Muscle endurance means the force a muscle, or group of muscles, must make to perform a repeated action against a resistance. To carry out several repetitions of an exercise is a form of muscle endurance the same as if you were running or swimming. If the muscles have to contract in a similar form more than once, it is muscle endurance.
Many factors contribute to muscle endurance such as strength, type of muscle fiber, training and diet. A larger, strong muscle can perform the same task many more times than a weak one. A large muscle also contains more glycogen or sugar for energy so that you can do a series or contractions or do work for longer periods of time.
Genetics of sport endurance
The distribution of muscle fiber is largely determined by individual genetics and is established just after birth. The percentage of Type I fiber in a sedentary middle aged person is between 45 – 55% (this percentage increases slightly in women). Sprinters tend to have more fast-contraction fibers in their legs while in long distance runners, there are more slow-contraction fibers. Biopsies of leg vastus medial muscle show that the proportion of fast fibers in shot-putters and jumpers and weightlifters can have up to 3 times more (60% fast fiber) than long distance runners (17% fast fiber) and a 50% more than body builders, for example (40% fast fiber).
Recent studies show the genetic susceptibility to distinct types of fiber and consequently, a greater ability for one sport or another. Therefore, there can be a genetic predisposition to be a sprinter (fast fiber) or an athlete in endurance sports (slow fiber).