If you’re trying to get fit, slimming your waistline is probably a pretty high priority. Staying out of danger has to be a prominent goal, too, though. Today, one device — the heart rate monitor—addresses both these objectives extremely well, provided you use it according to a few basic guidelines.
• Know your Maximum Heart Rate.
Your maximum heart rate (MHR) is the highest number of times your heart can beat in one minute. If you are out of shape or overweight and you force your heart to work near this rate for too long, your heart can give out and stop. Alternately, over time, the stress of the intense exertion can cause an inflammatory response that can scar the heart over time, potentially leading to a heart attack. Aside from doing a physical exercise test at home or testing your heart in a lab, the easiest (but admittedly not perfectly accurate) way to figure out your MHR is to use the formula 220 (men) or 226 (women) minus your age. Once you know this number, aim to work at 80 to 100 percent of it no more than 20 percent of your workout time. Set the display on your HeartQ or other HRM to show you percent of max and watch your workout time, or set the device to sound an audio alert when your heart rate gets beyond 80 percent. If you’re working too intensely, slow down, extend your rest periods or lighten your weight.
• Set a minimum heart rate/percent of max to watch for.
Even though you can’t overexert yourself as you exercise, you need to do serious physical work to burn calories and slim down. This is just a reality there’s no getting around. At the same time, if you don’t challenge your ticker, it’s easier for dangerous plaque to form in your arteries, and your heart stays inefficient. If you’re recovering or are just looking to maintain general heart health, then a gentle workout that gets your heart rate to at least 60 percent of max is ideal. For improving cardiovascular fitness, aim to reach at least 70 percent. Most monitors won’t beep at you if your heart rate goes below your minimum, so you’ll need to rely on your display here. Depending on the model you have, you can see where your heart rate is on a target heart rate graph, the general beats per minute display option or the percent of max display option. If you’re not working intensely enough, speed up, shorten your rest periods or increase your weight.
• Pay attention to the time counter.
All fitness monitors will track the amount of time that has passed in your exercise session. With that in mind, if you’re a typical Joe or Jane doing a normal workout, your level of testosterone—a hormone known for helping to build muscle—drops somewhere around the 45 minute mark. The production of cortisol, however, rises, usually hitting its highest point about 60 minutes in. Cortisol is not your friend when it comes to losing weight safely. It makes it difficult to recover and build muscle while simultaneously increasing appetite and stimulating the production of excess glucose that ends up as stored fat. For this reason, for most workouts where you’re not working ultra close to max, keep your exercise time to less than an hour. If you’re really pushing, the high intensity will cause cortisol levels to increase more quickly, so stick to 30 minutes or less. If you have a calorie goal you don’t hit within these windows, look at whether you’re truly working as efficiently as you can. You might need to do two workouts, one in the morning and one in the evening, to put in the time needed without putting too much stress on your body. Remember, nothing says you can’t stop in the middle or even 10 minutes into a video or class if your monitor shows your intensity warrants it!
• Check the calories burned.
You need to burn more calories than you eat to lose weight, but at the same time, you need to make sure that you’re not creating such a big calorie deficit that your body thinks it’s starving. Check with your doctor or use an online calculator to figure out the minimum number of calories you need to eat per day and what you should aim to burn in each workout. Each time you exercise, check the calories burned option on your monitor to see if you’re on target. If you’re routinely not hitting your goal, up your intensity or add more workout sessions. If you’re blasting way more calories than is truly safe, lower the intensity, eat more or take some rest days.
How long should I workout ? – by Dennis Heenan
How long should a workout last ? – by Jason Ferruggia
How long should a workout be ? – by Tony Schober, CPT
Cortisol – by Sara Mahoney