Monday, 19 December 2011

A Holiday Treat (From: Science)

Well my friends, its that time of year again!  Regardless of what holiday you celebrate, I think it is safe to say that most of our diets take a little bit of a dive in the month of December.

Take me for instance; yesterday I ate cookies and milk for breakfast followed by leftover chips and cheeses for lunch.  Then, logically enough, I consumed chips, cheese and cookies for dinner while watching this movie.  A classic film for a classic holiday season diet.

All of these treats reminded me of something my mom always used to tell me growing up (and still does to this day), "chocolate is good for you."  Yes, when I felt completely full and unable to ingest more Christmas chocolate, my mom would cheer me on with encouraging phrases such as, "eat it, it's good for you," or "it's cocoa, eat it."  So I would.  

Was she right all along?  I decided I had to go to the literature and find out.


In my search I came across this study published in 2008 in the American Journal of Clinical Nutrition.  Luckily for all of you, this one is available in full text for free online-it's a Christmas miracle!  Enjoy this nice holiday read as a gift from me to you!

One of the historically accepted benefits of chocolate involves its impact on the cardiovascular system.  Specifically, the active ingredient within cocoa (flavanoids) are thought to improve endothelial function.  What is endothelial function?  Well, the endothelium is the internal layer of your blood vessels.  If it is functioning well, you will be less likely to have high blood pressure, and less likely to experiencing blood clotting.

So, by having an impact on your endothetlial function, the flavanoids in cocoa could potentially decrease your blood pressure and the odds of developing a clot - that is what this study looked at.

How it was done:

In the study, there were two phases. During each phase, subjects were randomly assigned to consume either:

  • 74g chocolate containing 22g of cocoa
  • 74g placebo chocolate containing 0g cocoa
  • 22g of sugar free cocoa
  • 22g of sugared cocoa
  • placebo (no cocoa)
Then, the researchers measured parameters including blood pressure (BP) and flow-mediated dilation (FMD).  FMD is essentially a measure of the diameter of the blood vessel and therefore one way of measuring endothelial function.

What they found:

Here are the main conclusions the researchers reached: 

  1.  FMD and BP improved after eating chocolate compared to the placebo group in Phase 1.
  2.  FMD improved after eating both the sugared and sugarless cocoa compared to the placebo group in Phase 2.
  3. BP improved after eating the sugarless cocoa compared to the placebo group in Phase 2.
What does this mean?

My mom was right.  Again.

But really, I thought this study was fascinating.  With ingestion of chocolate containing cocoa, or pure cocoa itself, the subjects consistently showed better endothelial function.  The researchers attributed these changes to the cocoa flavanoids rising in concentration within the blood.  This study also shows that while both sugared and sugar free cocoa can have a positive impact on endothelial function, the sugar free option has an even more significant impact.

Nevertheless, there are a few things you should keep in mind when analyzing these results.  First of all, these changes were measured only once, not over a period of time.  So, even though these benefits were seen at the initial point of measurement, that does not mean they will persist days or even hours later.  Secondly, it is also important to keep in mind that these measurements were taken after eating cocoa once.  Perhaps the vascular response would not have been as profound if the individuals consumed cocoa on a regular basis.   

Either way, this study does show that a one time episode of cocoa ingestion will have an acute, positive impact on endothelial function.  Based on that, you can enjoy your dark chocolate a little more guilt free!

Happy Holidays!

Thursday, 1 December 2011

Elliptical VS Treadmill

As some of you may know, I decided to run a marathon at the beginning of November on very little training.  In fact, my longest run prior was about 18 km, while the marathon itself is 42.2 km.  So, I almost did half of the distance beforehand- that's good enough, right?  WRONG!

Not the smartest training strategy, and definitely not what I would recommend.  Nevertheless, I had a lot of fun, and the race was actually not that painful.  If you ever want to try a really fun and fast marathon (or half), give the Road2Hope Hamilton Marathon a shot!

So, while the race itself did not rank overly high on the pain scale, I soon after realized that my lack of training would come back to haunt me.  The recovery has been slow- including abnormal walking of 7-10 days duration, which has been followed by a few random, slow, awkward, painful runs.  Note to self- "do long runs in training prior to marathon."  If  only it were as simple as this guy made it seem.

In desperation to get some exercise in, I have resorted to something I never thought I would: the elliptical machine.  Laugh if you want, the machine is actually great; it gets my heart rate up, and my legs feel amazing as I do it (amazing= not quite as injured).  I just hope I don't turn into this guy.


Naturally, I started to wonder how effective the elliptical is as a replacement for running.  In my search of the literature, I came across this study published in the Journal of Strength and Conditioning Research.

In the study, 18 subjects aged 19-24 were put through a series of tests on both the treadmill and elliptical machines.  The study measured the following parameters: oxygen consumption, energy expenditure and heart rate at a set level of perceived exertion.

What they found:

This is what they researches found when comparing the elliptical and treadmill trials:

1) No difference in VO2 max (measure of maximum oxygen consumption)

2) No difference in TOTAL oxygen consumption

3) No difference in energy expenditure (measured in kcal)

4) Interestingly, the elliptical trials resulted in a higher average heart rate then the treadmill trials in both females and males.

So, in other words, these people were sucking up just much oxygen and burning just as many calories regardless of which machine they were on.

So what does all this mean?

Overall, as you can see based on these results, the elliptical is undoubtedly a great way to cross train for running, at least from a cardiovascular standpoint.  The most interesting component to these results, however, is that at a set level of perceived exertion, the subjects were able to push themselves harder on the elliptical resulting in a higher heart rate.

Why would this be?  Well one idea stems from the subjects themselves.  The population was noted as being healthy, but also not committed to any regular exercise program.  So one possibility is that the elliptical's non-impact and fluid motion allowed the people to push themselves harder at the same level of perceived effort when compared to the jarring and uncomfortable nature of running.  I think it would be really interesting to repeat this same study with trained runners to see if they would get more out of the treadmill workout compared to the elliptical (if I had to guess, I would say they would). 

Another obvious possibility mentioned by the authors is that the elliptical does include arm movements that are more exaggerated then that of the average runner. This could also account for the increased metabolic demand without increasing the perceived level of effort. 


So is the elliptical a good way to compliment running training?  Absolutely.  This is especially true for people (like myself) who are injured, and want to maintain some fitness while they recover.  On a scale of  "doing nothing" all the way to "running," these results show that the elliptical is much closer to the "running" end of the spectrum.

BUT, can the elliptical machine replace the treadmill as a means to train for running?  No.  If you want to get better at running, the obvious thing to do is run.  The elliptical undoubtedly will help from a cardiovascular standpoint, but from a biomechanical and muscular standpoint, running is best.  I suspect that if you train hard on the elliptical, you will potentially turn into a decent runner...but surely an amazing elliptical-er (such as Tony Little).