On today’s episode of Live Lean TV, I’m answering an interesting question about fast twitch vs slow twitch muscle fiber training.
I received this question from my Instagram, so click here to follow me and ask questions over there as well.
The question went something like this:
I used to train for strength, but I got bored, so I switched to marathon training. I’ve run my marathon, but I now notice I’ve lost strength. So I’m now back in the gym lifting weights. My problem is I notice I’m getting stronger in my upper body, but I’m not able to lift as much as I used too with my legs. What’s the deal? Did my marathon training ruin my leg strength?
Essentially someone starts lifting weights, then they switch to endurance training.
After they run a few marathons, they change their training goal to rebuild lost strength.
They notice the strength builds back up in their upper body, but they’re confused as to why their leg strength is not growing as fast.
Well this all comes down to your body’s muscle fibers.
Muscle fibers can be broken down into two different types:
Slow twitch muscle fibers fire slower, so they are not as explosive, but they can go for longer periods of time before fatiguing.
These slow twitch muscle fibers are mainly used for endurance training.
This means a marathon runner would use more slow twitch muscle fibers.
Fast twitch fibers, on the other hand, generate short bursts of speed and strength, but fatigue much quicker.
Sprinters and weight lifters would use more of these ballistic, fast twitch muscle fibers.
So as you can tell, the muscle fiber type you possess can influence which activities you’re good at.
If you’re better at endurance sports, such as long distance running, your body probably possesses more slow twitch fibers.
If you can run fast for short periods of time, and jump high, your body probably possesses more fast twitch muscle fibers.
When it comes to training, think about your fitness goal is.
Is it endurance based like running a marathon?
Or is it to get stronger, faster, and more explosive for a specific sport.
Whatever your goal is, your training needs to be focused on using those specific motor units and muscle fibers.
Why did this person quickly gain strength back in his upper body, but is having problems gaining strength back in his legs?
Well there is evidence showing that specific long-term endurance training can make fast twitch muscle fibers take on the properties of slow twitch muscle fibers in your legs.
Since you’ve been training for a marathon, the fast twitch muscle fibers in your legs may have taken on the properties of slow twitch muscle fibers, thus you’re not able fire the leg muscles to lift as much.
Fortunately, the conversion of muscle fiber types is not permanent.
Within 6 months of continued strength training, you should be able to fire up those fast twitch muscle fibers and hit new personal bests with your legs.
Thanks for the question.
Be sure to follow me on Instagram, and ask your questions over there as well.
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Brad Gouthro is the founder of Live Lean TV, a media company focused on helping men and women “Live Lean” 365 days a year. Brad’s programs and content have helped millions of people all over the world learn how to get in shape, and more importantly, sustain it for life.