(13) SIMILAR BLOOD PRESSURE RESPONSES FOLLOWING HIGH- AND LOW-INTENSITY ISOMETRIC FATIGUE IN YOUNG MEN AND WOMEN

Purpose: This study examined the pre-to-post change in systolic (SBP) and diastolic blood pressures (DBP) following an isometric ramp knee extension protocol at 30% and 70% maximal voluntary isometric contraction (MVIC) in recreationally active young men and women. Methods: 24 college-aged adults (M/F:12/12; age:22±2yr) completed a familiarization visit, as well as two fatiguing bouts of isometric knee extension exercise that were randomized and counterbalanced 48 hours apart. All participants were fitted to an isokinetic dynamometer, and their upper body and dominant leg secured with their knee aligned to the axis of rotation of the device. A commercially available blood pressure (BP) cuff was attached to the participants’ dominant upper arm. Following a series of warm-up contractions and 3-4 MVIC attempts, participants were given a 5 minute rest and pre-exercise (PRE) SBP and DBP were taken. Then, depending on the visit, participants completed time-matched (i.e., 20s) isometric ramp contractions for knee extensions at either 30% or 70% MVIC. Isometric contractions were held for a total of 14s and 6s at 30% and 70% MVIC, respectively. Participants were asked to perform as many isometric contractions as possible until failure. SBP and DBP were taken again immediately post-exercise (POST). Separate three-way 2 (Condition; 30%/70% MVIC) 2 (Time; PRE vs. POST) 2 (Sex; M/F) repeated measures ANOVAs were used to examine mean differences for SBP and DBP. Bonferroni post-hoc assessed significant interactions and main effects. A 2 (Condition; 30%/70%) 2 (Sex; M/F) repeated measures ANOVA was run to examine the mean difference for the number of repetitions completed until failure by sex for both conditions.Results: There were no significant three-way interactions for either SBP (p=0.567) or DBP (p=0.168); however, there was a significant time sex interaction for SBP (p=0.034). Specifically, SBP was greater for males than females at PRE (M:128.3±12.1 vs. F:111.0±9.1 mmHg; p < 0.001) and POST (M:142.8±10.8 vs. F:119.4±9.3 mmHg; p < 0.001). In addition, POST SBP for males and females was greater than PRE SBP within their own sex (p < 0.001 for both). For DBP, there was only a main effect of Time (p < 0.001), such that POST was greater than PRE (POST: 87.3±10.0 vs. PRE: 82.0±10.4 mmHg). Females completed more repetitions at 30% MVIC than males (p=0.032); however, there was no sex difference (p=0.275) for completed repetitions at 70% MVIC. Lastly, regardless of sex, more repetitions were completed at 30% vs. 70% MVIC (M:38.0 ± 30.2 vs. 7.5 ± 4.0 reps, p=0.006) and (F:79.9 ± 50.5 vs. 12.1 ± 12.8 reps, p=0.001). Conclusions: SBP and DBP increased from pre-to-post exercise; however, BP responses were not greater following the condition of a higher intensity fatiguing isometric exercise. Although not measured, an increased vascular resistance across the exercise set may have increased BP. In addition, sex only affected SBP, and this may be a factor of sympathetic response (i.e., blunted sympathetic response in females). Lastly, the total number of repetitions completed did not appear to influence these results. Practical Applications: High intensity isometric exercise should not be avoided out of fear of a significant increase in BP following exercise. Strength and conditioning coaches can consider including easily measured BP variables as an index of health in addition to performance. Acknowledgements: None