Mya Care Blogger 25 Sep 2023

Have you ever wondered why some people have bigger muscles than others but are not necessarily stronger? Or why some people can lift heavier weights than others but do not seem as muscular? These questions reflect the difference between muscle size and strength, two aspects of fitness that are often conflated.

In this blog post, we will explain what muscle size and strength are, how they are related, and how to train them depending on your fitness goals.

What is Muscle Size?

Also known as muscle hypertrophy, muscle size is the increase in the cross-sectional area of muscle fibers. When a muscle grows, so do the number and size of contractile proteins that make up each of its fibers.

Muscle size is different from strength in that hypertrophy requires continuous muscle use and not necessarily a high degree of force. Muscle strength relies on the muscle’s size as well as its ability to contract and generate a force, which requires time and practice.

Factors Affecting Muscle Size and Growth

Muscle size is influenced by several factors, such as:

  • Genetics determine the baseline size and shape of your muscles, as well as your potential for growth. This also tends to shape one’s optimal height, weight, BMI, and overall body composition.
  • Training Volume refers to the amount of work you do with your muscles, such as the number of sets, reps, and exercises you perform. It is one of the main drivers of muscle hypertrophy[1], as it promotes physiologic stress, metabolic adaptation, and stimulates muscle breakdown (catabolism), which, in turn, triggers muscle protein synthesis and muscle building (anabolism). There is a specific range of stress that bodybuilders take advantage of in order to stimulate muscle hypertrophy that demands a higher frequency of muscle contractions compared to strength training.
  • Nutrition is also essential for muscle growth, as it provides the energy and nutrients needed for muscle repair and recovery. A positive energy balance (consuming more calories than you burn) and adequate protein intake (around 1.2 to 1.7 grams per kilogram of body weight per day) in combination with resistance training are recommended for optimal muscle hypertrophy[2]. Growth factors, antioxidants, and minerals such as zinc can also contribute beneficially towards muscle growth.

Aging is known to influence genetics and nutrition in such a way that it often promotes muscle loss. Muscle-building exercises can help provide a buffer against age-related muscle loss, yet strength training is still required to help sustain muscle strength and maintain optimal mobility during advanced age.

What is Muscle Strength?

The ability of a muscle, or group of muscles, to produce force against an external resistance is known as muscle strength. Muscle resistance is induced through weightlifting, which is also referred to as resistance training.[3] The strength of a muscle is not necessarily related to its size, yet it does define the overall muscle quality.

Factors Influencing Muscle Strength

Muscle size is one of the main limitations for improving muscle strength in under-developed muscles, yet it is not the only factor involved and often improves with strength training irrespectively.

Muscle strength is influenced by several other factors, including:

Neuromuscular Adaptations refer to the changes in the nervous system that enhance the communication between the brain and the muscles. The brain and muscles are connected by motor units, which comprise a single nerve that innervates a group of fibers. The ability of the motor unit to activate and coordinate muscle fibers contributes towards muscle contraction and strength, yet not size. Hence, one may have large muscles yet lack sufficient motor unit coordination or activation to produce adequate muscle strength.

Aged individuals can benefit from strength and endurance training as these can preserve motor unit function and muscle quality.[4]

Muscle fiber type. Different types of muscle are stronger or weaker depending on their contractile speed and metabolism. Muscle fibers are mainly of two types[5]:

  • Type I fibers mainly consist of the core postural muscles along the spine. They require more oxygen, are slower to activate, and are more resistant to fatigue yet produce less force (are less strong) than type II fibers.
  • Type II fibers make up most of the peripheral muscles in the arms and legs. They are less oxygen dependent, using up stored energy reserves to swiftly contract. Type II fibers tire out quicker and produce more force (are stronger) than type I fibers.

The more type II fibers one possesses, the stronger one can work through the course of training. The proportion of muscle fiber types in your muscles is largely determined by genetics and aging, but it can also be influenced by training.

The activation of various muscle fiber types and sizes based on the strength and duration of the contraction is referred to as muscle fiber recruitment. The more muscle fibers you can recruit, especially the larger and faster ones (type II fibers), the stronger you can be. Working the core muscles typically recruits both type I and II fibers and is renowned for contributing toward overall muscle strength.

More muscle fibers can be recruited by including workout variations that engage “obscure” muscle groups near frequently used muscles. Muscle strength can be further enhanced in type I fibers by incorporating breathing techniques in a core muscle workout.

Muscle Strength vs Endurance

Muscle endurance is the ability of a muscle or muscle group to continue contracting against resistance over a given time period. It answers the question of how long a muscle or group can hold a weight, as opposed to how much weight the muscle or group can lift. Exercises for improving muscle endurance are slower, tend to activate type I (slow) fibers[6] and make use of minimal loading (lighter weights) for a longer time. Improved muscle endurance enhances muscle strength training by allowing for longer sets between rests.

Relationship between Muscle Size and Strength

Generally speaking, there is a positive correlation between muscle size and strength since larger muscles have more proteins that can contract and produce greater force. Both the size and strength of a muscle can lend to increasing its weight, which in turn contributes towards enhancing both size and strength during future workouts.

Muscle size and strength also tend to increase in tandem at similar rates, yet strength can be specially trained by using higher loads (heavier weights) and resting for longer in between. The process for both is known to be slower in women and older adults, as well as in the lower body muscles and torso.

There are few situations where one can increase over the other, such as during aging, muscle strength can be affected by lower neuronal firing, yet the muscle may still grow in response to physical activity and adequate protein intake.[7]

What is the Strongest Muscle in the Body Relative to Size?

The tongue is often mistakenly believed to be made up of the strongest muscles in the body. [8] Depending on how strength is measured, there are, in fact, several muscles that could be the strongest:

  • Quads and Glutes. Overall, the quadriceps (outer thighs) and gluteus maximus (buttocks) are the strongest due to being the largest and generating the most force.
  • The Masseter Muscle in the jaw is known to produce a higher degree of force when corrected for size.
  • The Heart. When looking at endurance, the heart muscle continuously contracts to pump blood around the body, having the highest strength levels relative to fatigue.

Muscle Size and Strength Misconceptions

The most common misconceptions about muscle size are that size is directly proportional to muscle strength and that building muscle relies on specific forms of exercise. Neither of these are true. Muscles of any size can be made stronger, and muscle building typically occurs in all forms of exercise yet is most noticeable in those with a higher frequency of muscle contraction.

Why Are Women Unable to Increase Muscle Size as Much as Men?

Women are known to have smaller muscles than men due to having a lower muscle mass, less testosterone, and an estrogen-based biology. While truthful, this is not 100% accurate, as it depends on the muscle type, area, and fitness level of the individual.

Studies revealed that between male and female athletes, men have a higher muscle mass than women in the arms and torso, yet an equal muscle mass in the legs relative to height[9]. This suggests that height-matched women can increase the size of their leg muscles similarly to men, yet not their arm or torso muscles.

Is Female Muscle Stronger than Male Muscle?

When muscle size and type are taken into account, female muscles are not stronger than male muscles. Female upper body strength and strength during concentric contractions is lower by comparison to men due to having a lower muscle mass and type II fiber density[10].

However, females are known to have higher muscle endurance and recover faster with respect to concentric contractions (muscle shortening). Male and female muscles appear to have similar endurance during eccentric contractions (muscle lengthening).[11]

Training Approaches: Muscle Size vs. Strength

Different training methods can be used to optimize muscle size or strength, depending on the specific adaptations you want to elicit[12]:

  • How to Increase Muscle Size: Hypertrophy-focused training aims to maximize muscle growth by increasing training volume, using moderate to high loads (65% to 85% of one-rep max) and short to moderate rest periods (30 to 90 seconds). Unlike in muscle strength training, the muscles are used to contract and relax more in muscle-building exercises with less emphasis on heavy weightlifting.
  • How to Increase Muscle Strength: Strength-focused training aims to improve muscle force production by enhancing neuromuscular efficiency, using higher loads than those seen in muscle building (85% to 100% of one-rep max), shorter set intervals and long rest periods (2 to 5 minutes). This contracts and tires the muscles more due to using heavier weights and gives them a longer chance between sets to regenerate.

Either approach will increase both muscle size and strength as both are forms of resistance training.

Which Approach is Best?

The choice of training approach depends on your personal fitness goals and preferences:

  • For bodybuilding, hypertrophy-focused training can help achieve a more muscular and aesthetic physique.
  • For powerlifting, strength-focused training can help to lift heavier weights during squats, bench presses, or deadlifts.
  • For enhanced athletic performance, a balance of both training aspects can improve speed, power, agility, and endurance.

Irrespective of the goal, it is important to consider both muscle size and strength in your fitness training routine. They are equally essential aspects of fitness that complement one another to enhance your overall physical capabilities.

To achieve the best results possible, you should seek guidance from qualified fitness professionals who can design a customized training program for you based on your specific needs and goals.


Muscle size and strength are interconnected aspects of overall fitness that can enhance physical well-being and help delay age-related muscle loss, strength reduction, and declining mobility. Both muscle strength and size are improved through resistance training, although muscle strength relies on higher loads, shorter set intervals, and longer periods of rest in between. By understanding the difference between them and applying the appropriate training methods, you can optimize your fitness potential and achieve your fitness goals better.

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