Can heart rate values obtained from laboratory and field lactate tests be used interchangeably to prescribe exercise intensity for soccer players?

Abstract

This study was undertaken to investigate the relationship between blood lactate concentration ([La]) and heart rate (HR) values obtained during treadmill and field tests at fixed velocities with respect to interchangeability of results to be used in exercise prescription. A total of 22 male soccer players participated in the study. Each player performed exercise tests on a motorized treadmill and in the field with 3-min runs and 30 s allowed for blood sampling. During both tests, velocities at the first, second, and third stages were 8, 10, and 12 km x hr(-1), respectively. Velocity was then increased by 1 km x hr(-1) every 3 min until exhaustion. During the field test, players ran on artificial turf on a 120-m hexagonal track marked with cones placed 20 m apart. Running velocity was controlled by means of audio signals. Blood samples were analyzed immediately with an automated lactate analyzer. HR was monitored continuously at 5-s intervals. Data were analyzed with Student's paired t tests to look for differences between treadmill and field data. Coefficients of variation and Blan-Altman plots assessed agreement of HR and blood [La] values between the 2 tests. Although running velocities corresponding to a fixed blood [La] of 4 mmol L-1 showed significant differences between treadmill and field tests (15.9+/-0.9 vs 14.1+/-0.7 km x h(-1), respectively) (P<.01), no significant difference between HR values was noted (190+/-7 vs 187+/-7, field vs laboratory, respectively). Overall, the mean intermeasurement coefficient of variation was 4.8% (+/-0.9%) for HR. Although the lowest coefficient of variation (2.4%) was found, fairly wide differences between individual field and laboratory HR values at velocities corresponding to fixed blood [La] of 4 mmol.L(-1) cast doubt on the interchangeability of tests.