• Anatomy Of Fitness

How SCIENCE Defines FITNESS?

Updated: Sep 5

Information and opinions flood us. Right from financial planning to fitness, individuals have their idea(s). Such views lurking around fool us into believing blatant unscientific lies on fitness. Since science can define fitness, we need not rely on opinions.

What is fitness? Can science define fitness? Or do we always have to rely on opinions?


People have perceptions about lifestyle, especially exercise. Let's highlight the most common ones:

  • I am very fit; I don't need to exercise.

  • Skipping is the best exercise.

  • Walking is the best exercise.

  • I'm not a bodybuilder, so I don't need to go to the gym.

  • Running is the best exercise, and my doctor has asked me to run for 5 kilometres a day.

  • I don't want to get bulky and not have huge muscles; hence I will exercise only a little.

Am I fit?
Am I so fit that I don't need to exercise at all?
Is skipping the best exercise?
Is skipping is the best exercise?
Do I need to go to a gym?
Do only professional body builders need to go to a gym?
Is running the best exercise?
Is running is the best exercise?

If we ask someone about the reason behind their perception, most people will be clueless or vaguely say they say this is the best form of exercise, or I've heard this is good, that is bad, etc. But, in fact, in most cases, none of their fitness philosophies stem from science.


Often, some people may refer to individuals who have been there and done that to achieve dramatic results. However, these results may be coincidental, or their understanding of what these individuals achieved is limited.

Opinions on fitness confuse us.
Is fitness opinionated or scientific?

Physiologically, all humans are the same. So it means what physiologically works for me should also work for you. Google dictionary defines fitness as - the condition of being physically fit and healthy or the quality of being suitable to fulfil a particular role or task.

As defined by science, there are five components of fitness. Each part is equally important.


The Five Elements of Fitness:

  1. Muscular Endurance: The ability of a skeletal muscle or a group of skeletal muscles to continuously contract at sub-maximal levels for an extended period.

  2. Cardiovascular Endurance: The ability of the cardiovascular system and respiratory system to transport oxygenated blood to the working skeletal muscles for an extended length of time without fatiguing.

  3. Musculoskeletal Strength: The combined strength of muscles, bones, tendons and ligaments, is what makes up this component. It includes muscular power, which is the ability of a skeletal muscle or a group of skeletal muscles to perform against a load or resistance in a given time frame.

  4. Ideal Body Composition: It is defined as the ability of an individual to maintain the ideal ratio of adipose tissue (fat) to lean body mass. A male has an ideal body composition if no more than 15% of his overall body weight comprises adipose tissue. A female has an ideal body composition if no more than 20% of her total body weight comprises adipose tissue.

  5. Body Flexibility: It can be defined as the ability of the body to sustain a complete range of motion around joints. It can be achieved by not allowing the skeletal muscle to lose its elasticity. If body flexibility interests you, do check this blog on The Importance of Stretching.

Opinions Don't Matter When Science Can Define FITNESS.

Importance of the Five Elements of Fitness:

  1. Muscular Endurance: A decrease in this fitness component makes an otherwise straightforward task a very demanding one. Simple tasks like climbing stairs, crossing roads, catching trains, lifting an infant from the ground become very difficult. Suppose the cardiovascular system is up to the mark and the muscular system is compromised, the source of early onset of fatigue in the body will be due to the compromised musculoskeletal system. For example, a person with a compromised musculoskeletal system resulting in reduced muscular endurance experiences discomfort while running. It is due to a sharp rise in lactic acid levels in the skeletal muscle which generates during the activity. Such a person would experience fatigue in their quadriceps, gluteal muscles, calves etc., not because of the compromised cardiovascular system but because the muscular endurance is not up to the mark.

  2. Cardiovascular Endurance: A decrease in this component of fitness causes problems similar to the muscular endurance component. Continuing with the same example mentioned above, the early onset of fatigue will be due to a compromised cardiovascular system. A compromised cardiovascular system may even cause a cardiac arrest due to a slight increase in the intensity of activities.

  3. Musculoskeletal Strength: A decrease in this component of fitness leads to early degeneration. It causes degenerative conditions like spondylitis, osteoarthritis etc. A weakened musculoskeletal system may expose the body to a high risk of injuries while performing even simple tasks involving force against resistance.

  4. Ideal Body Composition: Lean mass has a tone and a shape, whereas fat is untoned and shapeless. People who follow the fitness lifestyle appear toned because they carry more lean tissue and less adipose tissue (fat). An increase in lean mass causes the body to look firm and toned, with tremendous aesthetic value. Lean mass is metabolically active, whereas adipose tissue is metabolically inactive. Lean mass plays a vital role in increasing the body's basal metabolic rate or BMR and thus, help in reducing fat. The basal metabolic rate or BMR directly correlates with calorie burning. The primary purpose of your body storing fat is to use it later in emergencies like sustained periods of negative calorie deficits. An increase in lean mass leads to an increase in the strength of the musculoskeletal system. An increase in your fat store leads to an increase in the probability of acquiring lifestyle-related diseases.

  5. Body Flexibility: Adequate flexibility prevents injuries. A stiff muscle that has lost its elasticity is more likely to tear. In the event of a movement trying to go through a full range of motion around a joint would pull apart the muscle. A classic example of lack of flexibility causing postural problems is hamstring inflexibility.

It's crucial to lay equal emphasis on all five components of fitness. All the five pillars of fitness are interrelated, and it is equally essential to get better at all five elements.

Fitness is scientific and not opinionated.
Fitness is scientific.

Key takeaways:

  1. Fitness is scientific and not opinionated.

  2. Perceptions about fitness have zero scientific value.

  3. There are 5 components of fitness - muscular endurance, cardiovascular endurance, musculoskeletal strength, ideal body composition and body flexibility.

  4. Each of the five components of fitness are interdependent and equally important.

Now we understand how science defines fitness.

#fitness #fitnessscience #componentsoffitness #opinions

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