if building muscle is caused by microtears then how come we don’t get bruises from doing it?
In: Biology
Bruises are from tears/ruptures in blood vessels. Muscle growth is from tears in muscle tissue. You can tear muscles without tearing the blood vessels around them. Its like if a part breaks but it’s still hanging by the wiring, because the wires inside are still intact – except in this case the wires are your blood vessels.
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Bruises caused by damage to blood tubes. Blood tubes bring nice fresh blood to muscles to feed them and to clean their nappies (take away waste). Muscle damage does not damage blood tubes. Muscles made of many many fibres, fibres take some damage, like an old rope. Nice fresh blood comes and repairs the muscle fibres, making them even better than before, upgraded! 🙂
As many hypertrophy-related studies, the conclusions about muscle microdamage and its relation to growth are fairly ambiguous, but suggest [little to no correlation between damage and hypertrophy](https://www.strongerbyscience.com/muscle-damage/). Perhaps microtears do somewhat contribute to protein synthesis signalling, but it seems as though hypertrophy occurs regardless of muscle damage.
That said, bruising doesn’t occur since no blood vessels rupture, these truly are microscopic damages. With actual muscle tears, [major blood vessel damage and bruising can occur](https://symmetry.physio/wp-content/uploads/2019/08/Pectoral.jpg).
**Actual ELI5: when muscles break during exercise, most of the time it’s tiny cracks. Bruises are caused by blood leaking, but this kind of damage doesn’t affect blood vessels unless it’s an actual injury.**
Actually, if you work out with enough intensity you can get bruises. But it’s almost always a sigh of overtraining and I wouldn’t recommend it (from experience)
Because muscle growth isn’t caused by muscle damage. It’s a myth that’s spread everywhere because it’s so compelling; it’s one of those explanations that just clicks and makes sense. But it’s not supported by the science. The real drivers of muscle growth are mechanical tension and metabolic stress. Mechanical tension is basically your muscles freaking out over how heavy a weight feels, and deciding to get stronger so that it feels less heavy. Metabolic stress is your body trying to feed energy into your muscles and not being able to keep up with the demand, and deciding to level up the muscles so they need less metabolic support.
Edit: in response to people taking issue with “myth” – the popular meme “why does muscle grow from weight lifting? Cause they get damaged and grow back stronger/bigger” is ABSOLUTELY a myth. The best opposing case that could be made is that muscle damage is one of the three primary drivers of muscle growth, but every expert I’ve read has implied that research over the past decade or so has been building a case that muscle damage is merely correlated with muscle growth under many circumstances. It’s difficult to establish concretely that muscle damage has absolutely nothing to do with growth when pretty much all weight training causes some damage. Here’s a review of some research that includes a study that showed similar hypertrophy rates between two training modalities that caused different amounts of muscle damage – [study ](https://res.mdpi.com/d_attachment/ijerph/ijerph-16-04897/article_deploy/ijerph-16-04897-v2.pdf)
Muscle damage does not cause muscle growth. There was never evidence to suggest that, it was a hypothesis that stuck.
Mechanical tension and signaling from metabolic byproducts appear to be the actual drivers.
I’ve never heard a satisfactory answer regarding why people get sore. Microtears is one hypothesis I’ve heard, but I don’t think it’s proven to be the case.
Anyone have any proof of what’s going on and not only a guess?
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Cause I’m a karate man! Karate man bruises on the inside, so they don’t show their weaknesses.
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