Proprioceptive neuromuscular facilitation (PNF)

Proprioceptive neuromuscular facilitation (PNF) is a stretching method that combines passive movement with concentric and isometric muscle actions, usually with a partner.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 340.} PNF stretching began in rehabilitation to relax muscles with increased tone, then was adopted to improve flexibility.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 340.}

The NSCA text explains two mechanisms: contracting a muscle before stretching stimulates the Golgi tendon organ and relaxes that muscle through autogenic inhibition; contracting the opposing muscle during the stretch relaxes the stretched muscle through reciprocal inhibition.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 339.}

What are the PNF techniques?

All three techniques start with a 10-second passive prestretch at mild discomfort.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 341.} In hold-relax, the client resists isometrically for 6 seconds, relaxes, then receives a 30-second stretch.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 341.} Contract-relax replaces the isometric hold with a concentric action through the full range of motion.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 341.} Hold-relax with agonist contraction adds a contraction of the opposing muscle during the final stretch; the NSCA text calls it the most effective of the three.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 342.}

In practice

• ACSM prescribes a light-to-moderate contraction (20% to 75% of maximum) for 3 to 6 seconds, then a 10- to 30-second assisted stretch.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 368.}
• The partner should prevent joint movement during the hold and avoid overstretching the muscle.^{6Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 291.}
• PNF takes time and a trained partner.^{6Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 291.} Since static and dynamic stretching work well and most clients don’t need superior flexibility, PNF often isn’t necessary.^{6Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 291.}
• Keep extensive PNF work for a dedicated flexibility session rather than right before exercise.^{7Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 367.}