Higher Precision of Heart Rate Compared with VO2 to Predict Exercise Intensity in Endurance-Trained Runners

The aim of the present study was to assess the precision of oxygen uptake with heart rate regression during track running in highly-trained runners. Twelve national and international level male long-distance road runners (age 30.7 ± 5.5 yrs, height 1.71 ± 0.04 m and mass 61.2 ± 5.8 kg) with a personal best on the half marathon of 62 min 37 s ± 1 min 22 s participated in the study. Each participant performed, in an all-weather synthetic track five, six min bouts at constant velocity with each bout at an increased running velocity. The starting velocity was 3.33 m·s^-1 with a 0.56 m·s^-1 increase on each subsequent bout. VO₂ and heart rate were measured during the runs and blood lactate was assessed immediately after each run. Mean peak VO₂ and mean peak heart rate were, respectively, 76.2 ± 9.7 mL·kg^-1·min^-1 and 181 ± 13 beats·min^-1. The linearity of the regressions between heart rate, running velocity and VO₂ were all very high (r > 0.99) with small standard errors of regression (i.e. Sy.x < 5% at the velocity associated with the 2 and 4 mmol·L^-1 lactate thresholds). The strong relationships between heart rate, running velocity and VO₂ found in this study show that, in highly trained runners, it is possible to have heart rate as an accurate indicator of energy demand and of the running speed. Therefore, in this subject cohort it may be unnecessary to use VO₂ to track changes in the subjects’ running economy during training periods.

Key points

• Heart rate is used in the control of exercise intensity in endurance sports.
• However, few studies have quantified the precision of its relationship with oxygen uptake in highly trained runners.
• We evaluated twelve elite half-marathon runners during track running at various intensities and established three regressions: oxygen uptake / heart rate; heart rate / running velocity and oxygen uptake / running velocity.
• The three regressions presented, respectively, imprecision of 4,2%, 2,75% and 4,5% at the velocity associated with the 4 mmol·L^-1 threshold.
• The results of the present study show that, in highly trained runners, it is possible to use heart rate as an accurate index of the external work rate during sub maximal running speeds.

Key words: Running velocity, internal load, relationships, standard error