Anatomy of normal human gait

To understand the muscle interactions that produce gait, a language is required to discuss them. Although anatomical language characterizes individual muscles, the language of the physical therapist describes how muscles work in groups during the activities of daily living. For example, the gluteus medius moves the hip out of anatomical position (abduction), but people rarely do this. Instead, they use this muscle to stand on one leg as the other leg swings forward. The physical therapist explains this by describing three types of muscle contraction: concentric, eccentric and isocentric. In gait, some muscles work as the prime mover (agonist), while others contribute by modulating the motion of the prime mover (antagonism or synergism) or stabilizing one joint to allow motion about another joint (fixation). This discussion can be simplified by focusing on the 12 muscles examined by general practitioners. Each represents a neuromuscular compartment. Since each compartment is innervated by a single nerve, this simplification facilitates a discussion of muscle interactions. In the example above, isocentric contraction of the gluteus medius “fixes” one hip to enable other muscles to move the hip on the other side. A language that describes normal activity helps students discuss and understand the underlying anatomical principles. Supported by US Dept of Ed P116B031017