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Table 2 Constructs related to muscle function

From: The effect on knee-joint load of instruction in analgesic use compared with neuromuscular exercise in patients with knee osteoarthritis: study protocol for a randomized, single-blind, controlled trial (the EXERPHARMA trial)

Constructs Definitions
Muscle strength The amount of external force that a muscle can exert
Muscular endurance The ability of muscle groups to exert external force for many repetitions or successive exertions
Functional alignment Lower limb alignment during weight-bearing. A correct functional alignment means that the knee is lined up over the second toe without tending to fall inwards/medially during knee flexion (Figure 2)
Functional performance test/measures A test that challenges muscle strength and postural control or dynamic joint stabilization in the lower extremities and the trunk (for example, various knee bending tests). A physical performance test is a quantitative test (for example, measuring length, number of repetitions, seconds) that evaluates the prerequisite for function
Closed kinetic chain exercise Weight-bearing exercise with distally situated axis of motion and a movement occurring in several joints, and where the distal segment is usually fixed to a supporting surface (for example, a squat)
Open kinetic chain exercise Non weight-bearing exercise, with a proximally situated axis of motion and a movement occurring at a single joint, and where the distal segment is free to move (e.g., extension of the knee in a sitting position)