Summary
Thermoregulatory and cardiorespiratory responses to bicycling 55 km (mean speed 9.7 m·s−1) outdoors (15‡ C DB) were compared to equivalent cycle ergometry (90 min at 65% \(\dot V_{O_{2\max } } \)) in the laboratory (20–23‡ C DB, 50% RH) in 7 trained cyclists. Outdoor environmental conditions were simulated with fans and lamps, and were contrasted with standard no-wind, no-sun laboratory conditions. Sweating rate was similar during outdoor and laboratory simulated outdoor cycling (0.90 and 0.87 to 0.94 l·h−1 respectively). During outdoor bicycling, mean heart rate (161 bt·min−1) was 7–13% higher (p<.05) than under laboratory conditions, suggesting a greater strain for a similar external workrate. The increase in rectal temperature (0.8‡ C) was 33–50% less (p<0.05) at the cooler outdoor ambient temperature than in the laboratory. Thermoregulatory stress was greater under the no-fan, no-lamp laboratory condition than during simulated outdoor conditions (36–38% greater (p<0.05) sweating rate, 15–18% greater (p<0.01) mean skin temperature, 6.4 to 7.8 fold greater (p<0.01) amount of clothing-retrained sweat). The cooling wind encountered in actual road bicycling apparently reduces thermoregulatory and circulatory demands compared with stationary cycle ergometry indoors. Failure to account for this enhanced cooling may result in overestimation of the physiological stress of actual road cycling. Additionally, core temperature and heart rate rose throughout the period of laboratory cycling at a constant velocity, indicating the need for caution in inferring relative metabolic rate (\(\dot V_{O_2 } \)/\(\dot V_{O_{2\max } } \)) from heart rate during prolonged exercise without adequate rehydration.
Similar content being viewed by others
References
Boulay MR, Hamel P, Simoneau JA, Lortie G, Prud'homme D, Bouchard C (1984) A test of aerobic capacity: description and reliability. Can J Appl Sport Sci 9: 122–126
Brooke JD, Davies GJ (1973) Comment on “Estimation of the energy expenditure of sporting cyclists.” Ergonomics 16:237–238
Costill DL, Kramer WF, Fisher A (1970) Fluid ingestion during distance running. Arch Environ Health 21:520–525
Davies CT (1980) Influence of air flow and skin temperature on sweating at the onset, during and following exercise. Ergonomics 23:559–569
Edwards RJ, Harrison MH, Cochrane LA, Mills FJ (1983) Blood volume and protein responses to skin cooling and warming during cycling exercise. Eur J Appl Physiol 50:195–206
Ekelund L-G (1967) Circulatory and respiratory adaptation during prolonged exercise. Acta Physiol Scand [Suppl] 70:292
Firth MS (1981) A sport-specific training and testing device for racing cyclists. Ergonomics 24:565–571
Greenleaf JE, Castle BL (1971) Exercise temperature regulation in man during hypohydration and hyperhydration. J Appl Physiol 30:847–853
Hubbard RW (1979) Effects of exercise in the heat on predisposition to heatstroke. Med Sci Sports 11:66–71
Kerslake D (1972) The stress of hot environments. Cambridge University Press, London
Nadel ER, Fortney SM, Wenger CB (1980) Effect of hydration state on circulatory and thermal regulations. J Appl Physiol 49:715–721
Nadel ER, Stolwijk JAJ (1973) Effect of skin wettedness on sweat gland response. J Appl Physiol 35:689–694
Nielsen B, Nielsen M (1965) On the regulation of sweat secretion in exercise. Acta Physiol Scand 64:314–322
Nielsen B, Rowell LB, Flemming B-P (1984) Cardiovascular responses to heat stress and blood volume displacements during exercise in man. Eur J Appl Physiol 52:370–374
Pimental NA, Sawka MN, Billings DS, Trad LA (1984) Physiological responses to prolonged upper-body exercise. Med Sci Sports Exerc 16:360–365
Pitts GC, Johnson RE, Consolazio FC (1944) Work in the heat as affected by intake of water, salt and glucose. Am J Physiol 142:253–259
Pugh LG (1974) Relation of oxygen intake and speed in competition cycling and comparative observations on the bicycle ergometer. J Physiol [Lond] 241:795–808
Ramanathan NC (1964) A new weighting system for mean surface temperature of the human body. J Appl Physiol 19:531–533
Rowell LB (1983) Cardiovascular aspects of human thermoregulation. Circ Res 52:367–369
Saltin B, Hermansen L (1966) Esophageal, rectal and muscle temperature during exercise. J Appl Physiol 21:1757–1762
Saltin B, Stenberg J (1964) Circulatory response to prolonged severe exercise. J Appl Physiol 19:833–836
Shaffrath JD, Adams WC (1984) Effects of airflow and workload on cardiovascular drift and skin blood flow. J Appl Physiol 56:1411–1417
Whiting PH, Maughan RJ, Miller JDB (1984) Dehydration and serum biochemical changes in marathon runners. Eur J Appl Physiol 52:183–187
Whitt FR (1971) Note on the estimation of the energy expenditures of sporting cyclists. Ergonomics 14:419–424
Wyndham CH (1973) The physiology of exercise under heat stress. Annu Rev Physiol 35:193–220
Author information
Authors and Affiliations
Additional information
Supported by grants from the Natural Sciences and Engineering Research Council of Canada, the Max Bell Foundation of Toronto, and The Institute for Human Performance at Simon Fraser University.
Rights and permissions
About this article
Cite this article
Brown, S.L., Banister, E.W. Thermoregulation during prolonged actual and laboratory-simulated bicycling. Europ. J. Appl. Physiol. 54, 125–130 (1985). https://doi.org/10.1007/BF00426312
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00426312