Effect of a 24-h continuous walking race on cardiac autonomic control |
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Authors: | François Cottin Jean Slawinski Philippe Lopes Andry Van de Louw Véronique Billat |
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Institution: | (1) Laboratoire d’Etudes en Physiologie de l’Exercice (LEPHE), Université d’Evry, E.A. 3872, Genopole. Boulevard F. Mitterrand, Evry cedex, 91025, France;(2) Laboratoire de Biomécanique et Physiologie, Institut National des Sports et de l’Education Physique (INSEP), 11 rue du Tremblay, Paris, 75012, France;(3) Centre hospitalier Sud Francilien, Service de réanimation, Quartier du canal. Courcouronnes, Evry cedex, 91014, France;(4) Département STAPS, Université d’Evry, Boulevard F. Mitterrand, Evry cedex, 91025, France |
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Abstract: | This study investigated the relationships between walking speed and heart rate (HR) variability (HRV) in eleven subjects during
a 24-h race. It was hypothesized that the nycthemeral rhythm on HR is preserved during the race. RR intervals and walking
speed were measured. Fast Fourier transform was applied to samples of 1,024 successive RR intervals collected every hour from
a HR monitor. Walking speed was averaged every hour and decreased (first lap: 8.8 ± 0.3 vs. last lap: 7.3 ± 0.8 km h−1, P < 0.001) with HR also decreasing (max at 19:00 h: 143 ± 9 vs. min at 7:00 h: 117 ± 14 beats min−1, P < 0.001) following a third order polynomial shape. HRV power spectral components followed distribution patterns similar to
the mean RR during the race with a minimum in the early evening (19:00–20:00 h) and a maximum in the morning (5:00–8:00 h).
Thus, as for mean RR, spectral components over time are also fitted to a third order polynomial regression. LF/HF ratio increased
linearly (min = 0.5 ± 0.3, max = 2.8 ± 5.3, P = 0.02). Although mean HF peak did not decrease significantly over time, it was positively correlated with walking speed.
In conclusion, this study showed that despite a constant decrease in walking speed, HR circadian rhythm is preserved during
a continuous 24-h walking race. The short-term HRV components remain linked to HR whereas the LF/HF ratio increases linearly
until the end of the race whatever HR is. |
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Keywords: | Walking endurance Walking speed Circadian rhythm Autonomous nervous system Fast Fourier transform |
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