There are many types of workouts you can include in your training to get faster: tempo runs, interval workouts, and hill repeats. Interval workouts are a broad term that can encompass many different types of workouts. When most runners think about intervals, they think about challenging reps at VO2max. While VO2max is not the sole predictor of running performance, there are benefits to including VO2max interval workouts in your training.
What is VO2max?
VO2max is a technical term that refers to how much oxygen you consume during a run. (This article explains more about VO2max and its relationship to running.) The higher your VO2max, the more oxygen you consume and deliver to your muscles, and the faster you run.
VO2max itself is not a pace. Instead, VO2max refers to the maximum amount of oxygen intake (measured in mL/kg/min) you can have during exercise. You may also hear it called “aerobic capacity.” For most runners, VO2max is an intensity you can only sustain for seven to 11 minutes.
Velocity at VO2max (vVO2max) is the pace that corresponds with your VO2max. vVO2max is sport-specific. You may have a high VO2max and a fast vVO2max in running, but if you are inefficient at swimming, your vVO2max in swimming is low.
VO2max can plateau even with training. However, repeated research (as summarized in articles such as this 2023 review in Sports Medicine) indicates that vVO2max can improve – and with that, bring improvements in performance.
We still do not fully understand how much vVO2max correlates with performance outcomes at various distances (half marathon, marathon, etc), as discussed in a 2020 review in the International Journal of Environmental Research and Public Health. However, most training theory supports the concept of training all physiological systems – including vVO2max. While it should not be the sole emphasis, we cannot ignore it in training.
How Can You Improve vVO2max?
Research demonstrates several effective approaches to improving vVO2max. Strength training can improve vVO2max. Most changes to running economy will improve vVO2max. One common and effective approach is VO2max interval workouts.
VO2max interval workouts are short intervals at or near your maximum oxygen uptake – or roughly at 10-15 minute race effort. For elite runners, that is 3K to 5K pace. For most recreational runners, VO2max is around mile to 3K pace. However, you do not have to be precisely at your exact VO2max pace to benefit. Approximately 95-105% of vVO2max will elicit the same physiological stimulus. So, recreational runners could pace these intervals at 5K effort and still benefit.
Training at VO2max triggers several training adaptations. As outlined in a 2023 study in International Journal of Environmental Research and Public Health, intervals at VO2max have both cardiovascular and neuromuscular benefits. Maximum cardiac output, plasma volume, heart mass, and stroke volume all increase. These central adaptations mean that your heart can send more oxygen-rich blood to working muscles. Peripheral adaptations include increased recruitment of motor units, increased capillary density, enhanced enzyme activity, and more mitochondrial activity in fast-twitch muscle fibers. Together, these changes help you produce more energy in the working muscles. Some neuromuscular changes to muscle fiber recruitment can also improve power output and fatigue resistance.
VO2max Interval Workout
When most runners think of VO2max intervals, they think of workouts done the track, such as 6 x 800m (½ mile or two laps around a standard track). However, you don’t need to hit the track in order to run fast. Time-based VO2max intervals on the road will still elicit the same adaptations.
Time-based VO2max interval workouts offer two benefits. First, the time-based interval removes the temptation to race the workout. You may feel tempted to run 800m as fast as you can to get it over with sooner. You can’t do that with a time-based interval.
Secondly, time-based VO2max interval workouts can be done in various locations. You can run them on a track, the roads, or even trails. Trail runners can even take these workouts onto hills.
Finally, time-based intervals ensure the workout triggers the appropriate physiological response. At this high intensity, distance-based workouts could actually elicit different physiological responses from different levels of runners. Sub-elite athletes may complete 1K repeats at in less than 4 minutes, while back-of-the-pack runners may take over 6 minutes to run 1K. The sub-elite runner is running an appropriately hard VO2max workout. Meanwhile the slower runner will be running a workout that risks overtraining or injury.
Research indicates that intervals lasting 2-4 minutes are optimal for improving your vVO2max. A 2022 review by top physiologists in Sports Medicine defines VO2max intervals as lasting 2-4 minutes in duration. Running at VO2max for less than 2 minutes and you may not fully reach your VO2max in the workout, while running at over 4-5 minutes makes it too strenuous to hold the appropriate pace.
You don’t want to skimp on the recovery intervals during VO2max interval workouts. Recovery intervals in VO2max interval workouts will last 50-100% of the interval duration (or roughly 2-3 minutes).
VO2Max Interval Workouts
The number of intervals you do will depend on your training volume and background. Beginner and/or low-volume runners may only do 10 minutes total of VO2max intervals. Intermediate runners might complete 12-16 minutes. High-volume and elite runners may do up to 15-20 minutes total across the intervals.
10 minute warm up at an easy, conversational effort
5 x 2 minutes hard, 2 minutes recovery jog or walk
5-10 minute cool down at easy pace
15-20 minute warm-up at easy run pace
3-4 x 4 minutes at 3K-5K race effort, 3 minutes recovery jog in between
15-20 minute cool down at easy run pace
For the hard intervals, you want to run about a 8-9 on a scale of 1-10 (1 being a light jog, 10 being an all-out sprint). The pace should feel like something you could sustain if racing a 3K to 5K race. Jog as lightly as you need to during the recovery intervals to bring your breathing back to normal.