Where do people get their info on muscle fiber type/percentages? The only things I've ever seen is an unreferenced chart at abcbodybuilding.com that seems to contradict popular dogma in a few areas.
Anyone have an easy, reputable resource that lists muscle fiber type by percentage?
Full Version: Muscle Fiber Types / Percentages
Bump -- anyone?
Or are you all just making this shit up when you say that "such and such muscle is predominantly fast twitch, and thus should be trained like this"?
Or are you all just making this shit up when you say that "such and such muscle is predominantly fast twitch, and thus should be trained like this"?
maybe check out exrx for info. heres a blurb from clicking on the calf on the male muscle map...
"During hopping, the gastrocnemius, with its greater proportion of fast twitch motor units, is preferentially activated over the soleus (Moritani et al., 1990). During stationary cycling, the gastrocnemius is also preferentially activated at higher pedaling speeds (Duchateau et al., 1986)."
"During hopping, the gastrocnemius, with its greater proportion of fast twitch motor units, is preferentially activated over the soleus (Moritani et al., 1990). During stationary cycling, the gastrocnemius is also preferentially activated at higher pedaling speeds (Duchateau et al., 1986)."
I didn't see anything at exrx, I'll probably look again soon. Bump again for reliable resources.
Found this today, interesting (IMO) that the lifelong strength trained showed higher percentage TII fibers than untrained. Usually we see the opposite, right? Possible that it's staving off atrophy?
EDIT: Looking again, percentage-wise the U still rocked S in IIX fibers, with S slightly higher than U in IIA, and E lowest in both.
Found this today, interesting (IMO) that the lifelong strength trained showed higher percentage TII fibers than untrained. Usually we see the opposite, right? Possible that it's staving off atrophy?
QUOTE
Mechanical muscle function, morphology, and fiber type in lifelong trained elderly.
Aagaard P, Magnusson PS, Larsson B, Kjaer M, Krustrup P.
Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark. paagaard@health.sdu.dk
PURPOSE: Maximal muscle contraction force and muscle mass are both reduced during the natural aging process. Long-term training may be used to attenuate this age-related loss in muscle function and muscle size. METHODS: Maximum isometric quadriceps strength (MVC), rate of force development (RFD), and muscle fiber composition and size (CSA) were studied in elderly individuals (68-78 yr) chronically exposed (> 50 yr) to either endurance (E) or strength (S) training, and in age-matched, untrained (U) elderly group. RESULTS: E and S showed greater MVC than did U. Contractile RFD was elevated in S compared with U, and S also demonstrated greater type II fiber CSA than did U and E. The proportion of type I fibers was greater in E compared with U and S. CONCLUSIONS: Muscle fiber size and mechanical muscle performance, particularly RFD, were consistently elevated in aged individuals exposed to chronic (i.e., lifelong) strength training. This relative preservation in muscle morphology and function may provide an important physical reserve capacity to retain muscle mass and function above the critical threshold for independent living at old age.
PMID: 17986907 [PubMed - in process]
Aagaard P, Magnusson PS, Larsson B, Kjaer M, Krustrup P.
Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark. paagaard@health.sdu.dk
PURPOSE: Maximal muscle contraction force and muscle mass are both reduced during the natural aging process. Long-term training may be used to attenuate this age-related loss in muscle function and muscle size. METHODS: Maximum isometric quadriceps strength (MVC), rate of force development (RFD), and muscle fiber composition and size (CSA) were studied in elderly individuals (68-78 yr) chronically exposed (> 50 yr) to either endurance (E) or strength (S) training, and in age-matched, untrained (U) elderly group. RESULTS: E and S showed greater MVC than did U. Contractile RFD was elevated in S compared with U, and S also demonstrated greater type II fiber CSA than did U and E. The proportion of type I fibers was greater in E compared with U and S. CONCLUSIONS: Muscle fiber size and mechanical muscle performance, particularly RFD, were consistently elevated in aged individuals exposed to chronic (i.e., lifelong) strength training. This relative preservation in muscle morphology and function may provide an important physical reserve capacity to retain muscle mass and function above the critical threshold for independent living at old age.
PMID: 17986907 [PubMed - in process]
EDIT: Looking again, percentage-wise the U still rocked S in IIX fibers, with S slightly higher than U in IIA, and E lowest in both.
QUOTE(dashforce @ Dec 3 2007, 02:28 PM) [snapback]440169[/snapback]
I didn't see anything at exrx, I'll probably look again soon. Bump again for reliable resources.
Found this today, interesting (IMO) that the lifelong strength trained showed higher percentage TII fibers than untrained. Usually we see the opposite, right? Possible that it's staving off atrophy?
EDIT: Looking again, percentage-wise the U still rocked S in IIX fibers, with S slightly higher than U in IIA, and E lowest in both.
Found this today, interesting (IMO) that the lifelong strength trained showed higher percentage TII fibers than untrained. Usually we see the opposite, right? Possible that it's staving off atrophy?
EDIT: Looking again, percentage-wise the U still rocked S in IIX fibers, with S slightly higher than U in IIA, and E lowest in both.
so could that study also be an argument that weight training reduces loss of type II muscle fiber, while untrained lose type II? is type I sacrificed as age gets older ( sort of makes sense as I don't see too many "old" people running long distance, of course they might have better things to do as well )
Don't know, I posted for discussion. Like I said, only IIA were elevated, not IIX (which is IIB/etc, right?)
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