Human Levers Flashcards
Define torque
Torque is a force which results in rotation movements. It is composed by :
- the force applied
- the length of the lever arm
- the angle between the force vector and the lever arm
Define mechanical advantage
Is the ratio between the distance from the fulcrum to point of force application (=effort arm) and the distance from fulcrum to resistance point of application (resistance arm).
When it is > 1 the input force (effort) will be amplified.
What is the role of anatomical pulleys ?
They deflect the action line of a muscle away from the joint axis, increasing the lever arm / moment, generating higher torque force for the same force.
When is the largest moment arm in knee flexion/ extension ?
When the knee is fully extended
When does the maximum resistance happens when pulleys are applied ?
When the angle of pul happening between the attached limb and the pulley’s rope is 90°
When does maximal resistance occur when using free weights ?
When the pull weight is perpendicular to the ground, regardless of the extremities position
What is the length - tension curve of a muscle ?
Relation between the tension developed in a muscle fibers and the length of its sarcomeres.
For each muscle there is an ideal length to produce force, it’s the intermediate length.
What is the torque-angle curve of a muscle ?
It is the relation between the torque produced in a joint and its range of motion.
It allow to determine the angle of peak torque = joint angle in which you have the most torque. It varies between individual due to flexibility. If you are flexible you display more force in longer amplitudes.
What is a lever ?
A simple machine made out a rigid barre and a fulcrum.
What is a first class lever ? Give an example.
The fulcrum is located between the point of force application and the resistance.
Ex : atlanto occipital joint :
- fulcrum = atlanto occipital joint
- resistance = center of mass of the head
- force = cervical spinal muscles
What is a second class lever ? Give an example
The resistance point is between the resistance and the point of force applicatio.
- fulcrum : metatarso phalangeal joint
- resistance : center of mass located between the calcaneus and metatarso phalangeal joint
- point of force application : gastrocnemius and soleus
What is a third class lever ? Give an example
The force is between the fulcrum and the resistance.
Ex : biceps curl
- fulcrum = elbow joint
- resistance = center of mass of body segment
- force = biceps tendon
