This past summer when I congratulated Lakewood resident, Lyle Hajdu on completing an Ironman triathlon - swim 2 miles, bicycle 112 miles and run a marathon 26 miles - he factitiously told me his training was designed to increase the number of mitochondria in his muscle cells. Wow, I thought, Lyle understood more about biochemical changes that occur during exercise that I did even though I was a biochemistry major in college, trained as a physician and a modest exerciser. I needed to catch up to his knowledge!
During man's early evolutionary history physical activity was vital to stay alive. Living a hunter-gather nomadic life, man walked and hunted for hundreds of thousands of years. Later, civilized man walked everywhere, to the market, to the well, to hunt, and to plant and harvest crops. Only in the past 100 years when the automobile replaced walking has man become more sedentary losing inherent physical fitness historically needed to survive. Fortunately for some, jobs such as a letter carrier or factory worker keep one physically fit: walking, lifting and standing all day. The rest of us need to exercise to meet the physical exercise our body desires and expects.
There are two types of exercise: aerobic and anaerobic. Aerobic exercise means using large muscles at a comfortable effort for 15 minutes or more. If increased effort or a faster pace is performed in running, bicycling or swimming as examples, labored breathing and muscle discomfort develops, a sign that insufficient oxygen is reaching the muscle. This level of exercise is called anaerobic (no oxygen). During anaerobic exercise, lactic acid, a byproduct of muscle action accumulates in muscle cells which interferes with contraction of muscle fibers. Fatigue, weakness and a desire to quit or slow can ensue.
Regular rigorous exercise produces microscopic and biochemical changes in the large muscles of the human body which can enhance emotional and physical health.
Photo by Robert M. Ungerer
Aerobic fitness can be measured in the laboratory. Oxygen inhaled and carbon dioxide exhaled are measured while running on a treadmill or pedaling on a stationary bicycle at maximum effort. The result is called VO2max or maximum volume of oxygen used per kilogram of body weight per minute. The physically trained individual will be able to consume more oxygen than the untrained because trained muscles are more efficient using oxygen to generate energy to move muscle. Training can double the VO2max compared to that of the untrained.
Training makes the heart pump more blood, increase lung capacity, and promote more oxygen use by muscles to produce energy. For those interested in estimating their own VO2max before starting an exercise program to compare to VO2max after training, a formula using age, time to walk one mile as fast as possible and heart rate at the end of the walk is available online. After listening to Lyle I became fascinated by the changes occurring in a muscle cell produced by endurance training. When a muscle cell is overloaded by effort it senses an oxygen deficit, which results in labored breathing. Microscopic structures in the cell called mitochondria produce energy from oxygen, fat and glucose which is used by muscle fibers to create a contraction. Mitochondria multiply thereby increasing the number of energy producing structures (furnaces) to accommodate increased demands on the muscle. Muscle contraction occurs when protein molecules, actin and myosin, slide over each other. This information is perhaps esoteric but high school biology students learn the specific reactions.
Another benefit of exercise is that it consumes fat such as triglycerides to generate muscle contractions. This removes fat from blood thus helping reduce fat deposits and plaque in coronary arteries enhancing cardiovascular fitness.
Although exercise has great benefits, the anonymous saying, "too much of a good thing can be harmful," also applies to exercise. Over training can contribute to poor performance and numerous physical and emotional symptoms. Endurance athletes learn to take days off and to taper training two weeks prior to a big event.
I recommend the book, "Fitness and Health" by Brian S. Sharkey and Steven E. Gaskill (2007) for greater understanding of physical fitness and to learn exercises for beginner and experienced exercisers. A muscle makeover resulting from regular exercise will have emotional and physical benefits you will enjoy.