ABSTRACT
High-intensity interval training (HIIT) involves brief, intermittent bouts of high-intensity exercise interspersed by periods of rest or low-intensity exercise. The physiological adaptations associated with HIIT enhance several outcomes, including cardiorespiratory fitness (CRF), exercise performance, skeletal muscle oxidative capacity, and insulin sensitivity. High-intensity exercise could be interpreted as training ‘all-out’ with maximal (100%) effort; however, not all HIIT involves working at this intensity. The contribution of energy production via the energy systems and the strain on the neuromuscular and musculoskeletal systems varies depending on the HIIT protocol. Sprint interval training (SIT) involves supramaximal (all-out) work periods lasting 10–30 seconds with long recovery periods 5 times the duration of the work bout. The distinguishing factor between SIT and short and long interval training is the exercise intensity. The intensity of SIT is simple to programme and regulate as the client exercises as hard as possible (all-out) with no pacing.
