suggest that high-load exercise may be more promising than low-load resistance exercise for inducing post-exercise hypotension, even when effort intensity is standardized. Neither HL-RE nor LL-RE elicited an acute reduction in 24-hour ambulatory BP. These results require confirmation in the full study sample.