Phasic Muscle Activity in Human Locomotion PDF

Human Locomotion: Phasic Activity of the Lower Extremity Cherri S. Choate, DPM Biomechanics I Applied Biomechanics Department Concept  Muscle function non-weight bearing Peroneus Longus  plantar flexes and everts foot  Muscle function in gait Peroneus Longus  plantar flexes 1st metatarsal at mid...

Human Locomotion: Phasic Activity of the Lower Extremity Cherri S. Choate, DPM Biomechanics I Applied Biomechanics Department Concept  Muscle function non-weight bearing Peroneus Longus  plantar flexes and everts foot  Muscle function in gait Peroneus Longus  plantar flexes 1st metatarsal at midstance  acts as antagonist to Tibialis Anterior Muscle Action in Gait  Muscles act more to stabilize than to move Therefore pathology occurs when stabilization fails to occur  Examples: PT Dysfunction & Hallux Limitus Muscle Action in Gait  Muscles must act in a coordinated fashion during gait  Focus on actions at each phase from heel contact to heel contact Muscle Action in Gait  Monophasic muscles act only once during each gait cycle  Biphasic muscles act at two different phases of each gait cycle Muscle Action in Gait  Criteria for muscle evaluation P- percentage of gait cycle muscle is active S- segment of gait cycle muscle is active F- function of muscle during gait cycle P- pathology which can develop if muscle does not function properly 0% 10% 20% 30% 40% 50% 60% HS 80% 90% Swing Phase of Gait Stance Phase of Gait Contact Midstance Propulsion 27% 40% 33% 0% 70% 27% 67% 100% FFL HL TO 100% Monophasic Muscles Soleus Muscle  P- active from 5%-45% of gait cycle  S- starts right after HC → ends after HO Soleus Muscle  F-  Stabilizes lateral column against ground Extends knee at midstance Initiates HO as tibia moves over foot P- Limited AJ dorsiflexion leads to exaggerated soleus action and genu recurvatum results Gastrocnemius Muscle  P- active 10%-50%  S- right after heel contact → right before toe off Gastrocnemius Muscle  F- prevents full extension of the knee after heel contact  F- Assists in heel off and propulsion Gastrocnemius Muscle  P- Genu Recurvatum in paralysis Soleus overpowers  P- Hip and knee flexion in Cerebral Palsy Posterior Tibialis Muscle  P- active from 1%-45%  S- starts at heel contact with pronation → ends just after heel off Posterior Tibialis Muscle  F- Maintains midtarsal joint stability in concert with peroneus brevis  P- Weakness: forefoot subluxation: PT Dysfunction Flexor Hallucis Longus  P- active 5%-55%  S- starts right before forefoot loading → ends right after heel off Flexor Hallucis Longus  F  P Stabilizes hallux against the ground Initiates resupination of the STJ Hallux hammertoe results if it overpowers extensors Found in iatrogenic situations and weakness disorders such as Charcot Marie Tooth (CMT) Flexor Digitorum Longus Muscle  P- active 10%-55%  S- starts before forefoot loading → ends after heel off Flexor Digitorum Longus Muscle  F Stabilizes lesser toes against ground Initiates resupination of STJ  P Lesser hammertoes in neuromuscular weakness of anterior compartment Peroneus Longus Muscle  P- active 25%-60%  S- starts well after forefoot contact → stops right before toe off Peroneus Longus Muscle  F Plantar flexes first ray to allow hallux dorsiflexion Allows transfer of GRF from lateral foot to medial landing gear  P- Weakness Functional hallux limitus Peroneus Brevis Muscle  P- active 25%-60%  S- starts well after forefoot loading → stops right before toe off Peroneus Brevis Muscle  F- antagonist to all muscles that contribute to STJ supination Biphasic Muscles Anterior Tibialis Muscle  P- active 90%-100% and then 60%-80%  S- last part of swing and during heel contact  S- toe off into swing Anterior Tibialis Muscle  F- holds the foot up to decelerate AJ plantarflexion caused by heel contact  F- dorsiflexes foot after toe off to clear ground  P- Foot drop in LMN lesion Extensor Hallucis Longus Muscle  P- Active 90%-5% and then 60%-80%  S- last part of swing and during heel contact  S- from toe off into swing Extensor Hallucis Longus Muscle  F- strongest dorsiflexor during swing  F- reinverts heel for heel contact  P- Foot drop in LMN lesions Extensor Digitorum Longus Muscle  P- Active 90%-2% then 50%-75%  S- last part of swing  S- first part of heel contact Extensor Digitorum Longus Muscle  F Assists in dorsiflexion during swing Prevents too much supination during swing  P- Foot drop Summary  Muscle have specific actions during gait  Muscles work more to stabilize than to move  The criteria for evaluation a muscle are: P- percentage of gait cycle muscle is active S- segment of gait the muscle active F- function of muscle during gait P- pathology which may develop due to poor muscle function  Evaluate gait from heel contact to heel contact Thank You Applied Biomechanics Department