Intra-individual physiological response of recreational runners to different training mesocycles: a randomized cross-over study.

On a group level, none of the interventions altered [Formula: see text], V2, V4 or TTE, while HVLIT and HFT improved [Formula: see text]. The mean adaptation index indicated similar numbers of positive, negative and non-responders to HIIT, HVLIT and HFT, but more very positive responders to HVLIT than HFT or HIIT. 46% responded positively to two mesocycles, while 23% did not respond to any. These findings indicate that the magnitude of responses to HIIT, HVLIT and HFT is highly individual and no pattern was apparent.