In late 2010 one of the more interesting studies on genetics and muscle growth was published in the Journal of Applied Physiology. This was a great study because they wanted to determine the genetic differences between high responders and low responders to strength training. In fact I thought it was somewhat ground breaking to a degree, and posted it on the forums shortly after it was e-published.
Mir'in my miRNA's?
MicroRNA's or miRNA's are approximately 22 short nucleotide ribonucleic acids. MicroRNA's essentially control the expression of messenger RNA's, which essentially tell a cell what to do (protein synthesis). What?! In simpler terms, MicroRNA's regulate gene expression. Why do we care? Well this research did something interesting. They took 56 men between the ages of 18 and 30 and put them through 12 weeks of resistance training that included weight training 5 days per week. The study controls were great as well and they monitored everything including:
- Training Status
- Initial Body Mass
After the training they split the 56 men up. They found the top 15-20% responders based on cross sectional muscle fiber increases (and vice versa for low responders). They took these two groups (high and low responders), and further analyzed them by completing 1 rep maxes in the leg press, knee extension, and hamstring curls. This resulted in the final two groups of 8-9 men that they dubbed High and Low responders.
High responders gained almost 4 times the amount of lean body mass in the same training period (remember diets & training were controlled). Over the twelve weeks it resulted in approximately 10lbs of lean body mass gain in the high responder group compared to only ~2.4lbs in the low responder group. Almost a difference of 8lbs! Clearly there must be a genetic influence involved.
The more important part of this study was their analysis of muscle biopsies, which included differences in miRNA abundance between each group. They measured 21 different miRNA's in each group. Only four were found to be statistically different in each group:
- miR-378 - positive correlation to muscle mass gains, and down-regulated in low responders
- miR-29a & miR26a - down-regulated in low responders, unchanged in high responders
- miR-451 - up-regulated in low responders
With this information we clearly have some "genetic targets" that we may be able to alter by supplementation. What exactly that is, we do not know yet. Much of the genetic research, particularly on microRNA's, is still in it's infancy. Still this leaves us with with some insight. We know that there is quite the disparity between the genetically gifted and the genetically inferior. Most of the 56 men fell somewhere in the middle in terms of lean body mass gain. So overall, even if you're in the bottom 15-20%, we know you can still achieve some level of personal success with weight training and dieting correctly.