The effects of blood lactate concentration on perception of effort during graded and steady state treadmill exercise

Studies have reported that ratings of perceived exertion (RPE) are a valid tool for exercise prescription when blood lactate concentration (BLC) is used as the intensity criterion. However, few have studied the relationship between RPE and BLC during commonly used graded exercise tests (GXTs) and simulated exercise training. The purpose of this study was to determine if the RPE: BLC relationship is transferable across GXTs and a steady state exercise trial (SST). Thirteen healthy males (25+/-5.3yrs) completed two maximal treadmill tests (Bruce and Balke protocols) followed by a SST which consisted of approximately 8 minutes of exercise at each of two intensities (approximately 40% and 70% maximal heart rate reserve). BLCs and other physiological measures were compared at matched RPEs across the GXTs and SST trial at each exercise intensity using a two-way repeated measures ANOVA. There were no significant differences in BLC at a matched RPE across the exercise trials at the lower exercise intensity with the BLCs being 1.5+/-0.3, 1.6+/-0.6 and 1.3+/-0.3 mM, respectively. However, at the higher exercise intensity BLCs were significantly lower during the Balke GXT compared to the Bruce GXT and SST (1.8+/-0.6, 2.8+/-1.8 and 3.0+/-0.8 mM, p < 0.05). These results suggest that the RPE: BLC relationship may be protocol dependent during graded exercise testing as it was only transferable from the Bruce GXT to the exercise training setting at intensities in the typical prescription range of 50-85% of VO2max.