Abstract / Summary
Isometric exercise has been shown to lower blood pressure. However, the acute dose–effect relationship of different contraction durations in prehypertensive individuals with substance use disorder remains unknown. To compare the acute dose–effect of three isometric exercise durations (1 min, 2 min, and 3 min) on 24‑hour blood pressure and brachial‑ankle pulse wave velocity (baPWV) in prehypertensive drug‑dependent individuals, and to determine the optimal duration. This study included 9 male prehypertensive drug‑dependent individuals who were randomly assigned to the sequence of four contraction-duration conditions in a crossover design (blank control, 1‑min, 2‑min, 3‑min), with each participant completing all four conditions (yielding a total of 36 observations), and 20 healthy prehypertensive males as a non‑randomized reference group (only 2‑min condition; n = 20).All exercise conditions consisted of isometric handgrip at 30% MVC, 4 sets, with 2 min rest between sets. Office blood pressure and baPWV were measured before, immediately after, 1 h after, and 24 h after the session. Twenty‑four‑hour ambulatory blood pressure monitoring (ABPM) was also performed. A two‑way mixed ANOVA (group × time) and Pearson correlation were used for analysis. In the 9 drug‑dependent participants (total of 36 observations across the four conditions), the 2‑min condition produced the optimal blood pressure‑lowering effect (SBP reduction of − 11.7 mmHg at 1 h post‑exercise, lasting 24 h on office measurement, and a mean 24‑h ambulatory SBP reduction of − 5.8 mmHg). The 1‑min effect lasted only 60 min. The 3‑min group showed a comparable peak reduction but the effect lasted only 12 h, with a higher incidence of adverse reactions (30% vs. 20% in the 2‑min group). Improvement in baPWV was positively correlated with exercise duration, and the reduction in blood pressure was significantly correlated with reduction in baPWV ( r = 0.624). The healthy reference group (2‑min condition) showed similar responses (SBP reduction − 11.0 mmHg at 1 h post‑exercise). No serious adverse events occurred. An acute 2‑minute isometric exercise session (30% MVC, 4 × 2 min, 2 min rest) provides the optimal blood pressure‑lowering effect and the longest duration (24 h) in prehypertensive drug‑dependent individuals, and is recommended for this population. Extending to 3 min confers no additional benefit and shortens the effect maintenance time.