Muscular endurance is the ability of a muscle or muscle group to exert a little bit of force to overcome a little bit of resistance in repeated efforts. Muscular endurance is based on the number of efforts, or repetitions, completed, instead of the amount of resistance, or weight lifted. Excessive training for muscular endurance goals may increase the possibility of muscle fatigue, soreness and injuries. Training for endurance results is different than training for strength.
Training with excessive repetitions may cause muscle fatigue. Muscle fatigue is related to specific demands of exercise. Prolonged resistance exercise reduces glycogen stores in muscles, depletes stored high-energy phosphates and impairs energy transfer to working muscles. This could interfere with muscle contraction abilities. When muscle fatigue occurs, it causes a decrease in neural activity, which hinders body control.
Prolonged exercise causes an accumulation of metabolites, chemicals that help burn energy, leading to muscle pain and swelling. Temporary or long-term soreness may occur, depending on the extent of exercise duration. Factors that contribute to soreness include minute tears in the muscle tissue, muscle spasms and overstretching of connective tissue. Excessive soreness has been attributed to repeated eccentric contractions, or the return to the starting position.
With increased endurance training, it may become difficult to maintain proper exercise form. Proper technique should not be sacrificed in order to increase repetitions. The most common training injuries are overuse injuries resulting from repetitive stresses placed on muscle groups. Strains and sprains of the shoulder, elbow, hip and knee are common overuse injuries. Muscle strains are the overstretching of muscles and the tendons connecting muscles to bones. Sprains are overstretching of ligaments connecting bone to bone. Sprains and strains reduce joint stability, increasing the potential for more serious injuries to the affected area.
For many, the goal of an exercise program is increased muscular strength and size. Increased size is based on hypertrophy, the increase in size of muscle fibers. Muscle fatigue, soreness and injury may inhibit gains in size due to muscle tissue breakdown. In addition, muscle atrophy or reduced muscle size is more likely to occur because of decreased training due to injury. Increased muscular endurance should not be confused with cardiovascular endurance training, which elevates heart rate and burns body fat. Increased muscular endurance does not elevate heart rate, which is essential for weight and fat loss.