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what kind of muscle fiber for steep climbs?(16 posts)

what kind of muscle fiber for steep climbs?non-sprinter
Nov 5, 2001 6:59 PM
What muscle fiber type is used to climb, steep slopes, while standing?
The light ones :-). nmColombian Climber
Nov 5, 2001 8:44 PM
Colombian ones work too :-), nmColombian Climber
Nov 5, 2001 8:45 PM
Colombian ones work too :-), nmJon
Nov 6, 2001 5:32 AM
It's all relative; all types are always recruited to some extent. But as force increases
more fast twitch fibres are recruited. To the extent that you can sit and spin a higher
cadence, more slow twitch fibres will carry the load.
Nov 6, 2001 6:42 AM
Ones the get a large supply of oxygen. Really.

All three t ypesPhysiologist
Nov 6, 2001 9:38 AM
Commonly we have Red fibers that run on O2, white fibers that run on Glycogen and therefore give us lactic acid and then we have Fibers that can run on either. It is these in between fibers that we can actually train. We can't change the amount of fibers we have so we must train to get the in-between fibers to run more efficiently with oxygen or to run more efficiently without oxygen. This is why not everyone can be a world class sprinter. If we could change the type of fibers and the amount, then the person who worked the hardest would be the fastest. We all know that on group rides this is not true.

So no on to your question. When you are riding, normally you are using red fibers, the ones for oxygen. When going up a hill you start to feel lactic acid build up. This is when you are starting to use white fibers and your intermediate fibers are starting to run on glycogen.

If you want to get better you need to train a little more at your lactic acid threshold, which is about 3-5 miles per hour faster than what is confortable. Do this for 10-15 minutes a couple times a week, and you won't feel as much as a build up. Also hill intervals work well
YES!, 1. Colombian; 2. Spanish; and 3. Italian...:-).nmColombian Climber
Nov 6, 2001 10:09 AM
Don't forget Texan :-) (nm)Dog
Nov 6, 2001 10:21 AM
All three t ypes is probably right...Wayne
Nov 6, 2001 10:30 AM
What's it matter? It's not like you get to pick which ones your going to use! Mr. Physiologist I think you're a bit off. What you're saying is probably true for your couch potato but with endurance training all three types of fibers become less fatiguable b/c they become better able to use oxygen for ATP generation, primarily thru the addition of mitochondria, enzymes involved in aerobic ATP production, and capillary density in the muscle as a whole. Also with any increase in activity Type IIx (the faster fast twitch)fibers tend to transition to type IIa fibers(the slower fast twitch fibers). Typically, there is thought to be little conversion between Type I (slow twitch) and Type II (fast twitch) fibers under normal circumstances. But you can convert a muscle to largely all type I fibers using chronic electrical stimulation, and it's well documented that paralyzed muscle (such as in spinal cord injured individuals) which are essentially never activated become largely Type IIx (the fastest fast twitch) within about 1.5 years post injury.
There are probably many other factors in addition to fiber type that determine ones ability to sprint. Clearly muscle size is important (look at track sprinters or even most road sprinters), muscle attachments, and even neuromuscular recruitment issues. Afterall, on a bike, you can just get in a bigger gear and turn it slower (so wouldn't be limited by contractile speed of muscle fibers) and go as fast as someone turning a smaller gear quickly.
I'm not sure if anyone has ever biopsied world class bike sprinters to look at their fiber types or any world class bike riders for that matter, it would be interesting to see their fiber make-up.
Nothing is ever as simple as it first appears!
All three t ypes is probably right...Physiologist
Nov 6, 2001 3:40 PM
I agree with most of what you say, but fast twitch muscles can't use oxygen, but the body can learn to deal with the lactic acid they produce more efficiently. I just think the bottom line is you have what you have, so get used to it.
All three t ypes is probably right...Wayne
Nov 7, 2001 5:52 AM
Respectfully sir, you're wrong. All muscle fiber types can use oxygen to generate ATP, it's just their relative ability that differs. And with endurance training you increase the oxidative ability of all fibers. I can provide a reference from a entry level physiology textbook if you want it.
The primary way that you increase your bodies ability to deal with lactic acid is by producing less of it at a given level of power output or % of VO2max by increasing the oxidative capacity of your muscles. That's why untrained individuals lactate threshold might be around 80% of their VO2max, but highly trained individuals LT might be 90+% of their VO2max. With the increase in oxidative capacity you can generate more ATP from fat and aerobic glycolysis (pyruvate enters the mitochondria) (these are efficient but relatively slow processes), nonetheless if you sprint or go hard enough, you're muscle cells demands for ATP will outstrip you're aerobic supply rate and the only recourse is to start producing ATP non-aerobically at a greater rate (which is quick but inefficient) which converts pyruvate to lactic acid. Above a certain threshold and your cells can't deal with it consequently it gets dumped into your blood and you've exceeded your LT (the lactic acid is primarily taken up by the liver and coverted back to glycogen), this type of effort can only be sustained for relatively short periods of time and is inefficient.
All three t ypes is probably right...peloton
Nov 7, 2001 11:20 AM
There are a lot of processes at work during exercise, and it is hard to say that one muscle type or source of ATP is responsible for any one situation. Different intensities require different reactions from the body, and your body uses all it's different energy production systems and muscles in some way in every activity you do. Some situations may be predominately sustained by certain reactions, but no muscle type or energy system shuts off during any one time, and turns on at another set time. Your body is using creatine phosphate right now, as well as guclose, and glycogen, and the body counts on these systems a little more at some times than others, but all are always working. Same with muscle tissues. Your cliimbing style, intensity, and speed would regulate which muscle fibers that you would recruit the most of but all would be working to some extent and ready during all times. Therefore, it is hard to say that only one muscle type or energy system is the sole workhorse for a given situation all though some may contribute more at different intensities.

I would say though that lactate isn't really a bad thing. I would add that the liver uses lactate to power it's own Kreb's cycle during exercise to produce ATP for it's own functions in addition to producing gylcogen. Lactate is a good thing. It is a storage form of pyruvate, and helps to grab some free radicals from the cell too, in this case H. Not that free radicals are all bad either. Your body couldn't break O2 off of hemoglobin without the free radical H. Everything in the body interplays and works together beautifully. There are so many reactions going on that it would be difficult to say any one thing is totally responsible for any one activity. There are just varying degrees of different systems at different times.
All three t ypes is probably right...Wayne
Nov 8, 2001 6:40 AM
Are you an exercise physiologist? Yeah, after I wrote the message I thought maybe I had made it sound too much like, "you're either using aerobic processes or anaerobic processes". Lactic acid not being the great evil everyone attributes to it is something I've been thinking about. In the lab I work in we tend to read muscle physiology research not exercise physiology lit., and I know recently it's been demonstrated that LA doesn't inhibit force production in muscle cells like it was once thought to. When exceeding your threshold do you think that it's actually the lactic acid that forces you to slow down at some point, or other factors? Seems to me that exceeding your LA threshold, is just indicative of greatly outstripping your muscles ability to derive ATP aerobically (and anaerobically at some steady-state rate that allows the LA to be cleared). It doesn't necessarily follow that lactic acid is what causes a loss in power or the need to slow down and repay the oxygen debt you've generated.
All three t ypes is probably right...peloton
Nov 8, 2001 1:41 PM
I agree. I think LA gets a bad reputation, and when muscles start to lose power that it is probably more a variety of factors like O2 debt and the ability to produce ATP at a sufficient rate. BTW- I didn't mean to contradict you in any way, I agreed with what you said and just wanted to add a little more for some of the good things lactate and even free radicals do in our musclular processes. It amazes me how different parts of our energy and musclur systems interact and how well things work out. I'm a coach and working post grad in kinesiology and exercise phys. You have to be impressed at how different systems interact and how complex they are without trying to say any one thing is soley responsible for any one result. Seems like the more I learn, the more questions I have. Do you find that when researching in the lab too?
All three t ypes is probably right...Wayne
Nov 9, 2001 5:07 AM
Yeah, like I said before nothing is ever as simple as it appears at first. I'm a physical therapist, who's working on a Ph.D. in a lab that studies the fatigue associated with the electrical stimulation of muscle (Christopher Reeve's walking type of stuff). So I don't have an exercise physiology background but I'm trying to pick that stuff up as well as basic muscle physiology. I even wonder if the lactic acid burn is really even lactic acid causing the "burn". I know individuals with McArdle's disease lack one of the enzymes for anaerobic glycolysis and therefore don't produce lactic acid. Yet (and this just highlights your point about how all of the energy systems interact and are parallel processes) they are extremely limited in what activities they can do, experiences muscle cramping, burning and rapid fatigue.
All three t ypes is probably right...peloton
Nov 9, 2001 9:57 AM
Here is something that might interest you. I have a buddy who is a biochemist and is working on an experiment that might have relevance to your work and CNS injuries as a whole. There is a technique to create nuerons out of other tissues that works in lab settings now, and tests are being done to see if these nuerons might be viable when implemented in living subjects, ie rats. Could be big for possible regeneration of tissue, and that could be huge if it works in real world applications. Very cool stuff happening now.

That is interesting about the patients with McArdle's disease not producing lactate, yet still feeling burning sensations. I had read some of the studies that indicated lactate not having an effect on force contraction of skeletal muscle. Those two things together really do seem to suggest that there is a lot more going on with muscle burn than what people have said in the past. As a student as well, I think one of the cool parts of the field of physiology right now is the fact that we are learning so much about the human machine right now and there is a real possibility to research and contribute to the current knowledge base. I think all the new findings and understandings also are the reason I cringe when I hear about and see athletes putting 'supplements' into their bodies without any real understanding of what chemical processes are being affected and what effects interruption of any process might have. Just the fact that we are now finding lactate might not be the reason your muscles burn now tells me we should think a lot more about what other things are doing to our bodies on limited understandings of the human body. It's all pretty interesting stuff, and it's fasinating to me to find out some of the new lab and field studies that are now being worked on.