Many gym-goers naturally gravitate toward moderate-intensity cardio sessions, assuming they’re working hard enough to see results. But you’re probably not getting the most out of your workout if you’re not monitoring your heart rate and considering your anaerobic threshold (AT), the point at which your body shifts from aerobic to anaerobic activity and starts burning primarily carbs as fuel. (For details on why this matters, go to “The A.T. Factor“.)
The most accurate way to determine your AT requires a heart-rate monitor and professional assistance (like the assessments available at many health clubs).
If that’s not in your budget, this do-it-yourself method can provide a good estimate — and help you get closer to meeting your fitness goals.
1. Warm up for three minutes on your preferred cardio equipment — bike, treadmill, or elliptical. Stop completely and step off the machine for 30 seconds of recovery before starting step 2.
2. Gradually increase your intensity over a 10-minute period, paying close attention to how you feel. Keep going until your breathing is heavy and you can’t speak more than a few words at a time.
3. Stop your workout and take your pulse for 10 seconds. Multiply that number by six; this is an estimate of your AT. For example, if you count 25 beats in 10 seconds, your AT is around 150 beats per minute (25 x 6).
To Work Out
• Try to stay below your AT for 80 percent of each workout to burn fat, and just above it for 20 percent of the time to improve fitness. (For help determining your heart-rate zones based on your AT, see “The A.T. Factor“.)
• Retest every six to eight weeks to maintain an accurate measurement. Your AT is a highly individualized number; it will decline as you age and change based on your overall fitness level at any given time.