RVP wrote: more importantly, it fails to recognize that the lower the relative exercise intensity, the more unrecruited/underrecruited motor units there are in the leg extensors, which can, if necessary, also be called upon to either increase the power output or sustain the same power output longer. To put it another way: performance during exercise requiring significantly less than VO2max is not limited by the available muscle mass, so bringing the hip flexors into play more serves no purpose. The only time that recruiting additional muscle can improve performance is if
A) you could provide those muscles with the additional O2 needed via an increase in maximal cardiac output to achieve a true VO2max, instead of merely a VO2peak (e.g., addition of arm cranking to leg cranking in untrained persons). However, this possibility doesn't exist in individuals trained at cycling, because they can achieve a true VO2max (i.e., a VO2 limited by maximal cardiac output, not the amount of muscle recruited/vasodilated).
B) the exercise intensity is so high that it requires >100% of VO2max, such that supplementing the power output using the newly-recruited motor units' anaerobic capacity leads to an increase in performance. In this situation (not really relevant to triathlons), recruiting the hip flexors, etc., could indeed result in a temporary increase in power output - which undoubtly explains why trained cyclists pull up significantly in this, and generally only this, situation. Notably, however, they have learned and trained themselves to do without ever using PCs.
Thanks for your response:
I still don't understand why you say since the extensors have unrecruited muscle fiber in a sub-max work rate, it would do no good to recruit other muscle groups to assist. I 100% agree that there are muscle fibers not being used in the extensors in a sub-max effort...BUT, the extensors will STILL evenutally fatigue (defined as a decrease in power produced) at let's say, 70% of maximum cardiac output, or let's say, 70% of VO2max. Don't say all you have to do is to utilize the unused extensor fiber units...doing so causes the extensors to fatigue even more quickly. SO, why not use hip flexors, hamstrings, etc. to do some of this work (allowing the extensors to go even longer before fatigue)...or, to add to this constant extensor work rate (therefore increasing power somewhat), when we have underutilized cardiac output available to supply the extra blood needed to supply the hip flexors/hamstrings?
Secondly, I 100% agree that at supra-max VO2 efforts, recruiting hip flexors/hamstrings makes sense, and that obviously, almost every cyclist in history that has learned to do this to some extent, has learned to do this without PowerCranks. That's a given. This doesn't mean PowerCranks aren't suitable to train a cyclist to pull up...just that they weren't available. It also doesn't mean PowerCranks are better to teach one to do this, either. That isn't germaine to the discussion about recruitment being a positive thing. We both agree recruiting can be a good thing in supra-max VO2 situations...and we both agree that this supra-max VO2 state isn't applicable to most situations in triathlon.
I still don't understand your opposition to recruiting in sub-max VO2, sub-max cardiac output states. I certainly disagree that firing unused muscle fibers in the extensors would be appropriate, because, in this case, using more muscle fibers would fatigue the muscle group more quickly. That only makes sense...if the rider can ride 97 minutes using only his extensors at lets say 250 watts, and this is at 70% of his VO2 max, firing those unused-underused fibers to get more power will fatigue the extensors more quickly, so he will ride less than 97 minutes at the given workrate. So, we are left with only one alternative...using other muscles to assist them. Please don't try and say the rider should practice more to increase his efficiency of his extensors...I'm talking about a theoretical rider that has done all the training possible to maximize his extensor efficiency/fiber recruitablility, etc...he's at his OPTIMUM extensor function....what now? Why not bring in hip flexors and hamstrings to assist? He obviously has cardiac function in reserve.
I know that this recruitment of "less efficient" hip flexors will increase HR, it will also increase the amount of oxygen used per unit of time, as would simply using more extensor fibers...but, keep in mind that we are talking about a workrate that will result in the extensors' fatigue in a period of time...so, we cannot simply use more extensor fibers...that would decrease the time before the extensors' power decreased. I don't see why this isn't a good strategy. It doesn't matter that your reports state that cyclists don't have much, if any, backpressure on the pedals. It's immaterial. I am talking about effecting a change in the cyclist example above.
Thanks again for a response.
Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
A) you could provide those muscles with the additional O2 needed via an increase in maximal cardiac output to achieve a true VO2max, instead of merely a VO2peak (e.g., addition of arm cranking to leg cranking in untrained persons). However, this possibility doesn't exist in individuals trained at cycling, because they can achieve a true VO2max (i.e., a VO2 limited by maximal cardiac output, not the amount of muscle recruited/vasodilated).
B) the exercise intensity is so high that it requires >100% of VO2max, such that supplementing the power output using the newly-recruited motor units' anaerobic capacity leads to an increase in performance. In this situation (not really relevant to triathlons), recruiting the hip flexors, etc., could indeed result in a temporary increase in power output - which undoubtly explains why trained cyclists pull up significantly in this, and generally only this, situation. Notably, however, they have learned and trained themselves to do without ever using PCs.
Thanks for your response:
I still don't understand why you say since the extensors have unrecruited muscle fiber in a sub-max work rate, it would do no good to recruit other muscle groups to assist. I 100% agree that there are muscle fibers not being used in the extensors in a sub-max effort...BUT, the extensors will STILL evenutally fatigue (defined as a decrease in power produced) at let's say, 70% of maximum cardiac output, or let's say, 70% of VO2max. Don't say all you have to do is to utilize the unused extensor fiber units...doing so causes the extensors to fatigue even more quickly. SO, why not use hip flexors, hamstrings, etc. to do some of this work (allowing the extensors to go even longer before fatigue)...or, to add to this constant extensor work rate (therefore increasing power somewhat), when we have underutilized cardiac output available to supply the extra blood needed to supply the hip flexors/hamstrings?
Secondly, I 100% agree that at supra-max VO2 efforts, recruiting hip flexors/hamstrings makes sense, and that obviously, almost every cyclist in history that has learned to do this to some extent, has learned to do this without PowerCranks. That's a given. This doesn't mean PowerCranks aren't suitable to train a cyclist to pull up...just that they weren't available. It also doesn't mean PowerCranks are better to teach one to do this, either. That isn't germaine to the discussion about recruitment being a positive thing. We both agree recruiting can be a good thing in supra-max VO2 situations...and we both agree that this supra-max VO2 state isn't applicable to most situations in triathlon.
I still don't understand your opposition to recruiting in sub-max VO2, sub-max cardiac output states. I certainly disagree that firing unused muscle fibers in the extensors would be appropriate, because, in this case, using more muscle fibers would fatigue the muscle group more quickly. That only makes sense...if the rider can ride 97 minutes using only his extensors at lets say 250 watts, and this is at 70% of his VO2 max, firing those unused-underused fibers to get more power will fatigue the extensors more quickly, so he will ride less than 97 minutes at the given workrate. So, we are left with only one alternative...using other muscles to assist them. Please don't try and say the rider should practice more to increase his efficiency of his extensors...I'm talking about a theoretical rider that has done all the training possible to maximize his extensor efficiency/fiber recruitablility, etc...he's at his OPTIMUM extensor function....what now? Why not bring in hip flexors and hamstrings to assist? He obviously has cardiac function in reserve.
I know that this recruitment of "less efficient" hip flexors will increase HR, it will also increase the amount of oxygen used per unit of time, as would simply using more extensor fibers...but, keep in mind that we are talking about a workrate that will result in the extensors' fatigue in a period of time...so, we cannot simply use more extensor fibers...that would decrease the time before the extensors' power decreased. I don't see why this isn't a good strategy. It doesn't matter that your reports state that cyclists don't have much, if any, backpressure on the pedals. It's immaterial. I am talking about effecting a change in the cyclist example above.
Thanks again for a response.
Quid quid latine dictum sit altum videtur
(That which is said in Latin sounds profound)
Last edited by:
yaquicarbo: May 18, 04 8:22