mardi 30 juin 2015

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

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 skip your morning cup (or two) of coffee in favor of 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?

It’s powdered caffeine; we mixed it up into little tablets, and they swallowed it with some water.

Is it possible to suggest that people drink caffeine before exercising?

Absolutely, they should drink caffeine. They should take caffeine in any possible form before exercising. There are 20 or 30 or 40 studies that have demonstrated a very similar thing to what we found in the legs. For endurance-type performance, caffeine is absolutely going to improve your performance.

Are there any caveats? For example, an excess of caffeine makes some people jittery, so could that wind up inhibiting muscle performance?

I don’t know that we have a lot of scientific data supporting the fact that it can in some people actually decrease performance. But, there is scientific data that in certain people, let’s say you’re a high-anxiety person, consuming large amounts of caffeine may exacerbate your anxiety. And it may make you more jittery.

There does seem to be — and this is, again, somewhat anecdotally — kind of a tipping point where, if the dose gets to be too high, you can’t concentrate and you’re fidgety. So it’s plausible to me that, at some high levels, caffeine could actually make performance worse. But, in these typically-tested doses, as long as you don’t have some sort of adverse reaction to the caffeine — which could be jittery, potentially in some people it might upset their stomach, although there’s really very limited data that suggests that’s going to be the case.

Then there are potentially some people that caffeine just does not affect. There are some people that we would term to be non-responders. It doesn’t really matter how much they have, they just do not exhibit the typical response.

And if people are not responsive to caffeine, would they not experience the improved exercise performance?

That’s a tricky needle to thread as a scientist. I’m unaware that there are data that support that conclusion, but that again seems very plausible to me.

Is there a risk for people with certain heart conditions because of the combined increased heart rate from exertion and caffeine consumption?

The general response is: not necessarily. I don’t know that caffeine plus exercise is necessarily riskier than exercise all by itself from that standpoint. Now that would be with the great caveat of: If you’re an at-risk population, then you should get physician’s clearance. I am unaware of any studies that have been done to say that caffeine makes exercising more dangerous, although exercise is inherently dangerous, especially if you’re a cardiac person.

We do tend to see a bit of an exaggerated heart rate response during exercise for the people that consumed caffeine. Heart rate is up a little bit, so there is theoretically greater stress being placed on the heart. So that could potentially be somewhat more dangerous.

It seems kind of counterintuitive, but there is some data suggesting that, if you have a cup of coffee and you sit and you rest, caffeine actually lowers heart rate. You would think, caffeine is a stimulant, so it should make my heart rate go up. And there are several studies that find that is actually not true.

What made you interested in embarking on this study?

It was well-known in our field that caffeine improves exercise performance. One of the questions that was out there, though, was: Why? How does it work? By doing arm and leg exercise, we thought that this would be a unique way to try and manipulate the effects of caffeine on muscular strength and the activation of those muscles.

Study participants also experienced less pain and less perceived effort, right?

If the exercise is done in a certain way, then they did actually experience less perceived exertion and less muscle pain. And again, that’s also a finding that is similar to several previous studies. But it only works that way in very controlled circumstances.

We prescribed an intensity of exercise to our folks; they rode either with their arms or their legs for 30 minutes. When we asked them to do that at about 60% of their maximal ability — that’s fairly similar to what a lot of people would train at, that’s kind of a jog to a somewhat brisk jog to a lot of people — it did reduce pain, and it did reduce perception of effort. When we increased that to a heavier exercise intensity, then it didn’t lower perception of effort, and it did not lower pain levels.

Is there anything else about the study you would like to share?

Caffeine does seem to improve muscle performance, and the reduced sensations of pain and effort are also potentially very useful for a general population.

If you have a cup of coffee or something before you go to your exercise bout, then you are likely to feel a little bit better during that particular exercise bout. A lot of people have probably anecdotally experienced that, especially if you tend to be a coffee drinker or someone who consumes a lot of caffeine.

Readers, thoughts? Experiences?

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