Effects of endurance training on resting and post-exercise cardiac autonomic control

Purpose: Endurance training induces reductions in both resting and postexer cise heart rate (HR). If adaptation in cardiac autonomic regulation is a co ntributing factor in these reductions, chances in cardiac autonomic nervous system (ANS) should correspond to those in HR during an endurance-training program. We investigated the changes in resting and postexercise HR variab ilities (both in the time and frequency domain) over a 6-wk training progra m. Methods: HR variability was measured five times in an endurance-training group (N = 7) and four times in a control group (N = 5) during the course of study. Results: Endurance training decreased HR and increased indices of parasympathetic modulation measured both at rest and during postexercise r ecovery periods. Noteworthy is that no changes in either HR or indices of A NS modulation measured during postexercise recovery periods were detectable after the first 7 d of the study despite continued changes in resting HR a nd indices in ANS modulation measured between the 7th and 42nd days of the endurance-training program. Conclusions: The study demonstrates that with e ndurance-training changes in cardiac ANS modulation partly contribute to a decrease in HR at rest and during postexercise recovery period, and that ad aptation of the cardiac autonomic control occurs sooner in immediate postex ercise periods than at rest.