Fig. 2

Outline of the 7-day intervention period and an exemplary training session. Outline of the 7-day intervention period (above) and an exemplary training session (below). Red bars represent intense runs and intervals at 90–95% HR_max. Green bars represent warm-up, active recovery and 30 min LIT at a velocity at 1.5 mmol/L blood lactate. HIIT = high-intensity interval training, LIT = low-intensity training, HSM = high-intensity interval training shock microcycle, HSM + LIT = high-intensity interval training shock microcycle with additional low-intensity training, R = Rest, AM = morning, PM = afternoon, black runner = self-directed HIIT session, blue runner = supervised HIIT session