Welcome back to my Sports Science Review of 2015, yesterday we looked at some of my favourite findings in sports science from this year. If you missed it, take a look here. Today we're rounding up, looking at the latest findings in these areas: The ACTN3 Gene, Ice Baths, Stretching and Can You Outrun a Bad Diet?
4. The ACTN3 Gene
I guess everyone working within a genetics related field has their favourite gene, and I’m no different. My all time favourite is ACTN3, probably because it is linked to speed and power performance, and I am a former speed-power athlete myself. As exercise genetics is a very new field, 2015 brought us plenty of new research within this area. My personal favourite was by Kikuchi & Nakazato, called Effective utilization of genetic information for athletes and coaches: focus on ACTN3 R577X polymorphism. I like this article because it represents another step forward in this field. We started off with research aimed at discovering genes and their functions – with ACTN3 the seminal paper was by Yang et al. (2003), describing the distribution of ACTN3 in elite power and endurance athletes, and comparing them to non-athlete controls. From this, and similar research, we know that individuals with an R allele are generally a bit more prevalent in elite power activities, and those with the XX genotype are more prevalent within elite endurance exercise. The step after this was to see how ACTN3 genotype can affect response to training, as per this Delmonico et al. (2007) paper.
All this previous research has led us to here, where we can now try to create guidelines based on an individual’s genotype, which is what Kikuchi and Nakazato do in this paper. The suggest that individuals with an R allele should utilise high load, low repetition weight training, and high intensity interval training, whilst XX allele carriers should utilise moderate load, higher volume weight training, as well as long, steady duration cardiovascular training. The next step in this ever advancing field would be to test this in the real world through training programme modification. Watch this space for some research conducted by DNAfit on this - coming very soon!
5. Ice Baths
As part of my role at DNAfit, I deliver parts of our education programme to individuals wishing to better understand the role of genetics in fitness and nutrition. Part of this education focuses on recovery, as DNAfit offer advice on how a person’s genetics can affect their recovery speed between hard sessions. I also use this part of the education programme to discuss how we might be able to enhance recovery in athletes and trainers, and one of the most often proposed methods is the use of ice baths. This generally prompts discussion between everyone in the room as to whether ice baths are useful or not. The general belief is that they are, however I often then provide some information that shows the regular use of ice baths might not be as useful as we might think. Whilst ice baths likely do promote recovery, they probably do so at a cost – and that cost is a reduction in adaptation to training.
2015 saw the publication of another research paper exploring this aspect, titled Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training (Roberts et al. 2015). The research paper itself was comprised of two separate experiments. In the first, subjects did a two strength training sessions per week for 12 weeks. After each session, the subjects either had an ice bath for 10 minutes, or underwent active recovery. After the 12-week training period, both groups had increased strength and muscle mass, but the active recovery group had done so to a much greater extent. Within the second study, subjects underwent strength training, again either followed by an ice bath or active recovery. This time, the researchers took muscle biopsies to try to find a mechanism underlying the findings of the first study. What they found is that the use of an ice bath after strength training leads to a decrease in satellite cell uptake into the muscle, as well as a decrease in activity of many anabolic signalling agents.
The main point here that bears repeating is that ice baths are not inherently bad. They likely do promote recovery, just at a cost. During periods of high training load, when the goal is adaptation to exercise, ice bath use should be minimised. However, during periods where recovery is important and adaptation isn’t, such as during competitions, the use of ice baths could be very useful.
I’m sure you’ve heard by now that static stretching is very bad before exercise. Except that, it probably isn’t. The problem with the studies that stated static stretching was bad were that they were generally comprised of subjects undergoing static stretching immediately before conducting explosive exercise. For example, subjects might hold a hamstring stretch for 60 seconds, and then immediately go and do a maximum speed sprint. In this case, static stretching is bad; it can reduce elasticity in the muscle, reducing performance and increasing injury risk. The problem here is that pretty much no-one warms up like this! Instead, people generally static stretch first, and then move onto dynamic, sport specific movements. And, when this happens, the dynamic movements appear to offset the negative effects of static stretching. This was made apparent in a 2015 article by Behm et al., titled Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. By looking at a total of 125 studies examining the effects of static stretching on performers, the authors found that so long as performance test and static stretching were separated by 10 minutes, static stretching had no negative effect on exercise performance, particularly if it was followed by dynamic exercise. Stretches held for longer than 60 seconds had a greater acute negative effect on performance. What is becoming increasingly clear from research like this is that static stretching can have a place in a warm up, provided that it is followed by some dynamic exercises (or 10 minutes rest), and isn’t of a long duration (held for about 30 seconds or less).
And finally… Can you outrun a bad diet after all?
Back in April, a group of researchers published at editorial in the British Journal of Sports Medicine titled It is time to bust the myth of physical inactivity and obesity: you cannot outrun a bad diet (Malhotra et al. 2015). This paper is a perfect example of how sometimes things can go wrong in science. The authors essentially purport that poor diet, not physical inactivity, is what is causing the rise in obesity within the Western world. They state their belief that physical activity levels are essentially the same as they were 30 years ago, and so cannot be the driver of obesity we general think they are. Instead, the authors point to diet, and especially carbohydrate, as the main driver here. It’s a fairly valid assumption, and certainly they aren’t the first people to think this is the case. However, they didn’t reference their piece at all well, leading to quite a bit of backlash from the academic community, with some individuals accusing them of cherry picking data.
Context here is also important – some of the authors of this editorial have published books advocating a low-carbohydrate lifestyle, and potentially stand to profit financially from an increased adherence of a very low carbohydrate lifestyle. This doesn’t automatically mean that their science is wrong, but that it should be subject to further scrutiny. Plenty of very good counter-points to their argument were made, including the fact that work-time physical activity almost certainly has declined over the past thirty years, indicating that physical inactivity may be a causative factor in the obesity epidemic. The fact that some of this evidence comes from a researcher who receives funding from Coca-Cola (who quite obviously would want you to not reduce carbohydrate intake from their drinks) illustrates how messy this has become. The pertinent point that I want to make here is that we quite often believe science to be black or white, right or wrong, but it’s actually very different shades of grey. Highly intelligent and well respected individuals can interpret the same set of results very differently, and come to their own conclusions. What is right for some people (a low carbohydrate diet in sedentary people) may not be appropriate for others (a low carbohydrate diet in elite athletes). This might seem negative, but it’s actually a positive, as it spurs on more research, which allows the true shade of grey for each particular issue to come into focus. With obesity, it is likely to be a multifactorial problem, of which excessive carbohydrate intake is certainly one (although what is excessive is up for debate), but so to is physical inactivity.
Hopefully you’ve enjoyed this review of the best/most interesting bits of research in the sports science field from 2015. Science is always moving forward, and every bit of new research always adds to the picture. Hopefully 2016 will bring some more interesting bits!
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