Understanding Fast-Twitch and Slow-Twitch Muscle Fibers
We’ve talked about the importance of training slow-twitch muscle fibers, especially for endurance athletes. Regardless of the ratio, we all have fast-twitch muscles that we can’t neglect. Understanding fast-twitch muscles and how they affect performance will help you incorporate training them into your regimen to give you the best results for whatever you’re training for.
The two types of fast-twitch muscle fibers
Fast-twitch muscle fibers are the largest and most powerful in the body and store a great deal of carbohydrates. They have much lower endurance but exert more force than slow-twitch fibers.
Type IIa – the middle of the muscle fiber spectrum, less fatigue resistant, produce more muscular force, and contract at a faster speed than slow-twitch fibers.
Type IIb – the last muscle fibers to be recruited during activities that require an all-out burst of power for a short period of time and produce maximal strength.
All easy running is handled by slow-twitch muscle fibers. As running intensifies, more and more fast-twitch fibers are recruited (type IIa first followed by type IIb). Regardless of whether you’re working on your short or long-distance training, you need to incorporate a mix of fast-twitch workouts to make sure they can come to the rescue when you need them.
2 Ways to Train your Fast-Twitch Muscle Fibers
1) Speed work
Short repeat intervals – traditional interval workouts help recruit intermediate and fast-twitch muscle fibers. By being used together, these two fiber types learn to interact more efficiently.
Sprint work – hill sprints and maximum effort sprints help recruit the maximum amount of fast-twitch muscle fibers. Even for long-distance runners, speed work is important to make each stride more explosive, helping you get more bang for your buck with a maximum efficiency stride.
2) Strength training
Fast movements – box jumps, jump squats and kettle bell swings help target and train fast-twitch muscles for explosiveness.
Heavier power exercises – exercise like power cleans and back squats focus on the power side of your type IIb fast-twitch muscle fibers. These are the gym equivalent of short distance sprint work for your fast-twitch training.
When you’re lifting, lift as fast as you can at lower reps. If you’re an endurance athlete and you’re a little hesitant to add too much weight when lifting, focus on explosive, high intensity exercises instead. It’s important to remember that working on your fast-twitch muscle strength isn’t going to turn you into a bulky body builder unless you stop all of your endurance training.
Hopefully you’re sold on why you shouldn’t shy away from training your fast-twitch muscle fibers. Don’t worry…you won’t turn into the Hulk or even get a sprinter’s physique as long as a majority of your training continues to be high mileage and slow-twitch training.
Here are a few resources for more info on fast-twitch training:
Check out this series on supplements to help your training, recovery and overall health.
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What a good exercises for fast twitch for softball swing power?