When you’re running intervals, the goal is usually to run a single, uniform intensity for the entire duration of the interval. Some workouts may vary the intensity from interval to interval, but during each bout of hard running, you’re trying to maintain a steady pace throughout. Scientists from the University of Kent found, however, that by varying your intensity during the interval, you can have a greater impact on your VO2 max without making the workout itself any harder. While this study was done on cyclists, it can easily be applied to running intervals to get more bang for your workout buck.
For the study, which was published in the International Journal of Sports Physiology and Performance, the researchers created and tested a workout consisting of six, five-minute intervals separated by 2.5 minutes of active recovery. In the first session, the cyclists performed each interval at about 80 per cent of their max, each interval done at a consistent pace. In the second session they lowered the intensity to about 77 per cent of their max, but within each bout of hard cycling, they added in three 30-second surges at 100 per cent effort.
14 trained cyclists completed the two workouts, and on average, they spent 6:50 above 90 per cent of their VO2 max during the variable-intensity workout, compared to 4:46 in the steady-intensity workout. Interestingly enough, when the athletes were asked to rate the difficulty of the two workouts, they rated them almost equally, despite spending more time at a higher percentage of their max in the second workout. That means they got a greater physiological benefit without making the workout psychologically any harder.
How does this translate to running?
You can easily apply this knowledge to a running workout. In your next hard training session, instead of trying to maintain a consistent pace for each interval, throw in a few short bursts of higher-intensity running during the work period. The key, of course, is not to slow down too much during the interval after a surge. For example, if your workout is 5×5 minutes at 4:30/km, try running them at 4:35/km pace, but with three or four 30-second surges where you speed up to 4:25/km pace. When you slow back down, the goal is to get back onto 4:35 pace, not slower. Using a GPS watch that can tell you what speed you’re running is particularly beneficial during a workout like this to help you avoid slowing down too much.
This is a great way to up the intensity of your workouts without adding any length. Because you’re playing with the pace during the intervals, it also helps you stay more mentally engaged in the workout and can even make it a little more fun. Finally, adding some surges in during a workout will teach you how to do the same thing during a race, which will help you when you’re trying to pass another competitor, surge at the top of a hill, or even kick it in to the finish line.