Acute effect of oral water intake during exercise on post-exercise hypotension

Influence of Fluid Ingestion on Heart Rate, Cardiac Autonomic Modulation and Blood Pressure in Response to Physical Exercise: A Systematic Review with Meta-Analysis and Meta-Regression

A systematic review was undertaken to investigate the involvement of hydration in heart rate (HR), HR variability (HRV) and diastolic (DBP) and systolic (SBP) blood pressure in response to exercise. Data synthesis: The EMBASE, MEDLINE, Cochrane Library, CINAHL, LILACS and Web of Science databases were searched. In total, 977 studies were recognized, but only 36 were included after final screening (33 studies in meta-analysis). This study includes randomized controlled trials (RCTs) and non-RCTs with subjects > 18 years old. The hydration group consumed water or isotonic drinks, while the control group did not ingest liquids. For the hydration protocol (before, during and after exercise), the HR values during the exercise were lower compared to the controls (-6.20 bpm, 95%CI: -8.69; -3.71). In the subgroup analysis, "water ingested before and during exercise" showed lower increases in HR during exercise (-6.20, 95%CI: 11.70 to -0.71), as did "water was ingested only during exercise" (-6.12, 95%CI: -9.35 to -2.89). Water intake during exercise only revealed a trend of avoiding greater increases in HR during exercise (-4,60, 95%CI: -9.41 to 0.22), although these values were not significantly different (p = 0.06) from those of the control. "Isotonic intake during exercise" showed lower HRs than the control (-7.23 bpm, 95% CI: -11.68 to -2.79). The HRV values following the exercise were higher in the hydration protocol (SMD = 0.48, 95%CI: 0.30 to 0.67). The values of the SBP were higher than those of the controls (2.25 mmHg, 95%CI: 0.08 to 4.42). Conclusions: Hydration-attenuated exercise-induced increases in HR during exercise, improved autonomic recovery via the acceleration of cardiac vagal modulation in response to exercise and caused a modest increase in SBP values, but did not exert effects on DBP following exercise.

Total Fasting and Dehydration in the Operating Room: How Can Surgeons Survive and Thrive?

OBJECTIVES

Hydration and nutrition are critical to achieving optimal performance. This study aimed to assess the impact of limited oral intake in the operating room environment on surgical resident health, well-being, and performance.

DESIGN

Electronic survey was sent to 94 surgical trainees at our institution in 2020. Chi-square analyses were performed to assess for differences in survey responses by sex.

SETTING

A single tertiary-care institution.

PARTICIPANTS

Surveys were sent to surgical residents and fellows in general surgery, neurosurgery, and orthopedic surgery. Seventy-nine (80%) of the 94 residents and fellows responded.

RESULTS

Of the 79 responses, most trainees (79%) experienced dehydration within 6 hours of operating. Forty-four (56%) reported no fluid intake for greater than 6 hours on average, and 39 (49%) reported that they frequently had difficulty rehydrating in between cases. Most of the respondents (70%) frequently experienced symptoms of dehydration, including orthostasis, headache, and constipation. Fifty-six (71%) believed that dehydration frequently affected their performance. Compared to men, women were more likely to feel dehydrated within 4 hours of operating (58% vs. 25%, p = 0.005). Women were also more likely to have difficulty rehydrating in between cases (75% vs. 38%, p = 0.0026), experience symptoms of dehydration (92% vs. 60%, p = 0.0049), and report that dehydration affects surgical performance (88% vs. 64%, p = 0.0318).

CONCLUSIONS

Prolonged fasting and dehydration are common issues that may negatively impact performance and wellbeing of surgical trainees. Also, dehydration may affect men and women differently.

Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies

A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat by examining the benefits of heat acclimation, cooling strategies, and hyperhydration. Finally, contemporary controversies are summarized and future research directions are provided.

Effect of ice slurry ingestion on core temperature and blood pressure response after exercise in a hot environment

Delays in the restoration of thermoregulation after exercise in a hot environment has been associated with post-exercise hypotension. This study tested the hypothesis that simultaneous internal cooling and rehydration by ingesting ice slurry prevents the excessive decrease in mean arterial pressure (MAP) and promotes recovery of core and skin temperatures in male athletes. Seven male athletes participated in this randomized controlled trial with a crossover design. The participants ran on a treadmill at 75% of their maximal oxygen uptake in the heat (35 °C, 60% relative humidity), up to exhaustion. Immediately after exercise, participants ingested either 4 g⋅kg ^-1 body weight of ice slurry (0.5 °C, ICE) or a control beverage (28 °C, CON). The participants then recovered by sitting for 20 min. We measured participants' rectal temperature (T_re), skin temperature (T_sk), mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), and physiological strain index (PSI) before exercise (Pre), after running to exhaustion (PEx), and at 0 (P0), 10 (P10), and 20 (P20) minutes after ice slurry or control beverage ingestion. MAP, CO, HR, TPR, or PSI did not change significantly during the recovery period. At P10 and P20, T_re and T_sk significantly decreased in the ICE group compared to the CON group (p < 0.05). These results suggested that ingestion of ice slurry, post-exercise, promoted core and skin temperature recovery but did not affect the central and peripheral cardiovascular responses during the acute recovery period.

Hydration Does Not Change Postexercise Hypotension and Its Mechanisms

BACKGROUND

Drinking water is recommended before and after exercise to avoid dehydration. However, water ingestion may mitigate or prevent postexercise hypotension. This study investigated the effects of intentional hydration on postaerobic exercise hemodynamics and autonomic modulation.

METHODS

A total of 18 young men randomly underwent 4 experimental sessions as follows: (1) control with intentional hydration (1 L of water in the previous night, 500 mL 60 min before the intervention, and 1 mL for each 1 g of body mass lost immediately after the intervention); (2) control without intentional hydration (ad libitum water ingestion before the intervention); (3) exercise (cycle ergometer, 45 min, 50% of VO2peak) with intentional hydration; and (4) exercise without intentional hydration. Hemodynamic and autonomic parameters were measured before and after the interventions and were compared by 3-way analysis of variance.

RESULTS

Intentional hydration did not change any postexercise hemodynamic nor autonomic response. Exercise decreased systolic blood pressure and stroke volume (-4.1 [0.8] mm Hg and -4.9 [1.5] mL, P < .05), while increased cardiac sympathovagal balance (0.3 [0.3], P < .05) during the recovery. In addition, it abolished the increase in diastolic blood pressure and the decrease in heart rate observed in the control sessions.

CONCLUSION

Intentional hydration does not modify the hypotensive effect promoted by previous aerobic exercise and did not alter its hemodynamic and autonomic mechanisms.

Carotid baroreflex control of central and peripheral hemodynamics during recovery after moderate leg cycling exercise

This study aimed to examine the carotid baroreflex (CBR) control of the central and peripheral hemodynamics after exercise using the neck pressure (NP) and neck suction (NS) technique. Sixteen healthy young male participants (age: 27 ± 1.5 yr) were in a supine position for 30 min preexercise, followed by 60 min of cycling exercise, and then returned to a supine position for an additional 60 min postexercise. Both pre- and postexercise, the CBR-mediated responses of the central and peripheral hemodynamics were evaluated using 5-s periods of NP and NS (-60, -40, or +40 mmHg). As the central hemodynamics measurements, heart rate (HR), mean arterial pressure (MAP), cardiac output, and total vascular conductance were assessed. To determine peripheral circulation, vascular conductance in active and inactive limbs was measured. Eight participants [responder (RE) group] showed substantial postexercise hypotension (PEH) during recovery from exercise (Δ MAP: approximately -5 ± 0.9 mmHg, P < 0.05). The other eight participants did not display a reduction in MAP after exercise (non-RE group). In the non-RE group, the responsiveness of CBR-mediated changes in HR, MAP, and vascular conductance increased, particularly in response to -40 mmHg NS during postexercise compared with preexercise. However, in the RE group, any alterations in responsiveness to NP and NS were unchanged during PEH compared with preexercise. In conclusion, some normotensive individuals do not show PEH because the responsiveness of the CBR in central and peripheral hemodynamics following exercise is augmented, particularly to high blood pressure.NEW & NOTEWORTHY The carotid baroreflex (CBR) control of central and peripheral hemodynamics was investigated after exercise in both the presence and absence of postexercise hypotension (PEH). In individuals with no PEH, the responsiveness of CBR-mediated changes in all hemodynamics was augmented after exercise, particularly to high blood pressure; conversely, the CBR responsiveness remained unchanged in individuals with PEH. These findings provide insight into the mechanism of CBR control after exercise.

Pathophysiology of Noncardiac Syncope in Athletes

The most frequent cause of syncope in young athletes is noncardiac etiology. The mechanism of noncardiac syncope (NCS) in young athletes is neurally-mediated (reflex). NCS in athletes usually occurs either as orthostasis-induced, due to a gravity-mediated reduced venous return to the heart, or in the context of exercise. Exercise-related NCS typically occurs after the cessation of an exercise bout, while syncope occurring during exercise is highly indicative of the existence of a cardiac disorder. Postexercise NCS appears to result from hypotension due to impaired postexercise vasoconstriction, as well as from hypocapnia. The mechanisms of postexercise hypotension can be divided into obligatory (which are always present and include sympathoinhibition, histaminergic vasodilation, and downregulation of cardiovagal baroreflex) and situational (which include dehydration, hyperthermia and gravitational stress). Regarding postexercise hypocapnia, both hyperventilation during recovery from exercise and orthostasis-induced hypocapnia when recovery occurs in an upright posture can produce postexercise cerebral vasoconstriction. Athletes have been shown to exhibit differential orthostatic responses compared with nonathletes, involving augmented stroke volume and increased peripheral vasodilation in the former, with possibly lower propensity to orthostatic intolerance.

Fluid intake restores retinal blood flow early after exhaustive exercise in healthy subjects

PURPOSE

It remains unclear whether rehydration restores retinal blood flow reduced by exhaustive exercise. We investigated the effect of fluid intake on retinal blood flow after exhaustive exercise.

METHODS

Blood flow in the inferior (ITRA) and superior temporal retinal arterioles (STRA) was measured before and after incremental cycling exercise until exhaustion in 13 healthy males. After the exercise, the subjects rested without drinking (control condition: CON) or with drinking an electrolyte containing water (rehydrate condition: REH) and were followed up for a period of 120 min. To assess the hydration state, the body mass was measured, and venous blood samples were collected and plasma volume (PV) was calculated.

RESULTS

Body mass decreased in CON after the trial [- 1.1 ± 0.1% (mean ± SE), p < 0.05]. PV was lower in CON than in REH during recovery. The ITRA and STRA blood flows decreased immediately after exercise from the resting baseline (ITRA; - 23 ± 4% in REH and - 30 ± 4% in CON, p < 0.05). The ITRA blood flow recovered baseline level at 15 min of recovery in REH (- 9 ± 3%, p = 0.5), but it remained reduced in CON (-14 ± 3%, p < 0.05). The STRA blood flow was higher in REH than in CON at 15 min (2 ± 3 vs. - 5 ± 3%, p < 0.05).

CONCLUSIONS

The results of this study suggest that the reduction in retinal blood flow induced by exhaustive exercise can be recovered early by rehydration.

Heat and Dehydration Additively Enhance Cardiovascular Outcomes following Orthostatically-Stressful Calisthenics Exercise

Exercise and exogenous heat each stimulate multiple adaptations, but their roles are not well delineated, and that of the related stressor, dehydration, is largely unknown. While severe and prolonged hypohydration potentially “silences” the long-term heat acclimated phenotype, mild and transient dehydration may enhance cardiovascular and fluid-regulatory adaptations. We tested the hypothesis that exogenous heat stress and dehydration additively potentiate acute (24 h) cardiovascular and hematological outcomes following exercise. In a randomized crossover study, 10 physically-active volunteers (mean ± SD: 173 ± 11 cm; 72.1 ± 11.5 kg; 24 ± 3 year; 6 females) completed three trials of 90-min orthostatically-stressful calisthenics, in: (i) temperate conditions (22°C, 50% rh, no airflow; CON); (ii) heat (40°C, 60% rh) whilst euhydrated (HEAT), and (iii) heat with dehydration (no fluid ~16 h before and during exercise; HEAT+DEHY). Using linear mixed effects model analyses, core temperature (T_CORE) rose 0.7°C more in HEAT than CON (95% CL: [0.5, 0.9]; p < 0.001), and another 0.4°C in HEAT+DEHY ([0.2, 0.5]; p < 0.001, vs. HEAT). Skin temperature also rose 1.2°C more in HEAT than CON ([0.6, 1.8]; p < 0.001), and similarly to HEAT+DEHY (p = 0.922 vs. HEAT). Peak heart rate was 40 b·min⁻¹ higher in HEAT than in CON ([28, 51]; p < 0.001), and another 15 b·min⁻¹ higher in HEAT+DEHY ([3, 27]; p = 0.011, vs. HEAT). Mean arterial pressure at 24-h recovery was not consistently below baseline after CON or HEAT (p ≥ 0.452), but was reduced 4 ± 1 mm Hg after HEAT+DEHY ([0, 8]; p = 0.020 vs. baseline). Plasma volume at 24 h after exercise increased in all trials; the 7% increase in HEAT was not reliably more than in CON (5%; p = 0.335), but was an additional 4% larger after HEAT+DEHY ([1, 8]; p = 0.005 vs. HEAT). Pooled-trial correlational analysis showed the rise in T_CORE predicted the hypotension (r = −0.4) and plasma volume expansion (r = 0.6) at 24 h, with more hypotension reflecting more plasma expansion (r = −0.5). In conclusion, transient dehydration with heat potentiates short-term (24-h) hematological (hypervolemic) and cardiovascular (hypotensive) outcomes following calisthenics.

The influence of high-intensity compared with moderate-intensity exercise training on cardiorespiratory fitness and body composition in colorectal cancer survivors: a randomised controlled trial

PURPOSE

Following colorectal cancer diagnosis and anti-cancer therapy, declines in cardiorespiratory fitness and body composition lead to significant increases in morbidity and mortality. There is increasing interest within the field of exercise oncology surrounding potential strategies to remediate these adverse outcomes. This study compared 4 weeks of moderate-intensity exercise (MIE) and high-intensity exercise (HIE) training on peak oxygen consumption (V̇O2peak) and body composition in colorectal cancer survivors.

METHODS

Forty seven post-treatment colorectal cancer survivors (HIE = 27 months post-treatment; MIE = 38 months post-treatment) were randomised to either HIE [85-95 % peak heart rate (HRpeak)] or MIE (70 % HRpeak) in equivalence with current physical activity guidelines and completed 12 training sessions over 4 weeks.

RESULTS

HIE was superior to MIE in improving absolute (p = 0.016) and relative (p = 0.021) V̇O2peak. Absolute (+0.28 L.min(-1), p < 0.001) and relative (+3.5 ml.kg(-1).min(-1), p < 0.001) V̇O2 peak were increased in the HIE group but not the MIE group following training. HIE led to significant increases in lean mass (+0.72 kg, p = 0.002) and decreases in fat mass (-0.74 kg, p < 0.001) and fat percentage (-1.0 %, p < 0.001), whereas no changes were observed for the MIE group. There were no severe adverse events.

CONCLUSIONS

In response to short-term training, HIE is a safe, feasible and efficacious intervention that offers clinically meaningful improvements in cardiorespiratory fitness and body composition for colorectal cancer survivors.

IMPLICATIONS FOR CANCER SURVIVORS

HIE appears to offer superior improvements in cardiorespiratory fitness and body composition in comparison to current physical activity recommendations for colorectal cancer survivors and therefore may be an effective clinical utility following treatment.

Post-Exercise Hypotension and Its Mechanisms Differ after Morning and Evening Exercise: A Randomized Crossover Study

Post-exercise hypotension (PEH), calculated by the difference between post and pre-exercise values, it is greater after exercise performed in the evening than the morning. However, the hypotensive effect of morning exercise may be masked by the morning circadian increase in blood pressure. This study investigated PEH and its hemodynamic and autonomic mechanisms after sessions of aerobic exercise performed in the morning and evening, controlling for responses observed after control sessions performed at the same times of day. Sixteen pre-hypertensive men underwent four sessions (random order): two conducted in the morning (7:30am) and two in the evening (5pm). At each time of day, subjects underwent an exercise (cycling, 45 min, 50%VO₂peak) and a control (sitting rest) session. Measurements were taken pre- and post-interventions in all the sessions. The net effects of exercise were calculated for each time of day by [(post-pre exercise)-(post-pre control)] and were compared by paired t-test (P<0.05). Exercise hypotensive net effects (e.g., decreasing systolic, diastolic and mean blood pressure) occurred at both times of day, but systolic blood pressure reductions were greater after morning exercise (-7±3 vs. -3±4 mmHg, P<0.05). Exercise decreased cardiac output only in the morning (-460±771 ml/min, P<0.05), while it decreased stroke volume similarly at both times of day and increased heart rate less in the morning than in the evening (+7±5 vs. +10±5 bpm, P<0.05). Only evening exercise increased sympathovagal balance (+1.5±1.6, P<0.05) and calf blood flow responses to reactive hyperemia (+120±179 vs. -70±188 U, P<0.05). In conclusion, PEH occurs after exercise conducted at both times of day, but the systolic hypotensive effect is greater after morning exercise when circadian variations are considered. This greater effect is accompanied by a reduction of cardiac output due to a smaller increase in heart rate and cardiac sympathovagal balance.

Influence of population and exercise protocol characteristics on hemodynamic determinants of post-aerobic exercise hypotension

Due to differences in study populations and protocols, the hemodynamic determinants of post-aerobic exercise hypotension (PAEH) are controversial. This review analyzed the factors that might influence PAEH hemodynamic determinants, through a search on PubMed using the following key words: “postexercise” or “post-exercise” combined with “hypotension”, “blood pressure”, “cardiac output”, and “peripheral vascular resistance”, and “aerobic exercise” combined only with “blood pressure”. Forty-seven studies were selected, and the following characteristics were analyzed: age, gender, training status, body mass index status, blood pressure status, exercise intensity, duration and mode (continuous or interval), time of day, and recovery position. Data analysis showed that 1) most postexercise hypotension cases are due to a reduction in systemic vascular resistance; 2) age, body mass index, and blood pressure status influence postexercise hemodynamics, favoring cardiac output decrease in elderly, overweight, and hypertensive subjects; 3) gender and training status do not have an isolated influence; 4) exercise duration, intensity, and mode also do not affect postexercise hemodynamics; 5) time of day might have an influence, but more data are needed; and 6) recovery in the supine position facilitates systemic vascular resistance decrease. In conclusion, many factors may influence postexercise hypotension hemodynamics, and future studies should directly address these specific influences because different combinations may explain the observed variability in postexercise hemodynamic studies.

Similar hypotensive effects of combined aerobic and resistance exercise with 1 set versus 3 sets in women with metabolic syndrome

The aim of the present study was to compare the response of systolic blood pressure (SBP), mean blood pressure (MBP) and diastolic blood pressure (DBP) following combined training with 1 set or with 3 sets of resistance exercise (RE). Sixteen women with metabolic syndrome (MetS) were randomly assigned to perform two combined exercise protocols and a control session (CON): 1-set, 30 min of aerobic exercise (AE) at 65-70% of reserve heart rate and 1 set of 8-12 repetitions at 80% of 10-RM in six resistance exercises; 3-sets, same protocol but with 3 sets; and CON, 30 min of seated rest. The SBP, MBP and DBP were measured before and every 15 min during 90 min following the experimental sessions. The SBP displayed a decrease (P ≤ 0.05) during the 90 min following the RE session with 1-set and 3-set, while MBP was decreased (P ≤ 0.05) up to 75 min after 1-set and up to 30 min after the 3-set exercise session compared with pre-intervention values. There was a decrease in DBP only for the greatest individual decrease following 1-set (-6.1 mmHg) and 3-set (-4.9 mmHg) combined exercise sessions, without differences between them. The rate-pressure product and heart rate remained significantly higher (P ≤ 0.05) 75 min and 90 min after the combined exercise session with 1- and 3-sets compared with the CON, respectively. In conclusion, a low-volume RE combined with AE resulted in similar decrease of SBP when compared with RE with 3-sets in women with MetS, which could be beneficial in situations of limited time.