Nycthemeral Variations in Core Temperature and Heart Rate: Continuous Cycling Exercise versus Continuous Rest

Circadian rhythms have formed the subject of many researches in man during bed rest or usual routine, but have been little studied during continuous and sustained physical exercise. This study deals with the influence of time of day on biological markers in competitive cyclists during continuous physical exercise versus continuous rest. Ultra-distance cyclists were studied over a 24 h period (13:00 to 13:00 h the next day) in the laboratory. The subjects were requested to maintain a constant speed (set at 65 % - 70 % of their maximal aerobic speed obtained during a preliminary test) on their own bicycles which were equipped with home trainers. Workload, core temperature and heart rate were monitored continuously. The same measures were also recorded while the athletes were resting awake until 13:00 h the next day. Results show that in both situations, core temperature and heart rate exhibited significant circadian variations (p < 0.001). Furthermore, during exercise, an accentuation of amplitude and mean of every rhythm (p < 0.05) with a phase lag (p < 0.05) were observed. Despite a strenuous and continuous physical exercise requiring special physiological adaptations, the rhythmic variations observed at rest persisted, which highlighted the influence of biological clocks.

Key words:

Circadian biological rhythms, ultra-endurance, constant routine protocol.

References

• 1 Ahnve S, Theorell T, Åkerstedt T, Fröberg J E, Halberg F. Circadian variations in cardiovascular parameters during sleep deprivation.  Eur J Appl Physiol. 1981;  46 9-19
• 2 Atkinson G, Coldwells A, Reilly T, Waterhouse J M. A comparison of circadian rhythms in work performance between physically active and inactive subjects.  Ergonomics. 1993;  36 273-281
• 3 Atkinson G, Coldwells A, Reilly T, Waterhouse J M. An age-comparison of circadian rhythms in physical performance measures. In: Harris S, Suominen H, Era P, Harris WS (eds) Towards Healthy Aging: International Perspectives Part 1. Physiological and Biomedical Aspects Vol. 3 Physical Activity, Aging and Sports. Albany, NY; Center for Study of Aging 1994: 205-216
• 4 Bastuji H, Jouvet M. Intérêt de l’agenda de sommeil pour l’étude des troubles de la vigilance.  Electroenceph Clin Neurophysiol. 1985;  60 229-305
• 5 Brown R N, Czeisler C A. The statistical analysis of circadian phase and amplitude in constant routine core-temperature data.  J Biol Rhythms. 1992;  7 177-202
• 6 Cable T, Reilly T. Influence of circadian rhythms on arm exercise.  J Hum Mov Stud. 1987;  13 13-27
• 7 Davenne D, Lagarde D. Circadian rhythm of vigilance and temperature during 24 hours of continuous and strenuous exercise.  Med Sci Res. 1995;  23 767-770
• 8 Dawson D, Lushington K, Lack L, Campbell S, Matthews C. The variability in circadian phase and amplitude estimates derived from sequential constant routines.  Chronobiol Int. 1992;  9 362-370
• 9 Degaute J P, Van de Borne P, Linkowski P, Van Cauter E. Quantitative analysis of the 24-hour blood pressure and heart rate patterns in young men.  Hypertension. 1991;  18 199-210
• 10 Di P rampero. The energy cost of human locomotion on land in water.  Int J Sports Med. 1986;  7 55-72
• 11 Douglas P S, O’toole M L, Miller W BD, Hackney K, Reichek N. Cardiac fatigue after prolonged exercise.  Circulation. 1987;  76 1206-1213
• 12 Hill D W, Smith J C. Circadian rhythm in aerobic power and capacity.  Can J Sport Sci. 1991;  16 30-32
• 13 Horne J A, Ostberg O. A self-assessment questionnaire to determine morningness-eveningness in circadian rhythms.  Int J Chronobiol. 1976;  4 97-110
• 14 Kräuchi K, Wirz-Justice A. Circadian rhythm of heat production, heart rate, skin and core body temperature under unmasking conditions in man.  Am J Physiol. 1994;  267 819-829
• 15 McKechnie J K, Leary W P, Noakes T D, Kallmyer J C, McSearraigh E TM, Olivier L R. Acute pulmonary oedema in two athletes during a 90 km running race.  S Afr Med J. 1979;  56 261-266
• 16 Meney I, Waterhouse J M, Atkinson G, Reilly T, Davenne D. The effect of one night’s sleep deprivation on temperature, mood, and physical performance in subjects with different amounts of habitual physical activity.  Chronobiol Int. 1998;  15 349-363
• 17 Minors D S, Folkard S, Waterhouse J M. The shape of the endogenous circadian rhythm of rectal temperature in humans.  Chronobiol Int. 1996;  13 261-271
• 18 Nielsen B, Sjogaard G, Bonde-Petersen F. Cardiovascular, hormonal and body fluid changes during prolonged exercise.  Eur J Appl Physiol. 1984;  53 63-70
• 19 Niemelä K O, Palatsi I J, Ikäheimo M J, Takkunen J T, Vuori J J. Evidence of impaired left ventricular performance after an uninterrupted competitive 24 hours run.  Circulation. 1984;  70 350-356
• 20 Reilly T. Human circadian rhythms and exercise.  Crit Rev Biomed Eng. 1990;  18 165-180
• 21 Reilly T, Brooks G A. Selective persistence of circadian rhythms in physiological responses to exercise.  Chronobiol Int. 1990;  7 59-67
• 22 Reilly T, Robinson G, Minors D S. Some circulatory responses to exercise at different times of day.  Med Sci Sports Exerc. 1984;  16 477-482
• 23 Reilly T, Walsh T J. Physiological, psychological and performance measures during an endurance record for a 5-side soccer play.  Br J Sports Med. 1981;  15 122-128
• 24 Reinberg A. Les Rythmes Biologiques, Collection “Que sais-je?”. Paris; Presses Universitaires de France 1993 6th ed: 128
• 25 Reinberg A, Motohashi Y, Bourdeleau P, Andlauer P, Lévi F, Bicakova-Rocher A. Alteration of period and amplitude of circadian rhythms in shift workers.  Eur J Appl Physiol. 1988;  57 15-25
• 26 Rietveld W J. Circadian rhythms. Physical performance as function of the time of day.  Int J Sports Med. 1984;  5 25-27
• 27 Rietveld W J, Minors D S, Waterhouse J M. Circadian rhythms and masking: An overview.  Chronobiol Int. 1993;  10 306-312
• 28 Rogers C D, Paterson D H, Cunningham D A, Noble E G, Pettigrew F P, Mules W S, Taylor A W. Sleep deprivation: effects on work capacity, self-paced walking, contractile properties and perceived exertion.  Sleep. 1995;  18 30-38
• 29 Rognum T O, Vartdal F, Rodahl K, Opstad P K, Knudson-baes O, Kindt E, Withey W R. Physical and mental performance of soldiers during prolonged heavy exercise combined with sleep deprivation.  Ergonomics. 1986;  29 859-867
• 30 Tafti M, Vergé M, Besset A, Billiard M. Record du monde du marathon de tennis: privation de sommeil et performances.  C R Soc Biol. 1989;  183 474-481
• 31 Thomas V, Reilly T. Circulatory, psychological and performance variables during 100 hours of paced continuous exercise under conditions of controlled energy intake and work output.  J Hum Mov Stud. 1975;  1 149-155
• 32 Von Euler U S. Sympatho-adrenal activity in physical exercise.  Med Sci Sports. 1974;  6 165-173
• 33 Waterhouse J, Minors D. The circadian rhythm of core temperature in humans. In: Hagasaka T, Milton AS (eds) Body Temperature and Metabolism. Tokyo; Int. Press Editing Center Incorporation 1995: 213-218
• 34 Winget C, Deroshia C W, Markley C L, Holley D C. A review of human physiological and performance changes associated with desynchronis of biological rhythms.  Aviat Space Environ Med. 1984;  55 1085-1096