Mechanical Strength Flashcards
What are the 4 mechanical factors of strength?
- Joint angle
- Joint velocity
- Muscle action
- Muscle arm
Describe the force length relationship and explain why.
- Force is greatest at intermediate lengths
- Lower at long and short lengths
- Greater binding sites & crossbridges
What are the challenges of whole muscle force-length relationship?
- Length of MTU, fascicle, fibre or sarcomere
- Reliance on torque-angle relationship
Provide examples of when force-length relationship is seen practically.
- Sticking point
- Testing protocols
- ROM
How do nordics prevent injury?
- Shifts force-length relationship to be stronger @ longer lengths
Describe single fibre force-velocity relationship and state why.
- Force decreases as velocity increases
- Less binding sites available & crossbridges
At what % of maximal shortening velocity is most force created?
approx. 33%
What decides a muscle’s maximal shortening velocity?
- Fibre type
- Fibre length
- Pennation angle
- Rate of change in pennation angle
Why is the greatest force generated in eccentric action?
- Stretching of completely inactive sarcomeres
- Faster reattachment phase
What causes variation in muscle torque?
- Attachment location
- Contribution of multiple muscles
Define moment arm
Shortest distance from joint centre to line of action of force (tendon)
What are the characteristics of a longer moment arm?
- Greater peak torque
- Has to contract more to move through ROM
How much do muscle fibres shorten in isometrics?
30%
What can be modified to influence joint torque?
- Resistance arm
- Effort arm
