+ 9 Muscle fiber types and how to modify them
We go to the gym day in and day out to either get bigger or get stronger. Some of us have worked out specific body parts and either found no changes, plateaus, or no strength improvements.
The average person has about 60% fast twitch fiber and 40% slow twitch fiber. It boils down to muscle fibers. Some of us have FT (fast twitch), and ST (slow twitch). its rather easy to find out which muscle fiber types you have in a given body part so your workouts will be more productive and you will either grow or get stronger. If before you worked out you played a lot of sports you might be FT dominant like myself. I was an avid boxer and played football growing up so my muscle fibers are predominantly fast twitch which changes how I workout now. You can modify the types of muscle fibers you have as well by changing your routines but lets 1st figure out what fiber types you have by using the tried and true Dr Hatfield and Charles Poliquin muscle type tests. here is what you need to know and have to do this:
Someone to spot you
Exercises you do that you want to find out.
Determine your one repetition maximum (1RM) on an exercise
Rest for 15 minutes
Perform as many reps as you can with 80% of your 1RM
Less than 7 repetitions – Your fast twitch (FT) dominant
7 or 8 repetitions – You have a mixed fiber type
More than 8 repetitions – You are slow twitch (ST) dominant
If you are FT dominant, you should be using heavier weights and less reps. ST dominant means you will respond better to lighter weight and higher reps
More research can be found here:
http://www.topendsports.com/testing/tests/muscle-fiber-composition.htm
http://www.brianmac.co.uk/musclefibre.htm
Charles Poliquin:
Determine your one repetition maximum (1RM) on an exercise
Rest for 15 minutes
Perform as many reps as possible with 85% of your 1RM
Less than 5 repetitions – you are fast twitch (FT) dominant
5 repetitions – you have mixed fiber type
More than 5 repetitions – you are slow twitch (ST) dominant
Modifying Muscle fiber types:
Different exercises bring about changes in the fibers. Endurance such as running or swimming, cause a gradual transformation. The muscles show a slight increase in diameter, mitochondria, blood capillaries, and strength. Endurance exercises result in cardiovascular and respiratory changes that cause skeletal muscles to receive better supplies of oxygen and carbohydrates but do not contribute to muscle mass. On the other hand, exercises that require great strength for short periods of time, such as weight lifting, produce an increase in the size and strength of the fibers. The increase in size is due to increased synthesis of thin and thick myofilaments. The overall result is that the person develops large muscles.
You can develop fast-twitch fiber by complex training and performing weight/strength training to the point where you can release exercise-induced growth hormone.
happy training everyone and please do more research on muscle fiber types so you can achieve what you are set out to do.
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I have not tested myself n a long time I'm curious which fibers has taken over the years
I was going to change the post name because you can alter your muscle fiber types but you cant modify, if that makes sense.
I guess it does lol. I know definition of both words I will be honest tho u had me looking like wait what
This is very interesting +2
Needs a bump!
I actually tested this last summer, but I can't exactly remember my results. I might think about doing it again. I so believe I was very slow twitch dominant in a lot of muscle groups.
Muscle fibers bundled together are termed "motor units". In a nutshell, what the OP is emphasizing is "motor unit recruitment".
I believe I have some things posted in my forums on these topics, although not necessarily titled as such.
Understanding the physiology here is a bit more complex, however. Total isolation of a motor unit is physiologically impossible. This is because all three types are stimulated at the onset of applying a load. What determines which is dominant, or predominately used during the movement, is the type of load being applied.
It all boils down to energy pathways governed by mitochondrial composition of the given motor unit. And it is never as simple as doing certain number of reps per set. You absolutely MUST apply the overload principle of training when using the "reps per sets" method; meaning rep to unassisted failure.
I am a firm believer in unassisted failure and overload to at minimum "train" the muscle types to try and change. For example; my biceps. I can take a 90 pound curl bar and do 30 reps before reaching failure; but I can add another 30 pounds and hammer curl the bar even easier. Although I am still using my long head muscle I have switched the positioning to start using either the FT or ST. Total isolation may or may not assist the average person but it should at least guide them to find that happy medium where metabolic changes could happen to some lesser extent.
You misunderstand... Total isolation of a particular fiber type is physically impossible. For example, when a heavy load is lifted, you are not allowed to continue beyond the limitations of the white fast twitch motor units bc the red fast and slow twitch are incapable of supporting the load; however, they assist during the lift.
These muscular contractions are stimulated via an electrical impulse to the targeted muscle group as a whole. The CNS is not selective beyond the muscle group; it cannot stimulate selective fibers out of the bundle to contract and leave the remaining ones in a relaxed state. Isolation of fiber stimulation is not possible.
The reason this is taught in physiology is to guide yourself or your client towards meeting the desired results and goals. If you want size/strength, train with loads heavy enough to cause tissue damage to the white fast twitch fibers. If you want strength and stamina, train with loads that cause tissue damage to the red fast twitch. If you want muscular and/or cardio respiratory endurance, use loads that can be sustained for longer periods, meanwhile utilizing the mitochondrial elements comprising the red slow twitch fibers.
Understanding and using working rep maxes is a great tool for anyone. Just as long as the person doesn't get confused and think they can isolate only portions of a muscle group. When a muscle contracts, it does so as a whole. How long it is allowed to continuously contract is dependant on the type of load applied, which in turn is governed by the fiber types that are mostly responsible for supporting the given load. But they all contract simultaneously at the onset. They fail in the order of WFT, RFT, RST.
Got it; I confused isolation with failure like an idiot. Thanks for pointing that out.
No worries. Failure is key to applying these principles tho. For example, with the size and strength goal, pumping out 4-6 reps to unassisted failure will target the WFT fibers. But doing 4-6 reps with any weight will not.
waltrThat's interesting, I never knew about those tests.
I think I may have to try that out on one of my weekend days off from the gym and see what happens.
If I actually remember to do it this saturday or sunday I'll share my results.
+1 for something interesting to read this morning.