The Consequences of Exercise on Thirst and Fluid Intake

Greenleaf, J. E.

doi:10.1007/978-1-4471-1817-6_27

Cited by 7 publications

(6 citation statements)

References 32 publications

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“…In a review, on the fluid replacement of athletes Casa and colleagues (2000) reported that dehydration of 1-2% body weight increases physiological stress and decreases performance. However, in reality, it is often difficult and sometimes impossible to prevent at least some dehydration during repeated heat stress (Convertino et al 1996) and this has been considered of little consequence by some authors (Noakes et al 1988;Greenleaf 1991), on the basis that this readily occurs during repeated heat exposure. In summary, we postulate that the increased physiological strain of restricted fluid replenishment during DEH acclimation may have resulted in adaptation of the fluid-regulatory system.…”

Section: Fluid Regulation and Blood Volume Response To Repeated Heat mentioning

confidence: 99%

Induction and decay of short-term heat acclimation

et al. 2009

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Abstract:Most advice for heat adaptation is to use long-term (>10 d) regimes, in which hydration status is maintained. We tested the hypothesis that short-term (5-day) heat acclimation would confer substantial improvements in physiological strain and exercise tolerance for exercise in the heat, and fluid regulatory strain provides a thermally-independent stimulus for such adaptations. Ten moderately-fit males were heat acclimated using controlled hyperthermia (rectal temperature 38.5°C) for 90 min on five consecutive days (T a = 40°C, 60% RH), on two occasions separated by a five-week washout, in a randomly assigned, cross-over design; one with euhydration (EUH) and one with dehydration (DEH) during acclimation bouts. One week before, then on the 2 nd day after each acclimation regime, a heat stress test (HST) was completed, comprising cycling at 40% peak power output for 90 min (T a = 35°C, 60% RH), before incrementing to exhaustion. Plasma volume (PV) at rest was measured using CO rebreathing. Acclimation exercise-induced response of[aldo] p became more pronounced across DEH (  178 pg . mL -1 ; 95%CI: 33 to 324) but not EUH (  -47 pg . mL -1 : -209 to 115) and this difference was significant (P=0.02).Compared to EUH, permissive DEH during acclimation bouts conferred larger acclimation-induced increases in resting PV (4.1%: -1.5 to 9.8%; P=0.06), F Q  (4.2: 0.7 to 7.8 ml . min -1. 100 ml -1 ; P=0.009), FVC (0.06: 0.02 to 0.10 ml . 100ml Tissue -1. min -1. mmHg -1 ; P=0.006) and decreased end-exercise c f by 17% (19: -29 to 9 b·min-1; P=0.05). In conclusion, short-term (5-day) heat acclimation was effective with several adaptations more pronounced after fluid-regulatory strain from a dehydration acclimation regime.

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Section: Fluid Regulation and Blood Volume Response To Repeated Heat mentioning

confidence: 99%

Induction and decay of short-term heat acclimation

et al. 2009

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“…Interestingly, athletes tend to ingest¯uid at a rate that replaces, at most, about 50% of the volume that is lost as sweat during exercise (Pitts et al 1944, Wyndham & Strydom 1969, Coyle & Montain 1992). This subjective behaviour, which results in involuntary dehydration, has been considered of little consequence by some authors (Noakes et al 1988, Greenleaf 1991 and indeed it has been suggested that ingestion of large volumes during exercise may increase the risk of hyponatraemia (Noakes et al 1988). Although plasma sodium concentration fell during exercise in FR-100 ( Figure 2), it remained above clinical hyponatraemia levels (< 130 mmol L A1 ) throughout exercise.…”

Section: Discussionmentioning

confidence: 97%

Influence of ingested fluid volume on physiological responses during prolonged exercise

McConell

Burge

Skinner

et al. 1997

Acta Physiologica Scandinavica

110

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The effect of different rates of fluid ingestion on heart rate, rectal temperature, plasma electrolytes, hormones and performance was examined during prolonged strenuous exercise conducted at 21 degrees C. Seven well-trained males (24 +/- 1 yr; 68.6 +/- 2.9 kg; VO2 peak = 4.69 +/- 0.17 L min-1; mean +/- SEM) cycled for 2 h at 69 +/- 1% VO2 peak while receiving either no fluid replacement (NF), a volume of water estimated to prevent body weight loss (FR-100 = 2.32 +/- 0.10 L 2 h-1) or 50% of this volume (FR-60 = 1.16 +/- 0.05 L 2 h-1). The 2-h exercise bout was followed by a ride to exhaustion at a workload estimated to be 90% VO2 peak. After 2 h of exercise, NF was associated with a 3.2 +/- 0.1% weight loss, while FR-50 and FR-100 resulted in losses of 1.8 +/- 0.1 and 0.1 +/- 0.1%, respectively. Compared with FR-100, heart rate and rectal temperature were elevated (P < 0.05) during the second hour of exercise in NF, with FR-50 intermediate. Reductions in plasma volume during exercise were greater in NF and FR-50, compared with FR-100 and plasma sodium concentration was elevated in NF, decreased slightly in FR-100, with FR-50 intermediate. Plasma renin activity, aldosterone and atrial natriuretic peptide increased to similar extents in the three trials. Plasma vasopressin remained unchanged for FR-100, increased for NF, with intermediate values for FR-50. Exercise time to exhaustion at 90% VO2-peak was longer in FR-100 (328 +/- 93 s) than NF (171 +/- 75 s) with FR-50 (248 +/- 107 s) not significantly different from either FR-100 or NF. In conclusion, the responses of heart rate, rectal temperature, plasma sodium, and vasopressin during, and performance following, prolonged cycling exercise conducted at 21 degrees C are related to the amount of fluid ingested (i.e. the degree of dehydration).

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“…Hypohydration of 1-2% body mass can increases physiological stress and decrease performance (Casa et al, 2000), depending on fitness (Merry et al, 2010) and ambient heat stress (Cheuvront et al, 2010). However, it is often difficult and sometimes impossible to prevent at least some dehydration during heat stress (Convertino and others 1996) and this has been considered of little consequence by some authors (Greenleaf 1991;Noakes and others 1988). Irrespective, these are issues of acute functional affects, and the purpose of acclimation bouts is to stimulate adaptation.…”

Section: Discussionmentioning

confidence: 99%

“…In a review on fluid replacement in athletes, Casa and colleagues (2000) reported that dehydration of 1-2% body mass increases physiological stress and decreases performance. However, in reality, it is often difficult and sometimes impossible to prevent at least some dehydration during repeated heat stress (Convertino and others 1996) and this has been considered of little consequence by some authors (Greenleaf 1991;Noakes and others 1988), on the basis that this readily occurs during repeated heat exposure. It is also unknown if in trained individuals, who are glycogen loaded, if 1-2% mass loss necessarily reflects dehydration.…”

Section: Fluid Regulation and Blood Volume Response To Repeated Heat Stressmentioning

confidence: 99%