Losing weight is a bit more complicated than just burning and cutting calories. You can burn 500 calories during a workout, but if these aren’t calories from stored body fat, you’re not optimizing your workouts. Burning muscle tissue for fuel is obviously not a desirable outcome, so it’s important to use the right exercises to help minimize muscle loss and maximize fat loss. The best cardio workout for fat loss depends on your physical fitness level. If you’re in pretty good shape with a healthy body mass index (BMI), you can try high-intensity interval training, or HIIT. But if the last time you exercised it was to N'Sync's first cassette tape, you may want to try a low-intensity fat-burning cardio workout to start.
Interval training done at a high intensity burns a substantial number of calories since you’re working out a vigorous pace. HIIT involves doing a short work interval at a high intensity followed immediately by a short rest interval. Your target heart rate for HIIT should be between 80 to 100 percent of your maximum heart rate, or MHR. Your MHR is 220 minus your age. The key to HIIT working to reduce body fat and maintain lean muscle mass is to make sure you exercise at full tilt -- don’t hold back. An effective HIIT cardio workout may include sprinting for 10 to 15 seconds followed by lightly jogging or walking briskly for the next one or two minutes. Repeat this rest-and-work cycle for 20 or 30 minutes total.
The advantage of low-intensity exercise is that your body actually burns a higher percentage of fat calories compared to high-intensity exercise. This is the whole idea behind the "fat-burning zone" you may have heard about. You enter the fat burning zone by exercising at about 60 percent of your MHR. The key here is to maintain a steady heart rate over a long duration to maximize fat loss. Low-intensity exercise doesn’t promote muscle loss or build up of lactic acid and cortisol. You can try any number of cardio workouts to get your heart pumping at 60 percent MHR, including walking briskly, elliptical training or cycling. About 60 percent of the calories you’ll burn will be straight from jiggly body fat. So, if you burn 300 calories walking for a half hour, about 180 of these will be fat calories.
As the body fat begins to noticeably melt from your hips and thighs over the first four to six weeks of training, it’s important to increase the intensity and/or duration of your workouts to continue the fat loss. For example, if you started out using the low-intensity fat-loss strategy, try integrating HIIT into your weekly workout regimen – maybe swap out one low-intensity exercise per week with an HIIT workout. If you’re already using HIIT, add one or two more rest-and-work cycles to your workout every couple of months.
Signs of Muscle Loss
Steady-state exercise done at a moderate pace can improve your cardiovascular health and reduce your body weight, but it can also lead to a higher percentage of muscle loss compared to low-intensity or vigorous workouts. If you notice a buildup of lactic acid in your muscles following a cardio workout – a feeling of burning in your muscles – it may be a sign you’re working out at the wrong intensity. To avoid this problem, monitor your heart rate during your cardio workout and adjust your intensity accordingly. Another sign of muscle loss is rapid weight loss exceeding a pace of about 2 pounds per week. You can also simply look in the mirror to determine if you’re losing muscle. If your body is trending toward looking like an Olympic marathon runner instead of a sprinter, you may be burning muscle in addition to body fat.
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