ISSN:
1439-6327
Keywords:
Submaximal exercise
;
Endurance training
;
Heart rate kinetics
;
Sympathetic nervous system
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary To find out whether endurance training influences the kinetics of the increases in heart rate (f c) during exercise driven by the sympathetic nervous system, the changes in the rate off c adjustment to step increments in exercise intensities from 100 to 150 W were followed in seven healthy, previously sedentary men, subjected to 10-week training. The training programme consisted of 30-min cycle exercise at 50%–70% of maximal oxygen uptake ( $$\dot V$$ O2max) three times a week. Every week during the first 5 weeks of training, and then after the 10th week the subjects underwent the submaximal three-stage exercise test (50, 100 and 150 W) with continuousf c recording. At the completion of the training programme, the subjects' $$\dot V$$ O2max had increased significantly(39.2 ml·min−1·kg−1, SD 4.7 vs 46 ml·min−1·kg−1, SD 5.6) and the steady-statef c at rest and at all submaximal intensities were significantly reduced. The greatest decrease in steady-statef c was found at 150 W (146 beats·min−1, SD 10 vs 169 beats·min−1, SD 9) but the difference between the steady-statef c at 150 W and that at 100 W (Δf c) did not decrease significantly (26 beats·min−1, SD 7 vs 32 beats·min−1, SD 6). The time constant (τ) of thef c increase from the steady-state at 100 W to steady-state at 150 W increased during training from 99.4 s, SD 6.6 to 123.7 s, SD 22.7 (P〈0.01) and the acceleration index (A=0.63·Δf c·τ−1) decreased from 0.20 beats·min−1·s−1, SD 0.05 to 0.14 beats·min−1·s−1, SD 0.04 (P〈0.02). The major part of the changes in τ and A occurred during the first 4 weeks of training. It was concluded that heart acceleration following incremental exercise intensities slowed down in the early phase of endurance training, most probably due to diminished sympathetic activation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00571556
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