1. A Deep and Personal Look at Your Muscles
When we ask a bodybuilder to make a muscle, few of us realize just how much is going on underneath the skin. Muscles are made up of bundles of fibers. Strands of proteins (actin and myosin) in each bundle grab onto each other and allow a muscle to shorten and contract. On average, our muscles are made up of 60 percent fast-twitch muscle fibers and 40 percent slow-twitch fibers.
2. Keeping Up With Fast-Twitch Muscle Fibers
Fast-twitch muscles allow the fibers to contract more rapidly. These muscles come into play when, say, a bodybuilder lifts a heavy weight a few times over a very short period of time or when a runner is running sprints. Fast-twitch muscles do not provide more force than slow-twitch muscles, they simply provide speed and are used for short bursts of power. Fast-twitch muscles use glycogen, a form of glucose, and not oxygen as their energy source.
3. Fibers So Fast, They Need More Than One Type
While there is only one type of slow-twitch muscles (Type I, using only oxygen), fast-twitch muscles are broken down into two types (Type IIa and IIb). Type IIa are intermediate fast-twitch muscles that exhibit characteristics of both fast and slow-twitch muscles (mainly, they are able to use both oxygen and glycogen for energy). Type IIb are solely fast-twitch fibers, responsible for short bursts of speed and energy. These muscle fibers are not used for endurance as they tire more quickly.
4. When It Comes to Fast-Twitch Muscles, Don't Turn the Other Cheek
The best exercise program incorporates movements that benefit both types of muscle fibers. Building slow-twitch muscles is great for endurance. Cardio workouts and higher sets and repetitions are great for slow-twitch muscles. Fast-twitch fibers react best to short bursts of activity. Powerlifting (very low repetitions and sets with heavy weights) is one way you can make sure you are not ignoring your fast-twitch muscles.
5. Fast-Twitch Muscles Like Exercise Too
Isometric training is perhaps the best way to ensure you are focusing on only your fast-twitch muscles when exercising. Isometric exercises contract the muscle without any movement of the joint, keeping the muscle in a static contraction. For example, curling a weight to your chest and holding it there would be an isometric exercise. Working out with a resistance band is another form of isometric exercise that greatly benefits the development of fast-twitch muscles.
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