It shouldn't be that difficult to see why instructors incorporate strength training into their aerobics classes. According to a fitness handout from IDEA (International Association of Fitness Professionals) (1995) by Wayne L. Westcott, PHD with the headline "Strength Training Update", sensible strength training can produce these benefits:
The article also mentions: "...Although endurance exercise improves cardiovascular fitness, it does not prevent muscle tissue loss. Only strength exercise maintains muscle mass and strength throughout midlife. ..."
and for those interested in getting rid of excessive fat:
"...Adults who add muscle through sensible strength exercise use more calories all day long, so are less likely to accumulate fat. ..."
People who do aerobics 2-3 times a week often don't do additional strength training. In fact, many persons want to spend some of their spare time outside the gym as well. (yes - it's actually true...).
So - the REAL challenge for aerobic instructors should be: how to fit strength training into a program in a way that won't get these persons to join the "60-minute-jumparound"- class (well... you know what I mean, anyway..?). Instead of saving all the st. tr. to after the cooldown after the "cardio phase" do some after the warm-up. The customers won't be exhausted so they'll have more energy to concentrate about the right technique and also you will give the signal that you give priority to the strength training.
Now, when that's said, there is important to remember that strength training should be done at a moderate tempo; it's better to be too slow than too fast. This, of course, to avoid injuries and also for a better effect.
Mads Olsen firstname.lastname@example.org Norway