Whether HIIT increases or decreases VLamax depends on the athlete’s existing metabolic profile. For athletes with low VLamax (low glycolytic power), short HIIT intervals like 40/20 at 130% of threshold can produce VLamax utilization above 25%, which is a strong stimulus to increase glycolytic power. For athletes with already-high VLamax, the same session may produce comparatively low utilization levels, providing little glycolytic stimulus or even contributing to decreased VLamax over time. The response is determined by the ratio of the athlete’s aerobic capacity (VO2max) to their glycolytic capacity (VLamax). INSCYD quantifies both metrics to predict the glycolytic training effect before the session is performed.