Why Some People Have an Easier Time Building Muscle Definition

Everyone knows those people — the ones who go to SoulCycle once and somehow seemingly emerge into the light with visible biceps. Many refer to this as muscle tone: biceps peeking out, back muscles visible, strong-looking abs. But "muscle tone" has no specific definition, says Wayne Westcott, Ph.D., former director of exercise science at Quincy College in Massachusetts. It's just, more or less, muscles that appear to stand out, he says.

And it's not always an indication of strength. After all, someone with very little body fat might have much more visible musculature even if they don't have the strength gains to match it, and someone with more body fat might be mega-strong, even if their muscles aren't visible. The same goes for if you lose weight (and thus the fat on top of the muscles), but don't necessarily gain muscle. "You will become smaller and the muscles, regardless of how developed they are, will show more," notes Michele Olson, Ph.D., C.S.C.S., senior clinical professor of exercise physiology at Huntingdon College in Montgomery, Alabama.

So if it's that muscle-defined look you're really after (you know, the one that looks good but also, more importantly, powers you through your day-to-day and your workouts), it's important to know that it involves a mix of genetics, lifestyle choices, and exercise, note the experts. And it's not as simple as you think.

Here are the deets on why some people have more defined muscles than others, and what you can do to build noticeable muscle mass for your body type.

The Genetics of Defined Muscles

Part of how muscular you look comes down to genes, notes Westcott. "Some people are born with long muscles and short tendons," he says. And this is ideal for that super-defined look. 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 definition. "Someone born with short muscle bellies does not have as much muscle to work with," notes Westcott.

And while it makes sense that a tall, athletic person would have longer bones — and thus, longer muscles — just because you have long arms and legs (or are tall) doesn't necessarily mean you have long muscle bellies compared to your bones, says Westcott. Someone who's short, for example, can still have a longer muscle belly relative to their bone and have just as much potential for expanding their muscle mass.

Along those same lines, everyone is born with slow-twitch and fast-twitch muscle fibers, says Westcott. When you strength train, the fast-twitch ones are more responsive and grow more easily, he says. So: "People born with a higher-than-average percentage of fast-twitch fibers respond quickly and more effectively to the strength training stimulus," explains Westcott.

Then, there's body fat. "If you have a higher level of body fat, it's like having extra blankets covering you on your bed," says Olson. "This plays a huge role in being able to see your lean muscles," she notes. Body fat distribution is also at least partially genetic — and don't forget that body fat is not a bad thing to have! Just because your muscle gains aren't as visible, doesn't mean you aren't strong and powerful. However, if you're set on seeing your defined muscles, there are ways to safely lose body fat while maintaining those gains.

How to Develop Your Muscles

The good news? Genetics aside, everyone has muscles and everyone can work to develop them, notes Olson. Unfortunately, there's not much you can do differently if you have a shorter muscle belly, but you can adjust your training based on your muscle fibers. If you have more slow-twitch muscle fibers (think: marathon runner), you'll likely be better at endurance-type activities as these muscle fibers fatigue more slowly than the fast-twitch kind (think: sprinter). That also means they respond better to high reps.

So while someone with fast-twitch muscle fibers (which fatigue more quickly) could get away with doing fewer reps and seeing definition faster, you might just need to put in say, 15 or 20 reps to see similar results, explains Westcott. But that doesn't necessarily mean it's more work for you. After all, if you're full of slow-twitch fibers, you likely won't mind the extra work as it doesn't necessarily feel like "extra."

If you're simply born with a higher level of body fat, you could also benefit from more aerobic and cardio work on top of strength, notes Westcott. This can help elevate your resting metabolic rate, burn more calories (called the afterburn effect), and is a huge factor when it comes to keeping a healthy body weight. After that, the general recipe is simple. "In order to sculpt and develop the muscle, you need to engage in resistance training — and to lose body fat, you need to burn calories efficiently," says Olson.

A combination of aerobic and anaerobic — strength and endurance training — is a solid strategy, says Westcott. Interval and circuit training — where you alternate between several exercises (usually five to 10) that target different muscle groups or alternate periods of moderate- to high-intensity work with periods of either active or passive rest — boosts the metabolism and keeps it boosted for hours to come, notes Westcott. Coupled with a high protein intake, this can help you lose fat and build muscle.

Since muscles are 75 to 77 percent water, hydration is important too, adds Westcott. "Being hydrated keeps your muscles functioning better and looking better, and does your skin well," he says.

Then, there's diet. Sparingly eating foods that can be stored as fat (think: white bread, sugars) and focusing on protein, which doesn't tend to go into fat storage, and produce, which contains large amounts of water, is key, says Westcott. If you have a moderate amount of both fat and muscle, you'll likely see more visible musculature within four to six weeks, notes Westcott. If you have a bit more fat, it might take longer — about eight to 12 weeks.

One other thing: Instead of using looks as a gauge of success, use how you feel instead, suggests Westcott. "Even if you can't see it, if you feel some hard parts when you're contracting your muscles, you're moving in the right direction to getting the muscle harder, firmer, and toned," he says.