If you haven’t recognized these athletes, then let me introduce you to eight times world champions and sprinter Michael Johnson, and gold medalist marathon winner, Haile Gebrselassie.
Both are runners, but their built shows a kind of eccentricity if you look closely.
As you can see, while Johnson appears to be strong and sturdy, Haile Gebrselassi, on the contrary, looks much leaner. Wonder why?
Reason Behind Their Appearance
The answer lies in the composition of our muscles, which determines how will you perform in a particular activity, and whether your body is suited to perform certain activities better than others.
Slow-twitch muscles are characterized by lower intensity but higher endurance movements such as distance running. Fast-twitch muscles are engaged in more powerful movements such as sprinting or hurdling, but they fatigue quickly.
Not clear enough? Okay, lets know a little bit more about them.
Slow Twitch Muscles
Type 1 muscles contract slowly and use oxygen to produce energy which is why they sustain longer than fast twitch fibers. The same science enables us to jog, cycle and dance for extended periods.
Slow twitch muscles produce less but constant flow of energy so that we can exercise longer or swim multiple lengths. Even when we walk, these fibers are in action.
Fast Twitch Muscles
Fast twitch muscles are categorized under two types, type 2A and type 2B.
Type 2A fibers are also known as hybrid fibers, as they show characteristics of both fast twitch and slow twitch fibers. Type 2A fibers contract quickly and rely on oxygen to produce energy.
Our body engages them to perform sustained powerful activities like sprinting 400muscle-fiber-typem or doing repeated lifts with medium weight. So, you see, they give out high energy as well as short level of endurance.
Type 2B fibers contract faster than Type 2B, and their energy level is explosive in nature. They rely on glycogen for generating fuel. Perfect example of activities include jumping, sprinting 100m, shot put or discuss throw, hurdling and lifting heavy weights.
So, as powerful as they are, these muscles fatigue as quickly as they contract, even quicker than type 2A. Type 2B fibers are also used to give you a kick start in any sport, like to provide acceleration in a race.
So, what exactly makes one a sprinter or a distance runner?
An ideal Sprinter like Johnson, has almost greater percentage of fast twitch muscles, at times up to 80%, which enables him to run fast like a gazelle. Same goes for weight lifters who perform repeated lifts.
Moving further, distance runners like Gebrselassie have larger number of slow twitch fibers which provide them enough stamina to complete a 5K or a 10k run.
The fact that they are lean and skinny, is because they don’t focus on building strength or speed. Their main goal is to work on their endurance level. Marathoners need constant flow of energy to keep going for hours. So, their ultimate key to touch the finish line is not strength or agility, but sustainability.
Is the fiber composition genetic?
Studies give an affirmative nod to this one. As I said, we are born with more or less equal number of both these fiber types. But, the fact that the proportion varies in cases of different athletes, is being determined partly by genetics.
A 2011 study discovered its association with muscle variation up to 45%.
So, you understand, why east Africans have flooded the distance running sports and west Africans shine as sprinters.
While sprinters weigh more than distance runners, most of their weight comes from their muscles which gives them the power to run at high speed and against the wind.
Distance runners need to cover miles over miles, so they can’t afford to carry much body weight. Hence, you need to train yourself accordingly, to realize your full genetic potential.
Can training change the muscle type?
Well, this is one most frequently asked question that has no definite answer yet.
Most studies say that it is not possible to bring change across the inherent muscle type I.e. from slow twitch to fast twitch and vice versa. However, researchers agree that through exercise training, it can be possible to change your muscle type within the same category, i.e. from type 2B type 2A.
Now, since it is highly unlikely to change your muscle type from slow twitch to fast twitch, you better remove that from your goal list. However, you can grow your existing muscle type by focusing on specific training.
Most of you might want to grow your muscles for power and strength, and for that your training method should focus on tapping those fast twitch fibers.
So How Do You Train?
So, before you begin with your light to moderate weight lifts, you can try doing push press, ball throws and repeated jumps to stimulate your fast twitch fibers that are otherwise hard to tap in.
Also,increasing the number of repetitions while lifting light weights can help, if you are aiming for both strength and endurance. Add bands. Bring some innovation in your routine, and you can see changes in your muscle tone and size.
The Ideal Workout:
Fast twitch exercises helps you build muscle mass and strength. It also triggers weight loss as it burns considerably more energy in a shorter period. So, combining both will give you a better workout.
When you force your muscles to work differently, your body is out of its comfort zone and you achieve the desired result. However, your muscle type is just one aspect of your performance. So, do not obsess about it.
Like I said, make an attempt to intertwine your training with elements of both speed and endurance and your body will take care of the rest accordingly.
Reference Simoneau JA, & Bouchard C (1995). Genetic determinism of fiber type proportion in human skeletal muscle. FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 9 (11), 1091-5 PMID: 7649409. ^Back to Top^ Jansson, E., & Kaijser, L. (1977). Muscle Adaptation to Extreme Endurance Training in Man Acta Physiologica Scandinavica, 100 (3), 315-324 DOI: 10.1111/j.1748-1716.1977.tb05956.x. ^Back to Top^ Staron, R., Malicky, E., Leonardi, M., Falkel, J., Hagerman, F., & Dudley, G. (1990). Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women European Journal of Applied Physiology and Occupational Physiology, 60 (1), 71-79 DOI: 10.1007/BF00572189. ^Back to Top^ Staron, R., Malicky, E., Leonardi, M., Falkel, J., Hagerman, F., & Dudley, G. (1990). Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women European Journal of Applied Physiology and Occupational Physiology, 60 (1), 71-79 DOI: 10.1007/BF00572189 . ^Back to Top^