Effect of Ambient Temperature on Metabolic Indices of Fatigue During Prolonged Exercise 1071

Febbraio, Mark A.; Parkin, J M; Baldwin, J. J.; Zhao, Shuang; Carey, Michael

doi:10.1097/00005768-199605001-01069

Cited by 9 publications

(4 citation statements)

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“…DISCUSSION We have previously observed that exercise capacity in the cold (11°C) is greater than that observed in warmer (21 and 31°C) environments (Galloway & Maughan, 1997), and, due to the longer exercise time, total CHO oxidation is also much greater at 11°C, thus implicating depletion of endogenous CHO stores as a possible main factor in the cause of fatigue at 11°C. This is supported by the muscle glycogen data of Febbraio, Parkin, Baldwin, Zhao & Carey (1996b), who observed that muscle glycogen concentrations (mean (S.E.M.)) at exhaustion from exercise at 70 % of VO2max in ambient temperatures of 40, 20 and 3 'C were 327 (31), 169 (40) and 153 (28) mmol (kg dry wt)-', respectively.…”

Section: Subjective Responsessupporting

confidence: 60%

The effects of substrate and fluid provision on thermoregulatory, cardiorespiratory and metabolic responses to prolonged exercise in a cold environment in man

Galloway¹,

Maughan²

1998

Experimental Physiology

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SUMMARYDuring prolonged exercise in a cold environment, fatigue is generally associated with a depletion of endogenous glycogen stores. This has lead many authors to hypothesize that the carbohydrate (CHO) content of fluids ingested in cool environments should be high, yet this hypothesis has not been specifically examined. In the present study, six healthy males cycled to exhaustion at approximately 80 % of their maximum oxygen consumption (Vo2,max) with either no drink (ND), a 15 % CHO-electrolyte drink (15 % CHO) or a 2 % CHO-electrolyte drink (2 % CHO). Dietary intake and exercise were replicated 2 days prior to each trial. Mean (S.D.) ambient temperature was 10.0 (0-3)°C with a relative humidity of 72 (2) % and an air velocity of approximately 0-7 m s-5 on all trials. Weighted mean skin temperature was calculated, and rectal temperature and heart rate were recorded at rest, during exercise and at exhaustion. Venous samples were drawn before and during exercise and at exhaustion for determination of haemoglobin, haematocrit, blood metabolites and serum electrolytes and osmolality. Expired air was collected for calculation of VO and respiratory exchange ratio which were used to estimate rates of fuel oxidation. Ratings ot perceived exertion (RPE) were also obtained. Exercise capacity was not different (P = 0.49) between trials, with median (range) times to exhaustion of 90 6 (66 8-106 0), 97-7 (60*9-112 0) and 102.0 (77.1-170.7) min for the ND, 15 % CHO and 2 % CHO trials, respectively. The 15 % CHO drink significantly (P < 0.05) elevated blood glucose concentration and total CHO oxidation compared with the ND trial. The 2 % CHO drink significantly (P < 0.05) reduced the estimated change in plasma volume and resulted in a lower serum osmolality than the other two trials. No differences were observed in any thermoregulatory or cardiorespiratory responses between trials. These data suggest that maintenance of blood-borne substrate and/or plasma volume does not influence exercise capacity in the cold, as is commonly reported during this type and intensity of exercise in warmer environments.

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Section: Subjective Responsessupporting

confidence: 60%

The effects of substrate and fluid provision on thermoregulatory, cardiorespiratory and metabolic responses to prolonged exercise in a cold environment in man

Galloway¹,

Maughan²

1998

Experimental Physiology

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“…The increase in body temperature at the end of the trials of this study was not caused by hypohydration since the indices of hypohydration remained stable. Similarly, we observed no significant difference in glycemia values at D4 and D8 compared to D0, or in [La], indicating that the cyclists were ensuring that their diet contained sufficient carbohydrates to allow for the increased carbohydrate utilization that occurs during exercise in the heat [7]. Despite the daily loss in body mass, no differences were observed in serum electrolyte concentrations between D0, D4, and D8, suggesting that there was similar fluid loss from the vascular compartments in all trials [34].…”

Section: Discussionmentioning

confidence: 53%

Heart Rate, Thermoregulatory and Humoral Responses During a 9-Day Cycle Race in a Hot and Humid Climate

Hue

Voltaire²,

Hertogh³

et al. 2006

Int J Sports Med

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Seven acclimated elite road cyclists were recruited from among the participants in the Tour de Guadeloupe, a 9-day cycle race (D1-D9) held in hot/humid climate (approximately 31 degrees C dry temperature and 76 % relative humidity). Each day of the competition, heart rate (HR) was recorded every 15 s, tympanic temperature (Ttym) was recorded before exercise and immediately at the end of each stage, and body mass loss (BML) was measured by changes in nude body mass at rest and after each stage. Blood lactate concentration [La] was measured at rest and 5 min after each stage. Venous blood samples were collected before the competition and on the 4 th and 8 th days (D4, D8) for hematological and serum determinations and biochemical analyses. No significant differences were found in cardiac, thermoregulatory, or [La] parameters at rest over the 9 days. The subjects spent 31 +/- 6 % of their time below the lactate threshold (LT), 52 +/- 8 % between LT and the onset of blood lactate accumulation (OBLA), and 18 +/- 6 % above OBLA. The increase in Ttym at D3 (0.48 +/- 0.3 degrees C) was significantly lower (p < 0.05) than at D1, D4, D5, and D6. No difference was found for BML between the different stages. Significant increases (p < 0.05) were observed in monocytes at D8 vs. D4 and pre-race values (D0) and in serum Cl-concentration at D4 vs. D0 and D8 (p < 0.05). A significant reduction was observed in mean corpuscular hemoglobin concentration (MCHC) at D8 and D4 vs. D0 (p < 0.01). No difference was found in other blood parameters at D0, D4, or D8. Taken together, these results suggest that a consecutive 9-day cycle competition in hot/humid climate did not alter homeostasis at rest in acclimated well-trained cyclists. No major effect of repeated cycling stages on thermoregulatory and blood parameters was observed during the Tour de Guadeloupe. Further research is needed to compare the cardiac adaptations of natives to tropical climate and un-acclimated subjects during long-duration exercise.

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“…However, much of what has been written relates to the aerobic nature of such activity in both hot and humid environments [32]. The general outcome of aerobic exercise in the heat is that subjects fatigue more quickly [14], they have a higher glycogen use when compared to normal conditions [8,9] and a decreased cardiac output [24]. Furthermore there is a higher body core temperature, higher heart rate and an increased rate of ventilation [3,20,25,26].…”

Section: Introductionmentioning

confidence: 99%

Effects of Differing Heat and Humidity on the Performance and Recovery from Multiple High Intensity, Intermittent Exercise Bouts

Backx¹,

McNaughton²,

Crickmore³

et al. 2000

Int J Sports Med

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The aim of this study was to determine the effects of different conditions of heat and humidity on two multiple bouts of high intensity cycling with 60 min recovery between each bout. Eight males (age: 25.5+/-1.8 yr, height: 179.0+/-3.7 cm; weight: 72.3+/-4.0 kg; VO2peak: 51.5+/-2.4 ml x kg(-1) x min(-1), Peak Aerobic Power: 366+/-13 W) volunteered for this study. After undertaking VO2peak testing, all participated randomly, in three consecutive 30 s Wingate tests in three different environmental conditions being: Normal (22 degrees C/30% RH), Wet (30 degrees C/85% RH), and Hot (40 degrees C/40% RH). Subjects were then monitored for the 60 min post-exercise period after which time they repeated the Wingate tests and were again monitored for 60 min. Blood samples were taken pre, immediately post exercise, and at 1, 5, 10, 15, 30, 45, and 60 min into each of the recovery periods and analysed for lactate, pH, and hematocrit. Heart rate was monitored continuously throughout exercise (5 s average) and recovery (60 s average). Weight was measured pre exercise and at 15, 30, 45, and 60 min post-exercise. Urine samples were collected at the same time and analysed for osmolality. The results of the experiment indicated that environmental conditions had no effect on the performance of either series 1 or 2 Wingate tests. Neither were there any changes in weight throughout the three conditions or across the condition. Post exercise pH levels were lower than pre exercise values (p < 0.0001) and the reverse was true for blood lactate levels (p < 0.0003). We conclude that anaerobic exercise is not unduly affected by hot or humid conditions when subjects can re-hydrate according to decreases in body weight.

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Effect of Ambient Temperature on Metabolic Indices of Fatigue During Prolonged Exercise 1071

Cited by 9 publications

References 0 publications

The effects of substrate and fluid provision on thermoregulatory, cardiorespiratory and metabolic responses to prolonged exercise in a cold environment in man

The effects of substrate and fluid provision on thermoregulatory, cardiorespiratory and metabolic responses to prolonged exercise in a cold environment in man

Heart Rate, Thermoregulatory and Humoral Responses During a 9-Day Cycle Race in a Hot and Humid Climate

Effects of Differing Heat and Humidity on the Performance and Recovery from Multiple High Intensity, Intermittent Exercise Bouts

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