If you look at a cross-country runner and a powerlifter, you can probably spot a few differences in their physiques. Athletes focusing on power and strength movements – sprints, heavy lifts, power lifts, are often stockier, broader and more heavily muscled than athletes focusing on endurance exercises – long-distance running, swimming, cycling – who tend to be lean and thinner. Do these differences come from their training or blessed genes?
While there are people who seem to touch a dumbbell and magically make some serious muscular gains, others will train hard for months and see only moderate progress. This is particularly obvious to those who consistently go to the gym and look up to those ‘big’ guys but never seem to reach that point of muscular mass (including me.)
Of course, difference in workout routines may be the reason for the variation in physiques, but let’s say that two people have optimized their routines for muscle mass gain and begin their training at the same time. Person A might make some serious gains within the first month, while person B only sees about half the amount of gains even though both are training equally as hard. That difference lies in your genetic muscle composition.
What is muscle composition? It’s the makeup of your muscle fibers; every muscle in your body is made up of different proportions of three types of muscles fibers. Slow twitch muscle fibers are optimal for aerobic exercises and take a long time to tire out; they perform the best during exercises that involve slower and less powerful contractions, but have a lot of endurance. In contrast, fast twitch muscle fibers, while optimal for powerful, quick exercises and producing a lot of force in a short amount of time, are quick to tire out. They perform the best during strength and power exercises and are the fibers primarily responsible for muscle mass gains. Individuals with higher proportions of fast twitch fibers theoretically can gain more visible muscle mass than those with higher proportions of slow twitch fibers. Then there are intermediate fibers that can take on the characteristics of either fiber depending on the training stimulus provided. This is where training can have a significant effect on athletic performance and body composition.
Each muscle in your body is comprised of different proportions of all three muscle fiber types. The slower your twitch fibers are, the more naturally inclined you will be toward aerobic exercises. The faster they are, the more naturally inclined you will be to power and strength exercises. Other factors that influence your ability to perform certain activities are anthropometric, such as your height, relative arm and leg length, and the broadness of your shoulders. All of these factors are predetermined by genetics and cannot, or are very difficult, to change. Unfortunately for a tall, lanky lifter, he will probably never be able to compete in a squatting competition against a shorter, stockier lifter who has less distance to cover in that particular lift and has more torque he can produce through his joints because of shorter limbs. Similarly, a shorter runner with a stocky build will have trouble keeping up with a taller, lankier runner who can cover more distance with each stride and has a relatively lighter upper body.
Does this mean you should give up on your fitness goals? Absolutely not. Training those intermediate fibers to act more like slow or fast twitch fibers will have tremendous benefits toward your goal, whether that be endurance or strength improvements. While persistence and consistency will help you to compete with those who seem to ‘get it’ more naturally than you, it is important to be realistic about your body’s limitations and not hold yourself to standards that will only serve to upset you.
Nicholas Remillard can be reached at [email protected].
