Muscular endurance is a muscle’s ability to work continuously against resistance over a long period of time. To build muscular endurance, an athlete must train her muscles to overcome fatigue. Gains in muscular endurance are not made by increasing the weight lifted, but by increasing the amount of time a muscle spends contracting against resistance. A muscular endurance training program should come after a maximum-strength building phase (high weights, low repetitions), because the greater a muscle’s strength, the more force it can exert during muscular endurance training. Muscular endurance training should not be done to muscle failure.
To improve athletic endurance, exercises must mirror the challenges that an athlete expects to encounter in competition. There are several kinds of muscular endurance, each used by different athletes according to the demands of their sport. The best muscular endurance programs train muscles in the same movements used in competition. For example, a swimmer may practice his stroke using resistance bands, while a cyclist would train on the leg press machine.
Power endurance is required for sports where a powerful movement is repeated over and over with little or no rest. Power endurance athletes include boxers, racquetball players and baseball pitchers. To train power endurance, lift about 50 to 70 percent of your one-rep max (1 RM, the maximum weight you could lift for one repetition). Choose three or four sport-specific exercises and complete them all, one after the other, before returning to the first exercise. Doing your workout as a circuit allows one muscle group to recover while another works.
Activities that require 30 seconds to 2 minutes maximum effort, such as 800-meter sprints and team sports combine aerobic and anaerobic energy metabolism. They require that muscles cope with fatigue and high levels of lactic acid. To train your short-term muscular endurance, use light loads of 40 to 60 percent of your 1 RM and lift for a specific period of time (i.e. one minute) or a high number of repetitions (i.e. 50 repetitions). Like with power endurance, doing a circuit of four to eight exercises will ensure your muscles recover adequately between sets.
Activities lasting more than two minutes, such as distance running, 500m freestyle or backpacking require that a muscle fire hundreds of times at a small fraction of its maximal capacity. In the weight room, training with 30 to 40 percent 1 RM improves long-term muscular endurance, but many athletes can improve their long-term endurance outside the gym. Runners and Nordic skiers use hill repetitions to improve long-term muscular endurance, for example.
Sports like rock climbing, acrobatics and men’s gymnastics require that an athlete remain immobile against resistance. This type of muscular contraction is an isometric contraction. Strength gains made through isometric training are specific to the joint angle trained, so athletes interested in improving their continuous tension endurance should hold the position that they plan to use in competition while holding a weight.