Maximal rate of increase in heart rate during the rest-exercise transition tracks reductions in exercise performance when training load is increased

Objectives: Heart rate kinetics are faster in well-trained athletes at exercise onset, indicating sensitivity to training status, but whether they track performance changes due to changes in training load is unknown. Design: Randomised, counterbalanced, cross-over. Methods: 17 cyclists completed two weeks of light and two weeks of heavy training. The day after each training period heart rate was recorded during 5. min cycling at 100. W to determine the maximal rate of heart rate increase. Participants then performed a 5. min cycle time-trial after which heart rate recovery was determined. Results: Work during 5. min cycle time-trial decreased 3.5% (P<. 0.04) in participants (n= 8) who increased training load (completed light training then heavy training) and, although maximal rate of heart rate increase did not change (P= 0.27), within-individual changes in work were correlated with changes in maximal rate of heart rate increase (r= 0.87, P= 0.005). Work during 5. min cycle time-trial increased 6.5% (P< 0.001) in 9 participants who decreased training load (completed heavy training then light training) and maximal rate of heart rate increase increased 28% (P= 0.002) but the changes in maximal work were not related to changes in rate of heart rate increase (r= 0.32, P= 0.40). Heart rate recovery tended to track changes in 5. min cycle time-trial work following increases and decreases in training load (r= 0.65-0.75, P= 0.03-0.08). Conclusions: Maximal rate of heart rate increases during cycling at 100. W tracks reductions in exercise performance when training load is increased, but not performance improvements when training loads are reduced. Maximal rate of heart rate increase may be a useful adjunct to heart rate recovery for tracking changes in exercise performance