During exercise, your body’s vasculature is working extra hard to make sure that sufficient blood supply is delivered to your muscles. The main purpose of this is to transport oxygen from the lungs via red blood cells. Hemoglobin, a protein on red blood cells for binding oxygen, also contributes to the blood’s buffering capacity and ATP and NO release from red blood contributes to vasodilation and improved blood flow to working muscles. However, it has been found that trained athletes, specifically endurance athletes, have a decreased hematocrit, sometimes called “sports anemia.” Athletes actually tend to have an increased total mass of red blood cells and hemoglobin, but the decrease in hematocrit by training is due to an increased plasma volume. This means that the decreased hemoglobin concentration allows for less delivery of oxygen to cells.
Figure 1: Both of these graphs show that during single muscle exercise (Graph A) and whole body exercise (Graph D) there is a decrease in hemoglobin concentration.
Because of the effects that hemoglobin concentration has on athletic performance, there is a need for a faster, accurate method that athletes can use during training to evaluate their training program. Hemoglobin concentration does not only change due to elevation, but also due to exercise intensity as well. Typically, athletes only get their hemoglobin concentration tested four times a year, making this a huge need for endurance athletes to determine the efficacy of the their training programs. So the question is: how can we measure hemoglobin concentration? By looking at how we measure hemoglobin, we can look for new, portable and fast ways for athletes to measure their hemoglobin levels while training.
One way to measure hemoglobin is to take a blood sample from athletes and then to perform an absorbance test on the blood. This follows Beer’s Law. We will now explore how Beer’s Law works and how the concentration of hemoglobin is found for athletes. First, we need to make some assumptions and simplifications.
- Assume that all the hemoglobin from the red blood cells in the sample will be be converted to cyanmethemoglobin.
- Assume only interaction between radiation (light) and the absorber (sample) is absorption.
- Assume these are at low concentrations ( < 0.01 M)
- Assume that the nature of the absorber does not change with concentration
First, the blood is diluted in Drabkin’s Solution by 1:201, meaning if you have 20 microliters of blood you will need 4000 microliters of solution. Then the tube is covered and inverted several times and left to sit at room temperature. In the solution, these two reactions occur:
where A is the absorbance, e is the molar absorbitivity (L/mol cm) which is specific for each compound, b is the path length of the sample (cm) and c is the concentration of the sample (mol/L). This equation tells us that there is a linear correlation between absorbance and concentration. If the solution is known, then we can create a linear graph like this:
Figure 2: This shows the Absorbance vs. Concentration graph from Beer’s Law and how to determine the concentration of an unknown.
Since we know that we are using cyanmethemoglobin (HiCN), then we can simplify Beer’s Law to calculate our hemoglobin concentration in our sample. Since we are comparing the absorbance to a HiCN standard with a known concentration, we can calculate the concentration of HiCN in the blood sample by:
where, the test sample is the cyanmethemoglobin from the blood sample and the standard is a solution of standard cyanmethmeglobin. Following this equation, once the absorbance of the sample and standard are known, then the concentration of hemoglobin can be determined. Based on our assumptions, most of them will hold true in clinical practice – with blood samples we are dealing with low concentrations of hemoglobin.
With Beer’s Law and the manipulation, we are able to determine the concentration of hemoglobin in a blood sample. Although this equation is effective in a laboratory, it takes time for an athlete to get a result. Perhaps improving technology, there could be a faster and portable device for athletes to use so that they can know their hemoglobin levels during their training sessions.
Recommended for Further Reading:
Questions for Readers:
How practical do you think it would be for athletes to measure their hemoglobin?
How do you think this would effect measuring for blood doping?
How can this apply to patients with anemia as well who wish to exercise?