An interval is a specific period of time or distance provided to complete one attempt at an exercise. Swimming 400 meters or cycling up a hill for five minutes both qualify as one interval in training.
In endurance sports, an interval is a segment of exercise performed at a specific intensity, followed by a rest or recovery period. Intervals form a key part of high-intensity training and are used to enhance specific physical capacities such as VO₂ max, lactate threshold, or neuromuscular efficiency. An athlete may perform multiple intervals during a single workout—commonly organized as repeats, such as 6 times 800 meters at 5K pace with 90 seconds rest between them. The interval is the work component, not the rest.
Interval training can be adapted to various sports and objectives. In running, intervals can be 200-meter sprints or repeat miles, for example. In cycling, you can do hill repeats or timed intervals such as 3 * 10 minutes at maximum effort. In swimming, intervals revolve around distance and recovery time, for example, 10 times 100 meters, 1:30 rest. All repeats are performed for a specific reason—to work on power, form, or speed—thus making intervals an excellent means of building endurance, power, and overall athletic competence. Recovery time can be active (such as running or riding lightly) or passive (such as walking or standing) based on training objectives. An appropriate combination of work and recovery in interval training influences what is emphasized in training intervals—to reduce susceptibility to fatigue or not, for example. Organized intervals are necessary for building up to endurancedue to them simulating race scenarios, adapting your body, and enabling increases in intensity to occur gradually.
