Lecture 14 Flashcards
What are the general functions of skeletal muscle?
Heat production, posture, movement and communication
What are the pros and cons of bipedal vs quadrupedal standing?
Quadrupedal standing has a large base of support but the legs are flexed at several joints, this means a high energy cost.
Bipedal standing has relatively small area of contact with the ground and hence a low base of support but the legs arn’t very flexed, meaning its more energy efficient.
What two roles can gravity play and how does this apply to our standing?
Gravity can act as an agonist or an antagonist to our movement.
In our upright stance the line of gravity falls posterior to the hip joint and hence its agonist movement is to push us into extension, in this state our ligaments are tight and hence locked
In our knees the line of gravity is anterior to the joint and as such the joint is in extension and locked.
In our ankle however the line of gravity is once again anterior but causes falling into dorsiflexion without action and as such our plantarflexors must stabilise us at our ankles, which consumes energy.
What are the main facts about human (bipedal) walking?
human walking is learnt, leading to a characteristic gait. The basic walking pattern is known as the gait cycle and consists of a stance and a swing phase. These phases end or start with heel-strike and toe-off.
What is the double stance phase? How many in each gait cycle?
The point at which both feet are on the ground, there are two in each gait cycle.
What is the early stance and what muscles are acting?
In the early stance heel strike has just occured, The hip is flexed due to action by the illiopsoas (concentric action), the knee is extended due to action by the quadricep femoris performing concentric action. The ankle is in a dorsiflexed position due to action by the tibialis anterior.
What is the mid stance and what muscles are acting?
In the mid stance the hip has moved into extension (via the gluteus maximus primarily and the hamstrings), in the knee the joint has been stabilised by the isometric action of the quadriceps femoris, in the ankle it has moved from dorsiflexion to anatomical position via gravity acting as an agonist and the tibialis anterior acting as an agonist.
What is the late stance and what muscles are acting?
Hip is now in hyperextension due to concentric action of the gluteus maximus, the knee is flexed passively due to the forward movement of the body, ankle is plantar flexed due to concentric action of the plantarflexors (triceps surae).
What is the early swing and what muscles are acting?
Hip is in slight flexion due to concentric action of the illiopsoas, knee is still passivle flexed due to forward movement of body, dorsiflexion of the ankel occurs due to concentric action of the tibialis anterior.
What is the mid swing and what muscles are acting?
Knee is being extended by pendulum motion so no muscles are acting, ankle has not changed postion and as such the tibialis anterior is working as a stabiliser and the hip is still being acted on by the illiopsoas to flex it.
What is the late swing and what muscles are acting?
Hip still flexing due to the illiopsoas acting concentrically, the knee is locked into extension by the quadriceps femoris and the ankle is still in a dorsal position (stabilised by the tibialis anterior).
