It can be argued that time is a valued commodity. Even so, keeping up with regular cardio workouts is a must for any fitness regimen – especially when it comes to weight loss. And despite how much time one sacrifices for a workout, skipping cardio-specific exercises can actually lower the quality and intensity of a workout. In order of intensity, below are the most effective cardio workouts for improving cardiovascular fitness and burning fat. 

Long, Slow Distance (LSD) Workouts

A low-intensity workout lasting at least 60 minutes in length cause many adaptations that increase aerobic fitness and burns fat; these include: an increase in the number of red blood cells and hemoglobin, a greater capillary network for a more rapid diffusion of oxygen into the muscles, and an increase in the amount of mitochondria in the muscle – all of which change the metabolic profile of one’s muscles, turning them into better fat burning machines. LSD workouts can utilize any cardio-targeted equipment, ranging from a treadmill and bike, to the elliptical or rowing machines; the more muscles involved and the more weight-bearing the exercise, the more calories burned. 

Lactate Threshold Workouts (LT)

The lactate threshold represents one’s highest sustainable exercise intensity, and demarcates the transition between exercise that generates purely aerobic energy versus a combination of aerobic and anaerobic metabolic energy output. LT workouts raise the lactate threshold to a higher percentage of the maximum heart rate, increasing aerobic fitness. These workouts are also great fat burners as they cause the highest rate of fat use. 

The lactate threshold is approximately 80 percent maximum heart rate for unfit people and about 85 percent max for those aerobically fit; subjectively, the workout should feel comfortably hard. It is recommended to engage in continuous workouts for 15 to 20 minutes at lactate threshold intensity or employ five minute segments with one minute recovery intervals. 

Interval Workouts

Interval workouts alternate high-intensity work periods with low-intensity recovery intervals.  Aerobic interval workouts target the cardiovascular system by increasing one’s maximum stroke volume (volume of blood the heart pumps with each beat) and cardiac output (volume of blood the heart pumps each minute), along with increasing muscle power by recruiting fast-twitch muscle fibers – thus sculpting the body; the more intense the workout, the greater and longer the post-workout elevation in metabolism, which burns more calories the rest of the day.

For cardiovascular intervals, exercise for three to five minutes at 95 to 100 percent max heart rate with recovery intervals equal to or slightly-less-than the time of the work periods. For anaerobic intervals, exercise at slightly-less-than an all-out sprint for 20 seconds to one minute with recovery intervals two to three times as long as the time of the work periods. 

About the Author

Dr. Jason Karp is a nationally recognized speaker, writer, exercise physiologist and owner of RunCoachJason.com, a state-of-the-science running coaching and personal training company. He holds a Ph.D. in exercise physiology and is founder and coach of REVO₂LT Running TeamÔ and Dr. Karp’s Run-Fit Boot Camp in San Diego. He writes for international running, coaching, and fitness magazines, is the author of "How to Survive Your PhD," "101 Developmental Concepts & Workouts for Cross Country Runners," and the forthcoming "101 Winning Racing Strategies and Women’s Running Bible."  To get in the best shape of your life, contact Dr. Karp at jason@runcoachjason.com.