Imbalanced Exercise Training – Ask most people over the age of 50 what type of exercise they do, if they exercise at all, and they’ll likely tell you they walk. While brisk walking is a decent cardiovascular exercise and a good stress reliever, focusing only on walking isn’t necessarily optimal for your health and physique.
Then, ask a few people over 50 whether they train with weights. If they do, and most don’t, they probably use lighter weights and do higher reps. At least they’re doing something, but they’re not fighting the aging process to the degree that they should be! That’s where weight training comes in.
Muscle Loss with Aging
It’s no secret that we lose muscle mass and strength as we age. What fewer people know is that we lose more of one muscle fiber type than the other. We broadly classify muscle fibers into two classes: type 1 muscle fibers and type 2 fibers. Type 1 muscle fibers are referred to as endurance fibers because they don’t fatigue easily and are optimized for long periods of submaximal exercise like walking or light jogging. These fibers do, however, lack the ability to generate significant strength or power. In contrast, type 2 muscle fibers are built for strength and power. They contract with force and can do so quickly. Unfortunately, they also fatigue fast too. You mainly use these fibers when you lift heavy weights, perform a power move, or sprint for a short distance. Think quick and powerful!
Of course, we want to retain as much muscle mass and strength as possible as we age because it’s strength and power that helps us get around, get the most out of life, and avoid becoming weak and frail. Having more muscle mass is also linked with better metabolic health and a lower risk of developing metabolic syndrome and type 2 diabetes. Insulin sensitivity declines with age, partially due to a loss of muscle and a rise in body fat. With age, the number and size of muscle fibers decline. Interestingly, loss of muscle strength and mass is greater in men than in women, especially in the muscles of the lower body.
All isn’t equal in the world of muscle aging. The loss of muscle tissue as we age affects one fiber type more than the other. As the years go by, it’s type 2 muscle fibers that take the biggest hit, the ones you need for strength and power. In contrast, type 1 fibers are better preserved. What happens is this. With disuse and aging, the motor neuron that hooks up to a type 2 fiber disconnects from the fiber. Then, a motor neuron that innervates a type 1 fiber steps in and connects up with the abandoned type 2 fiber, converting it into a type 1 fiber. So, you lose type 2 power and strength fibers and replace them with endurance fibers that lack strength and power.
It’s not hard to see how this process could lead to functional impairments. It takes strength and power to simply rise from a chair. You have to have power capabilities to generate the momentum to propel your lower body up and off the seat. So, you need strength and power and that comes from type 2 fibers. You also need muscle power to move your body into position to catch yourself should you start to fall. Lose too many of those type 2 fibers and you’ll lose function and become frailer.
Avoid Imbalanced Exercise Training
Based on what happens with age, it’s easy to see why many older adults are either not exercising or doing the wrong kind of exercise. Walking is good for cardiovascular health but it won’t preserve type 2 fibers, the ones you lose most of with age. In reality, an adult should devote a higher proportion of their training time to activating the type 2 fibers – not walking. You do that with challenging resistance training and power moves.
Why weight training? When you lift a weight, you recruit the low-threshold, type 1 fibers first. Type 2 fibers, the higher threshold ones, come into play when the type 1 fibers need extra reinforcement. If the weight is light enough, you recruit only low-threshold, type 1 fibers. However, if you keep lifting a light weight, the type 1 fibers will eventually fatigue and call upon the type 2 fibers to pick up the slack. So, it’s possible to challenge the type 2 fibers enough to elicit growth with lighter weights, as long as you take the exercise to fatigue.
Another way to target the fast-twitch muscle fibers is to simply lift heavy. Choose a weight that’s a high percentage of your one-rep max, preferably 80 to 90% so you’re focusing on strength. By doing this, you’ll quickly recruit and challenge your fast-twitch muscle fibers. Heavier weights and muscle fatigue are your friends when it comes to training your fast-twitch fibers.
Imbalanced Exercise Training: Add Some Power
Type 2 fibers are also power fibers. Power is simply force divided by time, doing a repetition in a shorter time frame boosts power. To make a movement more powerful, use a lower resistance, around 60% of one-rep max and increase the tempo of the rep. Training for power is every bit as important as training for strength. Power moves will help you to avoid imbalanced exercise training and preserve fast-twitch muscle fibers developing the skill you need to rise out of a chair quickly and with force.
The Bottom Line
Now, you know why it’s important to devote time to strength and power training and to avoid Imbalanced exercise training. You naturally retain more type 1 muscle fibers than type 2. In fact, you gain type 1 muscle fibers as the reorganization of the existing fibers takes place. Aerobic exercise is still important but don’t neglect strength and power training to challenge those type 2 fibers.
J Gerontol A Biol Sci Med Sci. 1995 Nov;50 Spec No:11-6.
Curr Opin Rheumatol. 2012 Nov; 24(6): 623–627. doi: 10.1097/BOR.0b013e328358d59b
University Health News. “How to Prevent Sarcopenia or Age-Related Muscle Loss”