GAIT CYCLE

Gait Cycle

Gait Cycle

The movement pattern that we observe in the lower limbs during walking results from the interaction between external forces (joint reaction and ground reaction) and internal forces (produced by muscles and other soft tissue). Knowledge of the ground reaction force is especially helpful to therapists who must understand how muscle activity and timing contributes to stability and propulsion. (Gage 1990)

Muscle activity is typically studied using electromyography (EMG). EMG records differ between individuals, and differ for a single individual according to variables such as velocity. The following summary draws on the findings of reliable investigators. (Gage 1990)

Loading Response (0 to 12 percent of gait cycle)

This is a period of extensive muscle activity. The ankle dorsiflexors act eccentrically to prevent slapping of the foot on the ground. The quadriceps act eccentrically to control knee flexion. Hip flexion is controlled by isometric action of the hamstrings (primarily biceps femoris) and gluteus maximus (primarily its lower portion). (Inman 1981)

In the frontal plane, activity in the hip abductors, tensor fascia lata, and upper portions of the gluteus maximus control drop of the contralateral pelvis, which is relative hip adduction. While activity in the the anterior gluteals (gluteus medius and minimus) might appear eccentric, these muscles simultaneously move the hip joint into internal rotation. In a closed chain, this hip rotation causes the pelvis to rotate forward on the opposite side. Thus, gluteus medius activity may be nearly isometric. Also contributing to both internal rotation and extension of the hip joint are the muscles of the adductor group. (Inman 1981)

The erector spinae are also active during loading response. Their activity during this period has been characterized classically as a mechanism to stabilize the trunk during weight transfer, and to prevent its forward flexion during the rapid slowing of forward movement which occurs at initial contact. Recent theory (Gracovetsky 1988) attributes to the paraspinal muscles a more active role in producing important trunk and pelvic rotation.

Midstance (12 to 31 percent of gait cycle)

As the body moves over the stance limb, activity in the foot's intrinsic muscles (which are primarily subtalar supinators) activate to convert the foot into an increasingly rigid structure. This supination force is augmented by activity in the ankle plantar flexors, which act eccentrically to control closed chain ankle dorsiflexion in the form of tibial advancement over the stable foot. The quadriceps act concentrically to initiate knee extension, and the hip abductors continue their activity, becoming isometric as they halt contralateral pelvic drop.

Terminal Stance (31 to 50 percent of gait cycle)

Foot intrinsics and ankle plantar flexors continue to function as during midstance, becoming isometric at around 35 to 40 percent of the gait cycle, when continued forward momentum in the body's upper part causes the heel to rise from the floor.

Similarly, the hip abductors move from eccentric to isometric to concentric activity, elevating the pelvis in preparation for swing. The iliopsoas becomes active, eccentrically controlling the rate of hip ...