The human body has 2 main types of muscle fibers: Slow Twitch (Type 1) and Fast Twitch (Type 2), and muscles have a certain percentage of both types. Type 1 Fibers are responsible for long duration contractions and they are found more plentiful in endurance athletes. Type 2 Fibers are short duration contractions and are more abundant in speed and power athletes. These fibers are innate, meaning that we are genetically predisposed to a predetermined makeup, however there can be shifts in the fibers. The shifts in the fibers are greatly influenced on the type of activities that we do, the frequency, and how much. This is when training “Developmental Athletes” can be tricky.
Individuals have qualities that can increase through natural maturation depending on their innate ability as long as those qualities are held in consideration. Simply, training inappropriately can affect a person’s natural performance increase. On the other side of that, proper training can increase a person’s performance. Not all training is created equal!
The right type of training can change the percentages of the fibers within the body, and because of this, it has the capability of helping athletes reach a high level of ability, especially when he/she starts training for the first time. This is true at any age. We know ourselves when you first start training, the progress is almost instantaneously but over time the returns diminish, and sometimes that is what leads to quitting. If you are a “Developmental Athlete,” (usually Middle School through High School), training should be a progressive process with the idea preparing for higher levels of training.
Until approximately the age of 8, there is a greater percentage of Slow Twitch Fibers and this is where the impact of shifting to Type 2 Fast Twitch can come into to play. But again, proper training can play a significant role in the development athlete depending on the sport he/she participates in. Then as we get older, our muscles once again begin to shift back to Type 1 Slow Twitch. One of the biggest qualities you notice in older adults is they lack the ability to produce power or quick twitch movements. All of this varies depending if you exercise, and what type you do.
Stabilization has a lot to do with the percentage of fibers. When we are young, we call on stability a lot and the same goes for when we get older. Balance and stabilization require more oxidation therefore requiring higher percentages of Type 1. As young children and older adults expend a lot of energy trying maintain balance and stability, more so than adolescents and young adults.
We’ve heard the quote; “train slow, become slow.” There is truth to that along with whatever you do the most of and what your innate makeup is. If you train endurance all of the time, you increase the percentage of Slow Twitch Fibers, and you lack the ability to produce a lot of force. This is why, if you are a Speed/Power Sport Athlete, such as Soccer, Football, Sprinting, Lacrosse, etc, you will want to avoid a lot of endurance training, because Type 2 Fibers are king in these sports. We know “Speed Kills” in field and court sports and we don’t want to take away from this.
If you are a Soccer Player and you train long slow runs, logging a bunch of mileage, you are potentially going to cause a detriment to your sport. The Fast Twitch Fibers that are needed to be explosive on changes of direction, or to beat someone on a ball rundown are not there because they shifted to Type 1 Slow Twitch.
This goes for the same when individuals want to do Cross Country to help keep themselves in shape for Speed/Power Sport. I have nothing against Cross Country (it is a great sport and very difficult) but Cross Country is only great for Long Distance Runners. I’ve seen track sprinters want to do Cross Country to help get them in shape for Sprinting, and it will get you in shape, but you will also become a slower sprinter. Sprinters should sprint.
I came across this information in the Altis Foundation Course, and found it very interesting. If you are going to work with athletes, I think this type of information is very important to know. I began to research this information and began reading several studies. I believe this is just the tip of it and I’m excited to dive in even deeper. I am in the process of compiling the studies which I read if anyone is interested in them. I believe you need to know your athletes, and know how to train them.