Large Inter-Individual Differences in Responses to a Block of High Intensity Aerobic Interval Training: A Case Series in National-level Cyclists and Triathletes.

UNLABELLED

The aim was to investigate individual responses on VO and performance to a block of high intensity aerobic interval training (HIIT) in national-level endurance athletes.

METHODS

National-level cyclists and triathletes (five men and two women, 31 ± 3.3 years, VO 65.1 ± 3.3 ml·kg·min) conducted 14 HIIT sessions (4×4 min uphill running at 90-95% maximal heart rate) in nine days during preseason. VO in running and cycling, lactate threshold (LT) in cycling, oxygen cost of cycling (C), and a cycling time-trial (TT) were tested two days pre and seven days post intervention. Feasibility was determined using attendance rates, adherence (defined as completing all sessions), and reported adverse events.

RESULTS

The results showed that adherence was 100% with 100% attendance rate. No adverse events were reported. TT (-75.6 ± 50.8 seconds, p < 0.0001) but not VO cycling (-0.2 ± 4.6 ml×kg×min, p = 0.53) or running (0.2 ± 1.2 ml×kg×min, p = 0.85) was improved on group level. The individual responses varied from -8.2% to +14.5% change in VO, and -7.5% to +0.8% in TT.

CONCLUSIONS

The large inter-individual differences in responses call for tailor-making HIIT blocks, mapping of biomarkers to avoid overtraining, and studying the effects of such blocks with longer follow-up than seven days.