At Nielsen Fitness, we know that effort, consistency, and lifestyle choices all play key roles in fitness. However, your genetics also have a significant impact on how your body responds to activity. In fact, in an article published by Science Daily “combining data from 24 separate studies, [researchers] discovered that genetic differences are responsible for 72% of the variation in outcomes for people following identical exercises” (2021). Understanding this influence can help you set realistic goals, allowing in-home and virtual personal trainers to design programs aligning with your capabilities.

The Role of Genetics in Fitness

MUSCLE FIBRES

Our muscles are made up of two main types of fibres: slow-twitch (type 1) and fast-twitch (type 2). Slow-twitch fibres are more efficient for endurance activities like long-distance running, while fast-twitch fibres are better suited for explosive movements like sprinting. However, “it’s important to understand that muscle fibres exist on a super micro level. For instance, you couldn’t look at a biceps muscle and say, “that’s a fast- (or slow-) twitch muscle.” Rather, “every muscle has some fast-twitch muscle fibres and some slow-twitch muscle fibres” (Shape, 2022),

Genetics determine the proportion of type 1 vs. type 2 fibres in your muscles, which can influence whether you naturally excel in endurance or strength-based activities. This is the kind of information our in-home personal trainers in Toronto, Collingwood, London, Hamilton, and Ottawa (and virtual personal trainers everywhere) collect during initial phases of training. Though it’s impossible to build new muscle fibres (you can only build muscle tissue), you can adapt certain hybrid muscle fibres to suit your training needs.

METABOLISM

Genetic variations can impact your metabolism, affecting how your body stores fat. “Age also affects metabolism, as it can slow over the years, even if you start out with a fast metabolism. Differences in metabolism speed are evident in how easy or hard it is for people to gain or lose weight. A slow metabolism burns fewer calories, which means more get stored as fat in the body; that’s why some people have difficulty losing weight by just cutting calories. A fast metabolism burns calories at a quicker rate, which explains why some people can eat a lot and not gain extra pounds. But you can’t entirely blame a sluggish metabolism for weight gain. The reality is that metabolism often plays a minor role. The greatest factors as you age are often poor diet and inactivity” (Harvard Health, 2024). Ideal exercise frequency, intensity, and duration varies between clients based on a number of factors, including body type and composition.

AEROBIC CAPACITY

Aerobic capacity (or VO2 max) refers to the maximum amount of oxygen your body can use during exercise. A higher VO2 max is associated with better endurance and cardiovascular performance. While training can improve your VO2 max, genetics can determine the baseline and potential for improvement. If you’re interested in improving your VO2 max, our in-home and virtual personal trainers can assess your current level and progress with quarterly assessments.

RECOVERY

Genetics can influence how quickly your muscles recover after exercise as well as your susceptibility to injuries. For example, variations in collagen production can affect your tendon and ligament strength, which directly impacts injury risk. That said, consistent resistant training is a fantastic tool for improving the strength of your tendons and ligaments.

HOW WE CAN HELP

Understanding genetic predisposition helps in-home and virtual personal trainers create customized fitness plans that optimize performance while minimizing risk of injury. For instance, clients with a higher proportion of fast-twitch fibres may naturally obtain greater benefit from high-intensity interval training (HIIT), while those with more slow-twitch fibres may thrive in endurance-style workouts. On the flipside, it can be ideal to focus on improving areas of weakness, depending on your goals.

FINAL WORDS

While genetics do play a role in fitness, they do not determine your potential. With dedication, smart training, and proper nutrition, anyone can improve their strength, endurance, and overall health. The key is to focus on what works best for your body and to celebrate the progress you make, regardless of your starting point. If you’re interested in learning more about how Nielsen Fitness can help you reach your fitness goals, contact us here!