USAWA

AGING AND STRONG

Part II: The Effects of Aging 

By Dan Wagman, Ph.D., C.S.C.S.

Ever since I got involved in all-round weightlifting I developed an interest in the aging and strength issue. This because of the age adjustment formula used and how arbitrary and capricious it appears to be. Still, just about anybody will tell you that as you age your performance declines. If this is true, to what extent might your strength decline? There are literally thousands of scientific studies on the topic of aging. As strength athletes our focus is on muscle. And with all those studies the human brain isn’t capable of determining the proverbial bottom line. For that reason, statisticians have developed a technique called meta-analysis. This method of data analysis allows researchers to input all sorts of information from an unlimited number of studies and on the other end come up with that elusive bottom line, such as whether your inescapable increases in age will make you weaker.

The Basics

The place to start is to develop an overall understanding of whether healthy non-athlete people lose strength as they age, then to ask what effects lifting weights might have. Some of the findings for non-athletes were presented in Part I.  But if you looked at all of the relevant research on muscle strength and activation between young and older people, then perhaps you could find out what the bottom line is. A group of researchers from Marquette University and the University of South Australia collaborated to find out.(4)

So how do you test an old muscle compared to a young one? The two most reliable ways are called the interpolated twitch technique (ITT) and the central activation ratio (CAR). Don’t worry, I won’t bore you to death with the details of these methods, but I do believe that you’ll find the basics of at least ITT interesting. What researchers do is have a subject, say a 25-year old, perform a maximal isometric contraction against an immovable object and take a reading on that muscle. Then, during that maximal contraction they deliver an electrical stimulation to that muscle’s main nerve. If additional force or activation is generated, that means during the subject’s own maximal contraction the muscle received inadequate neural input and thus contracted submaximally, and of course you can measure the difference. Then you repeat with a 60-year old and see to what extent, if any, the older person’s muscle contracts with less neural input. If that happens, then you know that aging could impact muscle activation.

There are, of course, other considerations to bear in mind, which is why the researchers set specific standards all of the studies had to meet to be included in their meta-analysis. Besides using only ITT or CAR studies had to look at young people between 18 and 35-years and those 60 and older, the study had to be published in English, only studies with the lowest bias risk were considered, etc.

A General View

As a whole, age made no difference in muscle activation capability in a healthy non-athlete population of men and women. As an example, 18 studies looked at the biceps with the age in the young people ranging between 19.9 to 30.6 and the older people between 69 and 84 years; 12 of the studies found no difference. Similarly, for the knee extension muscles 9 out of 17 studies found no difference; for the flexor group of the foot 9 out of 12 studies found no difference, etc.

The researchers found that across all muscles investigated (elbow flexors, wrist flexors, knee extensors, plantar flexors, and ankle dorsiflexors), with a total of 790 young subjects and 828 older ones, in 70% of them no significant age-related differences in muscle activation were observed and in 28% younger muscles were able to activate to a greater degree than older ones. In a general sense then, age would not seem to make a difference in a muscle’s ability to contract. But this represents a general analysis, not the actual meta-analysis.

Enter Meta-Analysis

Once the scientists applied the meta-analysis technique to sort through all the data points, a bit of a different picture emerged. What they learned was that voluntary muscle activation was greater in younger people than older ones. However, the difference was very small and the research team explained that this finding could be due to the muscle group that was looked at in different studies, how muscle activation was calculated in each study, the way in which the muscle was stimulated, and number of stimulations used.

In analyzing the number of muscle stimulations a study employed, if it was once there were no significant differences in the strength of muscle activation between young and old. If, however, the number of muscle stimulations were more than one, then the young people reached the level of significantly greater muscle activation over older ones. In looking at the different muscle groups, the scientists learned that younger subjects outperformed older ones in the plantar flexors, knee extensors, and elbow flexors but not in the wrist flexors and ankle dorsiflexors.

Interpretation

What this study of the studies found is that older, healthy, non-athletic people have, in the words of the researchers, “a reduced ability to maximally activate their muscle during isometric contractions.” One of the problems with this finding was, however, the large range of older subjects’ age from 60 to 84. As the researchers point out, “it is well known that the deficits in muscle function are accelerated in very old age (~80 yrs.).” This means that if you have a bunch of 80+ year olds along with people in their 60’s, the results might end up being skewed toward the muscle abilities of the 80+ year olds. Put another way, if you eliminated the 80+ year olds from analysis, then perhaps no differences between young and old muscle activation abilities would be found.

With that in mind I closely scrutinized all of the studies that found a deficit in older people’s muscle activation in an effort to ascertain at what age this might start to appear. The youngest age of the old group that displayed this deficit was 67 years. The vast majority of subjects were, however, in their 70’s and beyond.

Perhaps the most important consideration for the finding that younger muscle can activate to a greater extent than an older one is whether this difference is actually of any practical meaning. To put it in to a lifter’s terms, if you find that with 60 you end up lifting 100 pounds less than when you were 30, you might consider that meaningful. If, however, you find that with 60 you end up lifting 30 pounds less you probably wouldn’t consider that meaningful nor give it a second thought. After all, there are an infinite number of reasons for a young lifter to end up lifting 30 pounds less, too.

The researchers addressed this, though unfortunately not in a lifter’s terms. What they stated is that the loss in isometric muscle contraction force due to age was only “modest.” They therefore questioned the degree of meaningfulness of the overall findings. You also have to consider that the older subjects displayed a high degree of variability in muscle activation. In addition, multiple studies have found that when older subjects are able to practice the type of muscle contraction, they attain similar levels of muscle contraction as healthy young adults.(1-3,5).

So What?

That final consideration takes us in to the realm of people who lift weights. For those who don’t, the effects of aging are only moderate and don’t seem to make a noticeable difference until the late 60’s or so. This is most certainly a surprising finding, especially if you consider the issue of whole body disuse. If you’re a 30-year old healthy but sedentary person, then your years of body disuse has been about 15 years if you consider that even a non-athletic child and young teenager might get a little bit of exercise due to play. But that same sort of person who’s 60 has been sedentary for 45 years. If in that sort of person the effect of aging on muscle is only moderate, what might it be for someone who’s pumping iron religiously?

There are likely readers among you who will take this information as being exceptionally motivating, allowing them to make all this “getting older” talk disappear in a cloud of chalk as they prepare to crank out another set. But there will also be readers who’ll want to instead dismiss what they learned because it flies in the face of what they think they know. After all, everybody knows that as you get older, man or woman, your hormone levels decrease and that’s why you can’t be as strong as what you used to be. Part III will investigate.

 

References

1. Hunter, S., et al. Recovery from supraspinal fatigue is slowed in old adults after fatiguing maximal isometric contractions. Journal of Applied Physiology 105(4): 1199–209, 2008.
2. Hunter, S., et al. The aging neuromuscular system and motor performance. Journal of Applied Physiology 121(4):982–95, 2016.
3. Jakobi, J. and Rice C. Voluntary muscle activation varies with age and muscle group. Journal of Applied Physiology 93(2):457–62, 2002.
4. Rozand, V., et al. Age-related deficits in voluntary activation: A systematic review and meta-analysis. Medicine and Science in Sports and Exercise 52(3):549-560, 2020.
5. Rozand, V., et al. Voluntary activation and variability during maximal dynamic contractions with aging. European Journal of Applied Physiology 117(12):2493–507, 2017.