In recent years, advances in sports science and genetics have revealed the impact of an individual’s genetic information on muscle development and athletic ability. It has been shown that certain gene polymorphisms are involved in endurance, explosive power, and even responsiveness to training. In this article, we will provide a detailed explanation of the compatibility between genes, muscle development, and exercise, based on the latest research findings.
The relationship between genes and athletic ability
Alpha-actinin 3 (ACTN3) gene
The α-actinin 3 (ACTN3) gene encodes a protein that is specifically expressed in fast-twitch muscle fibers. This gene has R and X polymorphisms, and there are three possible genotypes: RR, RX, and XX. Research has shown that people with RR or RX types tend to have better explosive abilities and perform better in sprints and other events. On the other hand, people with XX types are said to be associated with endurance abilities. In particular, research on elite athletes has shown that RR types are more prevalent among top athletes in sprint and power events, while XX types are more prevalent among top athletes in endurance events.
The angiotensin-converting enzyme (ACE) gene is also one of the genes related to athletic ability. This gene exists in an insertion type (type I) in which a sequence is inserted in part of the gene, and a deletion type (type D) in which the sequence is absent. Research has shown that possessing type I may be advantageous for endurance ability.
The estrogen receptor (ER) gene plays an important role in the development and regeneration of skeletal muscles. In particular, ERβ is expressed in muscle fibers and muscle stem cells, and is involved in the female muscle development and regeneration mechanism. In a study, abnormalities were observed in the development and regeneration of skeletal muscles in female mice in which the function of ERβ was inhibited. This suggests that estrogen and its downstream signaling are involved in the female-specific muscle development and regeneration mechanism.
By utilizing individual genetic information, it is possible to maximize the effect of training. For example, high-intensity interval training that utilizes explosive power is effective for people with RR or RX types of the ACTN3 gene. On the other hand, long-term aerobic exercise to improve endurance may be suitable for people with XX type. In addition, training to improve endurance is thought to be effective for people with type I of the ACE gene. Furthermore, it is important for female athletes to design training and recovery plans that take hormone balance into account depending on the polymorphism of the estrogen receptor gene.
Use of genetic testing and points to note
In recent years, it has become easier to know one’s genetic characteristics using genetic testing. This makes it possible to create training programs and select sports based on individual genetic backgrounds. However, genes are only a factor that partially influences athletic ability and muscle development, and environmental factors, training, and nutrition also play important roles. Therefore, a comprehensive approach is necessary rather than relying solely on genetic information.
Genetic information and individual differences in performance
Gene to muscle fiber ratio
Muscle fibers are broadly divided into two types: “fast-twitch fibers (type II)” and “slow-twitch fibers (type I).” The ACTN3 gene and ACE gene are thought to affect the ratio of these muscle fibers. Fast-twitch fibers are suitable for explosive movements such as sprinting and weightlifting, while slow-twitch fibers are advantageous for endurance sports such as marathons and cycling.
Research has confirmed that many sprinters have the RR or RX ACTN3 type, while marathon runners have a high proportion of the XX type. In addition, the I type of the ACE gene is said to be involved in improving endurance and is common in endurance athletes, while the D type is thought to be related to explosive power. Thus, while it is clear that genetic factors affect muscle characteristics, it is also suggested that some adaptation is possible through training.
Mitochondrial genes and endurance
Mitochondria play an important role in producing energy in cells and are closely related to endurance. Because mitochondrial DNA (mtDNA) is inherited only from the mother, maternal genetic background may affect endurance. For example, it has been shown that mutations in the PPARGC1A gene, which is involved in mitochondrial function, are associated with improved endurance.
It has also been reported that certain mtDNA haplotypes (genetic lineages) are frequently found in endurance athletes, and it is possible that these genes affect oxygen utilization efficiency and energy production. However, mitochondrial function can also be improved by training, so it can be said that both genetics and environment are involved in improving endurance.
The influence of environmental factors and epigenetics
Regulation of gene expression
It is known that genes are not fixed, but that their expression is regulated by the environment. Epigenetics refers to the mechanism that controls gene expression without changing the base sequence of DNA. For example, it is known that lifestyle factors such as exercise, diet, stress, and sleep can turn genes on and off.
It has been reported that long-term endurance training promotes the expression of genes related to endurance. Conversely, it has been suggested that high-intensity resistance training increases the expression of genes that promote muscle hypertrophy.
Nutrition-gene interactions
Diet is also one of the factors that greatly influence gene expression. For example, omega-3 fatty acids have anti-inflammatory properties and may contribute to muscle recovery and improved endurance. It has also been shown that certain nutrients interact with genetic background to affect athletic performance.
For example, the FTO gene is known to be associated with energy metabolism and increase the risk of obesity, but this effect may be suppressed by eating a high-protein diet. Similarly, it has been reported that the effect of caffeine intake on exercise performance differs depending on the polymorphism of the CYP1A2 gene involved in caffeine metabolism.
By utilizing genetic information, it is possible to design an optimal training program for each individual. For example, people with the RR ACTN3 gene are suited to explosive training, and can improve muscle strength efficiently by focusing on short, high-intensity training. On the other hand, people with the XX gene may achieve better results by focusing on endurance training.
There are also individual differences in the ability of muscles to recover, and the COL5A1 gene has been shown to affect the flexibility of tendons and ligaments. Individuals with certain polymorphisms in this gene may be at increased risk of injury, so it is important to have an appropriate warm-up, stretching and recovery regimen.
Choosing sports based on genetic information
Genetic testing can help you choose the sports that best suit your constitution: for example, someone with a high proportion of fast-twitch muscle fibers may be better suited to power sports like sprinting or weightlifting, while someone with good endurance may be better suited to long-distance running or triathlons.
Furthermore, not only training, but also recovery and nutrition can be optimized taking into account genetic background. For example, people who are prone to inflammation may be able to maximize the effects of their training by eating an anti-inflammatory diet.
Genetic information is useful, but it cannot determine everything by itself. Athletic ability is determined by the interaction of multiple genes and environmental factors, so athletic performance is not determined by the difference in a single gene alone. In addition, current genetic tests cannot identify all genetic factors related to athletic ability, so further research is required.
Furthermore, if you place too much faith in the results of a genetic test, you run the risk of limiting your own potential. For example, if you believe that you are not suited to long-distance running because you do not have the genes for endurance, you may not be able to fully demonstrate the abilities that you would otherwise be able to develop. For this reason, it is important to use genetic information only as a reference and to determine your own aptitude through training and practice.
The best training methods for improving muscle strength
When genetic information is taken into account, the optimal training method for improving muscle strength will vary depending on individual genetic characteristics. For example, people with the RR type of ACTN3 tend to develop fast-twitch muscle fibers, so heavy weight and low repetition weight training and sprint training are effective. On the other hand, people with the XX type are suited to endurance exercises, so moderate intensity and high repetition training may be more suitable.
In addition, muscle recovery speed also differs depending on genes, so it is important to ensure adequate rest time. For example, it has been suggested that polymorphisms in the IL-6 gene affect inflammatory responses and lead to different recovery speeds. Therefore, by designing a rest schedule according to your own recovery speed, you can maximize the effect of your training.
Genetics and endurance training
Genetic factors also play an important role in endurance training. People with type I ACE gene have high oxygen utilization capacity and are suited to aerobic exercise, so they are thought to be suited to endurance events such as marathons and triathlons. For people with this constitution, LSD (Long Slow Distance) training and LT (Lactate Threshold) training may be effective.
On the other hand, people with type D blood are good at exerting muscle strength and power, so by combining interval training, they can improve both endurance and muscle strength. HIIT (high-intensity interval training) in particular is suitable for training both endurance and sprint ability, and even people with genetic elements of explosiveness can improve their endurance.
Flexibility is also known to be influenced by genetic factors: the COL5A1 gene is associated with the flexibility of tendons and ligaments, and people with certain polymorphisms may have reduced range of motion and a higher risk of injury.
For these people, a thorough warm-up and stretching routine is especially important to reduce the risk of injury and maximise the benefits of training. Combining flexibility training such as yoga or pilates can also help improve performance and prevent injury.
Genetics and muscle hypertrophy
Muscle hypertrophy (increasing muscle size) is influenced by many genes, with the IGF-1 (insulin-like growth factor) and MSTN (myostatin) genes receiving particular attention.
IGF-1 gene : IGF-1 is a hormone that promotes muscle growth, and people with certain variants of this gene are more prone to muscle hypertrophy, meaning they’re more likely to get the most out of weight training.
MSTN gene : MSTN (myostatin) is a protein that inhibits muscle growth. People with a mutation in this gene are known to be more likely to develop muscle. In fact, there are attempts to increase muscle mass by inhibiting the action of MSTN.
By designing a training plan that takes this genetic information into account, it is possible to promote effective muscle hypertrophy that is tailored to each individual’s characteristics.
The speed of recovery depends on your genes. For example, the SOD2 gene codes for an antioxidant enzyme and influences muscle resistance to oxidative stress. People with certain polymorphisms in this gene may recover slower from muscle damage.
So if you have slow recovery problems, these strategies can help you get the most out of your training:
Get 7-9 hours of sleep
Consume foods with high antioxidant properties (blueberries, nuts, etc.)
Use cool down and massage
Conversely, people who recover quickly can improve their strength and endurance efficiently by increasing the frequency of their training.
While there are many benefits to using genetic information, ethical issues must also be considered. For example, should genetic information be used to decide which sports a child should play? Should a child avoid sports that are not genetically suited to them?
Success in sports is not determined solely by genes, but also by effort, environmental factors, and psychological factors, so while genetic information can be a useful guide, the final decision should be based on personal choice and interest.
The relationship between genes and neuroadaptation
How genes affect nervous system development
Exercise performance is greatly influenced not only by muscles but also by the nervous system. In particular, neuromuscular adaptation plays an important role in the early stages of muscle strength improvement through training.
Some genes control neurotransmission and muscle contraction, and it has been suggested that these affect an individual’s motor ability. For example, the BDNF (brain-derived neurotrophic factor) gene enhances neuroplasticity and is involved in improving motor learning and reaction speed. People with certain BDNF gene polymorphisms are said to be more likely to undergo rapid neural adaptation through training, and may be better at skill acquisition.
Dopamine-related genes also affect nervous system performance. For example, the COMT gene determines the rate at which dopamine is broken down and is involved in concentration and judgment. It is said that people with certain COMT polymorphisms have a higher stress resistance and may be more likely to perform well in actual games.
The relationship between reflexes and explosive power
Quick reflexes are also important for sports performance . In particular, in combat sports and ball sports, the ability to quickly respond to the opponent’s movements is required. It has been pointed out that ACTN3 and CHRNA5 (acetylcholine receptor gene) may be involved in this ability.
People with the RR type of ACTN3 have the characteristic that fast muscle fibers are activated quickly, making them more likely to exert maximum force in a short period of time. On the other hand, the CHRNA5 gene is thought to affect the speed of nerve conduction, and people with certain polymorphisms may have faster nerve conduction and be better at quick movements.
In order to make the most of these genetic factors, it is effective to incorporate plyometric training (training that utilizes reflex muscle contractions) and drills that improve reaction time .
Success in sports requires not only physical ability but also psychological strength , and recent research has shown that genes also influence mental strength and motivation.
5-HTT (serotonin transporter) gene : This gene is said to affect stress resistance and mood stability. People with certain polymorphisms are said to be more resistant to mental pressure and more likely to remain calm during actual matches.
DRD4 (dopamine receptor) gene : This gene is involved in risk-taking and risk-taking behavior. People who are adventurous and have the ability to act in high-pressure situations may have a specific variant of DRD4.
By creating a training program that takes psychological factors into account, it is possible to take advantage of genetic characteristics to improve performance. For example, people with low stress tolerance can find it easier to achieve mental stability by incorporating mindfulness and meditation .
Genes and motivation
It is believed that genetics also influence motivation to continue exercising. The PPARGC1A gene is closely related to energy metabolism and is a gene that is often found in endurance athletes. People with a specific variant of this gene are said to have a higher energy efficiency during exercise and are less likely to feel fatigued, making them more likely to continue exercising for long periods of time.
On the other hand, the NRXN3 gene is involved in the reward system (the nervous system in the brain that controls pleasure) and has been suggested to affect motivation to exercise. People who frequently find exercise “fun” may have a specific variant of this gene.
Application of genetic information to sports strategies
Division of roles in team sports
Genetic information can also be used to determine the suitability of players in team sports. For example, the following genetic characteristics can be taken into consideration when selecting soccer positions :
ACTN3 RR type & CHRNA5 high-speed transmission type → Forward (instantaneous power and reflexes are important)
ACE I & PPARGC1A endurance type → Midfielder (requires physical activity)
COL5A1 flexible type & BDNF neuroadaptive type → Defender (requires endurance and judgment)
Genetics and the risk of overtraining
Overtraining syndrome refers to a state in which excessive training causes recovery to be unable to keep up, resulting in a decline in performance. In particular, the IL-6 gene and TNF-α gene are involved in inflammatory responses and may increase the risk of overtraining.
Therefore, by creating a personalized recovery plan based on the results of your genetic test , you can maximise the benefits of your training whilst preventing injury and fatigue.
Sports strategies that utilize genetic information are expected to continue to evolve in the future, but the following challenges remain:
Ethical issues : Risk of limiting children’s potential through sports selection based on genetic information
Privacy issues : proper management of genetic data required
Scientific limitations : Genetics is only one factor, and the influence of environment and training is also significant.
In the future, it will be necessary to use genetic information as a supplementary tool while combining it with training and experience to achieve optimal performance improvement.
Genetic information influences muscle strength, endurance, neural adaptation, and mental aspects, and is useful for developing individually optimized training strategies. However, environment and effort are also important factors, so taking a comprehensive approach that utilizes genetic information will lead to optimal performance improvement.
