Menstrual cycle effects on cardiovascular drift and maximal oxygen uptake during exercise heat stress

Acute work rate adjustments during high-intensity interval training in a hot and temperate environment

Heart rate drifts upward over time during interval exercise and during exercise in hot conditions. As such, work rate must be lowered to maintain target heart rate. The purpose was to characterize acute work rate adjustments during high-intensity interval training based on target heart rate. Seven humans (three females) completed five study visits: a graded exercise test on a cycle ergometer to measure maximal heart rate (HRmax) in ∼22 °C and four trials performed in ∼22 °C (TEMP) or ∼35 °C (HOT), consisting of an 8 min warm-up at 70% HRmax followed by one (15TEMP and 15HOT) or five (43TEMP and 43HOT) rounds of high-intensity interval training (one round = 4 min work at 90% HRmax and 3 min recovery at 70% HRmax) totaling 15 min or 43 min of exercise, respectively. Work rate was lowered 33 ± 20 W (p = 0.005) in 43TEMP and 56 ± 30 W (p = 0.003) in 43HOT between the first and fifth work intervals. Thermal strain (0.2 °C higher rectal temperature, p = 0.01) and cardiovascular strain (6 beats·min-1 larger increase in heart rate from first to fifth recovery interval, p = 0.01) were greater in 43HOT versus 43TEMP. Using target heart rate during high-intensity interval training may reduce the training stimulus, especially in hot environments, but it may also limit thermal strain and enable participants to complete the prescribed workout despite the heat.

Stroke volume response during prolonged exercise depends on left ventricular filling: evidence from a β-blockade study

Prolonged moderate-intensity exercise leads to a progressive upward drift in heart rate (HR) that may compromise stroke volume (SV). Alternatively, the HR drift may be related to abated SV due to impaired ventricular function. The aim of this study was to examine the effects of cardiovascular drift on left ventricular volumes and in turn SV. Thirteen healthy young males completed two 60-min cycling bouts on a semirecumbent cycle ergometer at 57% maximal oxygen consumption (V̇o2max) either under placebo condition (CON) or after ingesting a small dose of β1-blockers (BB). Measurements of HR, end-diastolic volume (EDV), and end-systolic volume were obtained by echocardiography and used to calculate SV. Other variables such as ear temperature, skin temperature, blood pressure, and blood volume were measured to assess potential changes in thermoregulatory needs and loading conditions. HR drift was successfully prevented when using BB from min 10 to min 60 (128 ± 9 to 126 ± 8 beats/min, P = 0.29) but not in CON (134 ± 10 to 148 ± 10 beats/min, P < 0.01). Conversely, during the same time, SV increased by 13% when using BB (103 ± 9 to 116 ± 7 mL, P < 0.01), whereas it was unchanged in CON (99 ± 7 to 101 ± 9 mL, P = 0.37). The SV behavior was mediated by a 4% increase in EDV in the BB condition (164 ± 18 to 170 ± 18 mL, P < 0.01), whereas no change was observed in the CON condition (162 ± 18 to 160 ± 18 mL, P = 0.23). In conclusion, blocking HR drift enhances EDV and SV during prolonged exercise. These findings suggest that SV behavior is tightly related to filling time and loading conditions of the left ventricle.

Effect of Work-to-Rest Cycles on Cardiovascular Strain and Maximal Oxygen Uptake during Heat Stress

Cardiovascular drift-a progressive increase in heart rate (HR) and decrease in stroke volume (SV) during prolonged exercise-is exacerbated by heat stress and thermal strain, and often accompanied by a decrease in work capacity (indexed as maximal oxygen uptake [V.O2max]). To attenuate physiological strain during work in the heat, use of work:rest ratios is recommended by the National Institute for Occupational Safety and Health. The purpose of this study was to test the hypothesis that during moderate work in hot conditions, utilizing the recommended 45:15 min work:rest ratio would result in cardiovascular drift 'accumulating' over consecutive work:rest cycles and accompanying decrements in V.O2max. Eight people (5 women; (mean ± SD) age = 25 ± 5 y; body mass = 74.8 ± 11.6 kg; V.O2max = 42.9 ± 5.6 mL·kg-1·min-1) performed 120 min of simulated moderate work (201-300 kcal·h-1) in hot conditions (indoor wet-bulb globe temperature = 29.0 ± 0.6 °C). Participants completed two 45:15 min work:rest cycles. Cardiovascular drift was evaluated at 15 and 45 min of each work bout; V.O2max was measured after 120 min. On a separate day, V.O2max was measured after 15 min under identical conditions for comparison before and after cardiovascular drift occurred. HR increased 16.7% (18 ± 9 beats·min-1, p = 0.004) and SV decreased 16.9% (-12.3 ± 5.9 mL, p = 0.003) between 15 and 105 min, but V.O2max was unaffected after 120 min (p = 0.14). Core body temperature increased 0.5 ± 0.2 °C (p = 0.006) over 2 h. Recommended work:rest ratios preserved work capacity but did not prevent the accumulation of cardiovascular and thermal strain.

Vagally Derived Heart Rate Variability and Training Perturbations With Menses in Female Collegiate Rowers

INTRODUCTION

The parasympathetically derived marker of heart rate variability, root mean square of successive R-R differences (RMSSD), and the daily fluctuations as measured by the coefficient of variation (RMSSDCV) may be useful for tracking training adaptations in athletic populations. These vagally derived markers of heart rate variability may be especially pertinent when simultaneously considering a female athlete's menstrual cycle.

PURPOSE

The purpose of this study was to observe the perturbations in RMSSDCV, while considering RMSSD, across a season in the presence and absence of menses with training load in female collegiate rowers.

METHODS

Thirty-six (20 [1] y, 25.6 [3.4] kg·m-2) National Collegiate Athletic Association Division I female rowers were monitored for 18 consecutive weeks across a full season. Seated, ultrashortened RMSSD measurements were obtained by the rowers on at least 3 mornings per week using a smartphone photoplethysmography device. Following the RMSSD measurement, athletes indicated the presence or absence of menstruation within the application. Individual meters rowed that week and sessions rate of perceived exertion were obtained to quantify training load.

RESULTS

Longitudinal mixed-effects modeling demonstrated a significant effect of menses and time, while also considering RMSSD, such that those who were on their period had a significantly greater RMSSDCV than those who were not (11.2% vs 7.5%, respectively; P < .001). These changes were independent of meters rowed, sessions rate of perceived exertion, body mass index, birth-control use, and years of rowing experience, which were all nonsignificant predictors of RMSSDCgV (P > .05).

CONCLUSION

The presence of menses appears to significantly impact RMSSDCV when also considering RMSSD, which may allow coaches to consider individualized training plans accordingly.

MEDICAL EFFECT OF SPORTS ON IMPROVING THE MAXIMUM OXYGEN

ABSTRACT Introduction: Maximum oxygen uptake is an effective indicator of the level of human cardiopulmonary function and aerobic work capacity. Observing the effects of aerobic training and formulating scientific training plans are of considerable value. Objective: To observe the effect of physical exercise on the human body's maximum oxygen uptake and arterial blood ketone body ratio. Methods: Before and after 4 weeks of physical exercise, the maximum oxygen uptake, blood lactic acid and heart rate changes, and ketone body content in the incremental load exercise experiment was measured in the human body. Results: The subjects’ maximum oxygen uptake, maximum exercise load, heart rate, and blood lactic acid levels increased significantly after physical exercise. Conclusion: The human body's maximum oxygen uptake is enhanced under sports. Level of evidence II; Therapeutic studies - investigation of treatment results.

Impact of Nutrition-Based Interventions on Athletic Performance during Menstrual Cycle Phases: A Review

Despite the steady increase in female participation in sport over the last two decades, comprehensive research on interventions attenuating the influence of female menstrual physiology on performance remains scarce. Studies involving eumenorrheic women often only test in one menstrual phase to limit sex hormone variance, which may restrict the application of these findings to the rest of the menstrual cycle. The impacts of nutrition-based interventions on athletic performance throughout the menstrual cycle have not been fully elucidated. We addressed this gap by conducting a focused critical review of clinical studies that reported athletic outcomes as well as menstrual status for healthy eumenorrheic female participants. In total, 1443 articles were identified, and 23 articles were included. These articles were published between 2011 and 2021, and were retrieved from Google Scholar, Medline, and PubMed. Our literature search revealed that hydration-, micronutrient-, and phytochemical-based interventions can improve athletic performance (measured by aerobic capacity, anaerobic power, and strength performance) or attenuate exercise-induced damage (measured by dehydration biomarkers, muscle soreness, and bone resorption biomarkers). Most performance trials, however, only assessed these interventions in one menstrual phase, limiting the application throughout the entire menstrual cycle. Improvements in athletic performance through nutrition-based interventions may be contingent upon female sex hormone variation in eumenorrheic women.