UNIT 1 Question 1 (5 marks): Discuss the rate-limiting factor. Why is it important to consider when studying exercise physiology and training? Provide one example to clarify your understanding. The rate-limiting factor is the “step” that limits performances (the “slow step”). If we know the rate-limiting step in a certain physiological pathway or training situation, we can manipulate the factors of this step to change and increase the rate of the pathway. This will improve overall training and performance.
For example, in an assembly line, there are different tasks required. The most difficult and time-consuming task is the rate-limiting factor. If there was a way to increase the efficiency of this particular task, it will increase the productivity of the entire assembly line, hence, the rate of the “pathway”. Question 10 (6 marks) a. Sketch the relationship between oxygen utilization and work rate for a 30-year-old individual with a VO2 max of 60 ml*kg-1 min-1. b. On a second graph, sketch the relationship between heart rate and oxygen utilization for this individual.
Include units on both your graphs. c. In a different colour on both graphs above, sketch in the relationships for a 30-year-old individual with a VO2 max of 40 ml*kg-1 min-1. d. Label the approximate HR responses for both individuals (on the second graph) when they are working at the absolute VO2 of 35 ml*kg-1 min-1 and at the relative rate of 75 percent of their own aerobic capacities.
There will be a linear relationship between oxygen utilization and work rate. The first graph assumes the work rate for aximal exercise for the individual with the greater VO2 max is 350 W, and the individual with the VO2 max of 40 ml*kg-1 min-1 reaches their VO2 max at a lower work rate of around 250 W. At a work rate of O, the subject will still be consuming oxygen so VO2 will not be exactly O ml*kg-1 min-1. For the second graph, maximal heart rate was calculated using the equation: 220 – age, so these two 30-year-old individuals will have a maximal heart rate of 190 beats per minute (bpm).
UNIT 2 Question 2 (6 marks): When we compare rest and maximal exercise, we see a rise in PAO2 and a change in the ventilation perfusion and ventilatory equivalent ratios. Describe these three concepts in more detail, and explain how each of them illustrates that ventilation does not limit VO2 max at sea level. Alveolar partial pressure (PA02) refers to the amount of oxygen in the alveoli of the lungs. When a person begins exercising, the PAO2 will be relatively constant during lower levels of pulmonary ventilation, and then begins to rise as pulmonary ventilation increases heavily and progresses into hyperventilation.
The increase in PAO2 during maximal exercise tells us that there is a greater amount of oxygen left in the alveoli in the lungs when compared the person at rest. Ventilation is not dependent on PAO2, since the PAO2 levels remain relatively constant while ventilation begins and only increases slowly when ventilation becomes harder. We are also able to increase the amount that we are breathing (ventilation perfusion) more than the increase in oxygen consumption or cardiac output (Q). This can be expressed by the ventilation perfusion ratio, which is VE/Q.
As illustrated by the example in the following figure, the ratio increases about 7 times from rest to maximal exercise. At Rest At Maximal Exercise VE 5 L/min 190 L/min Q5 L/min 25 L/min VE/Q 5/5 = 1 190/25 = 7. 6 Therefore, this shows that ventilation is able to increase much more than the cardiac output and it is not a limiting factor of the body’s oxygen transport system. Furthermore, the ventilator equivalent ratio (VENO2) increases in a linear manner with exercise levels until it reaches the ventilatory inflection point. At this point, it increases more sharply.
There can be more movement of air into and out of the lungs in comparison to oxygen consumption. Thus, ventilation is not a limiting factor of VO2 max at sea level since ventilation is able to change and increase without being greatly dependent on PAO2, ventilation perfusion, or ventilatory equivalent ratios. Question 3 (5 marks): Describe the effects of training on the cardiovascular parameters Q, HR, SV, (a-v) 02 difference, and VO2. Describe the changes for both rest and maximal activity, including approximate units. Cardiac output (Q) at rest is approximately 5. 0 L/min (Brooks et al. 2005, p. 342).
Resting Q does not change very much with training. However, Q will increase in response to exercise and it is caused by an increase in HR. This will cause a greater amount of oxygen to be delivered via the blood to the necessary tissues of the body. Maximal Q can reach to a range of around 25 L/min (Brooks et al. , 2005, p. 284). Athletes will have a higher cardiac output due to a greater stroke volume during exercise. At rest, HR is around 70 beats per minute (bpm). Elite athletes generally will have a lower resting HR than individuals who do not exercise periodically.
With exercise, sympathetic stimulation will increase HR and different feedback systems will modulate the response of the cardiovascular system, such as stretching of the blood vessel walls (mechanical stimulation) and metabolite changes (chemical stimulation). HR will reach a maximum during maximal exercise and it can be estimated by using this equation: 220 bpm – age of individual, with an error of +/- 12 bpm. Maximal HR is generally within the range of 180-200 bpm (Brooks et al. , 2005, p. 345).
Stroke volume (SV) is approximately 70 ml/min at rest (Brooks et al. 2005, p. 342). SV will increase linearly with exercise and will plateau before it reaches the maximum (only 25-50% of maximum). Training will also cause an increase in SV. However, there is no change in SV when the subject is in a supine position, since the heart does not need to pump as much and work against gravity when the body is laying down. From rest in comparison to maximal exercise, there will be an increase in consumption of oxygen as mentioned earlier. There will be an increased rate of oxygen transport and a greater (a-v) 02 difference (more oxygen extracted).
Resting a-v 02 difference does not change much with training, but there will be an increase with maximal exercise. At rest, a-v 02 difference is around 5 vol % and can reach a maximum of around 15 vol % (Brooks et al. , 2005, p. 342). Oxygen consumption (102) does not change at rest, but increases with training. Maximal rate of oxygen consumption (VO2 max) varies between different individuals depending on their fitness. It can be within the range of 30-40 ml*kg/min for untrained individuals and elite athletes will generally have much greater VO2 max values (Brooks et al. , 2005, p. 350).
