Intermittent exercise alters the heart rate-blood lactate relationship used for calculating the training impulse (TRIMP) in team sport players

Objectives: The training impulse (TRIMP) quantifies training dose by weighting heart rate according to the relationship between fractional elevation in heart rate (Delta HR) and blood lactate concentration (BLa). This study compared the physiological responses to intermittent and continuous exercise and their influence on TRIMP weightings. Design: Repeated measures crossover. Method: Twelve team sport players undertook a vVO(2max) test and then a continuous trial (CT) and intermittent trial (IT) in a randomised order. Each trial consisted of 4 x 4 min stages corresponding to 25%, 50%, 75% and 100% of vVO(2max). Trials were matched for distance and mean speed. Results: A repeated measures ANOVA revealed higher B La for IT at 75% vVO(2max) (p=0.023) and 100% vVO(2max) (p=0.012); higher VO(2) for IT at 25% vVO(2max) (p<0.001); higher Delta HR for IT at 25% vVO(2max) (p<0.001), 75% vVO(2max) (P=0.03) and 100% vVO(2max) (p=0.018); higher TRIM P weightings for IT at 0.9 Delta HR (p=0.018) and 1.0 Delta HR (p=0.005). Conclusions: Intermittent exercise alters the Delta HR-BLa relationship and TRIM P weightings at high exercise intensities. Determination of the training impulse from the Delta HR-BLa relationship derived from a continuous exercise protocol may underestimate the exercise 'dose' of training and/or matches in team sport players. (C) 2010 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.