Exercise Training for Diabetes: The “Strength” of the Evidence

Exercise is an essential component in the treatment of diabetes mellitus. Lifestyle factors affect the prevention, development, and treatment of diabetes mellitus and its close relation, the metabolic syndrome (1). The Finnish Diabetes Prevention Study (2) and the Diabetes Prevention Program (3) tested lifestyle interventions that included a physical activity program. Both studies showed the power of exercise, nutrition, and weight loss to prevent diabetes mellitus in at-risk individuals.

However, exercise comes in several flavors, and the clinician should think critically about the effects of different types of exercise training. It is useful to think of exercise training as a drug with a specific dose–response relationship (4). For example, exercise can be delivered in various “doses”: differing number of sessions per week (frequency), number of minutes per session (duration), or degree of effort (intensity). Exactly how to quantify the dose of exercise, and how different doses influence cardiovascular, musculoskeletal, or metabolic outcomes, are among the most important current issues in exercise science (5, 6).

In addition to dose, the type of exercise is important. Endurance exercise involves repetitive, rhythmic contraction of large muscle groups, as occurs in running or cycling; it also called aerobic exercise because it depends predominantly on oxidative energy sources to produce adenosine triphosphate. Strength training, also called resistance training, generally involves relatively slow, intense contractions at high force; weightlifting is the most common example. These types of exercise are similar in some ways but have important differences. For example, according to elegant studies done at the Copenhagen Muscle Research Center, little blood flows through muscle during muscle contraction, even during aerobic exercise (7). Nevertheless, endurance exercise (high frequency, multiple repetitions, and low force) induces alterations in contractile protein isoforms of skeletal muscle and stimulates mitochondrial respiratory enzymes and specific …