Acute fatiguing isometric handgrip exercise increased flow-mediated dilation similarly in both sexes at 60 minutes post-exercise (Δ=1.40%, 95% CI 0.38-2.39, p=0.042).
Observational (n=29)
Does acute fatiguing isometric handgrip exercise improve brachial artery flow-mediated dilation differently between sexes in healthy young adults?
Acute fatiguing isometric handgrip exercise increases flow-mediated dilation similarly in both sexes when accounting for baseline artery diameter.
Effect estimate: Mean difference 2.17% (95% CI 0.24 to 4.10%)
p-value: p=0.029
Background: Early-recovery reactive hyperemia following isometric handgrip exercise (IHE) in the brachial artery may be an important stimulus for improving endothelial function, particularly if repeated over time. Brachial flow-mediated dilation (FMD) is a common non-invasive technique used to assess endothelial function. Females typically have a higher FMD at rest, but whether this difference persists after IHE is unknown. Purpose: To investigate whether sex differences exist in brachial artery FMD after an acute fatiguing IHE in healthy young adults. Methods: Twenty-nine healthy adults (18–32 years; 15 females, 14 males) completed a right arm IHE at 30% of maximum voluntary contraction until task failure. Right brachial artery FMD was performed using high-resolution ultrasound at baseline, 5-, 30-, and 60-min post-exercise. FMD analyses were conducted offline using automated edge-detection/wall-tracking software. Shear rate, the key stimulus for FMD, was calculated as the area under the curve (AUC) until peak diameter. FMD was allometrically scaled for baseline diameter. IHE-induced changes in outcomes were examined with a two-way repeated measures ANOVA. Results: There was a sex difference in FMD, with females having a higher dilatory response than males (mean difference (Δ)= 2.17%, 95% CI: 0.24 to 4.10%, p=0.029), which was abolished after scaling for baseline diameter (Δfemale-male = 0.32%, 95% CI: -1.64 to 2.28%, p=0.739). Even though shear rate AUC was only increased 5 min post (interaction: p=0.479, Δpost5-bas = 1.08 s-1×103, 95% CI: 0.31 to 1.85 s-1×103, p = 0.048), FMD remained elevated 60 min post IHE for both sexes (interaction: p = 0.782, Δpost60-bas = 1.40%, 95% CI: 0.38 to 2.39, p = 0.042). Scaling FMD for baseline diameter did not change post-IHE response (interaction: p=0.739; time: p=0.012). Conclusion: Acute fatiguing IHE increases FMD regardless of sex, even when reactive hyperemic responses returned to baseline 60-min into recovery. Higher FMD of females observed at all time points was attributed to sex differences in baseline diameter. These findings suggest that both sexes exhibit similar potential to improve endothelial function with repeated IHE over time; however, training interventions are needed to support this assertion. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Borges et al. (2026) conducted an observational in Healthy (n=29). Acute fatiguing isometric handgrip exercise (IHE) vs. Males vs Females / Baseline was evaluated on Sex difference in brachial artery flow-mediated dilation (FMD) (Mean difference 2.17%, 95% CI 0.24 to 4.10%, p=0.029). Acute fatiguing isometric handgrip exercise increased flow-mediated dilation similarly in both sexes at 60 minutes post-exercise (Δ=1.40%, 95% CI 0.38-2.39, p=0.042).