Relationship of Training Load to Training Response During High Intensity and Continuous Cycle Training

Abstract

BACKGROUND: High intensity interval training (HIIT) has been promoted as an alternative to conventional aerobic training (AER). However, it is unclear if HIIT is more effective than conventional AER or moderate intensity interval training. PURPOSE: The aim of this study was to compare & correlate improvements in peak sprint (SPR) and incremental( INC) power output with various markers of training load, including percent heart rate reserve (%HRR), blood lactate ([BLa]), & session RPE (sRPE). METHODS: Untrained subjects (N=55) completed pre and post SPR and INC cycle tests & 24 sessions (random assignment to training group) of AER (20-min bout @ 90%VT), moderate intervals (INT) ( 13 x 30/60s @ 100% PPO/25W), or Tabata (TAB) intervals (8 x 20/10s @ 170% PPO/passive recovery). RESULTS: Following the 8-week training period, %HRR, BLa, & sPRE, followed study design, with intensity progressed so that relative training intensity remained stable. Despite TAB having highest average (vs AER & INT) %HRR (84 vs 76 vs 75 %HRR), sRPE (6.9 vs 4.3 vs 5.4), & [BLa] (11.5 vs 5.5 vs 8.3 mmol/L), it was not associated with significantly (p<0.05) greater increases in SPR (+9.7 vs +8.5 vs +4.7%) or INC (+8.3 vs +4.3 vs +6.7%) compared to AER & INT. None of the correlations betweeen training markers and changes in SPR or INC were strong. Even when intensity and duration were combined as the HR zone derived training impulse (TRIMP) (10.6 vs 40.8 vs 41.4) there was no clear relationship between training load and the response of either SPR or INC. CONCLUSION: Contrary to claims for the superiority of HIIT, the data suggest that two varieties of HIIT (INT & TAB) were not superior to conventional AER relative to improving either SPR or INC cycle power output in previously untrained subjects.