Lever Systems
1st Class – involves triceps
Elbow Joint (extension)
Fulcrum – elbow
Load – hand
Effort – triceps muscles
2nd Class – involves gastrocnemius
Ankle joint (plantarflexion +
dorsiflexion)
Fulcrum – ball of foot
Load – weight of body
Effort – gastrocnemius muscle
3rd Class – involves bicep and knee
Elbow/knee (flexion)
Fulcrum – elbow
Load – hand
Effort – biceps muscles
, Mechanical Advantage
Mechanical advantage depends on the distance between the effort and the
fulcrum compared to the distance of the resistance from the fulcrum
Mechanical Advantage = effort arm / resistance arm
1st and 3rd class levers
- Short effort arm compared to resistance arm
- Mechanical advantage is less than one
+ -
Speed – fast contractions Lifting heavy weight
Distance – large range of movement
2nd class levers
- Shorter resistance arm compared to effort arm
+ -
Lighting heavy weights Small range of movement
Short
1st Class – involves triceps
Elbow Joint (extension)
Fulcrum – elbow
Load – hand
Effort – triceps muscles
2nd Class – involves gastrocnemius
Ankle joint (plantarflexion +
dorsiflexion)
Fulcrum – ball of foot
Load – weight of body
Effort – gastrocnemius muscle
3rd Class – involves bicep and knee
Elbow/knee (flexion)
Fulcrum – elbow
Load – hand
Effort – biceps muscles
, Mechanical Advantage
Mechanical advantage depends on the distance between the effort and the
fulcrum compared to the distance of the resistance from the fulcrum
Mechanical Advantage = effort arm / resistance arm
1st and 3rd class levers
- Short effort arm compared to resistance arm
- Mechanical advantage is less than one
+ -
Speed – fast contractions Lifting heavy weight
Distance – large range of movement
2nd class levers
- Shorter resistance arm compared to effort arm
+ -
Lighting heavy weights Small range of movement
Short
