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Int J Sports Med 2006; 27(9): 690-696
DOI: 10.1055/s-2005-872919
Physiology & Biochemistry

© Georg Thieme Verlag KG Stuttgart · New York

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

O. Hue1 , B. Voltaire1 , C. Hertogh1 , S. Blonc1
  • 1Laboratoire ACTES, UPRES‐EA 3596, UFR-STAPS, Université des Antilles et de la Guyane, Campus de Fouillole, Pointe à Pitre, Guadeloupe, France
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Publication History

Accepted after revision: September 12, 2005

Publication Date:
01 February 2006 (online)

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Abstract

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 (∼ 31 °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 °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.

Key words

Wet - heat - thermoregulation - cardiac drift - cycling

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O. Hue

Laboratoire ACTES, UPRES‐EA 3596, UFR-STAPS des Antilles et de la Guyane

Campus de Fouillole

97159 Pointe à Pitre, Guadeloupe

France

Fax: + 33 590 90 17 68

Email: HueO@wanadoo.fr