I’ve been hitting the gym lately and can feel my muscles becoming more toned and stronger… and it led me to wonder how exactly it is that muscles grow bigger.

Firstly, it is important to note that we have three major muscles in our bodies: Smooth muscle, cardiac muscle and skeletal muscle

Smooth muscle is spindle-shaped and involuntary, which means you can’t consciously control it. It is mainly found in the gut and lining of hollow organs, including the stomach, lining of the walls of arteries and veins, and in the respiratory, urinary and reproductive systems.

Cardiac muscle is another type of involuntary muscle, which is found only in the heart and allows the heart to beat as a single unit.

Skeletal muscles are found attached to bones via tendons and are voluntary, meaning we can consciously control them to allow movement. Skeletal muscles are what we will be focussing on as we discuss how muscles grow!

Skeletal muscles can range from super tiny (such as those found in our ears and eyes) to extremely large masses (such as those in the thighs). Each skeletal muscle fibre is made up of a single cylindrical muscle cell. Skeletal muscle fibres, much like uni students, don’t like to hang out alone, so they find other muscle fibres and hang out in groups called fascicles. Lots of fascicles bunched together make up a whole skeletal muscle. With many layers of connective tissue fascia wrapped around and within this muscle structure to protect the cells, allow the passage of blood vessels and nerves and divide them into compartments.

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Muscles contract and shorten to allow movement. But before this can happen the muscle cell needs to receive information from the brain and spinal cord on what to do. This information is transmitted as a nerve impulse.

So how do muscles grow? When you lift light objects, for example a pencil, it is quite easy since only a few muscles in your hands are required. However, when you lift heavier objects which require you to use both hands, like presenting Simba to the entire Pride Lands,  multiple muscles in various locations of your body must be used to successfully lift said object. You brace your core, your feet are firmly planted on the ground, your thighs and back tense, and finally you lift the object, using all the strength in your arms (lion cubs can weigh up to 5kg).

Putting pressure on the muscles in your body, especially ongoing, such as in strength training and exercise, causes minor ‘damage’ to the skeletal muscle fibres at the cellular level. Now the word damage is usually negative, but in this case, it’s what will help the muscles grow. You usually feel the damage as soreness after a workout. The damaged cells release inflammatory molecules and immune system cells such as cytokines. These try to repair the minor injury to the skeletal muscle and activate muscle stem cells (or satellite cells) to add more nuclei to their parent muscle fibre allowing it to form new fibres. Upon being rebuilt, the muscles hypertrophy (grow bigger, either in length and/or thickness) and stronger.

This doesn’t mean that if you don’t feel sore after a workout, your muscles are not growing! Muscle hypertrophy takes time so don’t expect immediate results; it can take weeks to months to see visible growth. Muscle growth occurs when the rate of muscle protein build-up is greater than the rate of muscle protein break-down. You also need to provide your body with enough rest and nutrition otherwise, you’ll end up doing more harm than good.

So, the more stress that’s put on the muscles, the more damage the muscle fibres undergo, the stronger it will become when rebuilt. This damage-repair cycle makes muscles stronger and more able to withstand exercise and intense physical challenges as they are then well-trained to do so. This is why physical activity is important, you’re constantly using your muscles and building them up, leading to improvement in muscle mass and overall health. Some studies have suggested that loss of muscle mass starts occurring from the age of 25! Y’all better start hitting the gym cause as it turns out stressed muscles are not the worst thing for you.