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11.24.05 (3 years ago)
#2
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Hip muscles:
Gluteus maximus
is active just before the end of swing and this activity continues into the beginning of the stance phase, probably to control hip flexion (keeping the trunk erect).
Gluteus medius
acts throughout the stance phase to prevent the pelvis dropping to the unsupported side. Weakness in the hip abductors may result in Trendelenburg's Gait. In Trendelenburg's gait, the pelvis "drops" to the unsupported side, and as an adaptation, the patient oftens leans the trunk over towards the supported side.
Iliopsoas
is most active during the swing phase, presumably to produce hip flexion.
The group of lateral hip rotators is active during the first part of the swing phase when the pelvis is rotating about the supporting hip. Lateral hip rotation of the swinging limb occurs to keep the toes pointed in the right direction. The internal hip rotation occurring on the supported side is counteracted by opposite rotation on the unsupported side.
Thigh Muscles
Quadriceps femoris
has two main peaks of activity; just after heel strike to prevent knee flexion, and; around toe-off, also to prevent knee flexion when gastrocnemius is active and therefore tending to cause knee flexion.
Hamstring
activity just before heelstrike will aid in decelerating the lower limb at the hip, while continued activity after heelstrike will aid knee stabilisation. Sometimes, the hamstrings are active towards the end of the stance phase, presumably to prevent hip flexion.
Leg Muscles
Triceps surae
is active during mid stance to control the rate of dorsiflexion that occurs as the result of the forward progression of the trunk. Triceps surae is most active between heel-off and toe-off when the ankle is plantar flexing during the final propulsive phase.
The pretibial muscle group
has some activity throughout the walking cycle but is most active just after heelstrike when it acts eccentrically to control the rate of plantar flexion. Tibialis anterior
may also control hindfoot pronation that occurs just after heelstrike. The dorsiflexors are also active during the swing phase to prevent the toes "stubbing" on the ground. Anybody with dorsiflexor weakness, commonly from damage to the common peroneal nerve, will exhibit two obvious gait abnormalities. Firstly, "foot slap" will result from lack of foot/ankle control at heel strike, and; secondly, a high knee lift will be developed to prevent the toes dragging on the ground/floor. Peroneus longus
is most active during mid-stance when it may be responsible for returning the hindfoot to the neutral position and then maintaining this position.
Foot Muscles
Intrinsic plantar foot muscles may be active during the stance phase to aid in arch support.
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