The effectiveness of polarized versus high-intensity training in moderately trained cyclists: a randomized parallel-design study.

PURPOSE: Polarized training intensity distribution (POL) typically involves 80% of endurance training volume to be spent in the Moderate intensity domain (MOD) and 20% to be in the Severe intensity domain-commonly performed as high-intensity interval training (HIIT). POL is popular in all endurance sports, but the independent contributions of MOD vs. HIIT on performance outcomes have not been experimentally tested. We therefore sought to compare training adaptions following HIIT with (POL) and without (HIIT) the addition of MOD cycling in moderately-trained endurance athletes. METHODS: Nineteen cyclists and triathletes (17 men) were recruited and randomly allocated to 3 days/week of HIIT with (POL) or without (HIIT) an additional 240 min/week of MOD cycling for 6 weeks. Time trial (TT) performance, peak work rate (WRpeak), and lactate thresholds (LT1, LT2) were assessed pre- and post-intervention. WRpeak and lactate thresholds were re-assessed at week 3 to re-prescribe exercise intensities. RESULTS: Both groups reduced their TT time by an average of 8.5 ± 1.2%. Despite the POL group performing ~ 23 more hours of training across 6 weeks, we did not observe any time*group interactions in TT performance, WRpeak, LT1, or LT2. Exploratory analyses revealed that the modest between-group effect size (η2 = 0.4) would require > 100 participants per group to detect a statistically significant difference. CONCLUSIONS: We conclude that the addition of MOD training to a HIIT program does not yield further improvements in performance over a 6-week period. Performance improvements in a moderately trained population following 6 weeks of training appear to be driven primarily by the Severe-intensity component of training.