Flexibility

Flexibility is the ability to move a joint through its complete, pain-free range of motion.^{1Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 248.} It’s specific to each joint, so no single test can rate a client’s whole-body flexibility.^{1Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 248.} The NSCA defines static flexibility as the range available when an outside force, such as gravity or a partner, moves the joint, and dynamic flexibility as the range available during active movement.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 336.} The textbook describes dynamic flexibility as usually the larger of the two.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 336.}

Joint structure sets the possible range, which is why ball-and-socket joints such as the hip and shoulder move the most.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 337.} Young people tend to be more flexible than older people, and women more than men.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 337.} Muscle and connective tissue, stretch tolerance and activity level can all change with training.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 337.},^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 338.}

In practice

• Train for the range the activity needs: too little and too much flexibility can both raise injury risk.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 337.}
• Resistance training with free weights or machines improved range of motion about as much as static stretching in meta-analyses.^{5Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 370.}
• Heavy training through a limited range may reduce flexibility, so train both agonists and antagonists through their full range of motion.^{4Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 338.}
• Measure range in degrees with a goniometer or inclinometer after a general warm-up and static stretching, taking three trials and using the best.^{6Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 250.}