Thursday, December 6, 2012

You're not that tired

A few years ago, good friends of mine dragged me to a viewing of Touching the Void, a movie about the extraordinary survival of a mountain climber against all odds. I remember coming out of that movie thinking, “Wow, when I complain that I’m tired, I’m really not that tired – I have so much more in me”. It might sound corny, but over the years, I’ve thought about this movie several times, and it has inspired me in many ways.

Which part of your body decides when you can and can’t go on? In exercise science, the debate has been going on for years. Some researchers think it’s the heart – you can only exert your big muscle so much. Others link stamina and endurance to lung capacity – measures like VO2 max (how much oxygen your body transports and uses during exercise) have been linked to performance in sports. More recently, measures like the lactate threshold (the exercise intensity at which lactic acid starts to accumulate in your blood) have become popular. Professional athletes are poked and prodded to try to figure out what makes a winner, but somehow with each theory comes at least one or two outliers. 

In an effort to investigate what drives people to push themselves and what sets the limits, British researchers came up with an interesting experiment using cyclists.

Each cyclist in their study had to complete four trials of 4 kilometers on a stationary bicycle. The first trial was just to get used to the equipment and the setting. The second trial was the real deal – they had to go as fast as possible, and their time was stored and used as the “baseline” time, or their “personal best”. During the last two trials, the participants “raced” against themselves – an avatar representing them was projected onto a big screen in front of them, and they could track their progress in relation to that of their avatar. The idea is that the avatar on the screen was going at the same speed as the cyclist’s 2nd trial (the one used to set their personal best). The researchers were hoping to learn whether a cyclist could beat their trial time by chasing themselves to the finish line, thus establishing a new best time.

You can probably guess the outcome of the study: all the participants beat their best time when they raced against it. But there’s a twist: in one of the last two trials, the researchers tricked the cyclists: the avatar was actually going 2% faster than their previously established personal best. And every participant beat that time, too! So guess what? It’s not in your heart, or your lungs, or you legs. It’s all in... your brain.

What the study tells us is that you have a little energy reserve, even when you think you’re going all out. Your brain doesn’t want you to tap that reserve, because if you get into that habit, you might use it up and die. So it keeps it hidden. It makes you feel like you’re going to die even though you’re not. But the reserve is available – throw in a little deception and a little competitiveness (or, in the case of the mountain climber, a little actual fear for your life), and you can gain access to it.

So there you have it! Next time you didn’t sleep well and you’ve been going all day at work and running errands and working out and you just feel like collapsing on the couch and having a nap… Dr. Julie says… Collapse on the couch and have a nap. But do it knowing you could also clean the house if you really wanted to.

Reference: Effects of deception on exercise performance: implications for determinants of fatigue in humans. Stone MR et al. (2012) Med Sci Sports Exerc. 44(3):534-41.

10 Responses to “You're not that tired”

Fawn said...

Tricky, tricky scientists!

Glad I have permission to collapse. Because I know that when I *do* keep on going, I'm asking for it. I will pay for it later by succumbing to some kind of virus. Not as bad as dead, but still not helpful. :)

Dr. Julie said...

Thanks for the comment, Fawn!

We are indeed a tricky bunch. :) Though admittedly studies using deception are difficult to carry out since they are scrutinized very carefully by research ethics boards (as they should be!).

Oh, and yeah, you totally have permission. I wouldn't be able to get through half the things you get through on a regular day!

Anonymous said...

Accessing that reserve takes a disproportionate toll on you and is rarely worth tapping into. Perhaps only for life and gold. Other than that, couch it is.

Dr. Julie said...

Anonymous, you're absolutely right - we're definitely talking about life and gold situations here. The article was framing this reserve in the context of sports performance, not in the context of getting off the couch. :)

The warm couch... in front of the fireplace... next to the lit up Christmas tree... That sounds pretty good right now.

Anonymous said...

I wonder if learning to regularly tap into it is a sound training method for top athletes. I guess one tends to take nibbles and bites, but consistently going all out? Would that get your body used to it or break it - supposing it had ideal nutrition and rest in between?

Dr. Julie said...

Anonymous - that's a good question. I don't know to what extent the reserve can be pushed back. If you train into it and get used to it, does that become your new pre-reserve max?

All that said, the concept of "training into it" is much more challenging that it sounds - we're not talking about pushing hard, here, we're talking about tricking the brain into deception, which is very hard to do on your own...

Anonymous said...

Tricking or not, those cyclists did more than their 102% because they wanted to. And a 2% improvement is quite considerable. Though my feeling is they weren't giving it all they had in the first place. They certainly didn't have a reason to surpass themselves. Unless they wanted to impress that hot scientist. The third try, however, they had to beat an opponent. In conclusion, for best results, instead of pretending a hot scientist is watching you, imagine your double leaving you in the dust.

Dr. Julie said...

Anonymous - yes, 2% is definitely a considerable improvement. And you're right, there's some wiggle room when establishing a personal best in a laboratory setting.

In conclusion, for best results, you're definitely right about not pretending a hot scientist is watching you - a futile exercise, since they don't exist. :)

Anonymous said...

All scientists are hot!

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