How Can VO2 Max be Improved?
Basic aerobic endurance training that follows the ACSM's recommended guidelines for cardio-respiratory fitness training is known to improve VO2 Max. It is common for an average unfit person following the ACSM's guidelines to experience a 15% improvement in VO2 Max after 2 to 3 months of regular training. Although basic aerobic endurance training is usually sufficient for the general population, the most effective approach to improving VO2 Max, the one applied by many elite endurance athletes, is called high intensity interval training (HIIT).
How to Improve VO2 Max with HIIT?
HIIT is a method of training that involves performing intervals of high intensity exercise interspersed with rest intervals of lower intensity exercise. The specific intensity and duration of each high and low intensity interval can be modified to suit the training goals of the individual, however, in the case of someone whose goal is to improve their VO2 Max, the most effective approach is to maximize the total amount of training time that is spent at, or close to, VO2 Max. The more time you spend at or near VO2 Max, the greater your VO2 Max improvements will be.
Creation of an HIIT Program
Step 1: Determining the Length and Intensity of the High Intensity Interval:
To improve VO2 Max your high intensity intervals should be performed at an intensity of roughly 90% of VO2 Max (this correlates to approximately 95% of maximum heart rate). This is not absolute maximal exertion, but almost maximal exertion. The length of each high intensity period should be roughly 75% of the maximum amount of time that you could last at this intensity before fatiguing. To determine this, you'll need to time yourself while you perform a single trial interval at high intensity until you fatigue (do this a few days before beginning your HIIT sessions so that you have time to adequately recover, and be sure to properly stretch and warm-up before you do it). If, for example, you can last for 200 seconds (this is an example only, it might be more or less) before fatiguing during this trial period, then your actual high intensity intervals should be set to last for 150 seconds each.
Step 2: Determining the Length and Intensity of the Rest Interval:
Now that you know how long your high intensity intervals will last, you need to figure out how long your rest intervals will last. The relative duration ratio of your rest to high intensity intervals should be based on your comfort and fitness level. If you are a beginner, set your rest to high intensity interval time ratio at 2:1 (i.e. your rest interval duration should be twice that of your high intensity interval). If you are well trained then you will ideally have interval time ratios of 1:1 or even 1:2 (i.e. rest interval the same duration as your high intensity interval or rest interval half the duration of your high intensity interval, respectively). Therefore, using the example from Step 1, if the length of your high intensity interval is 150 seconds, your rest interval would last for 300 seconds if you are a complete beginner, or 150 seconds if you are well trained, or perhaps 75 seconds if you are very well trained. During your rest intervals, you should carry on your exercise activity while reducing your intensity level to approximately 70% of maximum heart rate.
Step 3: Determining the Total Number of Intervals:
Set the total number of intervals performed over the entire workout so that the total time spent at high intensity equals between 20 to 30 minutes. This variable should also be determined based on your comfort and fitness level. Therefore, using the example from Step 1, if your high intensity intervals last for 150 seconds (2.5 minutes) then you should perform at least 8 high intensity intervals to ensure a total of 20 minutes of high intensity activity. Start and end your training sessions with a rest interval (so you'll actually end up doing one more rest interval than the total number of high intensity intervals).
Step 4: Training Frequency, Activity Type, and Additional Notes:
Since these types of training sessions are fairly demanding, you should perform them no more than 2 or 3 times per week. The type of exercise activity performed during your HIIT sessions doesn't really matter, as long as it is a full body type of activity (i.e. running, swimming, rowing, cross-country skiing, speed skating, etc...) and you can achieve the necessary steady intensity levels discussed above for the appropriate periods of time. If you are training to improve your performance in a particular type of exercise activity, you should be performing that particular type of exercise activity during your HIIT sessions to benefit from the effects of training specificity. As with all training programs, you should modify the parameters of your HIIT sessions within the guidelines discussed above to suit your fitness level as it progresses.
Helgerud J, Høydal K, Wang E, et al. (2007). "Aerobic high-intensity intervals improve VO2max more than moderate training". Med Sci Sports Exerc 39 (4): 665–71.
Douglas S, Pfitzinger P, Advanced Marathoning, 2nd Edition, 2009, Champaign, IL: Human Kinetics.