Saturday, December 15, 2012

Wait for it

My commute, on a good day
On most days I bike to work. It’s my way of “walking the walk” – I write enough about the benefits of exercise, it would be a little embarrassing if I were a couch potato. Riding in involves climbing a big hill early(ish) in the morning, but I usually just get into a low gear and think about stuff and I barely notice it.

Not this morning.

This morning, there was a headwind. A cold headwind. It felt like I was pedaling against a wall. I was trying to convince myself that I was enjoying it – looking at the view, trying to feel the oxygen in my brain. But at some point I let out a big sigh and thought “who am I kidding, this is miserable!”.

Even so, I knew full well that tomorrow, I would be back on the bike first thing in the morning. So I wondered – why do I continue to bike in, even in the winter, in the rain, in the cold, up the hill – even though I sometimes don’t derive any immediate pleasure or benefit? The answer, of course, is that rationally, I know that no matter how miserable it is at the moment, in the long run it’s good for me – it’s good for my health, my weight, my ability to prevent and fight illness, and, as anyone who reads this blog knows, my ability to ward off cognitive decline as I get older.

This process of holding off on immediate rewards (driving in to work in a warm car with some Christmas music playing) to benefit from later rewards (health) is called delayed gratification. It was most famously studied using marshmallows: in a well-known study, young children were given the choice between eating one marshmallow immediately, or waiting a few minutes and receive two marshmallows (giving rise to some pretty hilarious antics). The researchers followed-up on the children many years later, and found those who were successful in displaying delayed gratification (and so resisted eating the one marshmallow) were doing better on several outcomes such as academic success and ability to handle stress.

In a more recent study, a team of researchers investigated whether there is a link between the ability to delay gratification as a child and weight in adulthood. They found that one’s performance on a delayed gratification task (similar to the marshmallow experiment) was associated with his or her body mass index (BMI) thirty years later. In short, the kids who were able to wait the longest for a bigger reward had lower BMIs as adults. Interestingly, another study found that children who already have a high BMI score poorly on a delayed gratification task – a nice convergence of evidence from different sources.

Avid Scientific Chick readers can no doubt point to an important limitation of this study. Repeat after me: correlation does not imply causation. The fact that kids who did well at delayed gratification later had lower BMI’s does not mean that being good at delayed gratification causes one to have a lower BMI. There are several potential confounders here, some of which were not controlled for, such as the BMI of the participants as children. That said, the findings remain interesting – it’s not completely out of the park to think that improving self-regulation and self-control could have an impact on weight.

There is a little coda to my earlier story about biking against a wall of wind.

About halfway up the hill, at the peak of my frustration, almost as if on cue, a huge coyote emerged from the forest, and started trotting along the bike path as I was biking. It was a big fluffy beast, and for a second I was scared, but it was minding its own business, and eventually started making its way across the street. Still excited from my encounter, I turned my head, and there was another equally huge coyote sitting just next to the bike path, in the forest, staring me down. I couldn't believe it. I've seen coyotes before, but never this big, never this close, and never on my way to or from work. They were beautiful creatures and my heart was warmed. Delighted with this turn of events, and with the fact that this morning’s gratification was instant and not delayed, I grinned like an idiot all the way to work. 

Reference: Preschoolers’ delay of gratification predicts their body mass 30 years later. Schlam TR et al. (2012) The Journal of Pediatrics Aug 18 [Epub ahead of print].

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.

© 2009 Scientific Chick. All Rights Reserved | Powered by Blogger
Design by psdvibe | Bloggerized By LawnyDesignz