In interval training, work intervals are typically performed at high intensity.

• A. Work intervals are performed at moderate pace.
• B. Work intervals are performed at high intensity.
• C. Rest intervals are optional.
• D. Pace remains constant across all intervals.

Answer: (B)

Interval training hinges on alternating bouts of hard work with recovery. The key idea is that the work periods are performed at high intensity, pushing your cardiovascular and muscular systems to a demanding effort. This level of effort drives important adaptations, like improved VO2 max, faster speeds, and better lactate tolerance, while the rest intervals let you recover enough to repeat those hard efforts. If the work segments were done at a moderate pace, the stimulus wouldn’t be strong enough to elicit the same gains. Making rest intervals optional removes the essential recovery, and keeping the pace the same across all intervals eliminates the purposeful alternation between hard work and recovery. So, work intervals are performed at high intensity.