Lecture 13 : Critical Time Periods for Force Application Flashcards
(27 cards)
what is power
the ability to exert force within a critical time period
connecting cross linkages and activity muscle fibres takes …
time and energy
why does the velocity of contraction decrease when load is increased
because we need more cross linkages to activate simultaneously
what is the ultimate limitation to how much force and how quickly we can generate force
primarily related to how quickly we can engage the mechanism that actually binds the actin and myosin proteins
by increasing the load beyond our eccentric tolerance we can increase the
force output but also the velocity of lengthening
direct representations of strength
- force
- acceleration
- duration - impulse
- change of force per change in time (RFD)
indirect representations of strength
- velocity
- power
high force at low velocity’s mean you have what power
low power
low force at high velocitys means you have what power
low power
what element about power is most important to us
rate of force development
the word power is useful in terms of load but what is it not useful in
not particularly useful in terms of programming, if you are trying to develop power it is useful to look at the force profile in terms of rate of force development
in sports like sprinting what is the critical time period
take off
in sports like throwing what is the critical time period
ball / object release
what type of contraction is best for measuring the absolute amount of maximum force of an athlete
isometric contraction
absolute force in an isometric contraction tells us
how many motor units you engage, how much force you can produce with those motor units given all the time needed
what is the key issue of measuring absolute force in isometric contractions
they are given as much time as needed, in competitive environments there is time pressure so they will not be able to produce as much force
if we want to make our athlete more powerful we have to focus on, not just increasing their total force production but alsp
also how much force they can produce in critical time windows
what is the sticking point
point where you slow down because you are at a position where the muscle less advantageous to force production
what must impulse be if the lift is successful
must have a positive impulse that is greater than the negative impulse
impulse must be greater than the impulse at the sticking point
what is a failed lift in terms of impulse
if sticking point impulse exceeds the acceleration impulse
why can the bar be still moving up even though the force is negative
just because the force is negative doesn’t mean the bar is moving down
the force indicates direction of load not direction of movement
at the sticking point the load is working against the upward movement of the bar
4 ways we can improve the success of the lift
- increasing peak force using the maximal strength method
- increasing rate of force development with the dynamic effort method
- extending the acceleration phase with accomodating resistance or pneumatics
- greater strength in the sticking region with isometrics
explain why increasing peak force using the maximal strength method will improve the success of a lift
if we increase the force we can produce, the entire line will shift upwards because we have more force (more area under the curve)
explain why increasing rate of force development with the dynamic effort method will improve the success of a lift
using a dynamic training method will increase the amount of force produced at the very start of a movement
you haven’t increased peak / total force
increased rate of force development which increases the area under the curve
