Which PNF technique is defined by the sequence of contract, relax?

The technique defined by the sequence of contract, relax is known as Hold Relax. This specific PNF (Proprioceptive Neuromuscular Facilitation) technique is designed to increase flexibility and range of motion. During the Hold Relax method, the individual first contracts the muscle group being stretched against resistance for several seconds, which activates the Golgi tendon organs, leading to a subsequent relaxation of the muscle. After this contraction phase, the individual then relaxes the muscle and gently stretches it further, allowing for an increased range of motion.

This sequence leverages the reciprocal and autogenic inhibition mechanisms, where the contraction followed by relaxation enables a deeper stretch than would be possible without the contraction. Hold Relax is particularly beneficial for athletes looking to enhance their performance by improving their flexibility, which in turn can help prevent injuries.

The other techniques mentioned, such as Slow-Reversal-Hold-Relax, involve additional movements and variations that differ from the straightforward contract-relax principle of the Hold Relax method. D1 and D2 positions refer to specific arm movement patterns used in PNF stretching but do not specifically denote the contract-relax sequence. Thus, the straightforward nature of "contract, relax" aligns closely with Hold Relax, making it the correct choice.