Short-term overtraining: effects on performance, circulatory responses, and heart rate variability

Purpose and Methods: Nine elite canoeists were investigated concerning chan ges in performance, heart rate variability (HRV), and blood-chemical parame ters over a 6-d training camp. The training regimen consisted of cross-coun try skiing and strength training, in total 13.0 +/- 1.6 h, corresponding to a 50% increase in training lend. Results: Time to exhaustion (RunT) decrea sed from 19.1 +/- 1.0 to 18.0 +/- 1.2 min (P < 0.05). (V) over dot (2max) a nd max lactate (L-max) both decreased significantly (P < 0.05) over the tra ining period (4.99 +/- 0.97 to 4.74 +/- 0.98 L.min(-1) and from 10.08 +/- 1 .25 to 8.98 +/- 1.03 mmol.L-1 respectively). Heart rates (HR) decreased sig nificantly st all workloads. Plasma volume increased by 7 +/- 7% (P < 0.05) . Resting cortisol, decreased from 677 +/- 244 to 492 +/- 222 nmol.L-1 (P < 0.05), whereas resting levels of adrenaline and noradrenaline remained unc hanged. The change brtween tests in RunT correlated significantly with the change in HRmax (r = 0.79. P = 0.01). There were no group changes in high o r low frequency HRV, neither at rest nor following a tilt. Conclusions: The reduced maximal performance indicates a state of fatigue/overreaching and peripheral factors are suggested to limit performance even though HRmax and La-max both were reduced. The reduced submaximal heart rates are probably a result of increased plasma volume. HRV in this group didn't seem to be af fected by short-term overtraining.