Spontaneous cardiac baroreflex sensitivity is enhanced during post-exercise ischemia in men but not in women
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To investigate the effect of isolated muscle metaboreflex activation on spontaneous cardiac baroreflex sensitivity (cBRS), and to characterize the potential sex-related differences in this interaction in young healthy subjects.
40 volunteers (20 men and 20 women, age: 22 ± 0.4 year) were recruited. After 5-min rest period, the subjects performed 90 s of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 3 min of post-exercise ischemia (PEI). Beat-to-beat heart rate and arterial blood pressure were continuously measured by finger photopletysmography. Spontaneous cBRS was assessed using the sequence technique and heart rate variability was measured in time (RMSSD—standard deviation of the RR intervals) and frequency domains (LF—low and HF—high frequency power).
Resting cBRS was similar between men and women. During PEI, cBRS was increased in men (Δ3.0 ± 1.1 ms mmHg− 1, P = 0.03) but was unchanged in women (Δ-0.04 ± 1.0 ms mmHg− 1, P = 0.97). In addition, RMSSD and HF power of heart rate variability increased in women (Δ7.4 ± 2.6 ms, P = 0.02; Δ373.4 ± 197.3 ms2; P = 0.04, respectively) and further increased in men (Δ26.4 ± 7.1 ms, P < 0.01; Δ1874.9 ± 756.2 ms2; P = 0.02, respectively). Arterial blood pressure increased from rest during handgrip exercise and remained elevated during PEI in both groups, however, these responses were attenuated in women.
These findings allow us to suggest a sex-related difference in spontaneous cBRS elicited by isolated muscle metaboreflex activation in healthy humans.
KeywordExercise pressor reflex Autonomic nervous system Heart rate Blood pressure Sex differences
Analyses of variance
Body mass index
Body surface area
Cardiac baroreflex sensitivity
Diastolic blood pressure
Heart rate variability
Intraclass correlation coefficient
Mean blood pressure
Maximal voluntary contraction
Nucleus tractus solitaries
Root of the mean of the sum of successive differences
Systolic blood pressure
Total vascular conductance
Vascular conductance index
Very low frequency
The time and effort expended by all the volunteer subjects is greatly appreciated.
MS and LCV conceived and designed research. MS, ALT, JLSC and LCV performed experiments. MS, ALT and LCV analyzed data. MS, ALT and LCV interpreted results of experiments. MS prepared figures. MS, ALT and LCV drafted manuscript. All authors read and approved final version of manuscript.
This study was supported by grants and scholarships from the Brazilian National Council of Scientific and Technological Development (CNPq), the Foundation for Research Support of Federal District (FAPDF), Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) and partially supported by an American Physiological Society Arthur C. Guyton Awards for Excellence in Integrative Physiology (to L.C. Vianna).
Compliance with ethical standards
Conflict of interest
None of the authors declares a conflict of interest.
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