Ask the Professional: Lactate Threshold and VO2 Max
by Devin Sarno, NSCA-CPT
Those that spend most of their exercise time partaking in some sort of cardiovascular specific training especially triathletes, competitive runners, cyclists and swimmers, should be aware of their VO2 Max and Lactate Threshold. Being aware of these could help you take your training to the next level. VO2 Max and Lactate Threshold very well may be the two most significant numbers a cardiovascular athlete can know along with maybe their paces and times, that is if you can utilize them correctly.
Your VO2 Max is the maximal volume of oxygen that your body can deliver to your working muscles per minute. This is a measurement of how efficient you are in utilizing the oxygen that you are taking in. This number is generated by multiplying your Maximum Heart Rate and Maximum Stroke Volume, the volume of blood pumped out to the muscles by the heart with each heartbeat. These two numbers alone give you your maximum Cardiac Output in Liters/minute, or the maximum amount of blood your heart can pump to your muscles in one minute. Then, the VO2 Max can be calculated by taking the Maximum Cardiac Output and multiplying it by your A/V Oxygen difference, how much Oxygen is taken out of the blood while it is making its way through the muscles you are working. The number you then end up with is the maximal volume of Oxygen your blood can deliver to the working muscles in Liters per minute.
Now this probably sounds like a lot technical, confusing jargon that may not mean a lot to anybody reading this and that's perfectly fine. You probably won't be calculating this by yourself because we typically measure VO2 Max with some sort of electronic device or machine.
You can improve your VO2 Max with Aerobic or Cardiovascular forms of exercise. Ironically, a greater VO2 Max can also help improve your aerobic performance. It may not be a direct indicator of how you will perform, but if you can increase your VO2 Max and are more efficient with your oxygen use it will definitely have an impact on your overall performance. We will circle back and talk about why this all important and how to apply it in part two.
The next important number to know is your Lactate Threshold, which may be your biggest enemy without you even knowing it! Blood Lactate is lactic acid that accumulates in the blood as a result of high intensity exercise that requires ATP (energy) at a faster rate than your body can produce. Your lactate threshold is the intensity of exercise where lactate starts to build up in the muscles faster than it can be removed; this causes an overwhelming amount of fatigue that in many cases will force you to stop (i.e. resting between sets or walking during your run). In simpler terms, it is the intensity of exercise where you can no longer continue to produce enough energy to keep up with the amount of energy your body requires. Testing for your lactate threshold is a little bit more complicated than testing for your VO2 Max. Typically it is done by using a treadmill (sometimes an exercise bike) and having the test subject run and increase the intensity (speed) of the treadmill every 3-5 minutes while also taking a blood sample from the finger at each stage of intensity to test the lactate concentration. The lactate concentration is then plotted against the percentage of your VO2 Max that you are working at during the stage that the sample was taken. Your lactate threshold is then the percentage of your VO2 Max in which there is a point of inflection on the line graph; or where the lactate concentration goes from a low, linear level to a significant increase in blood lactate with each increase of intensity. This is relatively easy to see because it is clearly the point where the lactate is starting to accumulate faster than it can be removed given the increase in blood lactate presence with each blood sample.
As you can see, VO2 Max and Lactate Threshold are very closely linked to one another. It is important to understand the purpose of both of these values and how they can influence your training. In part two, we will dive deeper into the importance of knowing these numbers and utilizing them to your benefit especially to evaluate and improve your performance levels.