Hynynen, E., Iglesias, X., Feriche, B., Calderón, C., Ábalos, X., Vázquez, J., Barrero, A., Rodríguez, L., & Levine, B. D. (2012). Heart rate variability in orthostatic test during different training periods in elite swimmers. Presentation 2990 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

"Intense training has been shown to change the autonomic modulation of the heart in endurance athletes assessed by heart rate variability (HRV) analysis. In overtraining state HRV diminished in athletes of different sports."

This study investigated the effects of intensified training and tapering on heart-rate variability in elite swimmers (M = 4; F = 7). Ss lived and trained for eight weeks before a national championships (qualifying for European championships). This period was divided into the following microcycles: preparatory-general, intensified-training, preparatory-specific, pre-competition (tapering), and competition periods. RR-intervals were recorded every morning in supine (8 minutes) and orthostatic (6 minutes) positions with beat-by-beat heart monitors. Breathing was paced at 12 breaths per minute. Heart-rate variability was analyzed from the last 5-minute period of both positions. TRIMPs of every training session were calculated to estimate training.

Training load increased during the intensified training period (+86%) and progressively decreased during the pre-competition and competition periods. HF spectral power during supine rest increased during intensified training (+38%) but recovered to baseline thereafter and stayed near baseline levels during tapering and competition periods. LF/HF ratio during supine rest progressively increased from preparatory general to tapering (+58%) and competition periods (+66%).

Implication. These findings are different from those of the previous literature on heart-rate variability in endurance athletes. Intensive training has been reported to decrease heart-rate variability acutely and rebound after a relative resting period. In this study, the increase of heart-rate variability seemed to be related to positive coping with an increased training stress of elite swimmers. The interpretation of the LF/HF ratio has been questioned, but it has been used as an indicator of the balance of the autonomic nervous system. These findings suggest that the sympathetic activity of elite swimmers may increase during rest as an anticipatory response toward the competition period.

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