Big muscles get bigger, faster -- duh
In what's probably the least surprising news in the world of exercise science, your larger muscle groups (generally speaking) are pretty much guaranteed to respond more quickly to strength training than your smaller muscle groups.
Think about it: You have muscles everywhere, from your forehead to your pinkie toes, but you don't see too many people walking around with excessively built thumbs, do you? Of course not. Smaller muscles, by their very nature, aren't designed to "get big," the way larger muscle groups are.
This difference in "buildability" is due to a surprisingly long list of factors, including, but quite possibly not limited to, the following:
- Anatomical cross-sectional area: Often measured as the widest point of a muscle along the muscle's length
- Muscle structure: The length and angle of muscle fascicles (basically just a bundle of muscle) in relation to the line of action of the muscle
- Individual anatomical differences: Specifically, moment arm length, which affects torque at different joints
- Neural drive: How effectively your brain recruits motor units (muscle groups) and how frequently these motor units fire
- Muscle fiber characteristics: Distribution of muscle fiber type, based on type I ("slow twitch") fibers and type II ("fast twitch") fibers within a given muscle, as well as presence and physiological predisposition to activate satellite cells
Whew. There's a reason it's called exercise science.
Very generally speaking, you can assume that larger muscle groups, particularly those with a larger cross-sectional area, such as the glutes, will be easier to get bigger, faster. It's also a fairly safe assumption that muscles that happen to have a higher percentage of fast-twitch fibers, including the pecs, lats, triceps, biceps, and quads, will also experience faster, more pronounced growth.
But as with all things fitness, the level of variability between individuals is a major confounding factor that could, quite possibly, explain why your calves look like scrawny chicken legs, while your best friend has no problem building gastrocs the size of bowling balls.
How you train matters
If your goal is to get bigger, training really matters. While all forms of exercise can effectively make you stronger, the extent to which muscle will grow is affected by training programming. When it comes to building mass, you should focus first on compound exercises that target multiple muscle groups (moves like squats, lunges, bench press, and pull-ups), and make sure you're lifting to failure.
"Lifting to failure" is the key phrase here. You can do this with lighter weight and more repetitions, or you can do it with heavier weight and fewer repetitions. It's your call, but one fast, effective way to do it is to perform more sets of fewer repetitions with heavier weight and more rest between sets.
For example, you might perform two to five sets of squats lifting approximately 70% to 80% of your estimated one-rep max, only performing six to eight repetitions per set. Focus on form and the time under the load, moving slowly through each repetition to maximize the stress you're placing on your working muscles.
Give yourself a few minutes of rest between sets, then repeat, accumulating two to four sets of each exercise. You really want to tax the muscles you're targeting to stimulate muscle protein synthesis.
Blame your parents if you can't put on size
The sad reality is that pretty much everyone has a few genetic blips that might prevent them from seeing exceptional results. Maybe you're genetically predisposed to put on body fat, or maybe you have fewer satellite cells or fast-twitch fibers than your bigger, stronger friends. Or maybe you just don't have as much cross-sectional muscle area through your ass, slowing you down from building the glutes of your dreams. These things happen. Sometimes you have to work a little harder to see the results you want to see because you're fighting an uphill battle against your genes.
Then there are those unfortunate souls termed "non-responders" who simply don't put on muscle mass the way others do. In a landmark study, "non-responder" participants actually LOST 2% of their muscle cross-sectional area after participating in a 12-week exercise program, whereas the best responders increased their cross-sectional area by almost 60%. These people got smaller with strength training. How's that for a slap in the face?
If you're worried you fall into this category, don't despair. You might never get as big as Arnold Schwarzenegger in his heyday, but with a solid nutritional program, a consistent exercise program, and possibly the assistance of a trainer or coach, you can still see improvements in physique. Just don't quit altogether, strength training is still good for you.
You can't overlook nutrition
Without going into a long lecture on sports nutrition, I'll say this: What you eat, how much you eat, and when you eat all matter.
Consuming high-quality protein throughout the day, including before and after your workout, is one important way to make sure your body is receiving the amino acids it requires to repair and develop muscle cells. Eating a meal that combines proteins and carbohydrates after your strength-training session will help speed recovery and prepare you for your next workout.
While the specifics are negotiable, protein shakes, cereal and a banana, spaghetti with meat sauce, and chicken and potatoes are all examples of quality post-workout meals. And if you're not seeing the results you want, talk to a sports nutritionist about your diet plan, and consider adding performance-enhancing supplements to your repertoire. Some of them actually work.