Is Muscle Mass the Key to Preventing Aging?
Research has proven that as humans age there is a decrease in muscle fibers and muscle fiber size. Almost all of this decrease occurs in what are known as Type II (fast-twitch) muscle fibers. The number and size of Type I (slow-twitch) fibers are not decreased nearly as much. Type II fibers are large and produce high levels of force for short periods of time and fatigue rapidly. Type 1 fibers are smaller and can produce lower force levels but are highly resistant to fatigue.
This loss of muscle is called sarcopenia – meaning “abnormal reduction”. It occurs for two reasons: first because individual muscle cells, aka muscle fibers, shrink and eventually die off. Because fibers are bundled together, when individual fibers shrink, the whole muscle loses size. In addition, every muscle fiber has a nerve, called a motor nerve, which innervates it. The motor nerve and the muscle fibers it controls are called a motor unit.
As we get older, motor nerves and associated muscle fibers die off. A small percentage of these fibers are rescued by nearby motor units. This process occurs when slow-twitch fibers rescue fast-twitch fibers and change them into slow twitch fibers. So not only do we lose total number and size of fibers, there is a net percentage loss of fast twitch fibers with aging.
The result is that we become weaker as we age. Once we go below a certain strength threshold we can no longer maintain activities of daily living, and we become chair or bed-bound. Once we stop standing and walking the body’s physiology rapidly declines. Although the problem starts with muscle loss, muscle loss becomes a catalyst for overall systemic degenerative issues including
Loss of insulin insensitivity (this is what snowballs into adult onset diabetes)
Osteoporosis (bones rely on muscles pulling on them to maintain strength and density)
Reduced cardiovascular capacity and endurance (muscles create the demand that keeps the cardiovascular system functioning properly)
Digestive issues (movement is key for proper digestive function)
Mental health – movement is key to the proper functioning of the brain and nervous system and depression that often accompanies aging can be eliminated through proper exercise.
Hormonal health – loss of muscle equals decreased testosterone and growth hormone which dramatically accelerate aging
Resistance Training to the Rescue!
Resistance training has an extremely positive effect on all aspects of the neuromuscular and biochemical decline that occurs with aging! Specifically, resistance training (and NOT cardiovascular/endurance training) increases the size of Type II (fast-twitch) muscle fibers and the ability of the motor nerves to recruit those fibers. Resistance training also increases the ability of fast-twitch muscle fiber’s ability to repair themselves.
Resistance training increases testosterone and growth hormone, and it increases blood glucose utilization (helping to eliminate insulin resistance).
The great news is that ANYONE, regardless of age or fitness level, can do some form of resistance training and reap its many anti-aging benefits! There are many different forms of resistance training from bodyweight exercise, to using resistance bands, to free weights (dumbbells and barbells), to selectorized weight training machines that are safe and effective for even the most deconditioned seniors to use.