Traditionally, gym based exercise has been segregated into weightbearing exercise, and cardiovascular exercise. I say ‘gym based exercise’, because before the development of exercise for the sake of exercise (as opposed to exercise in order to survive), no such segregation was made.
So accepted has this seperation of work capacities been, that research has followed suit. We now see not just a specialisation of athletes (to either strength or cardiorespiratory endurance), but a specialisation of hearts.
The structure of the ventricles actually remodels based on the specialisation achieved.
High levels of aerobic (endurance) training cause eccentric hypertrophy of the heart wall. This is where the internal diameter of the chambers of the heart increases, but the walls stay the same thickness. This results in a larger heart, and a greater capacity to pump blood around the body. The strength of the heart as a muscle is not improved however.
High levels of anaerobic (strength) training cause concentric hypertrophy of the heart wall. This is where the internal diameter of the chambers of the heart reduce in size, with the walls getting thicker. This results in the heart remaining the same size externally, but the internal chambers being smaller. The heart becomes stronger (as an adaptation to pumping blood through more developed muscle beds), but the ability to pump large volume of blood is impaired.
Both adaptations have advantages and disadvantages, but a constantly varied exercise prescription should elicit the best of both options. An all inclusive program, with little differentiation between strength and cardiorespiratory endurance will deliver an increase in the capacity to pump blood, coupled with the ability to deliver blood to more developed muscle beds.
More evidence to support the prescription of constantly varied, high intensity, functional exercise. Just as we should not specialise, nor should our hearts.
