You have probably heard that you need to exercise continuously for 30 minutes to become fit. Almost 80% of adults can't exercise vigorously for that long, so many people won't even try to start an exercise program because they feel that exercising
would just be a waste of time. However, according to the American College of Sports Medicine, you don't have to engage in vigorous exercise for sustained periods to gain substantial health benefits. If you exercise for 30 seconds, rest for 30 seconds
and alternate exercising and resting, you should be able to increase your exercise time without much discomfort and without injuring yourself.
This is called interval training, and top athletes in all sports use it. More than 35 years ago, the Swedish physiologist, Per Olof Astrand, showed that you can increase your exercise load markedly by alternating exercise with rest periods. He showed that
you could exercise for up to 30 seconds intensely and continuously without accumulating much lactic acid in your bloodstream. Lactic acid makes muscles hurt and feel tired. However, the amount that accumulates in 30 seconds of hard work is quickly cleared from your bloodstream. Then you can exercise for another short burst. Your muscles get stronger as you build up the number of intervals you can complete. An example of a typical workout is to start off by pulling on a rowing machine for 30 seconds, resting for 30 seconds and then alternating rowing and resting for several minutes. Stop when your muscles hurt or feel heavy.