The 4 x 4 protocol is an example of which type of CR fitness interval training?

• A. High Intensity Interval Training (HIIT)
• B. Sprint Interval Training (SIT)
• C. High Intensity Functional Training (HIFT)
• D. Resistance Training

Answer: (A)

This question is about how interval work is organized to boost cardiorespiratory fitness. The 4x4 protocol uses four work blocks, each lasting four minutes, performed at a high aerobic-to-very-hard effort (roughly 90–95% of max heart rate) with several minutes of recovery between blocks. That pattern—repeated, substantial-intensity work bouts with rests in between—defines HIIT. It emphasizes sustained high effort over a few minutes, rather than short all-out sprints or a circuit of diverse movements.

Sprint Interval Training relies on very short, all-out efforts (often 20–30 seconds) with longer recovery and is not about four-minute work bouts. High Intensity Functional Training combines intense cardio with varied functional movements and often resistance elements, rather than a pure cardio interval running or cycling protocol. Resistance training focuses on muscular strength or hypertrophy, not primarily cardio adaptations.