This article is part of Endurance Planet’s ultrarunning article series. If you have questions, comments or feedback about “Intervals in Ultramarathon Training”, please leave it below in the comments section…
More often than not intervals are narrowly associated with development of leg speed. Perhaps this is due to the fact that it’s short and middle distance runners who mostly use and directly benefit from this form of training. This may lead some runners to think that it has little or no place in preparing for an ultramarathon.
Actually interval training doesn’t have to be automatically equated with speed oriented workouts. That is if you take a broader definition of intervals as any form of exercise that involves alternating between high and low bouts of intensity. In any case, an ultrarunner can certainly benefit from adopting a more balanced approach by developing leg speed and power as well as endurance.
Aerobic and anaerobic intervals
The growth of your anaerobic capacity should always be understood in relation to your aerobic capacity. This is the reason why endurance building through progressively increasing mileage always comes first and serves as a base for later development of speed and power. If you can keep up a fast pace while still remaining within your aerobic threshold, then it only follows that you can also be fast when you go into your anaerobic zone.
Interval training can thus be inserted in both the initial endurance build up and later stages of speed workouts. The differences between aerobic and anaerobic intervals are: (1) the ‘high’ intensity periods in an aerobic interval are still done slower than your marathon pace while in anaerobic intervals the pace is far higher, (2) in aerobic intervals the low intensity periods are shorter and more controlled than the high intensity bouts while in anaerobic intervals the low intensity periods can be longer and should allow for full recovery.
Intervals in the long run
If you are performing your long runs in a run/walk fashion then you’ve already incorporated intervals in your ultramarathon training. This is the usual tactic used by those preparing for 100k and 100 miler events. Those who have the physical capacity for it or are targeting a 50 miler may alternate between fast and slow paces instead. Set times or distances can be used for demarcation but the fartlek approach of just going by feel to switch between high and low intensity can also work well. Just remember that the main objective here is still to build up endurance so run your ‘high’ intensity periods still near or at your aerobic threshold.
Doing some training runs on hilly courses is also an interval form of exercise. This has the added bonus of specificity in case you’re preparing for an ultramarathon that has similar terrain. The natural tendency is to do the high intensity portion on the uphill route and recover downhill. But as some more experienced ultrarunners have noted the opposite is actually more advantageous in a race. There is usually little time difference between a runner just shuffling uphill and a runner doing the climb in full speed. There is however a bigger time difference between a runner going downhill at a hard pace and one going down on a recovery pace.
Interval training also provides the ultrarunner a good opportunity to develop and maintain good running form. You really can’t keep your high intensity bouts if you’re not moving your hips and legs and landing your feet right. In a run/walk session, you should also be mindful about shifting smoothly between the two and learn how to ease down into the walk and lean in to the run. When you consciously maintain good form, it eventually becomes muscle memory and thus put out a more consistent performance.
Do you have questions about interval training for ultramarathons, or what you’ve read so far? Do you have any ultrarunning pointers of your own to add? Please leave your feedback, comments and questions below, and we promise we’ll respond.