A COMPARISON OF INTERNAL TRAINING LOADS BETWEEN OBJECTIVELY- VERSUS SUBJECTIVELY-DETERMINED HIGH-INTENSITY INTERVAL TRAINING

Abstract

High-intensity interval training (HIIT) is an effective and time-efficient method of aerobic training. Most HIIT programming relies on objectively determined work rate, velocity, or heart rate targets. There is very little evidence comparing HIIT that is programmed using objective measures and HIIT that is programmed using subjective ratings to determine the work and recovery intensities, even though subjectively-determined HIIT may have more real-world applicability. PURPOSE: To evaluate the internal training load generated by single treadmill sessions of objectively-determined HIIT (HIIT-Obj) and subjectively-determined HIIT (HIIT-Sub). METHODS: Thirteen (female n=7, male n=6) young (age 19.8 ± 2.0 years), healthy participants completed a baseline testing session to determine peak VO2 and HR, followed by two HIIT sessions on a treadmill in a randomized order. Both HIIT sessions consisted of 10x1-min work intervals, interspersed with 1-min recovery intervals, with the work rate obscured from participants' view. HIIT-Obj session work intervals used the work rate associated with 90% of VO2max, with recovery intervals completed at 4 km/hr. For HIIT-Sub sessions, participants were instructed to reach an RPE of 8-9 on the Borg CR-10 scale during work intervals and drop to an RPE of 3-4 during the recovery intervals. Internal training load calculations included Training Impulse (TRIMP) and HR zone methods. RESULTS: There were no significant differences in internal training load between HIIT-Obj and HIIT-Sub as determined via TRIMP (45.8 ± 12.3 vs. 47.8 ± 15.9 a.u., ES=0.03, p=0.59) and HR zones (57.9 ± 14.7 vs. 66.8 ± 22.6 a.u., ES=0.28, p=0.06) methods, though participants spent significantly less time in the lowest intensity HR zone (zone 1) while completing HIIT-Sub (HIIT-Obj = 3.57 ± 0.93 min; HIIT-Sub = 2.43 ± 1.13 min, ES=0.48, p=0.01). Peak HR reached during the sessions was also not statistically different (186 ± 12 vs. 188 ± 16 bpm, ES=0.07, p=0.38). CONCLUSION: Participants are able to generate similar internal training loads using real-time subjective measures of intensity during HIIT compared to objectively-regulated HIIT. This indicates that this simpler, more applicable method of HIIT programming may generate the desired training stress for a client or athlete without rigid work rate or HR targets.