Sports Nutrition Part 1: Muscle Function and Hormones
Would you like to get more out of your workout? How about increasing muscle strength, power and speed? Exercise is the key but nutrition plays a critical role in making the exercise pay off. This three part column will show you how to maximize your hormonal systems for the greatest athletic gains, detail the critical elements of sports nutrition and supplements, and tie it all together by focusing on specific nutrients taken before, during and after your workouts.
In order for muscle to work there must be a fuel supply. When muscles contract the energy is taken from the breakdown of a chemical called adenosine-tri-phosphate or ATP. ATP gives up a phosphate in the process to become adenosine-di-phosphate. There are three different systems in the body to produce and replenish ATP stores.
Endurance activities such as walking or running produce ATP slowly, but efficiently, utilizing oxygen via the “aerobic oxidative” process. Aerobic energy production happens deep inside muscle cells in “generators” called the mitochondria. The fuel for oxidation is glucose but there is only enough in the bloodstream for a few minutes of activity before the levels drop. At this point the body will need to produce more glucose from the breakdown of stored glucose polymers, called glycogen, found in the liver and muscles. As glycogen stores run out the body will also start breaking down protein, which the liver then converts into more glucose. Stored fat is finally broken down into fatty acids and delivered directly to the mitochondria for ATP production.
Strength building activities such as weightlifting and explosive sprinting or jumping require large amounts of energy produced very quickly. For this the body uses two different anaerobic pathways, which do not require oxygen. The first is the “phosphagen” pathway, in which a storage chemical called creatine phosphate (CP) provides an immediate source of phosphate for ATP production but runs out after about 10 seconds.
The second anaerobic pathway is the “glycolytic” pathway, which produces ATP by breaking down stored glycogen and glucose in the muscles. It kicks in a bit slower than the phosphagen pathway and runs out after about 90 seconds with lactic acid as a by-product. The lactic acid can build up causing muscle fatigue if it is not flushed away in the blood stream quickly enough.
Hormones and Muscle Growth
Hormones are chemical messengers that control most bodily functions, including metabolism and muscle growth. “Catabolic” hormones help breakdown tissue to provide fuel for exercise while “anabolic” hormones stimulate muscle and tissue growth. By supplying the right nutrients at the right time we can encourage the beneficial anabolic hormones to build more muscle while discouraging excess and even damaging effects from the catabolic hormones.
Catabolic hormones include adrenalin, glucagon and cortisol. At the onset of exercise the adrenal gland starts pumping out adrenaline to increase heart rate and blood flow. After the immediate blood supply of glucose is used up adrenalin stimulates the breakdown of glycogen from the liver and muscle (glycolysis) and the breakdown of fat for fuel.
Glucagon is made by the pancreas in response to low glucose and exercise, and like adrenaline it stimulates glycolysis and fat breakdown, but also turns on glucose production from amino acids and lactic acid supplies. Cortisol does all the above, plus causes the breakdown of muscle protein. Cortisol is in charge of controlling inflammation and during exercise torn muscle fibers cause inflammation. With more intense exercise cortisol can actually lead to muscle loss.
Anabolic hormones include insulin-like growth factor (IGF-1), testosterone and insulin. IGF-1 is produced in response to exercise, especially the high-intensity anaerobic phosphagen pathway type, and causes an increase in bone, cartilage and muscle growth.
Testosterone is the main anabolic hormone causing bone and muscle growth. It will counter-act cortisol thus preventing its muscle wasting effects. Testosterone stimulates protein production and slows protein breakdown thus leading to increased muscle size and strength. It will rise a bit during exercise but is not particularly the main anabolic hormone associated with exercise.
Insulin may be most important hormone for increasing strength and muscle mass while also speeding recovery from intense exercise. It is made by the pancreas in response to high glucose levels and is known as the “storage hormone” because it stimulates muscle and liver to take up excess glucose and rebuild glycogen stores. It also encourages the synthesis of fat from excess glucose, particularly during rest. Chronic elevations of glucose from too much sugar and refined carbohydrates, combined with not enough exercise, can lead to excess fat accumulation, obesity, and diabetes. But there is much, much more to insulin…
You may not believe what I’m about to write – sugar can actually stimulate the development of muscle and help minimize muscle breakdown, by causing insulin release. During exercise and for a few hours afterward the muscles are very sensitive to insulin. Insulin will turn on the genetic signals to make protein while preventing protein breakdown. It also encourages uptake of protein building blocks called amino acids into the muscle cells.
Insulin blocks the muscle wasting effects of cortisol and helps the immune system stay healthy by blunting the immuno-suppressing effects of cortisol. Furthermore, insulin is known to double the blood flow to exercising muscle, thus improving the delivery of oxygen and nutrients while helping remove toxins such as lactic acid and carbon dioxide.
Aerobic activity will increase the number of mitochondria in the cells, the size and strength of the heart, and the circulation that supplies the blood (thus oxygen) to the muscle, leading to increases in endurance and stamina. Anaerobic activity will increase the size of the muscle fibers and the organized contraction of more fibers leading to increases in strength, speed and power.
By understanding how muscles work and the role of hormones you can start to make sense of why the right nutrients at the right time can improve your workout.
In part 2, I’ll explain the macronutrients (protein, carbohydrates and fats), the micronutrients (vitamins, minerals and anti-oxidants) as well as sports enhancing supplements. Part 3 will put it all together into a formula designed to make your workout nutrients work for you!
Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine. He specializes in bioidentical hormone replacement for men and women, thyroid and adrenal disorders, fibromyalgia and other complex medical conditions. He is founder and medical director of the Integrative Medicine Center of Western Colorado (www.imcwc.com) and Bellezza Laser Aesthetics (www.bellezzalaser.com). Call (970) 245-6911 for an appointment or more information.