Monday, September 9, 2013

Genetics in the real world: Differences in training response


Alan Couzens, MS (Sports Science)

I’m currently reading David Epstein’s book “The Sports Gene” (pictured above) – A really interesting read that outlines the complexity of the factors that come together to produce great athletes. One of these factors that Epstein covers is the ‘talent of trainability’, i.e. the ability of some athletes to respond more quickly to a given training load than other athletes. A specific example is given in the book of Jim Ryun, the legendary track athlete who improved over the course of his first year of training from a 5:38 mile to a 4:10! And of course, eventually to the point of becoming the first sub 4 minute high school miler in US history.

In physiological terms, assuming an economy of 210ml/kg/km, Ryun went from a VO2max of ~4.3L/min to 5.7L/min over the course of 1 year of training (1.4L/min). This is clearly not a normal rate of improvement! Claude Bouchard has conducted considerable research on training response (specifically, the genetic impact on training response) and has found that the average improvement in aerobic capacity over the course of 20 weeks of training is 0.4L/min. Ryun’s rate of improvement is almost double this!

Indeed, within my own sample of unknowing guinea pigs, I track and witness a large variance in training response for a given load. The following chart outlines this response as change in FTP (w/kg) per 100hrs of training for a random sample of 15 athletes.

The data bears a striking resemblance to the histograms in Bouchard’s HERITAGE genetic study.

Clearly the data is normally distributed with a lot of folks falling within a response rate of 0.44-0.48 w/kg per 100hrs of training BUT, like the Bouchard data, the range of response is large, with the fastest responder getting more than double the benefit of a given dose of training than the slowest responder! Think about this for a second, the slowest responder in the group could put in the same amount of work as the fastest responder and improve half as much. It is not surprising that there is an element of natural selection in endurance sports.

Similar to the pattern of the Bouchard study, there is a small % of ‘outliers’ at the top that jump above the normal pattern of distribution. There is something going on here that moves from a pattern of ‘different shades of grey’ to that of black or white. The jump in the 0.65+ers suggests that they have something that the average bear doesn’t. I’ll leave it to the genetic researchers to define it (whether a mutation of the RUNX1 or something entirely different) but clearly, a certain percentage of folks seem to have an advantage when it comes to aerobic training response.

Non genetic factors in training response.

As a coach, I’m in a unique position when I look at data like this because each bar on the chart isn’t just a number. I’m able to see these differences in training response in the context of the different athletes’ personalities & the way they live their life. While perhaps not totally explaining the ‘outliers’ this looks to play a large part in determining where a given athlete falls within the ‘grey area’ and also, I believe, is a factor in explaining the ‘low responders’.

While Bouchard’s studies have shown a familial link in training response, they’ve failed to account for the impact of common personality traits/stress seeking behavior that may impact training response above and beyond any physiological similarities. For instance, do siblings exhibit similarities in sleep patterns that may come into play? Are their similarities in basal stress hormone levels within members of the same family which may be a factor in the results?

I’ve certainly seen a tendency toward this, i.e. that athletes who have the most stressful lives, with poorer sleep habits and poorer nutritional choices tend to fall towards the bottom of the chart in training response. This relationship was actually the subject of my thesis, & even among young athletes without the normal life stressors of your typical ‘grown up’ AG triathlete, I found stress to have a marked impact on the athlete’s adaptation to the training program.

On the flip side, for a given athlete, when life stress changes, training response can markedly improve. I’ve seen this time and time again in athletes who transition through a stressful period in their work or home life. Therefore, we shouldn’t see training response as 100% genetic. There are many factors at play here, a number of which the athlete has significant control over.  

How important is it to be a “high responder”?

When I look at the athletes at the top of this list, a fast training response clearly infers some advantages. Athlete number 11 for instance was able to move from low volume training in the midst of a full time stressful job to 2nd at the Ultraman World Championships within the space of 4 months! Number 13 is one of the top ITU athletes in the country, a competition schedule that DEMANDS athletes be quick training responders! However, a fast training response is not the end of the story.

Every year, I see less ‘talented’ athletes out-perform more talented athletes by simply out working them. A part of this may also be genetic, as in the physical capacity to absorb more work, but a larger part of it is continuing to ‘take your medicine’ during the toughest times of a training preparation when you simply don’t feel like it. It is here that I’ve seen ‘slow responders’ perform above and beyond their genetic station. For example, Number 3 in the above chart is a multiple Kona qualifier with a PR under 9:20 (despite his ‘slow’ training response!).  Number 9 is a former open national Ironman record holder! These are some of the hardest working, most consistent athletes that I’ve come across in my years of coaching.

The success of the above athletes (despite their categorization as ‘low responders’) speaks to one very important point: It’s one thing to be a fast responder, it’s entirely another to ‘take the medicine’ that you need on a consistent basis over a period of years, to elicit the response!

Yes, perhaps Ryun had a better physiology than most, but the dogged determination that he exhibited both in track & towards his young dream of becoming a major league baseball player (a sport at which he exhibited no talent) suggest to me that there was also something different about Ryun that existed a long ways from the mitochondrial signalers in his legs! I would make a similar argument for the success of Chrissie Wellington, a combination of a very strong physiology with a perhaps even more unique mindset, a unique passion to discover their full potential that will not quit.

I’m yet to personally witness the ‘perfect storm’ of talent, drive and capacity. I’ve been around some very high performing athletes (World record holders, Olympians etc) and, even among this group, it always seems that one or 2 of these traits (in extreme measure) dominate the athlete’s success. Perhaps there is a little fairness in the genetic lottery after all.

Train smart,




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