Postexercise hypotension and related hemodynamic responses to cycling under heat stress in untrained men with elevated blood pressure

The influence of vigorous physical exertion on cardiac demand under conditions of daily living among firefighters with elevated blood pressure

BACKGROUND

Firefighters have a high prevalence of cardiovascular disease. The poor heart health of firefighters is implicated in their increased risk of sudden cardiac death (SCD). Exercise may be protective against SCD partially due to the immediate blood pressure (BP) reductions of 5-8 mmHg following exercise, termed postexercise hypotension (PEH) OBJECTIVES: To examine PEH under ambulatory conditions after a maximal cardiopulmonary exercise test (CPET) among career firefighters METHODS: Firefighters (n = 19) completed a maximal CPET and non-exercise control (CONTROL) in random order on separate non-workdays and left the laboratory instrumented to an ambulatory BP (ABP) monitor. Ambulatory systolic BP (ASBP), diastolic BP (ADBP), and heart rate (AHR) were recorded at hourly intervals over 19hr. The ambulatory rate pressure product (ARPP) was calculated as ASBPxAHRx10-3 at each hourly interval. Repeated measures ANCOVA tested if the ABP, AHR, and ARPP responses differed after CPET vs CONTROL over 19hr RESULTS: Firefighters were middle-aged (39.5 ± 8.9 yr), overweight (29.2 ± 4.0 kg/m2) men with elevated BP (123.1 ± 9.6/79.8 ± 10.4 mmHg), while resting HR (67.7 ± 11.3 bpm) and RPP (8.4 ± 1.7mmHg*bpm*10-3) were in normal ranges. ASBP (16.6 ± 5.7 mmHg) and ADBP (3.1 ± 4.6 mmHg) increased after the CPET vs CONTROL over 19hr (ps<0.01), as did AHR (9.4 ± 7.9 bpm, p = 0.02) and ARPP (2.5 ± 1.1mmHg*bpm*10-3, p < 0.01).

CONCLUSIONS

Unexpectedly, the firefighters exhibited postexercise hypertension rather than PEH. The increases in ABP and AHR we observed indicated a sustained increase in cardiac demand. Further investigation is needed to confirm our findings and determine whether the adverse hemodynamic responses we observed contribute to the high prevalence of SCD that firefighters experience on the job.

Different humidity environments do not affect the subsequent exercise ability of college football players after aerobic high-intensity interval training

Previous studies have explored the effect of differing heat and relative humidity (RH) environments on the performance of multiple anaerobic high-intensity interval training (HIIT). Still, its impact on physiological responses and performance following aerobic HIIT has not been well studied. This study examined the effects of differing RH environments on physiological responses and performance in college football players following HIIT. Twelve college football completed HIIT under four different environmental conditions: (1) 25 °C/20% RH (Control group); (2) 35 °C/20% RH (H20 group); (3) 35 °C/40% RH (H40 group); (4) 35 °C/80% RH (H80 group). The heart rate (HR), mean arterial pressure (MAP), lactate, tympanic temperature (TT), skin temperature (TS), thermal sensation (TS), and rating of perceived exertion (RPE) were recorded continuously throughout the exercise. The heart rate variability (HRV): including root mean squared differences of the standard deviation (RMSSD)、standard deviation differences of the standard deviation (SDNN)、high frequency (HF), low frequency (LF), squat jump height (SJH), cycling time to exhaustion (TTE), and sweat rate (SR) were monitored pre-exercise and post-exercise. The HR, MAP, lactate, TT, Ts, TS, and RPE in the 4 groups showed a trend of rapid increase, then decreased gradually. There was no significant difference in HR, MAP, TT, or RPE between the 4 groups at the same time point (p > 0.05), in addition to this, when compared to the C group, the lactate, Ts, TS in the other 3 groups significant differences were observed at the corresponding time points (p < 0.05). The RMSSD, SDNN, HF, and LF levels in the 4 groups before exercise were not significantly different. The RMSSD and HF in the H40 and H80 groups were significantly decreased and other HRV indicators showed no significant difference after exercise. In sports performance measurement, the SJH and TTE were significantly decreased, but there was no significant difference in the 4 groups. The SR was no significant difference in the 4 groups after exercise. In conclusion, heat and humidity environments elicited generally greater physiological effects compared with the normal environment but did not affect sports performance in college football players.

Greater post-exercise hypotension in healthy young untrained men after exercising in a hot compared to a temperate environment

This research examined the effects of exercising in a hot compared to a temperate environment on post-exercise hemodynamics in untrained men. We hypothesized exercise in a hot compared to a temperate environment would elicit greater post-exercise hypotension, and this would be attributable to higher cutaneous vascular conductance and sweat loss, and lower heart rate variability (HRV) and cardiac baroreflex sensitivity (cBRS). In a randomized counterbalanced order, 12 untrained healthy men completed two trials involving 40-min leg-cycling exercise at either 23 °C (CON) or 35 °C (HOT). Post-exercise participants rested supine for 60 min at 23 °C whilst hemodynamic and thermoregulatory measurements were assessed. Post-exercise hypotension was greater after exercising in a hot than a temperate environment as indicated by a lower mean arterial pressure at 60 min recovery (CON 83 ± 5 mmHg, HOT 78 ± 5 mmHg, Mean difference [95% confidence interval], -5 [-8, -3] mmHg). Throughout recovery, cutaneous vascular conductance was higher, and cBRS and HRV were lower after exercising in a hot than in a temperate environment (P < 0.05). Sweat loss was greater on HOT than on CON (P < 0.001). Post-exercise hypotension after exercising in the hot environment was associated with sweat loss (r = 0.66, P = 0.02), and changes in cutaneous vascular conductance (r = 0.64, P = 0.03), and HRV (Root mean square of the successive difference in R-R interval [RMSSD]) r=0.75, P = 0.01 and and log high frequency [HF] r=0.66, P = 0.02), but not cBRS (all, r ≤ 0.2, P > 0.05). Post-exercise hypotension was greater after exercise in a hot compared to a temperate environment and may be partially explained by greater sweat loss and cutaneous vascular conductance, and lower HRV.

Effect of COVID-19 Lockdown on Cardiovascular Health in University Students

BACKGROUND

A decrease in physical activity levels among university students during the COVID-19 pandemic is well-documented in the literature. However, the effect of lockdown restrictions on cardiovascular fitness has not been thoroughly investigated.

METHODS

The aim of the study was to assess the possible changes in cardiovascular fitness among university students during a 14-week period of the COVID-19 pandemic. Thirteen female and seven male tourism and recreation students participated in the study. Examinations were conducted in November 2020 and in February/March 2021. Students performed the PWC170 test on a cycling ergometer. Maximal oxygen consumption was calculated based on the PWC170 test results. Blood pressure and heart rate were measured at rest, as well as in the 1st and 5th minute of post-exercise recovery.

RESULTS

No substantial changes were observed in maximal oxygen consumption level when comparing autumn and winter indices. Male students presented elevated blood pressure whereas female students presented normal blood pressure. Heart-rate and blood-pressure indices did not show substantial alternations in examined students during analyzed period.

CONCLUSIONS

Fourteen weeks of lockdown had little effect on the cardiovascular health of tourism and recreation students.

Acute cardiovascular responses of wildland firefighters to working at prescribed burn

Wildland firefighters at prescribed burns are exposed to elevated levels of wildland fire smoke (WFS) while performing physically demanding tasks. WFS exposure has been linked to increases in hospital and emergency admissions for cardiovascular disorders in the general population. However, knowledge about the cardiovascular effect of occupational WFS exposure among wildland firefighters is limited. To provide a better understanding of the effect of this exposure scenario on acute hemodynamic responses, resting systolic/diastolic blood pressure (SBP/DBP) and heart rate (HR) of wildland firefighters were measured before (pre-shift), after (post-shift), and the morning (next morning) immediately following prescribed burn shifts (burn days) and regular work shifts (non-burn days). A total of 38 firefighters (34 males and 4 females) participated in this study and resting BP and HR were recorded on 9 burn days and 7 non-burn days. On burn days, HR significantly increased from pre-to post-shift (13.25 bpm, 95% CI: 7.47 to 19.02 bpm) while SBP significantly decreased in the morning following the prescribed burns compared to pre-shift (-6.25 mmHg, 95% CI: -12.30 to -0.20 mmHg). However, this was due to the decrease of SBP in the firefighters who were hypertensive (-8.46 mmHg, 95% CI: -16.08 to -0.84 mmHg). Significant cross-shift reductions (post-shift/next morning vs. pre-shift) were observed in SBP on burn days compared to non-burn days (-7.01 mmHg, 95% CI: -10.94 to -3.09 mmHg and -8.64 mmHg, 95% CI: -13.81 to -3.47 mmHg, respectively). A significant reduction on burn days was also observed from pre-shift to the following morning for HR compared to non-burn days (-7.28 bpm, 95% CI: -13.50 to -1.06 bpm) while HR significantly increased in pre-to post-shift on burn days compared to non-burn days (10.61 bpm, 95% CI: 5.05 to 16.17 bpm). The decreased BP observed in wildland firefighters might be due to a high level of carbon monoxide exposure and exercise-induced hypotension. The increase in HR immediately after prescribed burns might be attributable to WFS exposure and physical exertion in prescribed burn shifts. The results suggest that wildland firefighting exposure might cause a distinct hemodynamic response, including SBP reduction and HR increment, especially for those who have pre-existing hypertension.

The Effects of Acute Aerobic Exercise on Blood Pressure, Arterial Function, and Heart Rate Variability in Men Living With HIV

PURPOSE

This study aims to investigate the effects of acute cycling on blood pressure (BP), arterial function, and heart rate variability (HRV) in men living with HIV (MLHIV) using combined antiretroviral therapy (cART).

METHODS

Twelve MLHIV (48.7 ± 9.2 years; 25.2 ± 2.8 kg m-2) and 13 healthy controls (41.2 ± 9.9 years; 26.3 ± 2.9 kg m-2) performed a cycling bout (ES) (intensity: 50% oxygen uptake reserve; duration: time to achieve 150 kcal-MLHIV: 24.1 ± 5.5 vs. controls: 23.1 ± 3.0 min; p = 0.45), and a 20-min non-exercise session (NES).

RESULTS

At rest (p < 0.05), MLHIV presented higher brachial systolic/diastolic BP (SBP/DBP: 123.2 ± 14.2/76.8 ± 6.3 vs. 114.3 ± 5.1/71.6 ± 2.6 mmHg) and central BP (cSBP/cDBP: 108.3 ± 9.3/76.5 ± 6.5 vs. 101.6 ± 4.9/71.3 ± 4.4 mmHg) vs. controls but lower absolute maximal oxygen uptake (2.1 ± 0.5 vs. 2.5 ± 0.3 L min-1) and HRV indices reflecting overall/vagal modulation (SDNN: 24.8 ± 7.1 vs. 42.9 ± 21.3 ms; rMSSD: 20.5 ± 8.5 vs. 38.1 ± 22.8 ms; pNN50: 3.6 ± 4.2 vs. 13.6 ± 11.3%). DBP postexercise lowered in controls vs. MLHIV (∼4 mmHg, p < 0.001; ES: 0.6). Moreover, controls vs. MLHIV had greater reductions (p < 0.05) in augmentation index (-13.6 ± 13.7 vs. -3.1 ± 7.2% min-1; ES: 2.4), and HRV indices up to 5 min (rMSSD: -111.8 ± 32.1 vs. -75.9 ± 22.2 ms min-1; ES: 3.8; pNN50: -76.3 ± 28.3 vs. -19.0 ± 13.7% min-1; ES: 4.4). Within-group (ES vs. NES; p < 0.05) reductions occurred in controls for SBP (∼10 mmHg, 2 h), DBP (∼6 mmHg, 20, 30, and 70 min), cSBP (∼9 mmHg, 30 min), cDBP (∼7 mmHg, 30 and 70 min), augmentation index (∼10%, 30 min), and pNN50 (∼20%; up to 2 h), while in MLHIV only cSBP (∼6 mmHg, 70 min) and cDBP (∼4 mmHg, 30 min) decreased. Similar increases (up to 5 min) in heart rate (∼22 bpm) and decreases in SDNN (∼18 ms) and rMSSD (∼20 ms) occurred in both groups.

CONCLUSION

MLHIV under cART exhibited attenuated postexercise hypotension vs. healthy controls, which seemed to relate with impairments in vascular function.