“Endurance" is the term commonly used to describe fatigue resistance. It allows your body to maintain your chosen workout intensity for as long as possible, or keep any lost intensity as low as possible, and stabilise your athletic technique over a prolonged period of time without fatigue. A typical load for developing endurance is the familiar endurance run, which causes your body to make specific adjustments when done regularly.
Regular endurance training will result in a so-called "athlete's heart". This is mainly due to an expansion of the heart cavities, and, to a lesser extent, hypertrophy of the cardiac chambers. As a result, the heart is able to pump a larger volume of blood under load. Another positive and important effect is the economisation of cardiac output at rest. Increasing the heart’s beating volume can decrease the heart’s beating frequency.
Similar to the adaptation symptoms of the cardiovascular system, respiratory factors are also improved by endurance training. The respiratory minute volume (tidal volume times the respiratory rate) should be mentioned in particular. While untrained individuals primarily increase their respiratory rate under loads, trained individuals increase their respiratory volume.
Even before adaptation symptoms of the cardiovascular system or other organs can appear, changes first take place on a metabolic level – that is, in the cells. An important adaptation to endurance loads is the enlargement and proliferation of the mitochondria ("the cell’s power stations"). As a result, energy release is increased, and glycogen depots in general are also increased, thus increasing the body’s energy depots for ATP/glycogen.
What you should pay attention to during endurance training
Despite the positive effects of endurance training on the cardiovascular system, it cannot replace strength training. The impact from regular strength training will affect completely different areas of the body, and produce a number of additional beneficial adjustments and effects.
It should also be mentioned that endurance training can also have a negative effect on muscle growth if it is done around strength training, or too intensely and too often. Intense strength training should always come first. If you want to do additional endurance training, then this should be done at a low pulse or intensity to promote regeneration, and improve basic endurance. However, this training should always be done separate from strength training.