By Adrian Western, MS,ATC and Anthony Spinelli, MS ATC, CSCS
VO2 max is short for maximum uptake of oxygen and is used as a measure of cardiorespiratory fitness as it relates to the amount of oxygen that the cardiovascular system can deliver to working muscles during exercise (Powers & Howley). Proper utilization of this test can be helpful in determining the fitness level of endurance athletes, customizing their training based on the results, and retesting to gauge adaptation to the workout instituted.
Testing endurance athletes helps to develop a specific training plan in order to effectively and efficiently meet client goals. At the conclusion of the test we are able to determine how effective your cardiorespiratory system is at supplying oxygen throughout your body. We are also able to determine the anaerobic threshold, or the percentage of VO2 max, that clients can perform at efficiently without hitting the wall. This number is the breaking point of where the body produces more carbon dioxide than it can expire through breathing (VCo2/VO2). This level correlates when lactic acid is produced more quickly than it can be removed. Lactic Acid is a byproduct of anaerobic metabolism, which takes over once an individual’s anaerobic threshold is met.
Influences of VO2 max and Anaerobic threshold
Maximal volume uptake is largely determined by genetics. However, different training protocols have been shown to increase oxygen utilization. Participating in interval training can improve VO2 max between 5-20%. Another way to improve your score is to maintain lean muscle weight. Since the number is dependent on body weight, having a healthy, lean bodyweight can help with improving the number. Anaerobic threshold is very dependent on training and can be more easily modified than VO2 max. Participating in a structured training program designed to improve efficiency at the lactate threshold will result in better adaptation of the body to handle increased blood lactate. More easily put, the more you work near or beyond your lactate threshold, the more adapted you will become at clearing carbon dioxide, maintaining a stable blood PH, and sparring/storing muscle glycogen.
Testing Protocol
In our center, testing takes approximately 30-40 minutes, roughly 10-20 minutes is spent actually exercising. Our protocol is to have clients run, cycle, or even row while wearing a heart rate monitor and 2-way mask attached to a metabolic cart. We gradually increase the workload by increasing the level of intensity of the test while the cart measures three variables (% CO2 expelled, % O2 expelled, volume exhaled) and computes many more (respiratory exchange ratio, oxygen consumption, ventilatory breaking point). The test is complete when clients hit their peak and are unable to continue. We are then able to determine if this peak was indeed their maximum effort and the greatest amount of oxygen that the body consumed per unit of time measured in mL/kg/min.
Developing Training Zones
Since testing involves the correlation of heart rate with oxygen uptake it will show where the maximum heart rate lies with exercise. Knowing your true heart rate can establish better customization of training through creating heart rate zones. We utilize a 5 zone model with our clients where the first zone is recovery at less than 65% VO2 max. This ensures that on a recovery day our athletes are not over working. Zone 2 is 65-75 VO2 max and is the base training zone and is used predominantly to lay a solid training foundation. Zone 3 is 75-90% VO2 max and is the ventilatory threshold and is used during tempo runs to accommodate increases in lactate. Training zone 4 is 90-100% VO2 max and is used for interval training in which athletes work beyond their lactate threshold in order to improve anaerobic metabolism. Training zone 5 is over 100% VO2 max and is done infrequently in order to further stress the anaerobic system and is used more for athletes who need to improve their lactate threshold for medium duration events at extremely high intensity. We advise our clients to use a heart rate monitor in order to get accurate information during their training. This way they are training in the correct zone prescribed for that day’s workout. We also track their resting heart rate which can help us determine if they are over or undertraining and then modify the workouts accordingly. Ultimately the goal is to ensure our athletes are not working too hard on light days and hard enough on the hard days. This helps tax energy systems appropriately and better suit the individual for their own specific competition.
Retesting
Testing the VO2 max can be helpful in creating workouts for endurance athletes that are looking to improve their performance and crave a plan that is very time effective and efficient. This test allows for that customization. Since training can not only improve the maximal oxygen uptake but also lactic threshold, it is important to retest periodically throughout the year to evaluate progress and update the heart rate percentages. Once we start collecting more quantifiable data our athletes get more and more customized workouts to streamline their training for maximal adaptation.