Training with your muscles in mind

If you do 15 reps of 30 pounds or eight reps of 50 pounds, it’s pretty much the same thing, right? I definitely used to think this was the case, but you actually may be working your muscles in very different ways. Even though your muscles fatigue in both cases, you are fatiguing two different types of muscle fiber.

Even if you’re not trying to win races, you can still use muscular knowledge to make a smart workout for yourself.

More reps and less weight fatigues the slow twitch muscle fibers, which activate slowly but last longer. The fibers, therefore, contribute to endurance. These fibers can work longer because they use aerobic respiration, which uses oxygen for energy.

Fewer reps with more weight will fatigue the fast twitch muscle fibers, which activate quickly but fatigue quickly and give you immediate power. These fibers operate using anaerobic respiration, which uses alternate sources for energy and can’t keep activating for long periods of time because of this.

For runners in particular, the type of muscle fibers they work out is very important. Sprinters need their muscles to activate quickly, but they don’t require long periods of activation. They, therefore, need to work their fast twitch fibers. Long-distance runners, on the other hand, need their muscles to sustain activation for an extended time, so they need to work out their slow twitch fibers.

Kyle Merber, a Columbia track and field senior, runs 85-90 miles a week but also does a significant amount of other training, including doing core workouts five days a week, weightlifting a few times a week, and practicing lots of plyometric exercises. “For distance, it’s about maintaining lean muscle, so we do about three or four sets with 12 reps,” said Merber. “Whereas sprinters need to focus on getting muscles to fire quickly.”

The level of weight training that Merber describes is great to work the slow twitch fibers that he needs for distance running. Weight training for sprinters should use higher weights with fewer reps and can incorporate exercises like deadlifts.

Plyometrics actually tend to work type IIa fast twitch fibers, which are hybrid fibers that activate quickly but can sustain extended periods of work. Plyometrics are incredibly valuable for both sprinting and distance, since these fibers can be helpful in both types of running.

Training, however, is not everything. Some people are more suited to long-distance running because they are born with more slow twitch muscle fibers. The most successful marathon runners usually have around 80 percent slow twitch fibers, whereas the most successful sprinters have around 80 percent fast twitch fibers.

There is some speculation that muscle fibers can change from slow to fast or vice versa, but even if that were possible, it would be extremely unlikely to significantly change the ratio—so while you can work out your existing fibers, we’re all suited for different types of work.