Sex Differences in Blood Pressure Control Following a Single Bout of Isometric Handgrip Exercise
Authors: Samora Milena , Teixeira André L , Antonino Diego L , Carmo Jake C , Ritti‐Dias Raphael , Vianna Lauro C 
Published: November 2023

Background

Recent studies have shown that isometric handgrip (IHG) training reduces resting arterial blood pressure (BP) in both normotensive and hypertensive populations, but the mechanisms underlying these adaptations remain unclear. Furthermore, little is known regarding the effects of a single bout of IHG on the neural control of BP in humans. This becomes important given the fact that chronic adaptations may result from temporal summation of acute responses. In addition, the majority of studies regarding cardiovascular effects of IHG are performed in men and the possible sex differences in this context are unknown.

Aim

To test the hypothesis that neural control of BP following a single bout of IHG exercise are different between men and women.

Methods

Eight healthy men (24 ± 3 years) and 10 healthy women (23 ± 4 years) randomly performed a single bout (four 2‐min static contractions) of experimental (30% MVC) or sham (3% MVC) bilateral IHG exercise. All women are non‐oral contraceptives users and performed experiments in the early follicular phase of the menstrual cycle. Beat‐to‐beat heart rate (HR) and arterial BP was continuously monitored using finger photoplethysmography (Human NIBP, AD instruments) before and following IHG exercise (5–10 and 25–30 min of recovery). Spontaneous cardiac baroreflex sensitivity (cBRS) was assessed via sequence technique (CardioSeries v2.4, Brazil). Power spectral analysis of HR variability (HRV) was employed (CardioSeries v2.4, Brazil) and the ratio between low and high frequency of HRV (LF/HF) was used as a surrogate of sympathovagal balance.

Results

Baseline HR was greater while arterial BP and cBRS gain were lower in women compared with men (P<0.05). Following IHG exercise, SBP increased in men (Δ7 ± 1 mmHg, 10‐min vs. rest, P<0.05), but was unchanged in women (Δ2 ± 1 mmHg, 10‐min vs. rest, P>0.05). At 10‐min following IHG exercise, HR significantly decreased (Δ‐7 ± 1 bpm, P<0.01) and remained attenuated at 30‐min time point (Δ−3 ± 1 bpm, P<0.05) in women, but was unchanged in men (10‐min: Δ−2 ± 1 bpm, and 30‐min: Δ1 ± 2 bpm, P>0.05). In women, cBRS gain significantly increased from rest at 10‐min following IHG (Δ23.7 ± 7%, P=0.01) and returned to baseline values at 30‐min of recovery (14.9 ± 2.0 ms/mmHg, P>0.05). In contrast, no differences were found in cBRS gain in men following IHG (P>0.05). In addition, RMSSD and HF components of HRV, a proxy of cardiac vagal activity, were increased at 10‐min following IHG in women while no differences were found in men. LF/HF ratio was not affected by IHG trials. All physiological variables were unaffected by the sham protocol in both groups.

Conclusion

These results allow us to conclude that the acute effects of IHG exercise on neural control of BP is sex dependent and baseline sex differences in spontaneous cBRS were acutely abolished after a single bout of IHG exercise.

Support or Funding Information

CAPES, CNPq and FAPDF.