Intermediate exercisers already involved in heavy weight training
This is where it gets more complicated because there are so many different ways that people might be training. As mentioned above, interval training is another high intensity workout and that has to be considered within the context of the overall training structure.
Local overtraining (of the legs) is a very real issue when you try to add interval training to a heavy leg training schedule. Someone who is trying to train legs twice (or more) per week and who adds intervals to that load can quickly run into problems. This applies to bodybuilders, powerlifters, and any other athlete who has to develop multiple capacities at once. There are a couple of solutions. This is why I didn’t include intervals in the Ultimate Diet 2.0; it already included 3-4 lower body workouts/week. Adding intervals would have just made overtraining a near guarantee.
The first is to cut back leg training (which should really be done on a diet anyhow, I’ll talk about training for fat loss in another newsletter) to reduce the overall training load. Basically, leg training should be moved to maintenance loads, with a reduction in volume, frequency, or both (intensity should never be reduced). If you were training legs for 6-8 sets twice/week you can cut back to 2-3 sets twice/week or perhaps 4 sets once/week and maintain leg strength (and size) for quite some time. Adding two days of intervals to your training, plus 1-2 regular aerobic sessions, works just fine (see comments below on sequencing). If leg training is cut back to once/week, or the volume performed more frequently is very low, intervals might be possible up to three times/week.