When it comes to the impact of cycling on muscles, what girls are most concerned about is its effect on body shape. Let’s take a look at whether there really is any impact.
In fact, exercise is simply how human muscles work, and the essence of its impact on body shape is essentially an issue of muscle morphology. Exercise can change muscle morphology—that much is certain—but what kind of impact does each type of exercise have on muscles, and how does that impact affect muscle morphology?
For now, let’s not discuss the classification of muscles. From a purely morphological perspective, there are four types of regular changes in the shape of an object: getting longer, getting shorter, getting thicker, or getting thinner.
Since every muscle has fixed origin and insertion points—located on the bones—different muscles have different origin and insertion points. Therefore, from this angle, it’s impossible for muscles to become longer or shorter in a fully developed individual. As for muscle contraction during exercise, it’s actually the relative sliding between muscle filaments, which relates to the sliding filament theory. This is the most widely accepted theory about how muscles work, but it’s still just a hypothesis. The actual mechanics of muscle function are still being studied in physiology, but this has nothing to do with muscle morphology.
Without changes in length, we’re left with changes in thickness. Generally speaking, muscles don’t get thinner unless certain muscles atrophy due to long-term inactivity, which is actually a pathological condition. You can observe patients with lower limb paralysis—their legs are very thin due to long-term lack of movement, as most of the muscle has atrophied. Then there’s muscle thickening, which is essentially an increase in the cross-sectional area of muscle filaments. Generally, this is a response after muscles bear and adapt to loads. This response enhances the muscle’s ability to resist load, and can be attributed to muscle thickening as an adaptation to increasing loads. So for healthy individuals, although it may seem that muscle change only takes the form of thickening, this occurs only under certain conditions.
From a training science perspective, the condition that leads to muscle thickening is performing multiple repetitions under high-intensity loads. The effect is increased capacity to resist maximum resistance and improved endurance against such resistance, but movement speed will decrease as resistance increases.
For most sports, movement speed is crucial. Therefore, general training often emphasizes speed as the core, while also considering strength. The method involves quickly overcoming high-intensity loads with very few repetitions—typically just one or two times under near-maximal or maximal loads. This type of training increases the fast explosive power of muscles against resistance and enhances absolute muscle strength, without causing muscle thickening.
From the perspective of muscle performance speed, the smaller the resistance the muscle overcomes, the faster the movement speed; the greater the resistance, the lower the working speed of the muscle. This should be easy to understand.
When it comes to cycling, there is no external load involved. Muscle activity always occurs at a maintained speed—that is, pedaling frequency. The fact that muscles can maintain a certain frequency means the load they bear is one they’ve already adapted to. For an adapted load, muscle morphology won’t be affected. Even if the pedaling frequency can’t be maintained, muscle work can be understood as a form of movement where body weight serves as the load. This type of load is also within the range of human adaptation and won’t impact muscle morphology.
From the perspective of practical training, when training young athletes, strength requirements are generally not introduced too early. However, to ensure their strength level doesn’t become a limiting factor in performance improvement, some strength training is still included. But this training usually uses their own body weight as the load, with no additional load. The primary goal of this strength training is to improve coordination among various muscle groups and prepare for future sports techniques.
Actually, take aerobics as an example—something everyone can relate to. As a popular fitness and recreational activity, aerobics is especially favored by girls. In truth, aerobics is a form of movement that uses one’s own body weight as the load. Jumping or supporting movements of the upper and lower limbs use body weight as the load, or sometimes add very light extra weights, like small dumbbells, which don’t impose any real burden or affect movement speed. The training goals can be divided into two parts: one is to improve the body’s aerobic working capacity (which we’ll discuss in more detail later), and the other is to enhance the coordination among muscle groups. This second goal is the same as the foundational quality training mentioned earlier for teenagers.
After all this, the summary is actually quite simple: strength training can lead to muscle thickening, but the stimulus to muscles must involve gradually increasing loads. Cycling, on its own, is not a form of gradually increasing load, so its effects won’t lead to muscle thickening.
The above discussed the category of strength load. Now let’s touch on endurance activity and its impact on muscles. As mentioned earlier, low-load exercise won’t cause muscle thickening, and endurance exercise is a type of prolonged low-load activity. Based on the human body’s energy supply systems during exercise, it’s referred to as aerobic exercise. From a purely morphological standpoint, endurance exercise has no impact on muscles. From a physiological perspective, endurance exercise can increase the number of mitochondria within muscle cells, thereby enhancing the endurance of aerobic muscle work. Since endurance exercise doesn’t alter muscle morphology, and cycling doesn’t involve strength training factors, what then is changing the body?
In fact, many people have heard the term “exercise body shaping.” Here, body shaping essentially refers to how exercise affects the distribution of body fat—not a change in muscle morphology. Human fat is mainly distributed subcutaneously and around internal organs. To a large extent, the external appearance of the body reflects fat distribution. A simple way to check is to use your thumb and index finger, spaced three centimeters apart, to pinch the skin on any part of your body after tensing the muscle there, and observe the thickness of the pinched skin to assess the fat layer in that area. This is called the skinfold thickness method in anthropometry—a very simple way to estimate fat content, though also the least reliable.
After engaging in proper and suitable exercise, you’ll find that it’s actually the distribution of fat that changes—not the morphology of the muscles. Exercise leads to fat consumption and a thinner fat layer. A healthier fat ratio makes the body appear more slender, achieving a toned physique. Of course, for those who are too thin, some strength training is still needed to build up muscle volume. But this strength training should be targeted and moderate, using the right methods to achieve the goal.
What kind of exercise burns fat the fastest?
Simply put, if your goal is to burn fat, you should choose exercises that use fat as the energy source. Given the characteristics of fat—slow energy release and high oxygen consumption—it’s clear that aerobic exercise is the best method for burning fat.
So what is aerobic exercise? Essentially, it’s low-intensity, prolonged continuous movement. There are many forms of such exercise—for example: long-distance running, long-distance cycling, long-distance skating, skiing, and so on. Any sustained, long-duration movement falls under aerobic exercise.
Aerobics is also called aerobic fitness exercise, mainly because it shares the traits of low intensity and continuity. But this applies mostly to fitness aerobics. Competitive aerobics, on the other hand, is a mixed-energy activity with very little aerobic component. As for some aerobics fitness clubs nowadays, I feel that some classes are actually taught at overly high intensities. But that’s not entirely the instructors’ fault—the national examination content for aerobics instructors is largely based on simplified competitive aerobics. You’ll sweat a lot after class, but the fat-burning effect is minimal. As for the two benefits of aerobics for fitness mentioned earlier, its role in fat reduction is somewhat weakened, though its benefit in improving body coordination remains quite good.
Overall, if we look solely at the impact of cycling on the body, worrying about muscle thickening is definitely unnecessary. Cycling is indeed very effective for fat loss. If we’re talking purely about fat burning, cycling is absolutely better than aerobics—not only because it’s a long-duration, low-load activity, but also because cycling is more stable, making it easier to control intensity. That’s something aerobics can’t compare to. However, cycling’s downside is its high regularity, which limits the variety of muscles used and falls short in improving muscle coordination. From a fitness perspective, it’s recommended that you engage in a variety of sports to give your body comprehensive exercise.
The concerns that girls often have have been addressed. I hope this helps you better understand different forms of exercise. Ride with confidence from now on—I hope cycling brings you health and happiness.