[Listen to an audio version of this blog here.]
I have been running consistently since age 12, and I've been athletic and active for as long as I can remember. Inactivity, to me, is a dirty word (not to be confused with rest, tyvm). One thing that used to really bother me about my body, though, was how it doesn't look like other runner bodies. Lining up on the start line of most races, I'd notice how thin other women were. How lanky their limbs or how tiny and light they appeared. Even when I starved myself thin, I couldn't undo my natural, muscular frame. Even at the apex of anorexia, the only time I was able to shed significant pounds was when I wasn't able to work out. My muscles all but disappeared, the scale dipped and my fucked up brain thought I was winning.
On the other side of recovery, I've learned to love my muscles because I love being active. I like running up mountains and being able to lift heavy things. I like feeling strong and empowered in my body. But when I feel the most strong, I look the least "like a runner."' I've been unable to run for most of January due to a bum hamstring, and I turned to cross training to stay in shape. I found a nearby gym and started lifting heavier weights, biking, and (attempting) to swim. After a few weeks of my new regimen, I was visibly gaining muscle, most noticeably in my arms. A trainer at the gym asked if I'm into bodybuilding. "Ummmm no not really," I said, "not at all." "Well you could be!" was his kind reply. Bodybuilding doesn't suit my temperament, however. I like to climb mountains and chase sunsets, and the thought of staring at a gym wall day after day is enough to make my skin crawl.
But then I got to thinking, why is it so easy for me to gain muscle? I had a hunch it has mostly to do with my genetic makeup but I wanted a real answer. So the first thing I did was schedule a DEXA scan to determine by exact amount of lean body mass. It's one thing to look in shape and another to actually be in shape. My results showed that I have almost 24% body fat, with nearly 120 pounds of lean tissue on my frame. They also showed that my left arm and leg are slightly lighter than my right, and that nearly 130 pounds of my total body weight is in my legs and torso, which is one very good reason that pull ups are difficult for me. Overall, this was useful knowledge and fun to know. I will probably go back in a few months if I notice significant differences in strength from lifting more.
Body composition is a bit trickier to measure accurately than weight, but I find it to be a more useful tool for measuring health, especially as an athlete. According to just about every reputable source, the amount of essential fat differs between men and women, and is typically around 2-5% in men, and 10-13% in women. The healthy range of body fat for men is typically defined as 8-19%, while the healthy range for women is 21-33%.
Small, fun fact: I have a personal training certification through NASM that I believe is out of date. I'm not going to renew it because I don't train anyone but it gave me a base level knowledge about fitness. I know the right things to do to get stronger, and generally know the right things to eat at the right time (protein, 20-30 grams within 30 minutes of a hard effort). I know that individuals with higher levels of testosterone or growth hormones have an easier time gaining muscle mass, but I don't really know, in practice, what that means or if it can be manipulated through diet, exercise, or rest. So I did some research, and this is what I found:
Genetics can make it easier or harder to build muscle and lose fat. They don't make it impossible; you just have to work with your genetics and build a plan to suit your body's needs. "Genetic predisposition is mainly a combination of genetics and hormonal factors," says exercise physiologist Jonathan Mike, Ph.D., C.S.C.S Those with naturally high testosterone and growth hormone levels will build muscle faster and find it easier to maintain a leaner physique. Testosterone and growth hormones are interconnected: testosterone stimulates the pituitary gland to release growth hormone, which increases the availability of amino acids required for protein synthesis. Growth hormone, in turn, stimulates the release of insulin-like growth factor, which also stimulates muscle growth. The more of these hormones you have available, the more impact they'll have on the size (and strength) of your muscles.
You can manipulate your hormones through training, to some extent. If you can stress and manipulate the endocrine system, you can increase the production of growth hormones. Hormones are also influenced by stress, sleep, and nutrition. Even if you're training in a way that might increase growth hormones or muscle mass, bad sleep, stress, or poor nutrition could set you back.
There is one factor that science hasn't really explained: genetics also determine how responsive your body is to the muscle-building process. You could have lots of growth hormone but your body could, for various reasons, be less sensitive. Since growing muscle is complex, a system breakdown anywhere along the chain of events could impact your results: if your pituitary gland isn't functioning correctly, for example, or if your satellite cells are less responsive to the damage inflicted by training.
Wayne Westcott, Ph.D., director of exercise science at Quincy College in Quincy, MA. has a quick trick to figure out if you are genetically predisposed to build muscle easily. Long muscles and short tendons are ideal for looking super toned. To gauge how long your muscles are, put your elbow up at a right angle, and see how many fingers you can put in between your elbow crease and where your bicep starts. The less space you have (and fewer fingers you can fit), the longer muscle belly you have, which means the greater potential you have for building muscle size, strength, and tone.
What I've done since recovering from my eating disorder is to stop attempting to change my body and embrace it's natural strength/shape. Focusing on health rather than appearance is the most sane and sustainable route, but if you want to build muscle, you'll need to work with your specific genetic makeup. I'd strongly recommend working with a trainer who has experience driving the results you want, whether that's shedding extra pounds, training for a specific sport, or gaining muscle. Most trainers are somewhat specialized and a fair amount are (like me) not incredibly informed. Chose a trainer wisely and don't be afraid of ditching one.