Immediate Physiological Responses To Exercise

When an individual exercises, various physiological changes occur within their body to ensure that adequate amounts of oxygen and nutrients are being provided to the working muscles. This increase in demand forces the body to instantaneously make adjustments to the working systems and eventually adapt. The five major immediate physiological responses to training include heart rate, stroke volume, cardiac output, ventilation and lactate levels. These responses are directly proportional to the intensity, duration, frequency and type of exercise which the athlete undertakes. Physical activity will also impact on physiological responses depending on whether it is measured pre, during or post exercise.

Heart rate refers to the number of contractions the heart makes every 60 seconds and is expressed in beats per minute (bpm). The heart must contract regularly in order to supply sufficient amounts of oxygen to the working muscles which is provided by haemoglobin in the red blood cells. If muscle activity is increased, the amount of oxygen required will also increase, resulting in the heart to pump blood more rapidly throughout the body to ensure all muscles are obtaining enough oxygen.

Therefore, as an athlete begins exercise, the heart rate will gradually increase with accordance to the intensity of the exercise. Heart rate will then plateau and remain elevated as long as the same pace is maintained. If effort is increased, it will go even higher until it reaches the maximal capacity. Once the athlete stops exercising, the heart rate will decrease steadily and might take approximately 3-6 minutes to revert back to resting heart rate (for a fit person). The heart rate may also rise prior to any type of exercise as to prepare the body for activity and is a result of the involuntary nervous system.

An example is an athlete about to participate in a 800m sprint. The athlete’s heart rate would start to increase before the event starts given the amount of anxiety and anticipation. When the athlete begins the race, the heart rate will start to increase rapidly then remain constant once they maintain their pace. After the sprint, their heart rate will decrease and may take a few minutes to return back to the normal heart rate.

Cardiac Output

Cardiac output refers to the quantity of blood pumped out by the heart every 60 seconds and is expressed in litres per minute (L/min). The body must pump an adequate volume of blood to maintain a continuous supply of oxygen and nutrients to the vital organs and active muscles. Cardiac output is measured by multiplying heart rate and stroke volume, thus, it is reliant on their values. At the onset of exercise, the working muscles of an athlete signal the heart to accelerate the diastole and systole phases for increased blood flow to the active muscles. This results in a heightened cardiac output which will then decrease at the cessation of exercise and eventually return back to the regular volume.

The athlete may also experience a rise in cardiac output prior to exercise due to an increase in heart rate. Therefore, cardiac output variations occur in dependence of the value of heart rate and stroke volume. An example of this may be presented by an athlete commencing the multistage fitness run. As the athlete progresses from level 6 to level 7, the intensity and length of the workout is amplified, as a result the blood pumped from the heart increases and has to work harder to deliver more oxygen. At the end of the run, the athlete’s cardiac output will decrease with accordance to the heart rate and stroke volume.

Ventilation rate is the volume of air taken in by the lungs every 60 seconds and is expressed in breaths per minute (breaths/min). The lungs must regularly inspire and expire so as to provide oxygen from the external environment to the working muscles in physical activity. If muscle activity increases, the demand of oxygen will also increase, therefore, the ventilation rate will become more rapid in order to satisfy the requirements for the muscles. Consequently, as an athlete begins exercise, there will be an immediate adjustment to the respiratory system causing the athlete to have a faster ventilation rate.

The ventilation rate of the athlete will then alter with correspondence to the intensity of the exercise and may still remain rapid for a short period of time at the end of the exercise, then slowly returns to rest. The pace of breathing also increases before exercise begins as the body anticipates the need for more oxygen. An example is an athlete about to participate in a 800m sprint. The athletes ventilation rate will start to heighten preceding the event, then increase rapidly once the race starts. After the sprint, the ventilation rate of the athlete will persist rapidly, then gradually decrease as the body remains at rest.