LACTATE THRESHOLD > Choose a cardio training method, and warm up for 10 minutes. Then do a two-minute interval at 60 to 85 percent of your maximum heart rate, aiming for a level of intensity that is challenging but can be sustained for the length of the interval. (If you use a heart-rate monitor, visit http://www.active.com/fitness/calculators target=_blank>active.com/fitness/calculators to determine your max.) Back off the intensity to an easy pace for two to three minutes; then repeat. Do five or six intervals at the same pace, followed by a 10-minute cool-down. As you improve, gradually boost the intensity. You can also increase the interval time to up to three minutes.