Sweat Science

I posted a few thoughts last week about an article on sarcopenia — the gradual loss of muscle with age — and new attempts to find drugs that will slow it down. I’d be remiss if I didn’t point out some of the research on the obvious drug-free ways to avoid withering away to nothingness. For instance, I just noticed an article in the current issue of Medicine & Science in Sports & Exercise that compares the number of “motor units” in the muscles of masters runners (average age 65) with age-matched controls, and with a younger group (average age 25). The news is good.

First off, a motor unit is “a single alpha-motor neuron and all of the corresponding muscle fibers it innervates.” Losing motor units is one of the several mechanisms that combine to produce the muscle loss grouped as sarcopenia. In this case, it’s not the muscle fibres themselves that die; rather, it’s the motor neurons that control them. When you’re young, the orphaned neurons often sprout new axons that connect them to other motor neurons — so the number of motor units decreases, but the amount of muscle you can use stays the same. This can hide the problem until your 60s or 70s, at which point you’re no longer able to reinnervate orphaned fibres as well, and motor unit loss becomes a serious issue.

Anyway, the study itself was quite simple. Testing the tibialis anterior (shin) muscle, they found that the masters runners had 140 motor units on average, compared with 150 for the young group but just 91 for the old non-runner group. So there it is: consistent training preserves muscle — not the muscle fibres, in this case, but the motor neurons that control them. As the researchers put it:

The significance of the (…) findings centers on providing an improved understanding of the neuromuscular system through ‘‘elite aging’’ and provides support into the favorable value of long-term physical activity and exercise for protecting neural function.

aging

For an article I’m working on, I’ve been digging through the literature on sarcopenia, the age-related loss of muscle mass that most of us face starting in our 30s. I’ve found several conflicting estimates of how much muscle you can expect to lose, with a high end of 1-2% per year starting in your fourth decade (from this paper). That’s a lot more aggressive than I’d expected. I get the sense that it’s one of those problems whose implications we’re just now beginning to grasp — so I was interested to see this article by Andrew Pollack in the New York Times, which offers a good introduction to the topic:

Bears emerge from months of hibernation with their muscles largely intact. Not so for people, who, if bedridden that long, would lose so much muscle they would have trouble standing.

(Nice lede!)

Why muscles wither with age is captivating a growing number of scientists, drug and food companies, let alone aging baby boomers who, despite having spent years sweating in the gym, are confronting the body’s natural loss of muscle tone over time.

Comparisons between age groups underline the muscle disparity: An 80-year-old might have 30 percent less muscle mass than a 20-year-old. And strength declines even more than mass…

Much of the article focuses on attempts to agree on a clinical definition of the condition — which would then make it possible for drugmakers to win approval from regulators for drugs to treat it. But the key point for me is:

Researchers involved in the effort say doctors and patients need to be more aware that muscle deterioration is a major reason the elderly lose mobility and cannot live independently.

In other words, I need to start doing my push-ups again. Soon.

aging, resistance

One of the clearest signs that you’re getting older, microscopically speaking, is that your synapses start to degenerate. This means that signals from your brain have a harder time getting through to your muscles (for neuromuscular synapses) and to other parts of the brain (for brain synapses). Harvard researchers decided to investigate how exercise and calorie restriction — “among the most effective anti-aging treatments known” — affect the age-related changes in mouse neuromuscular synapses (PNAS abstract here, press release here). The results:

“With calorie restriction, we saw reversal of all aspects of the synapse disassembly. With exercise, we saw a reversal of most, but not all,” [lead researcher Joshua] Sanes says.

Score one for calorie restriction? Not so fast…

Because of the study’s structure — mice were on calorie-restricted diets for their whole lives, while those that exercised did so for just a month late in life — Sanes cautions against drawing conclusions about the effectiveness of exercise versus calorie restriction. He notes that longer periods of exercise might have more profound effects, a possibility he and [Jeff] Lichtman are now testing.

That makes me hope that, with longer and more consistent exercise, we might one day discover that all the benefits of calorie restriction are in fact available from consistent and vigorous exercise. (That being said, a month in a mouse’s life does correspond to a considerably longer period in human terms. The “old” mice were about two years old.)

On a somewhat related note, another just-published study found a correlation between how much blood your heart can pump and how quickly your brain ages. The study didn’t include anyone with heart disease, so it applies to people with normally functioning hearts: the more blood you can pump, the more blood gets to your brain, and the less the brain shrinks. The study can only measure correlation, not causation — but it sounds like more confirmation that aerobic exercise is the best “brain training” around.

aging

British researchers are presenting some new research on how calorie restriction works at a conference on aging research this week. In a mouse experiment, they found that it reduces cell senescence (the point at which a cell can no longer replicate) and helps protect telomeres (which exercise does too, researchers have recently found). Interestingly, the effects seems to be significant even if if it’s only started later in life and maintained for a relatively short period of time.

As I blogged about recently, I’m a little ambivalent about this whole calorie restriction thing. I just can’t see a happy ending — if it works, you feel guilty about eating for the rest of your life, and if it doesn’t, you die! Ultimately, I respect that we want to know how the body works, and this line of research is part of that. But I was happy to see some of this ambivalence reflected in the quotes from the press release describing the research:

Professor Thomas von Zglinicki, who oversaw the research, said: “It’s particularly exciting that our experiments found this effect on age-related senescent cells and loss of telomeres, even when food restriction was applied to animals in later life. We don’t yet know if food restriction delays ageing in humans, and maybe we wouldn’t want it. But at least we now know that interventions can work if started later.

And a recognition that extra years aren’t the only thing that counts:

Prof Douglas Kell, BBSRC Chief Executive and keynote speaker at the BSRA Conference, said: “As lifespan continues to extend in the developed world we face the challenge of increasing our ‘healthspan‘, that is the years of our lives when we can expect to be healthy and free from serious or chronic illness.

aging

Okay, that’s not really a fair headline or a good summary of the research I’m describing (which is a neat study by researchers at Princeton, explained in an excellent and detailed press release). But I have to admit, I’m not always perfectly neutral — like everyone, I prefer to see some results more than others. And research into caloric restriction is a good example: there’s been plenty of evidence over the past few years of the age-defying benefits of starving yourself:

To date, caloric restriction has been observed to extend lifespan in every organism tested, including worms, mice and monkeys, [Princeton prof Coleen] Murphy said. While the reasons for this are still under investigation, scientists generally believe that the benefits of caloric restriction go well beyond preventing diseases associated with obesity, such as heart disease and diabetes, Murphy added. It appears that limiting food intake actually slows the aging process.

In general, I’m used to leafing through studies and press releases that give me a nice pat on the back. Aerobic exercise is good? Super, I do tons of it! Eating lots of fruits and vegetables is good? Fantastic, I do pretty well on that front. But caloric restriction? That’s the antithesis of everything I stand for, which is doing ridiculous amounts of exercise and consequently being able to eat more or less until I get bored with no ill effects — or at least, no ill effects that I knew of until the emergence of this idea that eating less slows down aging.

So you should read the press release for yourself, and judge its merits in an unbiased manner… but here’s what I took from it:

Young worms whose calories were restricted had normal short-term memories, but their long-term memories were severely impaired; the memories faded within 24 hours, as opposed to 40 hours in normal worms.

(40 hours in worm time corresponds to about 15 people years.)

Now, the study has a lot more to say. While caloric restriction impaired long-term memory, the (impaired) memory abilities didn’t decline as much with old age as they normally do. The study also investigates how insulin-signalling pathways affect longevity and cognitive function (this appears to operate independently of the calorie-restriction effects). So there’s a lot of on-the-one-hand-this, on-the-other-hand-that going on. But it’s the first sign I’ve seen that caloric restriction, even if it extends life, may have some significant downsides:

“The assumption in the field of longevity research has been that organisms able to live longer will function longer as well,” said [Murphy]. “It seems we need to revisit that.”

aging, mental

[18/5 NOTE: I don't really understand this study. See the comments below -- and help out if you can!]

Researchers from the University of Rome just published a study in the journal BMC Physiology in which they analyzed blood samples from 10 recreational runners before and after completing a marathon (press release here). The chief finding:

Apoptosis, the natural ‘programmed’ death of cells, is arrested in the aftermath of strenuous exercise. Researchers… studied peripheral blood mononuclear cells (PBMCs), isolated from whole blood samples taken from people after finishing a marathon, finding that the balance between expression of pro- and anti-apoptotic genes is shifted after the race.

The idea that exercise helps your cells live longer has been in the news recently (see, for example, Gretchen Reynolds’ piece on telomere length in the New York Times a few months ago). This appears to be another piece of the puzzle — though a marathon is a pretty intense bout of exercise, so you have to wonder whether you’d get similar benefits from a shorter workout.

aging, genetics

A paper in last month’s International Journal of Sports Medicine takes a look at how much you slow down as you age, comparing the three triathlon disciplines. Researchers in France crunched data from the top ten finishers in each age group at the 2006 and 2007 world championships, for both Olympic-distance and Ironman triathlons. Since a picture is worth 1,000 words:

The top graph is for Olympic-distance, while the bottom graph is for Ironman. What sticks out is that cycling declines more slowly than running and swimming, and the researchers suggest a bunch of different explanations for this. One is that running and swimming rely more on fast-twitch muscle fibres, which atrophy more quickly than slow-twitch fibres. Another is simply that running is harder on the body, so older athletes have to spend less time running to avoid injuries, while cyclists are able to maintain higher training volumes as they age. There are also more subtle possibilities, such as the idea that identical declines in your power output would affect running more than cycling (since running speed is directly proportional to mechanical power, but cycling speed only proportional to the cube root of mechanical power).

aging, triathlon

Anyone who follows masters running will have heard the name Ed Whitlock. He’s the man who ran a 2:54 marathon at age 73 back in 2004, the first septuagenarian sub-three. That famous marathon is just the tip of the iceberg when it comes the records he’s set at a ridiculous range of distances over many years, thanks to his famous training regimen of up to three hours of slow, steady running around a local cemetery every day. But all has been quiet on the Whitlock front for the past few years, thanks to knee problems.

That may be about to change, according to a fantastic in-depth feature about Whitlock in the upcoming issue of Canadian Running magazine, by Michal Kapral. Ed is on the comeback trail! Definitely worth a read… (Heck, it’s worth clicking on just to see the photo of Ed racing in 1952 at the Hyde Park Relays — an event I competed in nearly 50 years later!)

aging, arthritis, Canadian Running mag

The Globe is running a special section on fitness in your 50s, so there are three Jockology columns in today’s paper:

The question

How should I train in my 50s?

The answer

When Ed Whitlock became the first septuagenarian to run a marathon in under three hours in 2003, it was thanks to a simple but gruelling training plan: two- to three-hour runs around a local cemetery, nearly every day.

That regimen presented two key challenges that are familiar to any masters athlete: staying healthy and – just as important but less obvious – staying motivated. In fact, when asked why his race performances in his 50s were less impressive than in the years before and after, Mr. Whitlock points to his motivation…

and

The question

How much will I slow down in my 50s?

The answer

The physical attributes that determine athletic performance – maximal oxygen uptake, as well as muscular strength and power – typically start to decline slowly at about the age of 35, and much more rapidly at about 60…

and

The question

Now that I’m in my 50s, what’s the cumulative effect of all the exercise I’ve done?

The answer

Unless you’ve made a dramatic turnaround after a severely misspent youth, it’s inevitable that some of your body parts don’t work as smoothly as they did a few decades ago. It may be tempting to blame that on the punishment you’ve inflicted on your body during years on playing fields, ice rinks and jogging paths – but the truth is more likely the other way around.

Researchers have a good idea of the average rates of decline you can expect for various systems. And for almost every sign of aging you can think of – muscle loss, weight gain, artery hardening, joint stiffening – there have been studies suggesting exercise slows it down…

There are also some neat graphics there, though the formatting is a bit messed up. Hopefully they’ll get cleaned up as the day goes on.

aging, jockology

There’s a fun article by John Leland in the New York Times looking at drug use among masters track and field athletes:

In his apartment outside Philadelphia, Frank Levine pulled a list of prescription medications from his refrigerator, his hands shaking slightly. There was metformin HCl and glipizide for his diabetes; lisinopril for his blood pressure; and Viagra.

“I need it,” he said recently.

Mr. Levine, who is 95 and has had operations on both knees, in June set the American record in the 400-meter dash for men ages 95 to 99…

Leland interviews a few athletes who suspect that some people are dipping into banned drugs in order to win prizes in advanced age groups. It’s hard to imagine an 80-year-old shot-putter injecting himself with steroids, but I guess we should never underestimate the power of human vanity. The grey area, as the article points out, is that there are plenty of performance enhancing drugs that also have real therapeutic benefits — and the older you get, the greater the chance that you’re legitimately being prescribed one of these drugs.

aging