Interval training can increase the rewards you get from working out. This method is one of the quickest ways to build fitness and burn calories, according to the Mayo Clinic. And the interval concept is easy to adapt to any type of exercise: Simply intersperse short periods of intense effort such as sprinting with active recovery -- longer periods of jogging or walking. Before you tackle this type of demanding workout, check with your doctor to make sure it's safe for you. For added safety and precision during your workout, you can track your heart rate with a monitor.
Maximum Heart Rate
You'll monitor all your efforts through percentages of your maximum heart rate, so make sure you know what your max is. The most accurate method is through a cardiac stress test under your doctor's supervision, though you can roughly gauge your max by subtracting your age from 220, according to the American College of Sports Medicine. For a 40-year-old exerciser, maximum heart rate would be 180 beats per minute (BPM).
Warm Up to High Intensity
Warming up is vital for any type of exercise, and that's especially true when you're doing interval training. During a high-intensity interval -- say, a 30-second sprint -- your heart rate will reach between 75 percent and 85 percent of your max. For a 40-year-old, that's between 135 and 153 BPM, and it will feel very demanding. Do some light exercise for five to 10 minutes before attempting that kind of effort.
Recovery Takes Time
After about 30 seconds into your recovery interval, check your pulse. According to the fitness experts at the American College of Sports Medicine you should recover at 50 percent to 65 percent of your max, which means a 40-year-old needs to follow a sprint with a recovery pace that gets his heart rate down around 90 to 117 BPM. If, after 30 seconds, your heart rate is still above your recovery rate, add more time to your resting interval.
Be Flexible When Timing Your Intervals
Since the goal of intervals is to make sure you can go all out during the high-intensity sections, your recovery interval needs to be long enough to ensure proper rest. In other words, you may need to lengthen your recovery intervals. When setting up your intervals, try starting with a 1 to 3 ratio: If you're sprinting for 30 seconds, walk or jog slowly for a minute and a half. Keep an eye on your monitor to make sure your heart rate drops before you begin your next interval.