Introduction
This week we take a look at a fascinating area of research that is beginning to inform us exercise practitioners: the role of genetics in how we recover from exercise. Have you ever wondered why after performing the same activity, perhaps going for a bushwalk, working in the garden or even a workout, right next to a friend of yours, yet the next day you are sore but they are not, or vice versa? Now obviously this could be due to fitness levels and how well behaved each of them was during the recovery phase, but recent research into genetics suggests there are probably genetic differences as well. I’m particularly interested in this area as we are all now able to get our genetics tested for just a few hundred dollars, and this is now forming part of many athletic development programs, so why not for all of us?

Article Title
Genetic variation and exercise-induced muscle damage: implications for athletic performance, injury and ageing, by Baumert, Lake, Stewart, Drust & Erskine, in European Journal of Applied Physiology (2016)

Background
Genetics are believed to be important for determining the response to strength training, particularly in relation to the amount of muscle mass that can be gained. Indeed, some individuals respond very well to resistance training and display marked hypertrophy (responders) while others fail to respond in a meaningful way (non-responders) although they are all subject to the same training program. In addition, some individuals seem naturally to display a higher degree of hypertrophy during development, resulting in more muscle mass in adulthood than others of the same height and gender, even when put in the same environment. Traditionally, researchers have had to rely upon twin studies for investigating the extent to which heritability influences muscle mass in adulthood. Based on this literature of twin studies, some reviewers have suggested that genetic factors are responsible for around 50 – 80% of the inter-individual variability in muscular size, but whether these twin studies are able to control adequately for differences in the lifestyle of the individuals involved is unknown. In contrast, more recent research has been able to explore the genetic influences more directly, by comparing gene expression between individuals. This research currently paints a very different picture from the twin studies. Indeed, only a small number of genetic traits and single nucleotide polymorphisms (SNPs) seem to be related to the ability to gain larger increases in muscle mass. Consequently, most reviews have concluded that, with a few minor exceptions, single variants in genetic polymorphisms explored using modern genetic testing methods can currently only explain very small amounts of inter-individual variability in the hypertrophic response to resistance training.
EIMD is a broad description, referring to damage to any part of the muscle fiber, but particularly the ultrastructure (the inner framework that maintains the contracting actin-myosin filaments in place), the extracellular matrix (ECM) (which is the framework that encapsulates each actin-myosin myofilament), in addition to the sarcomeres themselves, and the ttubules (which release calcium ions inside the muscle cell during excitation-contraction coupling). Some types of exercise are known to cause more EIMD than others, particularly those involving a high proportion of eccentric muscle actions. Although this has led some researchers to focus on EIMD produced along the length of a muscle fiber, a large proportion of force is in fact exerted laterally during muscle actions. This means that structures that transmit force in that direction (including the costameres that link the myofilaments to the ECM, and the ECM itself) are also subjected to high stresses and damaged.

Conclusion
The researchers found that there are early indications that the tendency to incur EIMD is a genetic trait, probably caused by differences in SNPs. If, with further research, this is proven to be the case, it fulfils the current suspicion that all people need to be trained as individuals not just because of their exercise and injury history, but because of genetic differences that change the way our bodies respond to exercise.
So the take home message is, if it’s true that we are genetically disposed to greater damage during exercise then we need to adjust our exercise program to include more protective elements such as:
– Greater rest periods between exercise
– More eccentric (lowering phase: slow down fast up) exercise
– More isometric exercise (holding in the middle or bottom of a movement
– More focus on biomechanical improvement
– More recovery enhancing activities
I’m off to get myself tested!

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