Cardiorespiratory Conditioning Guidelines (Peterson & Bryant / ACSM)

Based on the existing scientific evidence on exercise prescription for healthy adults, the American College of Sports Medicine developed a position paper on exercise prescription. It included the following recommendations on the quantity and quality of training for developing and maintaining cardiorespiratory fitness (and desirable body composition) in a healthy adult.

1. Frequency of training: 3 to 5 days per week.

2. Intensity: 60% to 90% of maximal heart rate. Note that exercise of low and moderate intensity may provide important health benefits and may result in increased fitness in some persons (e.g., those previously sedentary and low fit). Maximum heart rate = 220 − Age.

3. Duration of training: 20 to 60 minutes of moderate aerobic activity. The actual time you should exercise aerobically generally depends on the relative intensity of the activity — lower-intensity activities should be conducted over a longer period. Emphasis should be placed on the total work performed, which can be estimated by the caloric expenditure of the activity.

4. Mode of activity: Any activity that uses the large muscle groups, can be maintained continuously, and is rhythmical and aerobic in nature (see Mode of Aerobic Activity (Large-Muscle, Continuous, Rhythmic)).

5. Rate of progression: The body's ability to adapt to imposed stresses (the training effect) lets individuals gradually increase total work over time. The most significant conditioning effects are typically observed during the first 6 to 8 weeks (see Rate of Progression and the Training Effect).

This guideline set comes from Peterson & Bryant (1995); the more detailed, later version of the ACSM prescription appears in ACSM Exercise Recommendations for Healthy Adults (1998) (ACSM 1998).

The recommendations above are the manual's (1995) summary of an earlier ACSM paper. The current ACSM statement is the 2011 position stand (Garber et al.), which superseded the 1998 stand. Compared with the five points above:

• Frequency: ≥5 days/week of moderate, ≥3 days/week of vigorous, or 3–5 days/week of a mix.
• Intensity: moderate (40–59% HRR, 64–76% HRmax, RPE 12–13) and/or vigorous (60–89% HRR, 77–95% HRmax, RPE 14–17); light-to-moderate work may benefit deconditioned people.
• Duration: 30–60 min/day of moderate (≥150 min/week) or 20–60 min/day of vigorous (≥75 min/week); one session or bouts of ≥10 min.
• Volume: ≈500–1000 MET-min/week — the modern form of "emphasise total work".
• Mode: unchanged — regular, purposeful, continuous, rhythmic exercise using major muscle groups.
• Progression: gradual increases in duration, frequency and/or intensity until the goal is reached.

• Earlier edition (manual, 1995) — Frequency: 3–5 days/week.
• Intensity: 60%–90% of maximal heart rate; low/moderate intensity still benefits the unfit.
• Max HR = 220 − Age.
• Duration: 20–60 minutes of moderate aerobic activity; lower intensity → longer duration.
• Total work (caloric expenditure) is the emphasis, not just time.
• Mode: large-muscle, continuous, rhythmic, aerobic activities.
• Most significant conditioning effects in the first 6–8 weeks.
• Current ACSM (2011): ≥5 d/wk moderate (64–76% HRmax) or ≥3 d/wk vigorous (77–95% HRmax); 30–60 min/day moderate or 20–60 min/day vigorous; ≈500–1000 MET-min/week.