Effects of intensity distribution changes on performance and on training loads quantification

The present study analyses the effects of the high-intensity distribution change within sessions on physical performance and on training loads (TL) provided by quantification methods based on heart rate (HR) and on whole body indicators of exercise-induced physiological stress. Fourteen trained physical education students (21.9±1.2 years, 68.3±7.9 kg, 180±7.3 cm) performed two sessions with the same intensities, volumes and pauses but differing in the efforts’ intensity distribution: one was composed of exercises dissociating the intensities (12 repetitions of 30 m sprints then 12 min interval runs) and the second mixed the intensities (30 m sprint followed by 60 s rest and 2 runs of 15 s - 15 s at 100% and 50% of maximal aerobic velocity – MAV). Session TL was calculated using methods based on heart rate zones, training impulse, ratings of perceived exertion (session RPE) and endurance limit. Session-induced fatigue was observed using performances in repeated sprints and counter-movement jumps. The heart rate zone method provided higher TL for the mixed session (p=0.007), while training impulse described similar TL for the two sessions (p=0.420). The endurance limit method showed borderline significantly higher TL in dissociated sessions (p=0.058) and session RPE provided similar but the largest differences between sessions’ TL (p=0.001). The dissociated session induced larger losses in counter-movement jumps (p=0.010) but lower speed decreases in sprints (p=0.007). Change in intensity distribution within sessions induced contradictory effects on performances and on TL quantification according to the method used. When high intensities are programmed, methods based on heart rate may present limitations for TL quantification, as such methods based on whole body indicators of exercise-induced physiological stress should be preferred.