Endurance training, overtraining and baroreflex sensitivity in female athletes

Abstract

Summary We examined heavy training-induced changes in baroreflex sensirivity, plasma volume and resring heart rate and blood pressure variability in female endurance athletes. Nine athletes (experimental train- ing group, ETG) increased intense training (70-90% Vo2maJ volume by 130% and low-intensity training «70% Vo2maJ volume by 100% during 6-9 weeks, whereas the corresponding increases in six control athletes (CG) were 5% and 10% respecrively. Max- imal oxygen uptake (Vo2maJ in the ETG and CG did not change, but in five ETG athletes Vo2max de- creased from 53.0:t2.2 (mean:tSEM) (CI46'8-59'2) ml kg-1 min-l to 50.2:t 2.3 (43'8-56'6) ml kg-1 min-l (P<O'OI), indicaring overtraining. Baroreflex sensiriv- ity (BRS) measured using the phenylephrine technique and blood pressure variability (BPV) did not change, but the low-frequency power of the R-R interval variability increased in the ETG (P<0'05). The relative change in plasma volume was 7% in the ETG and 3% in the CG. The changes in BRS did not correl~te with the changes in plasma volume, heart rate variability and BPV. We conclude that heavy endurance training and overtraining did not change baroreflex sensirivity or BPV but significantly increased the lo\v-frequency power of the R-R interval variability during supine rest in female athletes as a marker of increased cardiac sympatheric modularion.