It’s no secret that you lose muscle strength and mass with age. In fact, the loss of muscle tissue begins as early as age 30 and continues throughout life, speeding up after menopause. How much muscle can you lose? If you’re sedentary, about a third of a pound a year after the age of 30. This adds up to significant muscle loss over time, about 40 to 50% of your muscle tissue by the time you’re 80. As you might expect, muscle loss is greater in people who don’t resistance train. What you might not realize is that your muscle fiber composition changes as well.
Two Types of Muscle Fibres
We have two main types of muscle fibres, slow twitch and fast twitch. The former are more resistant to fatigue and are what we use when we do endurance activities like walking or lifting light weights, many times. The latter, fast twitch fibres, are used when we need to generate force quickly like sprinting, lifting heavy weights or recovering from a stumble. Unlike slow twitch fibres, these ones fatigue easily.
Muscle Fibres and Aging
What does all of this have to do with the aging process? You don’t lose fast-twitch and slow-twitch fibres to the same degree. You lose more fast-twitch fibres as you age relative to slow-twitch. What happens is the nerve supply to fast-twitch muscle fibres dies off and a fibre that once had fast-twitch capabilities is converted to a slow-twitch fibre. While you still have a functioning muscle fibre, the fibre is now an endurance fibre. Unfortunately, it’s no longer designed for strength and power generation. As more and more fast-twitch fibres are converted to slow-twitch ones, you lose strength AND the ability to generate power.
What is Power?
Power is an aspect of strength that has a time component to it. It is our ability to generate force, quickly. Losing strength is bad as you reduce your ability to lift things up, including your own body. But losing power has a more protective aspect for us. Unless you have power, if you trip while walking on the sidewalk you have no ability to catch yourself and recover. Balance is one aspect of that, but power is an essential other one.
The importance of Power Training
While any form of exercise is better than sitting in a chair, most are not enough to maintain our fast twitch muscles. To reduce the loss of fast twitch fibres you have to stimulate them. Walking doesn’t do that, nor does slow and steady resistance training. What does target them is heavy resistance training and training using lighter weights at a faster pace (ie. kettle bell swings, snatches etc).
The importance of Sprint or High Intensity Interval Training
High intensity interval training (HIIT) or Sprint Interval Training (SIT) are also two other ways to stimulate the fast twitch fibres.
SIT has you doing any physical activity you can as quickly as you can for about 30 seconds. If you are doing true SIT, it is a 10/10 effort; you are at 100% of your capacity; you finish with nothing left to give. It should take you a couple of minutes to recover before you can do it again.
Whereas HIIT has you at about 75-80% of your capacity for 30 seconds, up to 3 minutes. At the end, you have a little left to give, but not much. You need to recover, but it happens faster than with SIT. Essentially both mean you are moving quickly and ideally you are moving your own body around, rather than a machine so you get the full benefit.
Examples would be sprinting, jumping, skipping, boxing, kettlebell swings etc
Conclusion
Power capabilities are important at any age but they become even more vital as we age. Having more power can mean the difference between falling and breaking a hip and staying functional.
As you age, you have to worry about losing muscle mass AND functionality, especially the ability to generate power. Keep lifting heavy weights at a slow to moderate speed to build strength and size but once you feel confident also include sets where you lift lighter and at a fast speed or try to add in some plyometrics or speed work that works for you.
