From: Dr. Louis W. Jankowski

Subject: Exercise for diving fitness

In response to the question asked by T.J. Adams in HYPBAR-LIST:

Based on some very old data from Goff et al published in the J.A.P. back in the 1950's the Oxygen cost of underwater swimming with SCUBA at a speed of just under one knot is close to 2.0 liters per minute. For a 70 kg person that comes down to about 28.6 ml/kg min-l or just over 8 METS. Extrapolating from these data one can estimate that the absolute minimum safe fitness level required to avoid excessive fatigue and/or a high proportion of anaerobic work while diving should be at least 10 METS or 35 ml/kg min-1. Obviously a greater physiological reserve would be all the better. For example a highly fit diver with a physical work capacity of 16 METS could theoretically swim underwater for a full hour before feeling the onset of fatigue, while the "warm water bottom scratcher" with their 10 met capacity would do well to limit their swimming speed to about half a knot.

Divers who maintain high levels of physical fitness are ideal dive buddies since a highly fit person would be more effective while towing a tired buddy through a strong current or a long way back to shore. The second portion of the question asked about ideal exercises for diver fitness and the answer is NOT swimming which often surprises divers.

Swimming is primarily an arm exercise which we normally do while breath holding or at least consciously limiting the normal respiratory frequency and pulmonary ventilation. SCUBA diving is a leg exercise and SCUBA divers must never hold their breath, limit their ventilation, or "skip breathe." The principle of specificity applies, in applies, in that the best exercise for training divers would be swimming with fins while snorkeling on the surface. In some small pools tethered swimming devices, which employ elastic ropes or surgical tubing for resistance, are sometimes used as training devices. Dry land exercises include mobile or stationary cycling, jogging, rope skipping or stair climbing.

The bottom line is simply to use the same muscles in the same way one would while SCUBA diving. Exercises designed to improve muscular strength and muscular endurance as well as flexibility are all good supplements to the basic aerobic leg exercise program. A diver who trains regularly to maintain a high physical work capacity is or is on the way to becoming a leaner and more muscular individual.

These physical characteristics translate to additional benefits in terms of smaller wet or dry suits, less buoyancy and therefore less weight required to attain neutral buoyancy in cold water. At the recent UHMS meetings in Seattle one investigator reported that divers frequently suffer from lower back pain. While we sometimes think that death, taxes, and backaches are the inevitable consequences of being human, the best defense against back-pain is to maintain a healthy and strong abdominal musculature.

Back in the 1950's Krauss and Weber reported that 96% of their patients with chronic back pain were relieved when they could do 25 sit-ups. Since divers are prone to back pain it seems reasonable to take some defensive action in the form of abdominal muscle training. Thanks your interest I was becoming convinced that the modern diver had all but forgotten the need to be physically fit.