Everyone is acquainted with those individuals — the ones who attend SoulCycle once and seemingly emerge transformed with noticeable arm muscles. Many describe this phenomenon as muscle tone: biceps peeping out, back muscles visible, well-developed abs. However, “muscle tone” lacks a specific definition, according to Wayne Westcott, Ph.D., former director of exercise science at Quincy College in Massachusetts. It essentially refers to muscles that appear prominent.

Nevertheless, muscle tone does not always correlate with strength. For instance, someone with minimal body fat may exhibit more visible musculature despite not possessing the corresponding strength gains. Conversely, an individual with higher body fat levels might be incredibly strong even if their muscles aren’t as visible. The same principle applies if one loses weight (thus shedding the fat covering the muscles) without necessarily gaining muscle. Michele Olson, Ph.D., C.S.C.S., senior clinical professor of exercise physiology at Huntingdon College in Montgomery, Alabama, explains that in such cases, individuals become smaller, making their muscles more evident regardless of their level of development.

Therefore, if you truly desire that defined, muscular appearance that not only looks good but also powers you through your day-to-day activities and workouts, it is essential to understand that it involves a combination of genetics, lifestyle choices, and exercise, according to experts. It is not as simple as it may seem.

Below, we provide details on why some individuals have more defined muscles than others and offer suggestions on how to build noticeable muscle mass according to your body type.

The Genetic Factors Influencing Muscular Definition

Genes play a role in determining how muscular one appears, as noted by Westcott. “Some individuals are born with elongated muscles and short tendons,” he explains. This anatomical composition is ideal for achieving that highly defined look. You can assess the length of your muscles by raising your elbow to a right angle and observing how many fingers you can fit between your elbow crease and the starting point of your bicep. The lesser the space available (and the fewer fingers you can fit), the longer your muscle belly is, indicating greater potential for muscle size, strength, and definition. On the other hand, those with shorter muscle bellies have less muscle mass to work with.

Furthermore, while it may seem logical to assume that tall, athletic individuals have longer bones and subsequently longer muscles, this is not necessarily the case. According to Westcott, having long arms and legs or being tall doesn’t automatically mean you have longer muscle bellies relative to your bones. Even individuals of shorter stature can have longer muscle bellies compared to their bone length and possess equivalent potential for expanding their muscle mass.

Likewise, everyone is born with both slow-twitch and fast-twitch muscle fibers, as explained by Westcott.

When you engage in strength training, the fast-twitch fibers exhibit a greater level of response and develop more effortlessly, according to his statements. Therefore: “Individuals who possess a proportion of fast-twitch fibers that exceeds the average are prompt in their reaction and reap greater benefits from the stimulus provided by strength training,” elucidates Westcott.

Then, there’s body adipose tissue. “If you have a higher level of body adipose tissue, it’s like having additional covers enveloping you on your bed,” says Olson. “This plays a significant role in being able to perceive your slender muscles,” she remarks. Body adipose tissue distribution is also at least partially genetic — and don’t forget that body adipose tissue is not a negative thing to possess! Just because your muscle gains aren’t as visible, doesn’t mean you aren’t strong and influential. However, if you’re determined to witness your well-defined muscles, there are methods to safely reduce body adipose tissue while preserving those gains.

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How to Cultivate Your Muscles

The positive news? Genetics aside, everyone possesses muscles and everyone can strive to cultivate them, notes Olson. Unfortunately, there’s not much you can do differently if you have a shorter muscle belly, but you can adapt your training based on your muscle fibers. If you possess more slow-twitch muscle fibers (think: marathon runner), you’ll likely be better at endurance-type activities as these muscle fibers tire more slowly than the fast-twitch variety (think: sprinter). That also means they respond better to high repetitions.

So while someone with fast-twitch muscle fibers (which fatigue more rapidly) could get away with doing fewer repetitions and seeing definition faster, you might just need to put in say, 15 or 20 repetitions 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 additional effort as it doesn’t necessarily feel like “extra.”

If you’re simply born with a higher level of body adipose tissue, you could also benefit from more aerobic and cardiovascular 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 significant factor when it comes to maintaining 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 adipose tissue, 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 various exercises (usually five to 10) that focus on different muscle groups or alternate periods of moderate- to high-intensity work with periods of either active or passive rest — enhances the metabolism and keeps it elevated for hours to come, mentions Westcott. Paired with a substantial protein consumption, this can assist in reducing fat and developing muscle.

Since muscles are 75 to 77 percent H2O, proper hydration is also important, emphasizes Westcott. “Maintaining adequate water levels improves the functioning and appearance of your muscles, as well as benefiting your skin,” he states.

Next, let’s talk about nutrition. Limiting the consumption of foods that can be stored as adipose tissue (consider white bread, sugars) and prioritizing protein, which has a lower tendency to be stored as fat, and produce, which contains high levels of water, is crucial, according to Westcott. If you have a moderate amount of both adipose tissue and muscle, you can expect to see more noticeable musculature within four to six weeks, as per Westcott. However, if you have a higher percentage of adipose tissue, it may take longer — around eight to 12 weeks.

Additionally, instead of relying solely on visual cues of progress, Westcott suggests using how you feel as a measure of success. “Even if the physical changes aren’t obvious, if you can sense increased firmness and tension in your muscles when contracting them, then you’re on the right path towards achieving harder, more toned muscles,” he explains.

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