People with diabetes mellitus—rapidly approaching one-third of the US population—either cannot produce insulin (Type 1 DM) or the insulin they produce is ineffective in stimulating the uptake of blood sugar (glucose) into the body’s cells (Type 2 DM). Accordingly, if diabetes is untreated, blood sugar rises to dangerously high levels that can eventually cause blindness, nerve damage, and other complications.
Blood sugar can be controlled by the appropriate administration of insulin and other drugs and/or by the manipulation of dietary carbohydrate and exercise.
During exercise, the contracting muscles produce their own insulin-like effect, causing the rapid uptake of glucose from the blood. In people without diabetes, the body naturally reduces its production of insulin to compensate; otherwise, blood glucose would fall precipitously. (A low blood glucose concentration is known as hypoglycemia.) Those with Type 1 DM (and those with Type 2 DM who use insulin to control their blood sugar) must adjust their pre-exercise insulin dosage and their carbohydrate intake before, during, and after exercise to avoid becoming hypoglycemic.
Regular exercise training is usually beneficial for those with diabetes because exercise can reverse many of the adverse metabolic effects of the disease, including the likelihood of becoming obese.
Although precautions must be taken, athletes with uncomplicated diabetes (no other serious diseases) have become champions at elite levels in a wide variety of sports.
Peter A. Farrell, Ph.D.Department of Exercise and Sport ScienceEast Carolina University
