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Can genes really tell us how to exercise?

Over the past seven months many of us have had our lifestyles completely upended. Our fitness routines are no exception. Recent studies have demonstrated a significant decrease in physical activity not only in the United States but worldwide. 

While reducing exercise volume may benefit some individuals for a shorter period of time, taking a substantial break from exercise is associated with decreases in aerobic capacity, insulin sensitivity, blood volume, muscle size, and overall muscle strength. Additionally, low physical activity along with poorer dietary habits may lead to increased body weight and risk of obesity. 

As we begin to adapt to new methods of working out, different layouts and rules that are enforced in gyms or other facilities, refining or adjusting previous workout programs may be beneficial. Whether you have exercised for years or are just beginning a new program, developing a deeper understanding of what types of exercise work best for your body and your goals can help to avoid the frustration and potential discouragement that can come with trial and error. 

In addition to maintaining an ideal dietary intake, understanding how to tailor an exercise program so that it is fun, effective, and minimizes injury can allow you to optimize your health, accomplish your goals, and reach your highest physical potential. 

How Our Genes Impact Our Exercise Response

There are many reasons we differ in physical activity ability. Like many variations between individuals, we can look to our genes to help understand the differences we experience. 

How Genes Influence our Muscle Fiber Composition

There are three types of muscles in our bodies that have different functions. The muscles that we use to produce movement are known as our skeletal muscles. Two types of fibers make up our skeletal muscles, slow-twitch fibers and fast-twitch fibers

Slow-twitch muscle fibers help us to maintain movement in endurance activities - think distance running, cycling, or swimming. They contract slowly but do not tire out quickly. Fast-twitch muscle fibers are opposite slow-twitch fibers in that they benefit our physical activities that require quick movement, such as sprinting. They are fast to contract, but also fast to tire out.


Variants in the gene ACTN3 have been found to influence the proportion of fast-twitch to slow-twitch fibers in our muscles. A protein called (α)-actinin-3, found in fast-twitch muscles, is produced due to the ACTN3 gene. One variant in this gene is associated with an increased proportion of fast-twitch muscle fibers, whereas another variant is associated with a decrease in fast-twitch and an increase in slow-twitch muscle fibers. Some studies suggest these gene variants determine if an athlete will excel at speed or endurance. 

Another gene that impacts skeletal muscle composition is the ACE gene. This gene instructs our bodies to produce angiotensin converting enzyme (ACE), which influences blood pressure control and the function of skeletal muscle. One variant in the ACE gene may lead to a higher proportion of fast-twitch muscle fibers.

How Genes influence our Aerobic Capacity

Aerobic exercise, meaning activity that requires oxygen, involves multiple body systems to coordinate and work efficiently. The lungs need to take in oxygen which gets perfused into the bloodstream; the heart needs to pump this oxygenated blood to the muscles; and the muscles need to utilize the oxygen to perform muscular contractions and produce work. 

The VO2max measurement is a way to assess how well this process works. It measures how well your body uses oxygen at maximum exercise efforts. Simply, VO2max is the maximum rate of oxygen your body is able to utilize during exercise. If you have a high VO2max, you are able to more efficiently perform aerobic exercises that require a lot of oxygen, such as swimming or running, compared to someone with a lower VO2max. 

If you have noticed you have a different response to exercise than a friend or even family member, this may be due to VO2max. The measurement of VO2max, or cardiorespiratory fitness, is impacted by factors such as environment, training, and diet. There have also been ninety-seven genes identified to impact VO2max trainability, meaning your ability to train and improve VO2 max. The genes identified show that people may have a higher or lower response to cardiorespiratory training due to genetics. With numerous factors contributing to VO2 max, genetics do not make up the entire picture. 

As mentioned above, the proportion of slow and fast-twitch muscle fibers impact endurance and power or “sprint” activities. Endurance exercise typically consists of a longer duration and medium intensity. Activities that challenge endurance include distance jogging, swimming, and biking. 

Power exercise combines force and velocity, and it is of shorter duration and a high intensity. Examples of exercises that require power include strength training, sprinting, high-intensity interval training (HIIT), and jumping. 

Although traditionally athletes and their nutrition needs have been classified by endurance vs power athletes, most athletes perform a combination of endurance and strength training. Recommendations for nutrients may fluctuate based on training schedule, intensity, fitness goals, and nutritional needs. For those that solely perform endurance or strength training, needs will still fluctuate based on varying workouts.

Nutritional needs for energy, protein, and carbohydrates are typically calculated by grams per kilogram body weight, but they are dependent on various factors. Some factors that impact nutritional need with athletic performance include the level of intensity, exercise duration, mode of exercise, the environment, appetite, and the individual’s response to exercise. More information on proper nutrition for exercise can be seen later in this blog post. 

How Genes Influence our Motivation to Exercise

Have you ever experienced lack of motivation to exercise? If so, you are not alone. 

Motivation in its simplest form is what moves us to act. What motivates one person may be different from what motivates another. For some people, motivation to exercise may be to maintain a healthy body weight or physical appearance. It may also be to improve quality of life by building muscular strength or cardiovascular endurance. Others may be motivated by competition. 

Regardless of what motivates you, having motivation to exercise is a huge predictor of adhering to a regular exercise routine. Those who feel they “want to” exercise versus those who feel like they “have to” participate in exercise are more likely to routinely exercise long-term. Recent studies, such as the study published by Liegro et al., have shown a link between how motivated you are toward working out and variants in the BDNF gene. training and performance. 

Research shows that individuals who are impactful for the BDNF gene are more likely to report positive mood changes from exercise and training, have a decreased perception of exertion, and are more likely to stick with an exercise regimen. These factors impact motivation to train. 

Enhanced motivation to exercise can have a multitude of physical and psychological benefits including improvements in body fat levels, blood sugars, blood pressure, blood lipid profiles, and mental health and attitude.

Optimizing Exercise and Muscle Recovery

Manage Oxidative Stress

Whenever you exercise, there is some degree of muscle breakdown that occurs. It may sound crazy, but we actually want this to happen. This is because when the muscle repairs itself, it will rebuild the muscle fibers to increase in cell size and cell number, hence muscle growth. As a result of this muscle breakdown, there is an increase in “oxidative stress” or an accumulation of reactive oxygen species (ROS) in the body

These reactive oxygen molecules are extremely reactive and unstable, because they possess an unpaired electron in their outer orbital. Although we want some oxidative stress to promote muscle breakdown and building, too much of anything is never good. While moderate levels of oxidative stress resulting from exercise can promote positive physiological muscle adaptations, having high levels of oxidative stress can result in damage to important structures such as DNA, RNA, and other proteins.

Thankfully, our bodies have built in mechanisms to deal with this oxidative stress resulting from muscle metabolism. Our bodies are equipped to handle a certain amount of oxidative stress with special enzymes in our muscle cells. One enzyme in particular is glutathione reductase, which requires adequate vitamin E and vitamin C to function. This enzyme plays a critical role in resisting the oxidative stress. 

Therefore, it is important to consume adequate amounts of vitamin C and vitamin E to support these antioxidant enzymes. Having sufficient levels of antioxidants will help “neutralize” the reactive compounds.

Reduce Injury Risk and Muscle Injury

Most people who have ever exercised or played a sport before have probably experienced some type of injury. Unfortunately, this is just a risk that comes along with exercising and moving our bodies. The most common types of injury from exercise include: 

-Sprains and Strains 

-Joint injuries (knee and shoulder) 

-Muscle cramps 

Often, these injuries occur in our joints, particularly the knees and shoulders as they are frequently used. In general, a strain is an injury to a muscle whereas a sprain is an injury to ligaments (fibers which hold bones together). Muscle cramps are an involuntary muscular contraction that may occur anywhere in the body and are often due to dehydration or electrolyte imbalances. Other factors increasing the risk of injury with exercise include age, sex, body composition, current fitness level, and health status. 

There are ways to reduce the risk of exercise-related injuries. One important step (that most people don’t like taking the time to do) is warming-up properly before a workout. Warming-up allows your heart rate to gradually increase, while loosening your muscles and joints. You can think of it as giving your body a “heads up” that it needs to get ready to do work. Dynamic stretching is one of the best ways to warm up. This is different from static stretching which involves holding a position in place. Dynamic stretching means stretching while moving. 

For example, performing a side shuffle, doing arm circles, or jumping jacks are all great examples of dynamic warm ups. Similar to warming-up, it is also important to cool-down. This could be a simple 10 minute walk after the exercise to gradually return the heart rate back to normal. 

Another way to reduce injury risk and reduce metabolic stress on the body is to ease into workouts. Meaning, don’t go out and run a marathon if you didn’t train for. When you ask your body to perform exercise it did not train for, it is not only more susceptible to injury, it also is not ready to handle the metabolic breakdown and stress that will occur with it. Slowly increasing the intensity, duration, and frequency of exercise provides your body with time to recover and adapt appropriately to handle the stress.

Fuel Properly

Proper exercise without proper nutrition is like trying to build a fire without any wood. It simply won’t work. We need fuel to be able to move our bodies properly. While it seems enticing to discuss supplements and ergogenic aids when talking about nutrition and exercise, most people need to be reminded of the nutrition basics. Adequate carbohydrate and protein intake is essential for exercise. 

 If you ever have been on a low carbohydrate diet and tried to workout, you probably have felt exhausted. This is because carbohydrates provide the energy we need to move our muscles. Therefore, it is important to not severely restrict carbohydrates when exercising. In addition to properly fueling and replenishing carbohydrates surrounding exercise, it is also important to provide our muscles with proper protein to rebuild muscles, especially after workouts. 

In general, adults require 0.8 grams of protein per kilogram of body weight per day. However, some athletes require up to 2 grams of protein per kilogram of body weight per day. The difference depends on the type of exercise and frequency of exercise performed. Talk to a registered dietitian if you want help determining your exact protein needs. 

Outside of proper carbohydrate and protein intake, there are certain foods that have proven to help with muscle recovery and reduction of oxidative stress. Tart cherry juice consumed after exercise has shown to reduce oxidative stress and inflammation due to its high levels of polyphenols (a type of antioxidant naturally found in cherries). Consuming 10 fl oz. of tart cherry juice after exercise may be beneficial especially for high-intensity and endurance exercises. 

As mentioned earlier, vitamins E and C help support enzymes that reduce oxidative stress in the body. Therefore, it is important to ensure adequate intake of these vitamins to prevent excessive oxidative stress. Fruits and vegetables are often good sources of vitamin C, particularly citrus fruits. Since vitamin E is a fat soluble vitamin, it is best absorbed from foods with fat. Examples of vitamin E sources include vegetables oils, nuts, and seeds.

How to Customize Your Exercise Plan

When looking to customize your own fitness plan it is always best to look towards fitness professionals for advice and programs. When investing in a personal trainer, make sure they are credentialed, such as trainers certified with ACE, CSCS, or NSCA-CPT. 

If you are not going to a gym at this time, that is okay! Thanks to technology, there are many apps you can download and subscribe to that allow you to attend live or previously recorded group fitness classes, as well as meet with a personal trainer. There are apps for all different styles of fitness, including yoga, strength, barre, running, and more! Search for an app that meets your fitness interests and goals. 

When customizing your own plan:

1. Remember genes are not the whole picture.

2. Find exercise you enjoy!

3. Select something that fits your schedule and that fits your space (home, gym, outside, whatever it may be).

4. Set S.M.A.R.T goals (specific, measurable, attainable, relevant, time bound).

5. Avoid overshooting - it’s best to start small and build up to a goal. If you have not worked out in a long time, try adding in simple exercise a few times per week. 

6. Stay safe and work with a professional.

What’s Next?

While it may be overwhelming, small tweaks to your physical activity, diet, and lifestyle can reap big rewards in the long run. If you would like to learn more about how genetic testing can influence customizing your exercise programs and your personalized nutrition plan, check out this post here Can a DNA Test Really Tell You How to Eat?


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