It will be performed on the lower limb and using eccentric exercise. We were wondering whether 50 max repetitions at 120 degrees per second would actually cause enough damage?
try these papers, they seem to have done a similar design to the one you want to do
Cockburn et al., 2010, App. Phys. Nut. Met. 35 (3) 270-7
Cockburn et al., 2012, Med Sci Sports Exer
Cockburn et al., 2012, Euro J Appl Phys 112(9):3187-94
Cockburn et al., 2008, App. Phys. Nut. Met. 33 775-783
First of all, if you want a great deal of injury, you're not going to get it with the knee extensors. Injuring the elbow flexors will get you ~50% more. See the attached book chapter in which we reviewed and compared the different models for inducing muscle injury, including the eccentric injury models.
Gordon,
Agreed, that elbow flexors are going to be damaged more, however we are looking at the knee extensors for comparison purposes with cycling exercise.
I have read your review...We are trying to work out the best angular velocity to induce damage, what would you recommend. From what I can tell, a slower angular velocity is more likely to induce damage.
Secondly, to enable a greater ROM, are we likely to see any significant differences if we did the exercise lying prone in order to lengthen the muscle as opposed to seated.
Finally, do you think there is a significant difference between doing (10 sets x 10 reps) or (5 sets x 20 reps). Perhaps the latter with reduced rest time may induce more damage?
My gut feeling is that angular velocity is not all that important in human "knee extensor" models. On the other hand, I've seen pretty good evidence that the longer a muscle ends an eccentric contraction at, the greater the injury. I don't think that doing 5 sets of 20 reps as opposed to 10 sets of 10 will do anything for you, except maybe induce more fatigue which you probably don't want.
I serve as a clinical instructor for Biodex and have seen a number of dynamometers that use what is called "reactive eccentric" modes. The problem with the reactive eccentric mode is the necessity of producing 5 - 10% of the peak torque set for the exercise to activate the dynamometer. This is problematic since the force velocity relationship clearly demonstrates that eccentric torque is greater than concentric or isometric torque. I know studies of intact muscle have sometimes reported less torque with eccentric dynamometry, but in using it with numerous patients in therapeutic settings I have observed that this is only the case when the velocity setting exceeds the capacity of the patient to perform at the given velocity.
The theory of eccentric muscle damage with eccentric muscle actions is based on studies using supramaximal loads in true eccentric muscle actions (the subject could NOT move the resistance using a concentric muscle action). The best way to do this using the Biodex is to set up the test in "Passive Mode." This doe not require the subject to provide a counter-torque to start the movement, and therefore they can resist the movement throughout the entire ROM of the test. For the knee, set up the ROM for the test. For your question of influence with cycling, I would seek to determine the velocity of movement for the performance. If that is considered too fast, I would do a spectrum from about 90 d/s to 180 d/s but this may require some learning because the change in direction occurs very rapidly. For the passive mode of a Biodex, you will be able to set a maximum torque for each direction, this should be set to exceed the maximal concentric torque of the subject at that velocity by 50% to insure they do not STOP the movement.
At velocities of 90 - 180 d/s it will take between about 20 and 10 seconds to perform 10 repetitions; 40 - 20 seconds for 20, respectively. Again you need to look at the specific aspects of performance you are attempting to study or modify through training to set up the protocol. The dynamometer should be set for REPS however, not time, when setting up the END BY mechanism.
If you have further questions you can contact me here.
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