Training intensity

Training intensity in strength training usually means load relative to the client’s one rep max: 80% of 1RM is higher intensity than 50%.^{1Rippetoe et al., Practical Programming for Strength Training, 3rd ed., p. 57.} Helms and colleagues distinguish this “intensity of load” from “intensity of effort,” how close a set comes to the client’s limit, often measured with rating of perceived exertion (RPE).^{2Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 62.} They caution against using intensity to mean soreness or how hard a session felt overall.^{2Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 62.}

Zatsiorsky and colleagues describe four ways to estimate intensity: percentage of best performance, reps per set, reps at maximal weight and workout density (sets per hour).^{3Zatsiorsky, Kraemer and Fry, Science and Practice of Strength Training, 3rd ed., p. 77.}

Where sources differ

Rippetoe and colleagues accept only percentage of 1RM, arguing that perceived effort, mental focus and fatigue can’t be quantified and are impractical for strength coaching.^{1Rippetoe et al., Practical Programming for Strength Training, 3rd ed., p. 57.} ACSM accepts RPE and reps in reserve (RIR) alongside repetition maximum (RM) testing as ways to prescribe intensity.^{4Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 356.}

In practice

• Expect different rep counts at the same percentage: trained men in one study completed 9 to 26 squat reps to failure at 70% of 1RM.^{5Helms et al., The Muscle & Strength Pyramid: Training, 2nd ed., p. 63.}
• ACSM gives 67% to 85% of 1RM for hypertrophy and strength endurance, above its 60% minimum for a strength stimulus.^{4Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 356.}
• Calculate average intensity from work sets: one squat example averaged 61% across all sets but 82% across work sets alone.^{1Rippetoe et al., Practical Programming for Strength Training, 3rd ed., p. 57.}