Open kinetic chain exercise (OKC)

Open kinetic chain exercise (OKC) lets the end of a limb move freely.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 631.} In the NSCA’s leg extension example, the feet and lower legs move freely, allowing the client to concentrate on the quadriceps at the knee.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 631.} The IPTA describes open-chain motion as the far end of a bone moving about a fixed near end, as in a dumbbell biceps curl.^{2International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 93.}

Open-chain movements usually involve a single joint moving against angular resistance, as in biceps curls or leg curls.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 71.} But open versus closed kinetic chain is a separate distinction from single-joint versus multijoint exercise.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 71.}

In practice

• Use open-chain work to concentrate on one muscle or joint.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 631.}
• In knee rehabilitation, open-chain force is usually directed parallel to the tibia’s joint surfaces, adding front-to-back stress.^{4Hoffman, NSCA’s Guide to Program Design, p. 221.} Avoid excessive forward or backward translation of the tibial plateau during these exercises.^{4Hoffman, NSCA’s Guide to Program Design, p. 221.}
• The NSCA’s program design guide recommends both open- and closed-chain work for functional knee stabilization in injured and uninjured athletes, because lower-limb movements occur in both conditions.^{4Hoffman, NSCA’s Guide to Program Design, p. 221.} During sprinting, the leg on the ground works in a closed chain while the other swings in an open one.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 631.}

Why the definitions vary

The NSCA’s strength and conditioning text classifies a chain by whether the terminal joint meets enough resistance to restrain its motion.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 631.} The IPTA looks at which end of the bone is fixed.^{2International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 93.} The NSCA’s personal training text notes that the squat and leg press are kinematically similar even though the foot is fixed in one and moving in the other; it says there is no exact consensus on the definitions.^{3Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 71.}