Conventional methods to prescribe exercise intensity are ineffective for exhaustive interval training

Abstract

Purpose To compare methods of relative intensity prescription for their ability to normalise performance (i.e., time to exhaustion), physiological, and perceptual responses to high-intensity interval training (HIIT) between individuals. Methods Sixteen male and two female cyclists (age: 38 ± 11 years, height: 177 ± 7 cm, body mass: 71.6 ± 7.9 kg, maximal oxygen uptake ($$ \dot{\text{V}} $$ V ˙ O2max): 54.3 ± 8.9 ml·kg−1 min−1) initially undertook an incremental test to exhaustion, a 3 min all-out test, and a 20 min time-trial to determine prescription benchmarks. Then, four HIIT sessions (4 min on, 2 min off) were each performed to exhaustion at: the work rate associated with the gas exchange threshold ($$ \dot{\text{W}} $$ W ˙ GET) plus 70% of the difference between $$ \dot{\text{W}} $$ W ˙ GET and the work rate associated with $$ \dot{\text{V}} $$ V ˙ O2max; 85% of the maximal work rate of the incremental test (85%$$ \dot{\text{W}} $$ W ˙ max); 120% of the mean work rate of the 20 min time-trial (120%TT); and the work rate predicted to expend, in 4 min, 80% of the work capacity above critical power. Acute HIIT responses were modelled with participant as a random effect to provide estimates of inter-individual variability. Results For all dependent variables, the magnitude of inter-individual variability was high, and confidence intervals overlapped substantially, indicating that the relative intensity normalisation methods were similarly poor. Inter-individual coefficients of variation for time to exhaustion varied from 44.2% (85%$$ \dot{\text{W}} $$ W ˙ max) to 59.1% (120%TT), making it difficult to predict acute HIIT responses for an individual. Conclusion The present study suggests that the methods of intensity prescription investigated do not normalise acute responses to HIIT between individuals.

Revisiting the ‘Whys’ and ‘Hows’ of the Warm-Up: Are We Asking the Right Questions?

“…However, these comparisons between warm-up and no warm-up should be interpreted with caution because (i) lack of differences in certain assessed variables does not mean there would be no differences in other groups of variables and, indeed, within a single study assessing the effects of a warm-up there may differences in some but not all variables (e.g., [ 17 ]); (ii) lack of differences in standardized tests does not imply lack of differences in more multifactorial (and difficult to assess) perspectives of performance or injury risk [ 51 , 52 ]; (iii) given the interindividual variability in response to any training protocol (not exclusive to the warm-up) [ 53 – 55 ], mean values of the assessments may be averaging out potentially relevant differences [ 56 , 57 ]; and/or (iv) the studies may simply have lacked statistical power (small samples and/or too many outcomes) [ 58 , 59 ].…”