When it comes to sports, we would all love to be strong and fast and still be a good endurance athlete. At the same time, even the best athletes are often happy when they excel in one of both. You never see a weightlifter running a fast marathon. You don’t even see a top cyclist win both a mass sprint and the general classification during the Tour de France. Why is that? And how should you adjust your training plan according to this fact?
To answer this question easily, we should have a look at our muscle fibers. First thing to know is that you can not increase the amount of muscle fibers via exercise. You have to work with what you got. You can make your muscle fibers thicker or thinner, and longer or shorter. Although the composition is partly genetically determined, exercise has the potential to shift the muscle fiber characteristics.
An active muscle needs energy to contract. Although there is some energy stored in the muscle cell, if you want to keep moving, you will need to produce new energy. Mitochondria are the energy factories that take care of this job. You can find them in the muscle cell. Mitochondria use oxygen from outside the cell to produce energy for the muscle cell.
Strength and Sprint
As said, your body can’t increase the amount of muscle fibers. So, if you want to get stronger in the gym or faster in a sprint, you need to make your muscle fibers thicker. Strength training or short sprint workouts can do the trick. This kind of exercise will enlarge your muscle fibers, so you can produce more power in a short amount of time.
If you look at weightlifters or sprinters you can immediately see that they succeeded in growing their muscles. Even within a sport, it is not difficult to distinguish the 100m sprinter from the long-distance athlete.
Both the weightlifter and sprinter won’t need a lot of mitochondria in their muscle cells, since they don’t need to keep moving for a long period. For the same reason, they also don’t need an optimal oxygen supply. But what if the sprinter decides he or she wants to sustain the speed for a long period of time. Why is he or she not going to be able to do so by simply adding some endurance training?
An endurance athlete won’t need large muscles because in endurance races it is more about being able to sustain power over a long period then being able to produce high power peaks. A large number of mitochondria in the muscle cell and a good oxygen supply are key.
Where large muscle cells are beneficial for strength, small muscle cells are better for an endurance athlete. Why? Let’s have a look at the picture below. The distance between oxygen (red circles) outside the cell (blue circle) and the mitochondria inside the cell (blue crosses) becomes smaller when the muscle cell becomes smaller. Oxygen can therefore travel to the mitochondria faster. As a result, the endurance muscle cell (left) can produce energy faster and sustain more power over a long period than the large strentgh muscle cell (right).
Reducing the size of muscle cells and increasing the number of mitochondria in your cells can be done via high volume, low intensity (endurance) training.
Where large muscle cells are beneficial for strength, small muscle cells are better for an endurance athlete.
Concurrent training tips
It soon becomes clear that large muscle cells are a must for weightlifters and sprinters, but are impractical for endurance athletes. Still, most races are won by a combination of both long-lasting power and high peak power in a sprint. A strategy to improve both is by doing concurrent training: a combination training that maximizes both strength and endurance. Concurrent training makes sure your endurance training only effects your endurance (type I) muscle fibers, and your sprint training only effects your sprint (type II) muscle fibers. This way you can make sure endurance fibers stay small and efficient and sprint fibers stay big and strong.
How? By making sure you don’t give your sprint fibers an endurance task. In other words: don’t use them for a long period. In practice, that means
- your high-volume endurance training is at a low intensity. You therefore won’t need your sprint fibers. They will not get tired and therefore will not shrink.
- your sprint training contains enough recovery between intervals. Your sprint fibers will not experience long lasting fatigue, so they won’t shrink.
In the future I hope technology will make it possible to measure whether you are using your endurance muscle fibers or your sprint muscle fibers. We can then not only plan concurrent training the right way, but also measure if we succeeded in doing so!