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Type of Muscle Fiber
One of the most influential factors is muscle fiber type. We have two basic types of muscle fibers, often referred to as “slow twitch” and “fast twitch.” Slow twitch muscle fibers are best used for cardiovascular (aerobic) activities. They produce small levels of force for long periods of time and thus are better suited for endurance activities. Fast twitch fibers are best used for anaerobic activities. They produce high levels of force for short periods of time and are best suited for power activities such as weightlifting.
Most men and women have an equal combination of both slow twitch and fast twitch fibers. However, some people inherit a high percentage of slow twitch fibers that enhance their performance in endurance activities, such as long distance runners. Most world class marathon runners have a very high amount of slow twitch fibers. World class sprinters or football players, for example, have relatively more fast twitch muscle fibers. Although both fiber types respond positively to strength training workouts, the fast twitch types experience greater increases in muscle size and strength, and thus may obtain greater and/or faster results from a strength training program.
Another factor over which we have little control is age. Studies show that people of all ages can increase their muscle size and strength as a result of a safe and effective strength training program. However, the rate of strength and muscle gain appears to be greater from age 10-20, the years of rapid growth and development. After reaching normal physical maturity, muscular improvements usually don’t come as quickly.
Gender does not affect the quality of our muscle, but does influence the quantity. Although men’s and women’s muscle tissue are characteristically the same, men generally have more muscle tissue than women do because muscle size is increased by the presence of testosterone, the male sex hormone. The larger the muscles, the stronger the person; this is why most men are stronger than most women.
Limb and Muscle Length
Another strength factor that is naturally determined is limb length. Persons with short limbs tend to be able to lift more weight because of advantageous leverage factors (arms and legs). Similarly, differences in strength development may come about because of variation in muscle length. Some people have long muscles, and some people have short muscles. Persons with relatively long muscles have greater potential for developing size and strength than persons with relatively short muscles.
Point of Tendon Insertion
Muscle strength is also influenced by the point of tendon insertion. For example, let’s say Jim and John both have the same arm and muscle length. However, Jim’s biceps tendon attaches to his forearm farther from his elbow joint than John’s does. This gives Jim a biomechanical advantage: he is able to lift more weight than John in biceps exercises such as the Biceps Curl.
Other Important Factors
All of these factors affect our ability to gain strength and muscle development through training. Keep in mind, however, that the most influential factor in achieving good results is using a very slow, controlled lifting movement and lifting to the point of muscle fatigue.
In addition to using good lifting technique, it is absolutely imperative that you not only train with intensity on a well-balanced program, but also give your muscles enough resting time between training sessions. Overtraining is a common mistake people make; it happens not only when you don’t allow your muscles enough rest, but also when you train with too many sets and exercises for each muscle group.
Another mistake people make is doing the same program over and over again even after they have reached a plateau. Any time you 1) stop gaining strength or muscle size or 2) get bored, it is crucial that you change the program, so that you can go through a whole new phase achieving new results.
We inherit most of these factors affecting strength from our parents, and they have a big impact on our size, strength, and appearance. It is very important that you not become obsessed with trying to look like a world-class body builder—or any other body type that is not your own. We are not all meant to look the same. It is very important that you learn about and accept your own body’s characteristics and type, so you can develop a reasonable program specific to realistic goals and personal interests.
Genetics does clearly play a role in your health and appearance, but they certainly do not determine how often or well you train. Even if you are born with a genetic predisposition to being overweight or weak, the way you live is what will ultimately determine whether you become fit and strong or fat and weak.
Weightlifting provides many important benefits that cannot be achieved by any other exercise or activity. Physiologically, the benefits of consistent strength training include an increase in muscle size and tone, increased muscle strength, and increases in tendon, bone, and ligament strength. Strength-training has also been shown to improve psychological health as well, by increasing self-esteem, confidence and self-worth. If you understand and accept your body, you will be able to work with it, not against it. Everyone can improve their strength, appearance, and performance level by consistently implementing an effective strength training program.