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How genetics affect the body shape and athletic performance

Sports progress is largely dependent on genetics. A 2005 study showed that the same strength training affects people differently.

After 12 weeks of training, some participants doubled in strength, and their muscles grew significantly, while in others the changes were insignificant or completely absent. Participants with worse results lost 2% of their muscle mass and did not increase their strength at all, while genetic lucky ones increased their muscle mass by 59%, a one-time maximum of 250%. And this is with absolutely identical loads.

Let’s see why the indicators are so different and how genetics affect muscle growth.

How genetics affects muscle growth

The number of satellite cells


In his study, Dr. Robert Petrella suggested that the difference in results with the same physical activity depends on the number and effectiveness of satellite cells – stem cells of muscle tissue.

In an earlier study, it was found that participants with good muscle hypertrophy had more satellite cells and their number increased rapidly thanks to training.

At the beginning of the experiment, participants with the best indicators had an average of 21 cells per 100 muscle fibers, and by the 16th week of training, the number of satellite cells increased to 30 per 100 fibers.

Participants whose muscles did not increase during the experiment had about 10 satellite cells per 100 muscle fibers. This amount has not changed after training.

Gene expression

The dependence of athletic performance on genetics has been confirmed by another study. As a result of the same training out of 66 participants, 17 increased the cross-sectional area of the muscles by 58% (let’s call them successful athletes), 32 participants – by 28%, and 17 genetic losers – by 0%.

The reasons for this scatter of results:

  • Increased synthesis of mechanical growth factor. Successful athletes – 126%, genetic losers – 0%.
  • Increased myogenin synthesis. Successful athletes – 65%, genetic losers – 0%.
  • Increased synthesis of IGF-IEa genes from a variety of mechanical growth factors. Successful athletes – 105%, genetic losers – 44%.

Another study showed that people with high expression of key hypertrophy genes adapt faster to strength training than ordinary people.

How genetics affect the amount of fat in the body

In the past, the genes that endow people with economical metabolism were an evolutionary advantage, because it helped to survive in hunger. Today, when our lifestyle includes sedentary work and excess calories, these same genes cause health problems and obesity.

A twin study showed that with the same diet, people gain weight in different ways. Twelve pairs of twins over 84 days exceeded their calorie norm by 1,000 per day and led a sedentary lifestyle.

With the same diet, the results of the participants were very different and ranged from 4 to 13 kilograms. People with a metabolic curse gained three times as much weight as lucky ones, accumulated 100% of extra calories and increased their visceral fat by 200%. For metabolic lucky participants, the amount of visceral fat has not increased.

Another study showed that heredity determines the amount of subcutaneous fat by 42% and visceral fat by 56%. This means that genetics directly affects how your body stores fat.

Another study suggested that changes in metabolic rate and energy expenditure on physical activity by 40% depending on genetics. Another study showed that body mass index is inherited by 40–70%.

A 1999 study found that genetics affects calorie intake. Other scientists who studied the nutritional behavior of 836 participants came to the same conclusion. They found six genetic links that increase calorie and macronutrient intake, including the adiponectin gene, a hormone that is involved in regulating glucose levels and breaking down fatty acids.

It turns out that not only eating habits and stress levels affect weight gain. Some people are simply genetically more prone to overeating and accumulating fat.

How genetics affects our strength

The best known physical performance-enhancing gene is ACTN3, known as alpha-actinin-3. This gene is examined to identify a predisposition to certain sports.

There are two types of alpha-actinin protein – ACTN2 and ACTN3. ACTN2 is found in all types of muscle fibers, and ACTN3 in type IIb is found in fast and large muscle fibers, which are activated during short-term loads and develop greater strength. Therefore, ACTN3 is associated with a powerful production of force.

About 18% of people worldwide have ACTN3 deficiency. Their bodies produce more ACTN2 to compensate for the shortage. These people cannot make explosive movements as fast as those who have enough of this protein. For example, among elite sprinters, there are no people with alpha-actinin-3 deficiency.

The angiotensin-converting enzyme (ACE) gene is also involved in athletic performance. An increase in the frequency of the ACE D allele is associated with strong athletes and sprinters, while an increase in the frequency of the ACE I allele is more common in athletes with impressive stamina.

One study showed that physical development is also affected by VNTR-1RN gene variants. This gene affects cytokines and enhances the inflammatory response and recovery processes after exercise.

Reichman’s study confirms these findings and links the interleukin-15 cytokine with increased muscle hypertrophy.

Final thoughts on how genetics affect body shape and athletic performance

After all these studies, it may be believed that a strong and beautiful body must be won in the genetic lottery. If no luck, then there’s nothing to be done. This is actually not the case.

First, everyone has genetics issues to work on. Some people are predisposed to the accumulation of fat, while others are difficult to build muscle. Even among elite athletes, there are no people with perfect genetics, but they still work on shortcomings and achieve their goals.

Secondly, these studies did not take into account the characteristics of specific people and did not select training and nutrition programs for each of them. Yes, with the same program, people with good genetics will show better results, but if you choose the right load, even the worst genetics will not stop you.

Continue to experiment, select a program, change nutrition and exercise, then you will certainly achieve your goal, despite genetics. Unlike genetic lucky ones, in your case, it will be a real victory.

Cover image by Elias Sch. from Pixabay

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