Mixed Intervals
As their name suggests, mixed interval workouts consist in a mixture of two or more of the three interval lengths discussed above. Because they do not focus on a single, specific intensity, mixed interval workouts are not as useful as short, middle-length or long intervals for boosting specific components of running fitness. However, they are very useful for maintaining fitness in each of the components addressed by the three interval lengths. Therefore runners typically rely on mixed intervals during the final weeks of training before a race, after they have already developed their speed, VO2max and lactate threshold with short, middle-length and long interval workouts and simply want to maintain these capabilities while sharpening for a race.
Mixed intervals are also useful as a secondary track workout for advanced runners training for shorter races (5K and 10K). The primary track workout of the week would focus on developing one specific component of running fitness, while the mixed interval workout would provide a smaller stimulus for the same component of running fitness plus a small stimulus for the components of running fitness addressed by the other interval lengths.
Following are examples of mixed interval workout formats for beginner, intermediate and advanced runners:
Beginner Mixed Intervals Workout
- 1600m
- 1000m
- 600m
- 200m
(400m active recovery after each interval)
Intermediate Mixed Intervals Workout
- 1600m
- 1200m
- 800m
- 400m
- 200m
(400m active recovery after each interval)
Advanced Mixed Intervals Workout
- 400m
- 800m
- 1200m
- 1600m
- 1200m
- 800m
- 400m
(400m active recovery after each interval)
Don't let marathon training steal your speed. Check out these suggestions from Mario Fraioli for running fast at short distances while training for a marathon.
Incorporating Track Workouts into Your Training
Regardless of the race distance you're training for, you should do short, middle-distance and long interval workouts. Mixed interval workouts are optional, and are best used as discussed above. Most runners, regardless of their experience and fitness levels, should perform one and only one track workout per week during the 8- to 16-week period preceding a race. The challenge level of your track workouts must be tailored to fit your current fitness level. And the particular order in which you sequence your track workouts should vary depending on the race distance you're preparing for.
Many runners break their training into distinct phases and do only one type of interval workout in each phase. However, I believe that runners should create a rotation in which they do each type of interval workout regularly throughout the training process. After all, what's the point of building up, say, a lot of speed by doing a block of short interval workouts relatively early in the training cycle if you're then just going to eliminate short interval workouts and lose that hard-earned speed later in the training cycle? Rotating your track workouts enables you to maintain the fitness gains you earn in each component of overall running fitness.
That said, you should give greater emphasis to specific types of track workouts at different points in the training process. During the peak period of training that immediately precedes your biggest race you should emphasize track workouts that target the intensity level that is closest to the intensity level of your upcoming race. For 5K runners, middle-distance intervals are closest to race pace. For 10K runners and half-marathon runners, long intervals are closest to race pace. Track workouts of any sort are not well suited to marathon-pace runs, so if you're training for a marathon I recommend that you do your marathon-pace runs off the track and focus on mixed-pace intervals in the peak period of marathon training to maintain speed, VO2 max, and lactate threshold gains established through short, middle-length and long interval workout performed earlier in the training cycle.
All road racers should emphasize short intervals in the earlier part of the training cycle, because it is helpful to establish a foundation of speed that you can then extend over longer distances as the training cycle progresses. Plus, the very high speeds that are involved in short interval workouts are less race-specific than the slightly slower speeds involved in the other types of interval workout, so they do not need to be emphasized in the peak period of training.