Muscle endurance is good not only for sports but for everyday activities as well.
Performance in sports like distance running, swimming, and weight lifting will all benefit from a boost of endurance. Daily tasks become easier with endurance training and there are many benefits of exercise on overall health.
What is Muscle Endurance?
Muscle endurance is the ability of a muscle to stay active for long periods of time without tiring. Strengthening muscle, increasing muscle energy stores, and generating energy to fuel work more effectively all boost one’s muscle endurance.
Muscle makes it easier to carry out physical activity. The more muscle we have to support a particular physical activity, the easier that activity becomes. Therefore, an increase in muscle mass will have a positive effect on muscle endurance and strength.
Muscle growth reduces the risk of injury as well as loss of muscle tone and bone density with aging. This is significant for healthy aging, as one becomes more susceptible to muscular injuries and bone fractures. Muscle growth also supports joints and act as shock absorbers for movement.
Muscle Energy Stores:
Skeletal muscle stores energy to fuel movement in the form of ATP, creatine phosphate, glycogen, and triglycerides. Endurance, as well as strength exercises, increase energy storages in the muscle. This is important because the depletion of muscle energy stores (mostly of carbohydrate) triggers fatigue in endurance activities.
ATP (Adenosine Triphosphate):
ATP is the energy molecule that acts as currency for physical work. Free-floating ATP in muscle cells (fibers) supports physical movement in routine tasks and the onset of exercise. Energy harvesting reactions in muscle aim to produce more ATP to meet the energy demands of exercise.
Creatine phosphate is stored in muscle and can be used for the generation of ATP from ADP (Adenosine Diphosphate) with help from the enzyme creatine kinase. In order for ATP to be used for fuel, one of its three phosphate groups must be removed, turning it into ADP. Creatine kinase then recycles ADP molecules by re-adding a phosphate taken from creatine phosphate, which yields ATP. The recycling of ATP molecules ensures that ATP stores in the muscle are sufficient to support physical work while other energy harvesting reactions activate.
Glycogen stored in skeletal muscle is converted back to carbohydrates to be used for ATP production via aerobic (oxygen dependent) and anaerobic (oxygen independent) pathways. To prevent the onset of fatigue, one must maintain carbohydrate levels in muscle. Thus, increasing glycogen stores improves endurance by delaying fatigue.
Athletes that engage in sports such as cycling and distance running have developed strategies for glycogen storage. Carbohydrate loading (eating lots of carbs) a few hours before exercise or a big event is a common strategy. This helps maximize muscle glycogen stores in the muscle by giving the body enough time to digest.
Triglycerides stores are also found in the muscle. These are broken down into fatty acids and oxidized for ATP production in the mitochondria. Beta-oxidation of fatty acids yields a lot more ATP than carbohydrates via either aerobic or anaerobic pathways; fatty acid depletion is not a concern.
Skeletal muscle adapts to endurance training by better utilizing fatty acids for energy production. Utilizing more fats for energy spares carbohydrates and muscle glycogen. This sparing of carbohydrates prolongs exercise.
Muscle Fiber Adaptations:
Skeletal muscle adapts its cellular (or fiber) composition to better perform different types of exercise. Therefore, the exercises a person performs determine how the muscle will adapt.
Muscle adapts to endure long periods of exercise by increasing type I (or slow-twitch) muscle fibers in their composition. Type I muscle fibers are dense in mitochondria, the cell component responsible for ATP production, and can better utilize fats for energy. These muscle fibers are also slow to tire and are more common in endurance athletes. More type I muscle fibers means greater muscle endurance.
A Few Recommendations:
Medium to high-intensity aerobic activity like swimming, running, and tennis supplemented with a nutrition plan will promote muscle endurance. One must routinely engage in endurance training to adapt skeletal muscle to sustain exercise for longer periods. For athletes that wish to take it a step further, gradually increasing exercise intensity will do the trick.
One wants to limit quick and explosive exercise since it tends to deplete muscle carbohydrates and glycogen stores more quickly. Some individuals reduce resting time in-between sets to improve muscle endurance, but this applies more to strength training than to endurance training.