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Archive for August, 2010

Exercise vs. calorie restriction for brain aging

August 8th, 2010

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.

High-intensity vs. low intensity exercise for weight loss

August 6th, 2010

This week’s Jockology column in the Globe and Mail takes a look at what workout intensity is best for losing weight. Some recent studies suggest that high-intensity exercise can help fight the “efficiency trap” that occurs when you start losing weight and your body tries to revert to your original weight. Other studies suggest that very low intensity physical activity can burn calories without stimulating your appetite hormones. The one suggestion that doesn’t check out is the so-called “fat-burning” zone, according to a recent Australian study in which mice were engineered to burn more fat than carbohydrate. For details, read the full article here.

Orthotics for knee pain: does pronation matter after all?

August 5th, 2010

After last week’s discussion of the presumed death of the “pronation control paradigm,” I came across this new Australian study posted online at the British Journal of Sports Medicine about using orthotics to combat patellofemoral pain syndrome (PFPS — the nasty affliction sometimes known as “runner’s knee”).

The basics: 52 volunteers suffering from PFPS were given off-the-shelf three-quarter-length orthotics to insert in their shoes, with “built-in arch supports and 4 [degree] varus wedging.” They were then immediately tested to see whether they had less pain and could do more single-leg squats, step-downs and rises from sitting. The results:

Prefabricated foot orthoses produced significant improvements (p<0.05) for all functional outcome measures.

Hurrah! But here’s the rub:

A more pronated foot type and poorer footwear motion control properties were found to be associated with reduced pain during the single-leg squat and improvements in the number of pain-free single-leg rises from sitting when wearing foot orthoses.

Hold on, I thought we decided pronation and motion control don’t matter because they were just invented to make money for shoe companies! But that’s not what the authors think. In fact, they conclude that

foot orthoses have greater effects in poorer-quality shoes, possibly as a result of a greater potential to improve motion control properties.

Let’s step back for a moment. This study has a lot of limitations, not least of which is the fact that it wasn’t blinded, randomized or controlled. Also, if you look closely, the results are rather mixed. For step-downs, 57% got better, but 27% got worse; for squats, only 38% got better, while 20% got worse. Is this because orthotics made pronators better and supinators worse? Maybe… sort of… but not quite. Even the researchers had to waffle a bit in their discussion:

Although supportive of traditional theory, the associations of foot posture and change in foot posture with functional improvements were only fair.

So what can we take from this? Well, this study certainly doesn’t “prove” the pronation paradigm. But the fact that more than half the people in the study got immediate relief from a shoe insert tells us that monkeying around with joint forces is capable of affecting running injuries, for better or worse. Now, if you put those knock-kneed, flat-footed volunteers on a minimalist program, it’s entirely possible that they’d compensate for their weaknesses and imbalances and get rid of their knock knees and flat feet — eventually. Proper shoes, on the other hand (or in this case, orthotics), seem to cure the problem for some people immediately.

In a perfect world, we’d all be patient, careful, and dedicated to our exercise regimens — and no one would need running shoes. But this study suggests to me that the pronation control paradigm is able to offer quick fixes to some people, in some circumstances. As a result, while I expect the minimalism trend to continue to grow (and I’ll be glad to see that), I also don’t expect current running shoe technologies to disappear. Not because shoe companies are evil, but because some people will continue to want what those shoes can offer.

Digesting a real cheese sandwich burns twice as many calories as a processed one

August 3rd, 2010
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We’ve all heard lots about why whole foods are better than processed ones (or, as Michael Pollan calls them, “edible food-like substances”). But this is a new one to me: your body has to work harder to process unprocessed food, so you actually burn more calories in the five to six hours after eating. It has to do with “diet-induced thermogenesis” (DIT), also sometimes known as the “thermic effect of food,” which is:

the energetic costs of postprandial processes such as food breakdown, enzyme synthesis, peristalsis, nutrient uptake/assimilation, and secondary metabolism (e.g. urea synthesis)… typically responsible for about 10% of daily energy expenditure in humans.

The quote comes from a new paper in Food and Nutrition Research [full text available here] by researchers at Pomona College. They ran a simple but elegant experiment with 17 volunteers who ate two types of cheese sandwich on two different days. One sandwich was cheddar on multigrain; the other was processed cheese on white. The sandwiches were matched to have identical calories and similar ratios of carbohydrate, fat and protein. Then they measured the metabolic rate at hourly intervals for six hours. The result: the volunteers burned 137 DIT calories after the whole food sandwich, compared to just 73 calories after the Kraft special.

That’s actually a significant number of calories. One thing I noticed is that the sandwiches weren’t identical in terms of nutrient composition. The whole-food sandwich had 40% carb, 39% fat and 20% protein, while the processed sandwich had 50%, 33% and 15% respectively. So maybe that accounts for some of the difference — but in some sense, that’s the point. Processed foods do tend to have more easily accessible carbohydrates, so the comparison is pretty fair. It’s also worth noting that bread and cheese are already processed foods; the authors note that the difference would be even more stark if you used something like a raw fruit or vegetable.

The fjords of New Zealand

August 3rd, 2010

A quick plug for a travel story I wrote that ran in yesterday’s New York Times travel section, about a trip Lauren and I took in Fiordland, New Zealand:

SLOWLY but surely, our ship was shrinking.

We were trolling down the middle of a New Zealand fjord, and the captain had asked us to pick a point on one of the towering cliff walls beside us that we believed to be about mast-height. But as we edged closer to shore, perspective morphed, and the point I’d chosen was suddenly three mast-lengths above us.

When we were almost close enough to touch the scale-distorting walls, the captain switched off the engine. A heavy silence fell, lifting gradually to reveal bird calls in the distance, and the faint babble of countless tiny waterfalls trickling off ledges hundreds of feet above us, tripping down slopes blanketed with moss and ferns.

We were in Fiordland, in New Zealand’s southwest corner, a tract of near-virgin wilderness the size of Connecticut with a permanent population — according to the most recent census — of 18. Amply stocked with snowy peaks, alpine lakes and primeval forests, this massive World Heritage Area is most celebrated for the 14 fjords that slash into its coastline, carved by glaciers from erosion-proof granite more than 10,000 years ago… [READ THE REST OF THE STORY]

It was an interesting trip. We went for a four-day hike, and for an overnight cruise on an awesome fjord (as you’ll see if you read the piece!). As die-hard hikers, we expected to love the hike, but we were skeptical about the cruise, since we don’t really like being crammed into small spaces with lots of other people. In the end, the opposite happened: the hike was good, but the cruise was incredible. I’ve never seen anything remotely like the fjord we visited, and kayaking on its surface was mind-blowing. I wish my photography was better able to capture it!
fiordland1

fiordland2

P.S. I guess this post doesn’t really have anything to do with exercise research. But right after we disembarked from the cruise, Lauren and I went for a short run on a gravel path through a forest. On the way back, I tripped over a root and supermanned along the gravel, scraping my whole body (even through my clothes) and cutting a big gash in my chin. So the moral of the story is: don’t run right after a cruise, when you still have “sea legs” (that’s what I’m blaming it on!).