The combination of strength and endurance results in muscular endurance - the ability to perform many repetitions against a given resistance for a prolonged period of time (1).
It is a crucial element of fitness for athletes such as distance runners, swimmers, cyclists and rowers. It's also important for success in many team sports like soccer, field hockey and Australian rules football.
Traditionally, muscular endurance programs have used moderate loads lifted for 12-25 repetitions. However, this is completely inadequate for many sports such as boxing, canoeing, distance running, cycling, swimming, rowing, x-country skiing, triathlon and many others.
Any form of training must mirror the specific demands of the sport. In resistance training, this means that the load used should match the resistance that must be overcome while competing. The number of repetitions or the duration of exercise bouts in a session should approach that during the event.
Recall that muscular endurance training makes up only one part of the annual strength program - even for endurance athletes. It should follow a phase of maximal strength training. This makes sense because the greater an athlete's maximal strength, the greater their potential for strength endurance - i.e. the more force they will be able to apply over a prolonged period. Heavy strength training has also been shown to improve exercise economy in endurance athletes (3,4,5). For more information on the the annual strength program see the the sport specific approach to strength training programs.
Different sports require different levels of muscular endurance. While each program will vary according to the athlete's needs, muscular endurance can be split into 3 groups:
Athletes like baseball pitchers, sprinters, 50-m freestyle swimmers, martial artists, wrestlers, fencers, tennis players and so on must produce powerful movements and repeat them several times with little or no rest. In order to maintain the same amount of power with each effort, a certain level of power endurance is required.
Power endurance is typically characterized by intense, repeated efforts for a relatively short period of time (less than 30 seconds) (1). A tennis player for example, has to produce several powerful shots in quick succession during a rally that may only last 10 seconds. A 100-m sprinter may take 48-54 powerful strides over a 10-12 second race and their success depends, in part, on maintaining a high power output in the last 20 meters.
Once maximal strength has been developed (earlier on in the annual strength program) it can be converted into explosive power through various methods of power training. Now power endurance training can be used to train the fast twitch fibres to resist fatgiue allowing explosive power to be maintained for longer.
Power endurance training uses moderate loads of 50-70% 1RM lifted for 15 to 30 repetitions. Because this can lead to a significant build up of lactic acid, rest periods between sets are long (5-7 minutes) and a minimum number of sport-specific exercises are used (about 3-4). Exercises are also completed in a circuit training format i.e. one set of one exercise is completed, then one set of the next exercise and so on. Alternating exercises allows maximum recovery and sufficient time for lactic acid to disperse.
This is a critical rule to follow. If rest intervals are too short and sets are completed while the athlete is fatigued the result will be hypertrophy (increase muscle mass) rather than power endurance. Sets should not be completed to failure but should end when repetitions are no longer powerful and rhythmic.
Here is a sample power endurance program for a tennis player:
Muscular Endurance - Short Term
When sports and events consist predominantly of bouts of exercise lasting between 30 seconds and 2 minutes, "short-term" muscular endurance training is advantageous. These could be continuous events such as the 800-m or multi-sprint sports such as soccer.
Muscular endurance training helps athletes to cope with fatigue and tolerate high levels of lactic acid. It uses relatively light loads of 40-60% 1RM and they can be lifted for a set period of time or a target number of repetitions. Again, a circuit training set up is suitable for this type of resistance training.
Below is a sample muscular endurance program for a field hockey player:
Muscular Endurance - Long Term
"Long term" muscular endurance is suitable for continuous, steady-state events such as the marathon, triathlon and rowing that last beyond 2 minutes. Light loads are used so that exercises can be sustained for a prolonged period. Rest periods are kept to a minimum and ideally the athlete should progress so that the only rest between exercises is the time it takes to move between equipment.
The program below is designed for a rower and gradually progresses until the athlete performs all the exercises non-stop. By the final week the athlete would be completing 6-8 minutes of continuous work per circuit - a similar duration to a competitive race!