Most of the time when we are diving, we are relaxed and swimming slowly, doing little more than finning along the reef. The level of fitness required for those circumstances is only slightly higher than that required to sit on your couch and watch TV. But there are times when a diver needs to swim harder to counteract an unexpected current or aid another diver, and that is when the divers overall level of fitness becomes a concern.
Recent research conducted by Dr. Petar Denoble at DAN indicates that 26 percent of all dive fatalities over a 10-year period were caused by cardiac events. Divers were succumbing to cardiac arrest in the water and the ability to rescue those divers was almost nonexistent. In a separate analysis of data conducted by Dr. Neal Pollock and Allison Ma for DAN, 48 percent of the divers who died over a three year period were found to have a body mass index greater than 30, putting them in to the obese category.
You can calculate your overall fitness by determining your exercise capacity. A MET is a standard metabolic equivalent of exercise. You’ve probably seen a MET rating on a treadmill at the gym. While there is some debate among diving physicians, divers who have undergone cardiac surgery are often required to reach a MET rating of 13 during a stress test before returning to the water. Many physicians, though, believe the ability to achieve a rating of 10 METs is adequate for the average diver. This is considered to be adequate for a moderately active lifestyle.
There are various methods to determine your maximum MET rating, called a METmax. The most accurate is a stress test at an exercise lab, but those are expensive and difficult to come by. A more basic tool for a general assessment of fitness is the University of Houston Non-Exercise Test for Predicting VO2max. (see Resources section below) This formula can help you determine your exercise capacity by estimating your level of physical activity and comparing it to your age and your body mass index. You determine your VO2max, and from there determine your METmax. Remember, though, this is just a guide and should only be used to help you get started on an exercise regimen that will help you be prepared to make the dives you want to make. Also, you should consult a physician before beginning any exercise program.
Download a form to help you assess your METmax here (PDF).