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Let’s get PHYSICAL

by Archives September 14, 2005

Math may not be your favourite subject, but if you’re looking to supercharge your workouts, keep your calories in check and fend off fat, you’d be well-advised to embrace the basics. A calculator just might trump the treadmill in helping you meet your weight-loss goals if you use it to compute the four vital stats below.

Resting Metabolic Rate

Your resting metabolic rate (RMR) is the number of calories your body burns at rest in a single day. Based on a simple equation that takes into account your height, weight and age, determining your RMR is the key to calculating your daily calorie count and, therefore, your optimal intake for weight loss.

Start by dividing your weight (in pounds) by 2.2 and multiplying the result by 9.6. Make note of the final number. Next, multiply your height (in inches) by 2.4 and multiply that result by 1.8. Jot the final number down. Now multiply your age (in years) by 4.7 and record the result. Lastly, add the first and second numbers you made note of together, subtract the third, add 655 to the result and VOILA! Your RMR!

Daily Calorie Count

Once you know your RMR, you’ll still have to take your level of physical activity into account to determine the total number of calories you burn each day. To calculate your daily calorie requirements, multiply your RMR by the appropriate factor: Sedentary (little or no activity) = RMR x 1.2, slightly active = RMR x 1.375, moderately active (moderate exercise/sports 3-5 times a week) = RMR x 1.55, very active (strenuous exercise/sports 6-7 days a week) = RMR x 1.725.

The number you get represents the minimum number of calories needed daily to maintain your current weight. Since you have to burn roughly 3,500 calories to lose a pound of fat, you need to create a 500-calorie deficit every day through diet and exercise to lose one pound per week.

Maximum Heart Rate

Maximum heart rate is a measure of your body’s ability to use oxygen, and equals the number of times your heart would beat per minute if you were exerting yourself at full force. While the most precise tests are done in a lab, it’s still possible to calculate your max heart rate with this simple formula: 208 – 0.7 x age (in years) = heart rate max. This figure can be used to determine your ideal exercise intensity for weight loss.

Target Heart Rate

A common misconception about exercising to lose weight is that low-intensity exercise – working at less than 55 per cent of your maximum heart rate – is the best way to burn fat. This is true to the extent that your body is burning a greater percentage of calories from fat when your heart rate is lower, but it’s the overall number of calories you expend during a workout that really counts.

So what’s your magic number? Beginners should aim for between 50-70 per cent of their maximum heart rate (simply multiply your max heart rate by 0.5 and 0.7), a number that can be gauged by either a heart-rate monitor (available in most sporting-goods stores), or the heart-rate grips on most fitness machines. The latter works best if your hands are slightly damp with sweat (water helps conduct your heart’s electrical signals), your arms are relaxed and your grip is light.

For advanced exercisers, shoot for at least 70 per cent of your max heart rate, but keep it below 92 per cent. This is where most of us cross our aerobic threshold and fat stores are ignored in favour of ready-to-burn carbohydrates. After about an hour at that pace, when stored carbs are depleted and your muscles are left without fuel, you would experience what atheletes call “hitting the wall”. You’d feel weak and light-headed, and your cardio-session would be kaput.

So while crunching numbers may not be your pastime of choice, your calculator may prove more effective than the elliptical trainer when it comes to whittling your waist.

Weight loss is nothing more than a numbers game, and if you’re looking to sculpt a svelte silhouette, it’s one I suggest you play.

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