As a result of aerobic exercise
Some remarkable things are happening at the level of the muscle cell as you become more aerobically fit. These are:
•There’s an increase in a substance called myoglobin which stores oxygen and helps escort it from the blood stream to the mitochondria (the cell’s power house) during exercise. The higher your myoglobin supply, the better your aerobic endurance.
•Mitochondria increase in size and number. This means your cells are capable of burning nutrients, including fat, more efficiently.
•Your muscle fibers develop a greater capacity to build up and store fat-burning enzymes , a special chemical that encourages your muscle fibers to burn fat for energy. In short, your muscle fibers are now capable of using up more fat.
•Aerobic exercise increases your VO2 max (your aerobic capacity), and this in turn enhances the ability of your muscles to better combust fat as
fuel. At the cellular level, the breakdown of triglycerides speeds up, and they’re released faster from fat cells. So the better trained you are aerobically the better your body can burn fat.
Certain muscle fibers also undergo important changes in composition. Your muscle is composed of two types of muscle fibers: slow-twitch fibers and fast-twitch fibers. Slow-twitch fibers contract at a relatively slow speed, compared to the fast-twitch variety and are used for endurance type
exercises such as long distance running. Of all muscle fibers, the slow-twitch variety have the most mitochondria in them. Slow-twitch fibers burn fat for energy.
Fast-twitch fibers contract quickly and are called into play during strength and power activities. It can burn fat for energy to power muscular contractions. Long-duration, high-intensity aerobics and high-intensity weight training, increase the total number of mitochondria in fast-twitch fibers to levels higher than those found in slow-twitch muscle fibers. By increasing mitochondria inside these muscle fibers, you turn your muscles into super fat burners.
Aerobic exercise makes your heart muscle pump with greater force. As the heart works harder, it becomes stronger. It does so by increasing in size, causing several positive conditions:
•Your heart can pump more blood with every beat.
•Your heart can recover faster after exercise.
•You gain a lower resting heart rate.
•There’s greater blood flow to exercising muscles; therefore, more oxygen is available
As a result of weight training
There are three types of muscles in your body: skeletal muscles, which is used for movement of the skeleton; smooth muscles, which lines internal
organs and intestines; and heart muscles. They all work the same way—contracting and relaxing. This is possible because the fibers that make up muscles can shorten their length by 30 to 40 percent.
Skeletal muscles represent the largest soft tissue mass in your body, comprising some 660 muscles and about 15 to 40 percent of your weight, depending on your muscular fitness. They contract when stimulated by nerve impulses and relax when the impulse is gone. The smooth muscles and the heart muscles aren’t under such control, but have their own mechanisms and contract without needing instructions from nerve impulses.
The muscle of interest to exercisers are the skeletal muscles. Skeletal muscles get larger and firmer because of the effect exercise has on muscle fibers.
Technically, muscle growth is known as muscle hypertrophy, which means that an individual muscle fiber gets bigger as structural changes take place inside it. When you build muscle, you are essentially increasing the amount of contractile proteins in your muscle fibers. This makes the muscle fibers increase in diameter, get stronger, and generate more force when they contract.
Exercise causes microscopic tears in your muscles. By lifting a weight, you force the muscle to lengthen when it wants to contract. This literally tears apart the tiny structures of the muscle which causes muscle soreness you feel 24 to 48 hours after a workout. Inflammation sets in, and immune systems cell rush to the scene to repair the damage. The tissues are restored in the process. But an interesting phenomenon takes place—the body makes the muscle fibers bigger and stronger to protect itself against future trauma. The building material for this growth and repair process comes primarily from protein, broken down in digestion into amino acids. They enter the bloodstream and are transported to cells to be resynthesized into body proteins.
Exercise builds bones and connective tissues, too. When you place stress on your bones with activity such as weight training, more bone-strengthening minerals are deposited within them. Consequently, bone width and bone thickness both increase, and your bones get stronger.
Although the exact mechanism hasn’t been identified, connective tissues such as joints, ligaments and tendons get stronger and denser as a result of exercise.
Taken together, these changes and those occurring inside and around muscle fibers greatly enhance your exercise
performance and overall health.
