Adaptations to long term exercise - Cardiovascular System
Intro to Adaptations
From a Darwinian standpoint humans have been adapting and evolving for millions of years, since we grew legs in order to deal better with being a land based mammal, evolving from primates and developing opposable thumbs and so on, these are genetic long term adaptations. These are not the form of long term adaptations that I will be looking at, when in reference to ‘long term adaptations’ I am referring to the much less debatable adaptations induced by exercise or participation in Sport for a duration of six weeks or longer, also not to be confused with short term acute adaptations lasting for little longer than the duration of the exercise itself, such as the sensation of being ‘pumped’ during a resistance training session, due to the cardiovascular systems acute response to dilate the blood vessels to allow an increased supply of oxygen and nutrients (Vasodilation).
Long term exercise encourages ‘Cardiac Hypertrophy’. Hypertrophy is a training adaptation and refers to the increase in length of the Sacromere of a muscle fibre and henceforth the overall size of the muscle altogether. Muscle within the heart is referred to as ‘Cardiac Muscle’ and predominantly operates autonomously. Hypertrophy of the ventricular chambers of the heart in particular will enable greater contractile strength, as the strength of a muscle is directly proportional to its cross-sectional size, this in turn facilitates a greater volume of blood to be delivered to body from a singular contraction of the right ventricle (This is known as an increase in stroke volume), it stands to reason that the bigger the pump, the bigger the output (The total amount of blood that is pumped around the body in a minute is referred to as ‘Cardiac Output’). However the hypertrophy of the body of the chambers themselves is not the only significant adaptation to be observed, the walls of the chambers become thicker, allowing them to better withstand greater Blood pressures that occur during exercise (Blood Pressure is the measure of force applied to the arterial walls as a result of passing blood), the rate of which, is in proportion with the intensity of exercise. Exercise of a high intensity such as the sport ‘Weightlifting’ is more likely to induce the latter adaptation, as greater blood pressures are generated from maximal work, the sub maximal work placed upon the cardiovascular system during a marathon or tour de France, is more likely to encourage the chamber of the heart to grow in size (Hypertrophy). Seven time ‘Tour de France’ winner ‘Lance Armstrong’ is reported to have a heart that is 30% bigger than average, this is likely to be a combination of genetics and long term adaptation to rigorous amounts of exercise. As is explained above, this increase in size allows a greater Cardiac Output, facilitating greater bouts and intensities of exercise.
Other adaptations observed are as follows;
Decrease in resting HR – Somebody who exercises regularly is likely to have a lower heart rate at rest. This is largely due to the hearts ability to pump more blood in one single contraction due to the aforementioned Hypertrophy of its ventricular chambers, by this means they are able to pump the same amount of blood around the body as a lesser trained individual with lesser beats per minute.
Increased Capillaristion – As an adaptation to training the quantity of capillaries surrounding the heart and muscles increases, this allows a greater transportation of oxygen and nutrients and in an increase in diffusion rate.
Increased Elasticity of Arterial walls – This allows them to withstand greater pressures of blood, the concern is when the Arterial walls are unable to cope with the pressure upon them from the blood and become damaged or rupture which will lead to health complications, providing the arterial walls resistance is able to match that of the bloods pressure then its fine and so a great resistance and greater elasticity to adapt to changes in pressures, allows the body to heart to better supply the body with oxygen and nutrients by pumping blood at higher pressures, increasing the cardiac output further still.
Increase in blood volume – It is believed as knock on effect of increase capilliarization the bodys total volume of blood in circulation at any one time is increase as a result of long term exercise. This represents an increase in the number of red blood cells and therefore haemoglobin sites for a greater amount of Oxygen to bind to, increasing the rate of transport of Oxygen, allowing greater periods of aerobic metabolism in the presence of Oxygen and more rapid clearances of Lactic acid.
Decrease in time for recovery – An untrained individual will take longer to recover from a bout of exercise than a trained individual, therefore it is possible to gage an individuals fitness by recording their heart rate immediately at the point exercise has finished and then testing it one minute after, as you have stopped exercising it should gradually decrease, the rate at which it drops is an indication of the individuals fitness, the time it takes to steady out to a rate similar to the individuals resting heart rate, is their total recovery time. This same principle can be applied to your blood pressure, though it also may rise during exercise, the time taken for it to return to normal is also an indication of health and fitness and with increasing parallels to heart rate, long term exercise may reduce blood pressure at rest.
Increased aerobic fitness – The core principle of specificity training is that in doing something, it better enables you to do that same thing again, therefore for a 2000m track runner, the most logical and best training for them to do would be to run 2000m metres. This is largely a consequence of the physiological adaptations that have occurred as a result of the training, most importantly the cardiovascular and respiratory systems improved ability to transport oxygen and nutrients to the working muscles and remove the consequential bi products of energy production. The key is that this allows the individual to perform better, faster and longer at whatever they do.