Interval Training
Interval training is a cardio method that alternates between high-intensity work periods and active recovery periods. In the NSW preparation program, interval sessions target running and swimming speed by training the body to sustain faster paces through repeated timed efforts.
Structure of Interval Workouts
A typical interval session prescribes a set number of repeats at a target pace with defined rest periods. For example, a running interval workout might call for 8 x 400m at a pace derived from the candidate's PST 1.5-mile run time, with 90 seconds of rest between repeats. Swimming intervals follow a similar structure using 50- or 100-yard repeats based on the PST 500-yard swim time.
Pace Calculation from PST Scores
Interval training paces are not arbitrary — they are calculated from PST performance. The NSW guide provides pace charts that translate a candidate's PST run or swim time into target splits for interval work. This ensures the intensity is calibrated to the individual's current fitness level and progresses as PST scores improve.
When Intervals Appear in the Program
The 26-week preparation plan introduces interval training after an initial base-building phase dominated by LSD work. As the program progresses, interval frequency increases while LSD volume is maintained. By the final weeks, candidates perform multiple interval sessions per week alongside their LSD and calisthenics work, simulating the intensity demands of BUD/S.
Hit your interval paces consistently — don't go out too fast on the first repeat and fade. Even splits build the pacing discipline BUD/S rewards.
Related Terms
Long Slow Distance (LSD) training is a cardio methodology that emphasizes sustained, moderate-intensity effort over extended durations. In BUD/S preparation, LSD sessions build the aerobic base required for long swims, runs, and the prolonged physical output demanded throughout SEAL selection.
Continuous High Intensity (CHI) training is a cardio method that sustains a near-maximal effort for a set duration, typically 15-20 minutes. In the NSW preparation program, CHI sessions bridge the gap between LSD endurance work and short-burst interval training by developing the ability to maintain a fast pace without rest breaks.
The 1.5-mile run is the final event of the Physical Screening Test (PST) and measures a candidate's running speed and cardiovascular endurance. Performed after the swim and calisthenics events, it tests the ability to produce a fast run effort on fatigued legs — a skill directly relevant to BUD/S demands.
The 500-yard swim is the first event of the Physical Screening Test (PST) and measures a candidate's aquatic endurance. Performed using either the combat sidestroke (CSS) or breaststroke, it tests the sustained swimming capacity required for BUD/S water-based evolutions.
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