A Scientific look at Viagra enhancing endurance performance? No, not that kind, actual running performance…

Chicago Bears wide receiver Brandon Marshall made a little bit of noise in the news when he said:

"I know guys, it's such competitive league and guys try anything just to get that edge…I've heard of guys using Viagra, seriously, because the blood, it's supposed to thin . I don't know. Some crazy stuff. It's kind of scary with some of these chemicals that are in some of these things, so you have to be careful."

(http://www.newsday.com/sports/football/bears-wr-brandon-marshall-heard-of-players-using-viagra-to-gain-edge-1.4275134)

Which led offensive coordinator Mice Tice to comment: “"Viagra? I've never heard of such a thing. He's making that up. He's got to be making that up. You've got to be kidding me."

So, where did this all come from?

Well, if you've been reading this blog for a while, you might remember I called the Viagra improving performance thing way back in 2009 when I was some kid in grad school making crazy guesses on stuff (not much has changed…) (http://www.scienceofrunning.com/2009/09/complex-to-simple-beware-of-gurus-and.html)

The first study came out in 2006 by Hsu et al. and found significant improvement in a number of factors.  That was in the research world.  In the real world, people seemingly caught wind of it’s effects as can be seen by this nice little clip of the British TV show Top Gear from 2010:

But does it work and what’s the deal?

Viagra actually got it’s start as a performance enhancer at altitude.  The simple idea behind it was that it causes pulmonary vasodilation, so the thought was that maybe this effect would help increase endurance at altitude under hypoxic conditions.  The theory is that you’d prevent a drop in Oxygen Saturation levels and get a nice bump in Cardiac Output.  So in essence, Viagra would mitigate the effects of high altitude/low oxygen levels.

So what does the research say? 

The first thought of using Viagra for exercise adaptation started with a study that looked at taking it during a Mt. Everest ascent.  They found that about half their group saw significant improvements in performance and cardiovascular performance markers while making the ascent.  The aforementioned 2006 study took the idea to the next level and found that at simulated altitude (12.8% O2 or about 3,900m altitude) taking Viagra beforehand improved performance on a 6km time trial by 15%, improved stroke volume, cardiac output, and O2 saturation levels.  Sounds good right? 

Well more recent studies have found slightly different results.  A 2011 study by Kressler et al. looked at the effects with more moderate altitudes.  They compared 3,900m, 2,100m, and sea level.  What did they find?  At high altitude, it helped with oxygen saturation numbers, keeping them higher during a 15km time trial and a steady state exercise, but other than that Viagra had no effect on any of the performance measures.

Similarly, another study by Jacobs et al. (2011) looked at Viagra and performance at 3,900m altitude and found similar results. This time they took endurance trained men and women and put them through a 6km time trial. No significant change in performance and only a difference in Oxygen Saturation levels (in women only).  However, they did find that some people had significantly greater performance (one male improved by 36sec for example)

So what the heck is the deal? Does Viagra work or not?

Responders and non-responders:

Of course the answer isn’t that simple and once again we’re brought back to a common theme: individual variation.

If we go back to the original 2006 study, although the group as a whole improved significantly, what they actually found was that they had two groups.  One improved performance by an average of 39% and one improved by an average of 1%!

That’s kind of a big difference.  Similarly, if we look at the 2011 study, they noted that there were outliers who had very significant improvement.

The reason is simple.  At high altitude, each person’s limiter is different.  Viagra seems to aid in one specific area.  If that area is your limiter, performance will be improved.  If not, well too bad.  For example, if you compare me and Jackie Areson’s oxygen saturation levels at different altitudes even with just sitting there and not exercising, you can see our bodies response/compensation to altitude is completely differently (and yes, it’s a fun thing to do…Just sit in an altitude tent for a few hours with an O2 saturation thing on your finger J).  

Altitude (Feet)	Steve O2	Jackie O2
3200	97	98
4400	96	98
5100	95	96
5900	94	96
6500	93	96
7100	92	95
8000	90	94
8200	88	94
8800	85	93
9000	84	93
9900	81

So what causes the difference?  No one is entirely sure but a couple notable things are of interest.  First, in the 2006 study, they found that responders tended to have lower O2 saturation levels.  That makes sense because if we look at the studies and see that Viagra generally increases O2 sat levels, then it makes perfect sense that those who naturally respond to altitude with lower O2 sats might get a boost in performance if those levels don’t drop as much.  Along similar lines, there’s been lots of research showing people susceptible to high altitude sickness “experience greater pulmonary vasoconstriction and exaggerated increases in Ppa when exposed to hypoxia (Hsu, 2006).”

So…Does Viagra improve performance?
At very high altitudes?  Possibly, depending if you are a responder or not.  If you want to take a wild guess if you are a responder or not, measure O2 saturation at high altitude and see if you are comparatively low or not.

At moderate altitudes like those which runners might actually train at or someone like Brandon Marshall might play at in Denver?  Doubtful unless you have severe Exercise Induced Arterial Hypoxemia.

At sea level? Doubtful son.

So…all those NFL guys taking it.  Does it work for them? I’m going to be very doubtful.  They don’t play at high altitude.  They might get some ummm interesting side effects which NFL players probably don’t need, but a performance boost? Doubtful.

What's interesting about this to me is two things.  First, how athletes will take almost anything if there is a hint of it improving performance.  I wonder how it spread to the NFL actually where very few games are played at even moderate altitude.  Secondly, it's another perfect example of individuality of response.  We all have different physiological limiters, thus why we can't all train the same way and expect to improve...

 And lastly, did I really just write an entire article on investigating the performance benefits of Viagra?

References:

http://jap.physiology.org/content/100/6/2031.long

http://www.ncbi.nlm.nih.gov/pubmed/21451938