title: Effect of exercise intensity and repetition on heart rate variability during training in elite trotting horse.
abstract: RR intervals of ten elite trotting horses were recorded during an interval training session performed on track. This study examined two hypotheses. Firstly, like in humans, the hyperpnea combined with a decrease in cardiac autonomic control on heart rate during heavy exercise could result in a prevalence of high frequency heart rate variability. Secondly, this prevalence could increase with the heavy exercise repetition. Two exercise intensities were compared: moderate (ME) and heavy (HE). Furthermore, heavy exercise repetitions were compared between the beginning and the end of the interval training session. When comparing ME and HE periods: heart rate was significantly lower (155 +/- 12 vs. 210 +/- 9 ms, p < 0.001), LF spectral energy (0.04 - 0.2 Hz) was significantly higher (ME: 6.94 +/- 4.80 and HE: 0.24 +/- 0.14 ms(2) . Hz (-1), p < 0.001) whereas HF (0.2 - 2 Hz) was significantly lower (ME: 7.09 +/- 2.24 and HE: 10.60 +/- 3.64 ms(2) . Hz (-1), p < 0.05). In relative terms, ME showed similar results in both LFn (LF/LF+HF) and HFn (HF/LF+HF) whereas HE showed a large prevalence of HFn energy compared to LFn (p < 0.001). The difference in LF/HF ratio between the two exercise conditions was significant (1.14 +/- 0.92 vs. 0.09 +/- 0.12, p < 0.001). Exercise repetition induced a significant increase in heart rate between the beginning and the end of the interval training session (207 +/- 10 beats . min (-1) vs. 212 +/- 9 beats . min (-1), p < 0.001) whereas LF energy decreases (1.54 +/- 1.65 vs. 0.32 +/- 0.24 ms(2) . Hz (-1), p < 0.01) and HF energy remained constant (10.79 +/- 4.10 vs. 10.40 +/- 3.35 ms(2) . Hz (-1), NS). This study confirmed the results observed in humans during heavy exercise conditions with a large prevalence of HF in contrast to LF, this prevalence increasing with exercise repetitions. The observed decrease in LF/HF ratio could provide an index of hyperpnea in horses during interval training.
authors.affiliation: Laboratory of Exercise Physiology (LEPH), University of Evry, E.A. 3872, Genopole, Boulevard F. Mitterand, 91025 Evry cedex, France. francois.cottin@bp.univ-evry.fr
authors.forename: F
authors.initials: F
authors.lastname: Cottin
authors.forename: C
authors.initials: C
authors.lastname: Médigue
authors.forename: P
authors.initials: P
authors.lastname: Lopes
authors.forename: E
authors.initials: E
authors.lastname: Petit
authors.forename: Y
authors.initials: Y
authors.lastname: Papelier
authors.forename: V L
authors.initials: VL
authors.lastname: Billat
mesh_terms: D000818:Animals; D004562:Electrocardiography; D005583:Fourier Analysis; D006339:Heart Rate / Q000502:physiology*; D006736:Horses; D010805:Physical Conditioning, Animal / Q000379:methods*