Muscle Actions and Phases of the Gait Cycle

A complete set of vocabulary flashcards covering the specific functions of lower limb and trunk muscles during gait, the functional goals of each gait phase, and types of muscle contractions.

Erector Spinae

Stabilizes the trunk and prevents excessive forward bending, with two activity bursts at initial contact–$20\%$ and $45\%$–$70\%$.

Rectus Abdominis

Stabilizes the pelvis and lumbar spine, giving hip flexors a stable base.

Gluteus Maximus

Activates in late swing to prepare for heel strike, controls hip flexion during loading response, and then extends the hip. Weakness causes forward trunk lean.

Iliopsoas

Eccentrically controls hip extension in late stance, then concentrically flexes the hip during pre-swing and initial swing.

Sartorius

Concentrically flexes the hip from toe-off through midswing to help advance the leg.

Gluteus Medius, Minimus and TFL

Stabilize the pelvis during single-leg support by eccentrically controlling hip adduction, then concentrically abducting. Weakness results in Trendelenburg gait and hip drop.

Hip Adductors

Stabilize the hip at initial contact and help initiate hip flexion after toe-off.

Hip Internal Rotators

Help rotate the pelvis forward during stance to advance the opposite swing leg.

Hip External Rotators

Eccentrically control internal rotation of the leg during early stance and help stabilize pelvic rotation.

Quadriceps (Knee Extensors)

Eccentrically control knee flexion after heel strike for shock absorption, then concentrically extend the knee in midstance. Weakness leads to knee buckling.

Hamstrings (Knee Flexors)

Eccentrically slow knee extension in terminal swing, and help with hip extension and knee stability during early stance.

Rectus Femoris During Gait

Helps initiate hip flexion during the transition from stance to swing and controls knee flexion.

Anterior Leg Muscles (TA, EHL, EDL)

Eccentrically control plantarflexion after heel strike to prevent foot slap, and concentrically dorsiflex during swing for toe clearance.

Gastrocnemius and Soleus

Eccentrically control forward tibial movement during stance, then concentrically plantarflex at push-off to propel the body forward.

Tibialis Posterior

Eccentrically controls pronation after heel strike, then concentrically supinates the foot to create a rigid lever.

Fibularis Longus and Brevis

Control excessive inversion and stabilize the foot; fibularis longus holds the first ray down for push-off.

Flexor Digitorum Longus

Assists deep posterior muscles with controlling dorsiflexion eccentrically, then helps plantarflex the foot.

Foot Intrinsics

Eccentrically control arch lowering during pronation, then concentrically raise the arch to create a rigid foot for push-off.

Initial Contact and Loading Response – Goal

Accept body weight without collapsing, with muscles mainly providing eccentric control and shock absorption.

Midstance – Goal

Maintain single-leg stability while controlling forward movement of the tibia over the foot.

Terminal Stance – Goal

Create a rigid foot lever and propel the body forward through plantarflexion and push-off.

Preswing – Goal

Unload the limb and prepare to lift the foot off the ground.

Initial Swing – Goal

Concentrically flex the hip and dorsiflex the ankle to advance the leg and clear the toes.

Midswing – Goal

Continue moving the leg forward while maintaining dorsiflexion for foot clearance.

Terminal Swing – Goal

Decelerate the leg, slow knee extension, and prepare for initial contact.

Isometric Muscle Contraction

Muscle produces force without changing length or creating joint movement.

Eccentric Muscle Contraction

Muscle lengthens while controlling or slowing a movement (the brakes).

Concentric Muscle Contraction

Muscle shortens to create movement.