Whether you are running, cycling, paddling, performing aerobics routines or using cardio machines, the traditional method for monitoring exercise intensity is to measure heart rate. For the purpose of general fitness improvement, this allows you to determine whether you are working within your aerobic training zone - the intensity that most effectively improves the cardiovascular system without becoming uncomfortable and causing premature fatigue.

However, few people are good at checking heart-rates: they either cannot find their pulse quickly enough to get an accurate reading, or they make any of a number of pulse-taking errors. Also, in order to take a pulse, exercisers generally have to slow down or stop which disrupts their workout.

The other option is to use a heart-rate monitor, but such equipment can be expensive and uncomfortable.

Fortunately, there is an easier, less expensive way to monitor exercise intensity - by simply listening to your breathing.

LOWER AEROBIC ZONE RANGE
You can determine the lower level of your aerobic training zone (that level of intensity is often called the aerobic threshold) by listening to your breathing - when it becomes audible, you have entered the aerobic training zone.

UPPER AEROBIC ZONE RANGE
When are you working too hard? When you are breathing so hard you can no longer carry on a conversation without gasping. This shows that you have passed out of your aerobic training zone and crossed the lactate threshold. You are now in the anaerobic training zone - a level of intensity that results in the buildup, in your bloodstream, of lactic acid and other fatigue-producing by-products of energy metabolism.

BREATHING STUDY
Robert Goode, a respiratory physiologist at the University of Toronto, has confirmed the effectiveness of using breathing to estimate exercise intensity. He performed a study in which 30 subjects pedaled stationary bicycles while heart rates and respiration levels were monitored.

Their heart rates were checked when they were first able to hear themselves breathing. He found that this point corresponded to the lower range of intensity for improving cardiovascular fitness (the aerobic threshold). Even better, this threshold changed depending on the age of the subject - a phenomenon that we know occurs as people age. For example, the aerobic threshold corresponded to about 110 beats per minute for a 65 year-old, and 150 beats per minute for a 20-year old.

Other studies have shown that the lactate threshold corresponds to the level of exercise intensity that causes you to gasp when breathing. The lactate threshold is upper range of the aerobic threshold.

CONCLUSION
If you want to exercise aerobically, work hard enough so you can hear your breathing, but not so hard that you cannot speak without gasping.

REFERENCES
1. Joe Taylor (Editor), Heavy breathing. Active Living, May 1997.
2. Phyllis Gorney Cooper (RN, MN), Editor, for the Aerobics and Fitness Association of America, Aerobics: Theory and Practice, HDL Publishing, 1987.
3. Dick Moss, Editor, Physical Education Update, 2008.