Median maximal heart rate for heart rate calibration in different conditions: laboratory, field and competition

The objective of this study was to evaluate the variability of maximal heart rate in three different conditions: laboratory tests, field tests, and competitions. Sixteen male endurance volunteers were tested in five exhaustive tests for each condition. All exhaustive events were heart rate monitored (Accurex plus, Polar Electro, Finland) and true maximal heart rates were assessed and compared with each other and with predicted maximal heart rates. Results show that under the three conditions HR(peaks) were not statistically different (p = 0.62, NS, Friedman test). Mean HR(peaks) (SD) were: laboratory = 194.3 (7.8), field = 193.8 (11.8), competition = 192.3 (10.1) beats x min(-1). Conditions for reaching individual heart rate peak were in the laboratory (treadmill VO(2)max protocol) for 5 subjects, in field tests for 7 subjects and in competitions for 6 subjects (two circumstances for two subjects). A large intra-individual variation existed in the three circumstances (+/- 6 beats x min(-1)). Absolute median maximal heart rate was 190.0 bpm (9.32) i.e 7.6 bpm lower than heart rate peak. Both were highly related (rho = 0.89, z = 3.449, p = 0.0006, Spearman test). Median maximal heart rates inter-condition relationship were higher. Median maximal heart rate was more stable and took more information into account than an isolated peak. It gives a central value that minimizes the potential risk of under or over estimation when calibrating exercise intensities with HR.