5 Fitness Myths Science Officially Debunked in 2026

Chapters:

00:00 1. Caffeine is ineffective in the morning

01:57 2. Women can’t build much muscle

03:40 3. Menopause destroys your ability to change your physique

04:22 4. Citrulline supplementation is a proven muscle builder

05:32 5. Slowly lowering weights improves muscle growth

06:52 Outro

Transcript:

The first myth is that caffeine is ineffective in the mornings. This myth originated based on some idea of how caffeine interacts with adenosine receptors. It was entirely theoretical, and it’s contradicted by a large body of research that shows that caffeine is perfectly effective in the mornings. Anyone who has ever had a morning cup of coffee can tell you you really feel the difference. Case in point, a recent study found that caffeine, unlike in previous research, when taken in the mornings, enhances muscle growth.

In exercise science studies caffeine actually seems to be extra effective in the mornings because it elevates core body temperature. In the afternoon your core body temperature is already elevated, and it’s no longer necessary to consume caffeine. In the morning, however, caffeine essentially speeds up this process, and offsets the negative circadian rhythm effects of training at a time earlier then your body is used to. Most sports records are set in the afternoons and early evenings because our body is optimized for performance at that time, unless you are habituated to training in the mornings. Caffeine basically fast tracks this habit and therefore is more effective for performance, at least physical performance, in the mornings.

Regarding caffeine improving muscle growth, though, that in itself might be a myth. In contrast to this small Iranian six week study, multiple other studies, seven in total, based on my review in my PT course, have found that caffeine does not improve strength development or body composition outcomes because the effect is too small to affect performance that much and you habituate to the effect. So tolerance basically blunts long term positive effects of caffeine.

Moreover, most of the benefit of caffeine is a mental. Caffeine makes you feel a lot better and can help you push yourself in a gym, but when effort is already very high, caffeine does not physically do much for muscle growth. So if you don’t like training on caffeine and you are highly motivated, caffeine most likely will not do much for your gains directly. But to the extent that caffeine might increase muscle growth, it is most likely to do so in the mornings.

Myth #2 is that women cannot build nearly as much muscle or strength as men. This myth originated from the idea that women have about 15 times less testosterone, and therefore probably also have about 15 times lower potential for muscle growth and strength development. However, research, including a recent meta analysis of 27 studies, actually decisively finds that women and men have the same relative potential for strength development and muscle growth. This means that men and women that start with the same body composition actually would have the same potential for total muscle growth and strength development. However, men, obviously, normally have more baseline muscle mass, meaning they start with a higher level of muscle mass to begin with, and relative to that level they gain the same amount as women, but the absolute amount is larger in men. So it is true that an absolute terms women do not gain as much muscle as men, but relative to a man of the same body composition at baseline, before they start training, their potential is actually the same.

Women’s muscular potential is thus far higher than you would expect based on the 15 times lower testosterone level compared to men. The reason for this is that testosterone is highly individual. It’s not just the total amount that matters, it is also how your body uses that amount. So you cannot make a clean hormonal comparison between men and women. Moreover, most research finds that testosterone mainly directly helps you build muscle, which explains why men have higher testosterone levels and they have higher levels of muscle mass. Testosterone does not seem to affect the rate of muscle growth nearly as much as you would think. Women that touch a loaded barbell are very unlikely to wake up the next day looking like the She-Hulk, but women can absolutely transform their physique in a major way, just like men, even after a menopause.

Myth number three is the menopause absolutely destroys your ability to change your physique. A recent meta analysis of studies looking at women doing strength training before menopause and after menopause found that strength development, muscle growth and fat loss were actually the same pre- and post-menopause. These findings fit with the overall research on aging, which shows that aging itself is not nearly as bad for our physique or our gains as commonly believed. It is being sedentary and having a poor diet for a very long period of time that wrecks havoc on our physique, not aging per se. And it’s never too late to start. Studies consistently show that people, men and women in their 90s still make significant changes to their physique when they start lifting.

Myth number four is that citrulline supplementation is a proven muscle builder. Citrulline in many circles has kind of sneaked into the list of evidence-based supplements for muscle growth. However, a recent meta-analysis of nine studies found that citrulline supplementation did not augment muscle growth from resistance training. The average effect size of lean mass in nine studies was almost exactly 0.0.

In citrulline’s defense, most studies were probably not adequately powered to detect a possible benefit of citrulline supplementation. However, the only mechanism by which citrulline would augment muscle growth is that it enhances performance, and the performance enhancement is marginal. You’re talking about a few repetitions at best during high rep sets in particular. And this performance enhancement might not even improve muscle growth because it is sort of a reverse blood flow restriction mechanism whereby metabolic stress decreases and therefore your performance goes up, but this might mean that you need to do more volume to get similar results, because metabolic stress increases motor unit recruitment. This is the opposite of KAATSU training or blood flow restriction training, which finds that you can reduce your training volume significantly and still make similar gains because of the increased metabolic stress, at least with very low weights.

Myth #5 is that slowly lowering your weights in the gym improves muscle growth. This myth is perpetuated even in evidence based fitness circles, but two recent meta-analysis show that lowering your weights more slowly, increasing the eccentric repetition duration, does not increase muscle hypertrophy. In the end, you are still lifting the same weight and taking it to the same fatigue endpoint. If we look at mechanical tension, we also see that what often happens with slower repetitions is that you do fewer repetitions, but they last longer, resulting in a similar total time under tension. If the time under tension is similar and you are using the same weight, it makes sense that the integral, the area under the curve, of mechanical tension is also similar.

Based on the totality of research, my default recommendation, which is also what my App uses is to use a controlled eccentric duration, controlling the negative the way down, and explosively lifting the weight up to maximize repetition performance. An explosive concentric has been found to improve at least strength development, if not muscle hypertrophy, and this tempo doesn’t make it difficult to track your performance. Actually counting your repetitions and using a metronome is very, very impractical. You don’t have to do that. So this tempo is intuitive, it maximizes strength and repetition performance, and it doesn’t make your tracking complicated. If you want to try out my Physique App, by the way, you can get a 2 week free trial with the link in the description below.

Boom! That’s five popular fitness myths busted. I know on social media, it seems like there is so much contradictory information and it’s hard to know what to trust anymore. That’s why I designed my online PT certification program for serious lifters that want to know absolutely everything about how to optimize their performance, physique, and their health. If that’s you, check out the link in the description. Hope to see you next time.