Aerobic vs. Anaerobic


  • Presidents day is Monday 2-21-11. No class that day.

UNR Triathlon Club is open to all levels of ability. We meet 4 times per week for 70 min. workout. Come try it for free for week. You just need a Lombardi Pass. The fee is $200 per semester.

Aerobic vs. Anaerobic

As you exercise your body is using different fuel at each level of intensity. That’s because the body requires two oxygen molecules to metabolize one molecule of fat. As the pace increases and working muscles are using more and more oxygen the body switches to carbohydrates. Carbohydrates require only one oxygen molecule to be metabolized as fuel. So, when you are working harder, you burn more carbohydrates and when you are going easier you are burning more fat. You may have heard the term conversation pace. If you are able to talk and exercise at the same time, then there is enough available oxygen to burn fat as fuel and talk at the same time.

The body has an unlimited supply of fat, even the skinniest person has enough fat stored to burn as fuel for several days. The trick is unleashing it through training. To do this, one must spend most of his or her training aerobically. Other sessions above this zone are also required but usually less then 1 hour per week. These are done at or above the anaerobic threshold. Anaerobic threshold(AT) is the point at which your body goes from using fat as its primary fuel source to glycogen. This occurs at 80% to 90% of your max heart rate in most cases.

Training at or near your anaerobic threshold(AT) for several hours per week is the most efficient way to improve performance, but only after a sufficient base is established. The best way to find your Threshold is to have a Vo2 max test done. This will identify which training level or heart rate you become anaerobic. Having a lab test performed can be expensive. If your resources are limited you can estimate AT by subtracting 12 to 15 beats from your max heart rate. This will give you a good ballpark figure.

You can also estimate your AT by using your recent race results. For example, a trained runner’s AT pace is usually 10 seconds per mile slower than their 10k pace. This pace lies just at the cusp of anaerobic metabolism, and can be performed continuously for one hour.