Static stretching

Static stretching involves moving slowly into a stretch and holding the position while the muscle relaxes and lengthens.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 289.} It’s the most common method for increasing flexibility.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 289.} Slow movement avoids triggering the stretch reflex, giving it a lower injury risk than bouncing, or ballistic, stretches.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 339.}

ACSM recommends holds of 10 to 30 seconds at tightness or slight discomfort; older adults may benefit more from 30 to 60 seconds.^{3Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 368.} Its prescription is about 90 seconds per exercise across 2 to 4 repetitions, at least 2 to 3 days a week, with daily stretching most effective.^{3Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 368.} The NSCA recommends 15 to 30 seconds, with diminishing returns beyond 30 seconds.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 338.}

In practice

Precede stretching with 5 to 15 minutes of activity, or stretch right after aerobic or resistance training.^{5Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 290.} A single session’s gains in range of motion fade within 3 minutes to 24 hours, while stretching twice a week for at least 5 weeks has improved flexibility.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 338.}

Where sources differ

The NSCA’s Guide to Program Design (2012) advises moving static stretching to the cool-down because most evidence showed reduced force, power, speed and reaction time when it preceded an event, sometimes lasting up to an hour.^{6Hoffman, NSCA’s Guide to Program Design, p. 69.},^{7Hoffman, NSCA’s Guide to Program Design, p. 70.}

ACSM distinguishes longer holds without other activity from short stretches within a dynamic warm-up.^{8Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 367.},^{3Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 368.} Holds longer than 60 to 90 seconds without dynamic activity hurt performance, but holds under 60 seconds per muscle group within a full dynamic warm-up are acceptable and may reduce muscle and tendon injuries.^{8Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 367.},^{3Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 368.}