Expert: Chris Bemis - 2/22/2010

Question
I am having a debate between me and a couple buddies of mine. If i am an average sized male and i work out for many years and gain a much larger muscle mass than what i started with, by the time i have a child, will the child grow up to be bigger and stronger than if i had not worked out at all in my life?

Answer
No matter how much you exercise, it will not change your genes.  Your genetic material is basically set from the moment you are conceived.  It is the blueprint for your physical potential.  Your genotype (the genetic basis for YOU) does not change when you exercise.  Exercising only changes your phenotype (your physical appearance- what you actually look like), and your phenotype is largely controlled by your genotype.  Your genes determine your metabolism, including how your muscle is built.  Because of genetics, some people's bodies build muscle easily, while for others it is more difficult.  However, someone may have genes for easily built large muscles, but if they don't exercise, then even though their genes allow for it, they may never see it in their physical appearance.  So, when you build large muscles, you are working within the constraints of your own unique set of genes.  

However, although getting in good shape does not affect your genetics (and therefore does not affect the genes you pass of to your children), being in good shape, eating healthy foods, avoiding drugs and alcohol makes you healthier person overall which allows your body to produce healthier sperm (more likely to fertilize, less likely to be affected by harmful negative mutations).  In addition, when your child is old enough to enjoy exercise, being a parent who can encourage physical activity by setting a good example and being that role model can greatly help your children achieve their physical potential!  The benefits of physical activity in childhood are incredible:  http://journals.lww.com/amjmedsci/Abstract/1995/12000/The_Benefits_of_Physical_A...

Hope this helps answer your question,

-C