Continuous High Intensity Run (Run CHI)
The Continuous High Intensity run is the Friday cardio session in the 26-week NSW preparation program. It is a sustained run at roughly 90 to 95 percent of the fastest pace you could hold for the prescribed time, with no rest inside the effort, and it grows from a single 15-minute block in week 1 to two 20-minute blocks in week 26.
How the Session Is Defined
A CHI run means moving without stopping for a set number of minutes at approximately 90 to 95 percent of the maximal pace you could hold for that duration. The guide describes the effort as very demanding but not totally exhausting. On a scale of 1 to 10, with 10 the greatest possible effort, the session should feel like 8 or 9. A candidate at a low fitness level does one block of 15 to 20 minutes. As fitness improves, the session becomes two blocks. Between blocks you recover for about half the work time while still moving at a slow jog or brisk walk. Warm up for 10 to 15 minutes or more.
How It Progresses Across 26 Weeks
The CHI run progresses in two stages. Weeks 1 through 12 use a single block that grows by one minute every two weeks: 15 minutes in weeks 1 and 2, 16 in weeks 3 and 4, 17 in weeks 5 and 6, 18 in weeks 7 and 8, 19 in weeks 9 and 10, and 20 in weeks 11 and 12. From week 13 the session becomes two blocks: 2 x 12 minutes in weeks 13 through 15, 2 x 14 in weeks 16 through 18, 2 x 16 in weeks 19 through 21, 2 x 18 in weeks 22 through 24, and 2 x 20 in weeks 25 and 26. Total work time rises from 15 to 40 minutes.
Where It Sits in the Week and How to Pace It
Run CHI is fixed on Friday and shares the day with upper-body and core strength work. It comes two days after the Wednesday interval run, so the legs are recovered but not fresh. The pacing rule is to pick an effort you can hold for the full block. If you have to stop before the time is up, you started too fast. The second block in the two-block weeks should match the first, not collapse. The guide says that beyond 26 weeks you should not extend CHI duration further; instead you increase the pace inside the same time.
Progression across the program
| Week | Prescription |
|---|---|
| 1 | 15 min |
| 6 | 17 min |
| 12 | 20 min |
| 18 | 2 x 14 min |
| 26 | 2 x 20 min |
Run the CHI on a measured loop and note the distance you cover. A 20-minute CHI at true 90 to 95 percent effort should land close to your PST run pace, which makes it a weekly check on your 1.5-mile readiness.
Related Terms
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 Long Slow Distance run is the Monday cardio session in the 26-week NSW preparation program. It is a continuous run at a low to moderate intensity, and it is the session that carries the largest distance progression in the whole plan, growing from 3 miles in week 1 to 9.25 miles in week 26.
The Interval run is the Wednesday cardio session in the 26-week NSW preparation program. It consists of repeated quarter-mile efforts at a pace slightly faster than your current 1.5-mile run pace, separated by recovery periods, and the number of repeats grows from 4 in week 1 to 10 by week 13.
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.
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