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Sinusoidal squat‐stand maneuvers (SSM) without resistance have been shown to produce ~30–50 mmHg swings in mean arterial pressure which are largely buffered in the brain via dynamic cerebral autoregulation (dCA). This study aimed to further elucidate how this regulatory mechanism is affected during SSM with added resistance (~20% bodyweight). Twenty‐five participants (sex/gender: 13 females/12 males) completed two bouts of 5‐min SSM for both bodyweight and resistance conditions (10% bodyweight in each arm) at frequencies of 0.05 Hz (20‐s squat/stand cycles) and 0.10 Hz (10‐s squat/stand cycles). Middle and posterior cerebral artery (MCA/PCA) cerebral blood velocities were indexed with transcranial Doppler ultrasound. Beat‐to‐beat blood pressure (BP) was quantified via finger photoplesmography. Transfer function analysis was employed to quantify dCA in both cerebral arteries across the cardiac cycle (diastole, mean, and systole). Two‐by‐two Analysis of Variance with generalized eta squared effect sizes were utilized to determine differences between resistance vs. bodyweight squats and between sexes/genders. Absolute mean and diastolic BP were elevated during the resistance squats (p < 0.001); however, only the BP point‐estimate power spectrum densities were augmented at 0.10 Hz (p < 0.048). No differences were noted for phase and gain metrics between bodyweight and resistance SSM (p > 0.067); however, females displayed attenuated systolic regulation (p < 0.003). Despite augmented systemic BP during resistance SSM, the brain was effective at buffering the additional stress to mitigate overperfusion/pressure. Females displayed less dCA regulation within the systolic aspect of the cardiac cycle, which may be associated with physiological underpinnings related to various clinical conditions/presentations.
A simple bodyweight squat is sufficient to cause substantial stress on the autonomic nervous system (ANS) via ~30–50 mmHg blood pressure (BP) oscillations. However, it is unknown to the extent of the ANS is impacted during and immediately following bodyweight and resistance squat‐stand maneuvers (SSM) while considering chromosomal sex. Thirteen females and twelve males performed four, 5‐minute bouts of squat‐stand maneuvers (SSM); two at 0.05 Hz (10‐second squat/10‐second stand) and two at 0.10 Hz (5‐s squat/5‐s stand). The SSM were performed using bodyweight resistance and additional external resistance (~20% of bodyweight). Five‐minutes of quiet‐sitting and quiet‐standing were completed immediately following both bodyweight and resistance squats. Heart rate variability (HRV) and baroreceptor sensitivity metrics were extracted from beat‐to‐beat electrocardiography and systemic BP recordings. Repeated measure Analysis of Variance with generalized eta‐squared effect sizes assessed differences between SSM task type and chromosomal sex on ANS metrics. Despite added resistance eliciting greater elevations in blood pressure, no differences in ANS function were noted during competition and recovery between SSM tasks (all p > 0.050; negligible/small effect sizes). During recovery, females had an elevated heart rate ( p = 0.017; small effect size), greater time‐domain HRV measures ( p < 0.047; small effect size), greater high‐frequency domain HRV measures ( p = 0.002; moderate effect size), and reduced low‐frequency domain HRV measures ( p = 0.002; moderate effect size). A healthy ANS can modulate repetitive cardiovascular stressors via squat‐stand maneuvers in a harmonious manner irrespective of added low‐level resistance. Females were more parasympathetically driven following low‐level resistance exercise/stress, which may be a cardioprotective trait.
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