|
Heart Rate
The heart is an efficient pump system that enables the transport of oxygen and nutrients around the body to working muscles, tissues and organs. Both heart rate and blood pressure are controlled by the autonomic nervous system. This nervous system is an unconscious, or 'automatic” nervous system, which consists of 2 parts - the parasympathetic nervous system and the sympathetic nervous system. These 2 systems have opposing roles and are activated according to the different needs of the individual. The parasympathetic nervous system is activated during rest and assists in energy restoration. During rest, the parasympathetic nervous system assists in the digestion and absorption of food and results in a decrease of heart rate. The sympathetic nervous system, on the other hand, prepares the body for an emergency and counteracts the parasympathetic nervous system in order to maintain the required energy supply. During any emotional or physical stress, adrenaline is released by the sympathetic nervous system, which acts to increase heart rate and blood pressure.
A unique feature of the human body is its ability to adapt in response to the demands placed on it. During exercise, the heart is exposed to a 'system overload” to which it responds by increasing the heart rate. This overload also acts as a training stimulus and results in a strengthening of the heart muscle. As a result, more blood is pumped out per beat, thereby resulting in a more efficient heart cycle. The measurement of heart rate has been used widely as a measure of exercise intensity, based on the understanding that there is a linear relationship between heart rate, work rate and oxygen consumption, as well as assisting individuals in training at different intensities.
Heart rate, however, is affected by a number of factors that may cause variability in the values recorded. Factors such as age, fitness level, medications, gravity, eating habits and diurnal variations are some of these factors to mention a few.
The measurement of heart rate is in beats per minute. Mark's heart rate response shows that there is a significant effect of gravity on heart rate.
|
|
