FREDERIKS, J., C. A. SWENNE, A. V. G. BRUSCHKE, E. T. VAN DER VELDE, A. C. MAAN, B. J. TENVOORDE, M. G. C. VANROOIJEN, W. L. MOSTERD, and P. SCHIERECK. Correlated neurocardiologic and fitness changes in athletes interrupting training. Med. Sci. Sports Exerc., Vol. 32, No. 3, pp. 571–575, 2000.
Purpose: We studied nine male Dutch top marathon skaters during a 1-month interruption of their training schedules after their last contest in the winter to investigate a possible decline in baroreflex sensitivity.
Methods: Before and after this period, a maximal exercise test was done, and at days 0, 4, 7, 14, and 28 neurocardiologic measurement sessions —heart rate and noninvasive baroreflex sensitivity, recumbent and tilt —were performed.
Results: Interruption of training resulted in a significant and relevant decrease in the maximal oxygen uptake (from 65.7 ± 5.8 to 61.6 ± 4.7 mL O2·kg−1·min−1;P = 0.03), most likely associated with decreased competitive possibilities. Resting heart rate modestly increased (from 54.6 ± 7.2 to 58.8 ± 7.5 bpm), however, not significantly. Heart rate during 60° tilt increased considerably (from 70.1 ± 6.1 to 80.1 ± 9.1 bpm;P = 0.01), possibly due to a decrease in blood volume and an increase in cardiopulmonary baroreflex gain. Arterial baroreflex sensitivity decreased significantly in the recumbent (from 13.3 ± 5.4 to 9.8 ± 3.8 ms·mm Hg−1, P = 0.04), but not in the 60° tilt position (from 6.7 ± 2.0 to 6.0 ± 2.5 ms·mm Hg−1). The relative decrease in baroreflex sensitivity and maximal oxygen uptake correlated significantly (r = 0.71, P = 0.02).
Conclusions: In summary, our data show that correlated detrimental changes in fitness and baroreflex sensitivity are measurable in these athletes after a month of interruption of training.
Endurance training is known to decrease the resting heart rate (HR) (19,21,25) and to increase maximal oxygen uptake (15,17) and arterial baroreflex sensitivity (BRS) (1,20). The magnitude and time course of these changes have amply been studied in various populations and with various training schedules (12). Inverse changes must occur with interruption of training and have indeed been demonstrated for maximal oxygen uptake (6). About the dynamics of the neurocardiologic changes during interruption of training, little is known so far, although this might well be relevant to competitive sports. A decline in maximal oxygen uptake after 2 wk of interruption of training has convincingly been demonstrated (11). Whether a decline in BRS is demonstrable, and whether this is related to a decline in maximal oxygen uptake is the aim of the current study.