Question

• Explain changes with exercise for: RHR, MHR, EHR, submax SV, max SV, submax Q, maxQ.
• What are the four main things that determine stroke volume?
• Draw a graph of heart rate as exercise intensity increases. ➢   Draw a graph of SV as exercise intensity increases.
• Draw a graph of Q as exercise intensity increases
• Draw and/or explain a map showing how exercise increases SV.
• What causes increases in Q at low/moderate intensity?  High intensity?
• Define and explain the concept of cardiovascular drift.
• What is the bicarbonate buffer and how does it work?
• What causes increases in pulmonary ventilation during exercise?
• Draw a graph of ventilatory threshold.  What can this be used to estimate and why?
• How does the respiratory system aid in the acid-base balance?  ➢ Why is active recovery important?

Answer 1

• Explain changes with exercise for: RHR, MHR, EHR, submax SV, max SV, submax Q, maxQ.

The RHR or resting heart rate is the time of heart contractions you make when in total lack of physical activity. During exercise you will lead you RHR behind, your heart rate will increase, but your known resting heart rate will remain the same.

The MHR or maximum heart rate is the maximum number of heart beats you can make during 1 minute of high physical activity. When exercising you are going to reach or at least approach this number.

The EHR or exercise heart rate is the actuall number of beats you make during a minute when doing physical activity, it tends to approach the MHR but it is not necessarily reached.

The max stroke volume is the maximum volume the heart can pump in a single beat. Normally the stroke volume tends to vary depending on the activity being made, during exercise the stroke volume approaches the maximum stroke volume.

Q max refers to the maximum cardiac output, it is the product of MHR and max sv, it is the quantity in liters of blood being pumped in a minute.Again, in exercise our Q will approach max q

Have in mind that these values per se will not be modified when exercising, but their observed in an actual individual will approach them when exercising.

• What are the four main things that determine stroke volume?

- Heart size: A bigger heart has more volume capacity, thus leading to larger stroke volume values

- Preload: The fast filling capacity of the heart

- Contractibility: The strength in contraction to pump the blood volume

- Afterload: The ability to eject the whole blood volume against the pressure being applied to the heart

• Draw a graph of heart rate as exercise intensity increases. ➢   Draw a graph of SV as exercise intensity increases.

Both of them will increase during exercise and will approach their maximum values.

Heart rate increases linearly reaching the maximum (tends to be 190 bpm), it is the blue line. Stroke volume is the curve in black, it reaches a maximum and stay there in further effort.

• Draw a graph of Q as exercise intensity increases

This curve is obtained with the previous 2 values, so the behavior is very similar:

It will reach a maximum and stay there in further effort.

• Draw and/or explain a map showing how exercise increases SV.

That answer is related to metabolism and energy requirements. Exercise demands a huge energy expending, cell must produce the energy that they will use, this is made through cleavage of carbohydrates and lipids. But such energy obtaining pathways require oxygen to be undergone, thus the heart must compensate it by increasing the stroke volume. A larger stroke volume will better cover the oxygen requirements.

• What causes increases in Q at low/moderate intensity?  High intensity?

Q may increase if heart rate or stroke volume or both increase. Heart rate increases more easily, it is the first regulator, even low activity will have a rising effect in it, that's why in low or moderate physical activity the elevation of heart rate is the one responsible for the increase in Q. In high intensity activity the stroke volume plays a role, it increases too, helping the cardiac output to increase even more, it is like the second regulator.

• Define and explain the concept of cardiovascular drift.

It is a common event that occurs when we make long periods of high intensity exercise. It is the maintainance of the cardiac output while the stroke volume is declining but the heart rate is increasing.

• What is the bicarbonate buffer and how does it work?

Blood has it's own buffer mechanism to avoid strong changes in pH, because such changes could be fatal for the organism. Every buffer is made of an acid and its conjugated base, in this case it is carbonic acid and bicarbonate

• What causes increases in pulmonary ventilation during exercise?

Let's retake the topic about why stroke volume increases during exercise. Remember the body needs higher levels of oxygen during physical activity, and the source of such oxygen is the air outside of the body. The only organ capable of intaking oxygen into the blood are the lungs, so if we require to take more oxygen and eliminate more CO2, then the lungs will get some pressure to overcome the requirements

• Draw a graph of ventilatory threshold.  What can this be used to estimate and why?

The threshold is the point where the ventilation starts growing at faster rates than the VO2 intake, as we can see in the graph the line changes direction, growing faster in the vertical axis than in the horizontal axis. This is important due to its relation to metabolism, as it tends to indicate endurance performance.

• How does the respiratory system aid in the acid-base balance?  ➢ Why is active recovery important?

Remember our buffer is made of carbonic acid and bicarbonate, and carbonic acid is produced when CO2 get diluted in blood. High cellular activity (ATP production through cell respiration) produce great amounts of CO2 that start to hit the buffer by turning into carbonic acid. Now, what does the respiratory system does? Intakes O2 while eliminates CO2, this CO2 elimination lowers the carbonic acid concentrations in blood, thus aiding in the acid-base balance