physiology

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You’re Not Lazy, You Just Quickly Minimize Exertion, Study Suggests

A new study finds we quickly change our gait for greater efficiency. (Peter Mooney/Flickr)

A new study finds we quickly change our gait for greater efficiency. (Peter Mooney/Flickr)

By Josh Eibelman
CommonHealth intern

If you’re feeling guilty and blaming yourself for being lazy, take heart: We evolved to minimize how much we move, and new research suggests we adjust our bodies quickly to expend the least possible energy.

In a new study, “Humans Can Continuously Optimize Energetic Cost During Walking,” published in the journal Current Biology, researchers found that people optimize their gaits — the manner in which they walk — in real time in order to expend less energy.

Subjects in the study were fitted with exoskeletons that forced them to walk in abnormal ways. The scientists found that participants automatically fine-tuned their manners of walking to more energetically efficient ones in response to the exoskeletons.

I spoke with Jessica Selinger, lead author of the study and a doctoral candidate at Simon Fraser University, to learn more.

How would you sum up your results?

What we found was that people quite readily will tune or change really fundamental characteristics of their gait — characteristics that have been established over millions of steps over the course of their lifetime — in order to move in a way that uses the least amount of energy.

That’s probably intuitive for a lot of us. We know that we like to do things that require the least effort and do them in the least effortful way. I might prefer to take a bus to work when I could walk or I might prefer to sit when I could stand. But what’s really interesting is that even when you make a conscious choice to exercise or spend energy, what our study shows is that your nervous system is optimizing and tuning behind-the-scenes your movements so that you’re burning the fewest calories possible.

What message do you want people to take away from these findings?

For one, it’s really remarkable that the body can do this. There are countless ways that someone could walk from point A to point B. We can choose different speeds, step rates and even muscle activity patterns, yet we have very strong preferences for particular gaits — the energetically optimal gait. It’s really amazing that our body is able to home in on what is the most energetically optimal way to move. It’s a complex problem and an impressive feat. You have to be smart to be that lazy!

And the other really interesting thing was that that people would adapt their gait even in response to very small savings in energetic cost. We’re talking about just a few percent of the body’s total energy use. It seems that the body is really sensitive to this measure. Energetic cost is not just an outcome of our movement, it is continuously shaping the way me move.

Can people do anything to counteract this laziness? Continue reading

Study: Jolt Of Java Before Exercise Makes Legs Stronger But Not Arms

(Wikimedia Commons)

(Wikimedia Commons)

By Marina Renton
CommonHealth intern

Wondering whether you should forgo your Starbucks run in favor of a cross-country run before work? According to a study just out in the June issue of the journal Medicine & Science in Sports & Exercise, no need to give up your morning cup (or two) of coffee for a trip to the gym. In fact, the caffeine could enhance your performance — particularly your legwork.

The study is titled “Caffeine’s Ergogenic Effects on Cycling: Neuromuscular and Perceptual Factors.” (Vocabulary note: “Ergogenic” means “enhancing physical performance.”) It consisted of two experiments in which young adults consumed caffeine — equivalent to between two and three cups of coffee — and then cycled using their legs and arms.

The researchers found that caffeine improved leg muscle performance but not arm muscle performance, and it decreased sensations of pain and perceived effort in both legs and arms when the exercise was at a moderate intensity level.

The takeaway? Barring any special circumstances — like being adversely affected by caffeine or having heart trouble — you needn’t hesitate to caffeinate before you exercise.

I spoke with Christopher Black, assistant professor of Health and Exercise Science at the University of Oklahoma and lead author of the study. Our conversation, lightly edited:

Could you summarize the study’s results?

There are multiple parts to the study but, in general, here’s what we found: Consumption of a 5-milligram-per-kilogram body weight dose of caffeine — which is the equivalent of maybe two to three cups of coffee depending upon how much you weigh and what kind of coffee it is — improves cycling performance if you ride the bike with your legs. But, that same dose does not improve cycling performance if you ride the bike with your arms. And that’s the big, real-world performance measure of things.

We ascribe that difference of effect to the fact that caffeine improved people’s strength in their legs but not in their arms. And it improved that strength by allowing them to turn on more of their muscle.

In what form were people given the caffeine? Continue reading