Chapter 17 Flashcards
What is the difference between a pull up and a chin up?
Nothing. There is only the pull-up, however, the type of grip should be specified (supinated versus pronated, wide versus narrow).
Are there differences in how men versus women complete pull-ups? Are there differences in the force production of a pul-up with wide versus narrow hand positioning?
No and no
What are the prime movers for a pull up exercise?
The shoulder extensors ( as well as large scapular stabilization)
Why is the elbow flexor moment so small during chin-ups?
Because the elbow stays in the line of force. Thus the force going through the forearm is strong, but the moment is very small - thus the elbow flexors perform little work.
More work is performed by the shoulder extensors and elbow flexors is larger in a pronated grip. Why?
Both pronated and supinated grips use the same muscles, however, the pronated grip is harder because you are moving through a larger ROM (increased extension at the bottom).
What is measured by electromyography (EMG)?
What is a limitation to EMG?
The muscles action potentials.
Just because a muscle is active, doesn’t mean it’s contributing to the movement.
Which muscles are activated throughout a pull-up movement?
Early Phase 0-70:
- upper pectoralis major (high)
- infraspinatus (moderate)
Late Phase 70-140:
- Latissumus dorsi (moderate)
- teres major (high)
- infraspinatus (moderate)
Why isn’t latissimus dorsi involved throughout the pull-up exercise?
This has to do with the level of cross bridging present in the latissimus dorsi with different positions of the arm.
In anatomical position, the lats are on the left edge of the plateau region in the force-length relation. As the arm is flexed, the muscle is lengthened, sliding to the right os the plateau region. Past 90 degrees of shoulder flexion, the muscle slides down the descending limb and is unable to generate as much force.
Thus, the lats are not used as much in overhead tasks.
Why is the pec major a large contributor in the first half of a pull-up?
When the arm is elevated above 90 degrees, the pec major changes its function to become a shoulder extensor, because of changes in its MOMENT ARM.
Below 90 degrees the pec major is a shoulder flexor/adductor.
Someone who can effectively perform the second half of a pull up, but no the first should train what muscle with what exercise?
Their pec major, with a pull-over exercise (laying supine).
