Request 4Help: Muscle Fibre Adaptation

Dear All,
I’m sure somewhere on the CF site someone must have written something profoundly wise about why kids should develop their speed instead of just their endurance with a view to ultimately superior performance as an adult athlete.

The argument I suppose would incorporate some reference to that section of (undedicated) muscle fibre which, when stimulated, will adopt (adapt to) the characteristics of either the red (endurance) or white (power) muscle depending on the type of training the athlete is exposed to.

While the type-2 red fibre (I believe it is known as) can always be converted from power to endurance, once it has been converted to the endurance end of the force spectrum, it cannot be shifted back to the sprint end again. IF THIS IS CORRECT, SOMETHING ON THIS SUBJECT IS WHAT I’M REALLY AFTER.

Anyway I can’t find anything here or elsewhere that is concise and not too technical for the layman to understand.

I would appreciate it if anyone can post an article on the subject, which is afterall pretty close to home for all coaches of young runners.

thanks,
kk :confused:

I know this is knot exactly what you are looking for but maybe you can pull something out of this??? Sorry for the scientific wording in some parts but most studies have this and are tough to get around…

Muscle fibre type adaptation in the elderly human muscle
Andersen, JL

Abstract This short review discusses changes in the fibre type distribution, myosin heavy chain isoform composition and histological appearance of the very elderly human skeletal muscle. Point of origin of the discussion comes from data that we have obtained from muscle biopsies from the vastus lateralis muscle of a group of frail very elderly subjects (age: 88 plus or minus 3 years, range 85-97). Myosin heavy chain composition of muscle homogenates and single fibres, fibre type distribution, fibre size and capillary density were examined and compared with muscle biopsies from the young vastus lateralis muscle. Histological preparations of the muscle biopsies from our elderly subjects showed extended “grouping” (Nygaard & Sanchez, Anat Rec 1992: 202: 451-459) of the fibre types as well as significant changes in the appearance and size of the individual muscle fibres. On average, the fibre type composition of our very elderly subjects do not seem to be different to what is observed in a corresponding young group when examined with ATPase histochemistry. Likewise, the MHC composition of the muscle homogenates is comparable to what is observed in young subjects. Nevertheless, a detailed examination of the MHC composition of single fibres from the old subjects revealed that the most prominent phenotype was fibres co-expressing MHC I and MHC IIA. This is very different from what is observed in the young muscle. Detailed investigation of longitudinally cut fibres indicated that some fibres in the very old muscle, in contrast to the young muscle, switch fibre type along the length of the fibre or contain areas or nuclear domains in which the MHC expression is different from the remaining part of the fibre.

here is another that you might be able to pull some ideas out of, sorry again for the scientific crap…these things are hard to read??? :confused:

Muscular adaptations in response to three different resistance-training regimens: specificity of repetition maximum training zones

Author Campos, GER; Luecke, TJ; Wendeln, HK; Toma, K; Hagerman, FC; Murray, TF; Ragg, KE; Ratamess, NA; Kraemer, WJ; Staron, RS

Abstract Thirty-two untrained men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body mass 77.8 (11.9) kg] participated in an 8-week progressive resistance-training program to investigate the “strength-endurance continuum”. Subjects were divided into four groups: a low repetition group (Low Rep, n=9) performing 3-5 repetitions maximum (RM) for four sets of each exercise with 3 min rest between sets and exercises, an intermediate repetition group (Int Rep, n=11) performing 9-11 RM for three sets with 2 min rest, a high repetition group (High Rep, n=7) performing 20-28 RM for two sets with 1 min rest, and a non-exercising control group (Con, n=5). Three exercises (leg press, squat, and knee extension) were performed 2 days/week for the first 4 weeks and 3 days/week for the final 4 weeks. Maximal strength [one repetition maximum, 1RM), local muscular endurance (maximal number of repetitions performed with 60% of 1RM), and various cardiorespiratory parameters (e.g., maximum oxygen consumption, pulmonary ventilation, maximal aerobic power, time to exhaustion) were assessed at the beginning and end of the study. In addition, pre- and post-training muscle biopsy samples were analyzed for fiber-type composition, cross-sectional area, myosin heavy chain (MHC) content, and capillarization. Maximal strength improved significantly more for the Low Rep group compared to the other training groups, and the maximal number of repetitions at 60% 1RM improved the most for the High Rep group. In addition, maximal aerobic power and time to exhaustion significantly increased at the end of the study for only the High Rep group. All three major fiber types (types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant increases were demonstrated for either the High Rep or Con groups. However, the percentage of type IIB fibers decreased, with a concomitant increase in IIAB fibers for all three resistance-trained groups. These fiber-type conversions were supported by a significant decrease in MHCIIb accompanied by a significant increase in MHCIIa. No significant changes in fiber-type composition were found in the control samples. Although all three training regimens resulted in similar fiber-type transformations (IIB to IIA), the low to intermediate repetition resistance-training programs induced a greater hypertrophic effect compared to the high repetition regimen. The High Rep group, however, appeared better adapted for submaximal, prolonged contractions, with significant increases after training in aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce similar muscular adaptations, at least after short-term training in previously untrained subjects. Overall, however, these data demonstrate that both physical performance and the associated physiological adaptations are linked to the intensity and number of repetitions performed, and thus lend support to the “strength-endurance continuum”.

I’m baaaaaack, I should get a life…Kelly B. wrote a good article on muscle fiber type , he also posts on here so maybe he can elaborate on any questions if you have em’!!!

http://www.higher-faster-sports.com/muscletyping.html

do you know where kelly’s follow up article is? or if it has even been done yet?

Maris I think this is it!

http://www.higher-faster-sports.com/fasttwitchmachine.html

Thanks man. Appreciated!

Thanks ASD123 and Maris,

I really appreciate the fact you’ve gone to the trouble of searching this out for me. ASD the early stuff was a bit too technical. I needed a lay explanation expressed in lay language. I will undoubredly learn when I read through all of the two linked articles, but I primarily was trying to get something to help the parents of a gifted nine-year-old girl athlete who they were taking to receive coaching which may have over-emphasised endurance in order to gain a result through “fitness” at the risk of messing up her long-term prospects.

thanks a lot

kk :slight_smile:

Inactivity causes the greatest expression of fast muscular characteristics in an individual. The fiber can shift back. The muscles themselves are extremely plastic. Check out those references at the end of IIX overshoot.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10883005

The important thing with doing the correct training at an early age is with regards to the nervous system mainly, along with hypertrophy and strength. You can’t get back those years of training. For example if you take 2 twins and have one run marathons from 14 to 18 years of age, and the other run sprints over that same period of time, then the sprinter will have a huge advantage in movement efficiency, recruitment capacity, size of type II muscle fibers, and strength. The endurance runner turned sprinter will have a lot of catch up to do.

Kelly B

That’s precisely the story I was trying to get the facts on. Thankyou again. BRILLIANT. Does an explanation of this process appear in writing the layman could read and understand?

kk :slight_smile:

KellyB,
I finally found enough time and silence to sit down and concentrate when I read through your two excellent and enlightening and really accessible articles.

Just one query please: I was advised by various lecturers (admittedly back in the ancient 80s) that while you could make the type IIA fibres adopt the characteristics of either Type I or Type IIB, once you trained for some time (presumably several years) towards endurance , the TypeIIA fibres would either not adapt (or would do so only with extreme difficulty) back to the IIB qualities.

Given your knowledge of contemporary studies, does this claim stand-up or is it bogus? Because either way it has major implications for development, particularly of younger athletes. And that was really why I posed the initial question.

Thanks again
kk

This is why I don’t want my athlete’s doing other sports during the winter. If only I could translate this into “teenager” so they could understand.