Here's what my physiology book says about Type 1 and Type 2 muscle fibers:
"Type I
Type I muscle fibers (slow-oxidative fibers) use primarily cellular respiration and, as a result, have relatively high endurance. To support their high-oxidative metabolism, these muscle fibers typically have lots of mitochondria and myoglobin, and thus appear red or what is typically termed "dark" meat in poultry. Type I muscle fibers are typically found in muscles of animals that require endurance, such as chicken leg muscles or the wing muscles of migrating birds (e.g. geese).
Type II
Type II muscle fibers use primarily anaerobic metabolism and have relatively low endurance. These muscle fibers are typically used during tasks requiring short bursts of strength, such as sprints or weightlifting. Type II muscle fibers cannot sustain contractions for significant lengths of time, and are typically found in the white meat (e.g., the breast) of chicken. There are two sub-classes of type II muscle fibers, type IIa (Fast-Oxidative) and IIb (Fast-Glycolytic). The Type IIa fast-oxidative fibers actually also appear red, due to their high content of myoglobin and mitochondria. Type IIb (Fast-Glycolytic) tire the fastest, and are the prevalent type in sedentary individuals. These fibers appear white histologically, due to their low oxidative demand, manifested by the lack of myoglobulin and mitochondria (relative to the Type I and Type IIa fibers). Some research suggests that these subtypes can switch with training to some degree. The biochemical difference between the three types of muscle fibers is their myosin heavy chains.
These types of muscles are in the categories of skeletal muscle"
While Gufbal's theory may be off a tad, he/she isn't too far off because most people will go overboard and if i read correctly, that's what he/she was saying.
Nothing in what your physiology book states contradicts anything I've said here. But I thank you for sharing it. I've read the studies that suggest that Type IIa fibers can be made to change to type I, but Type II cannot...and that's the majority of your muscle mass. So some change can be affected, but it won't be drastic.
Gufbal's theory wasn't a "tad" off...it was OFF
He stated
Each person is predisposed genetically to either type 1 or type 2.
People
are not predisposed to one type
OR the other. It is roughly a one to three ratio in
Everyone, give or take a
Tiny fraction
(scientists differ on how tiny of a fraction, but in general...if it's enough to make THAT much of a difference, it's not within the normal range of genetic fluctuation: ie; it'd be a mutation...not that that NEVER occurs) here or there, plus the stated ability to alter the Type IIa fibers through intensive musculo-endurance training. Other than this, it's not really the muscles responsibility to make a person an "endurance" athlete, that has more to do with number and volume of mitochondria
(which can have a greater degree of flux than muscle type, according to most research) and the body's ability to execute the Kreb's Cycle, replacing glycogen and ATP
(the muscles energy source) faster and more efficiently. THAT has a pronounced impact on endurance and can be Greatly affected through training.
most people will go overboard
...whos this "Most People" group your talking about, and how do You know so much about them?? :mst: hahaha....
No.
Most people do not 'go overboard'...
that'd be a portion of the "BodyBuilders", Pro, amateur and enthusiast , a great many of whom take controlled substances to over-ride their bodies somatotypic muscular thresholds and endanger their kidneys and livers.
A normal person (being a person who's body chemistry is pretty much standard, ie; no synthetic hormones) who pushes their body to the limit and seeks to progressively increase strength and muscle mass, and uses good technique and does at least a little flexibility maintenance work
WILL NOT get muscle bound and will do nothing but Improve their ability to Quickly/Rapidly and repeatedly contract their muscles over a FULL range of motion.
Period.
Limited range of motion lends itself toward injury! Why would the NFL trainers make HEAVY weight training such a main staple in their athletes if it in anyway limited mobility and ran a greater risk of making them suceptible to injury?
It is a sterio-type, this 'muscle bound' myth. It's often foisted by people who don't train for strength at all or have no knowledge of exercise physiology. IF people perpetuate this myth then some may listen to and believe it (as obviously some here have) and then some may not gain the good they might have through proper weight training.
...and that's really too bad.
Your Brother
John