Muscle Damage & Hypertrophy

The takeaway from this article is that:

*Muscle damage does not drive muscle hypertrophy however it's an inescapable by product of sufficient mechanical tension.

*Muscle damage at high enough levels could be useful for more advanced lifters due to the donation of nuclei by satellite cells. A greater number of myonuclei allows for greater muscular potential.

The whole concept of muscle damage and the restoration of this damage is often misinterpreted by your average lifter. The most common perception is that when you damage a muscle this sets into motion mechanisms that repair the muscle and build it back up a little bigger and stronger. In turn this implies that muscle damage is something that you should be shooting for every training session if you want to build as much muscle as possible which tends not to be the case.

Muscle repair and building muscle are two separate processes and I think much of the confusion comes from the fact that both processes require an increased rate of muscle protein synthesis. When a muscle is damaged the process of repair involves removing and then replacing damaged parts of a muscle fiber. Building new muscle involves increasing the protein content of a fiber by either increasing the number of myofibrils in parallel or in length but damaging one myofibril doesn't effect our ability to build another one.

Another thing to bear in mind is that excessive muscle damage can actually cause muscle fibers to become necrotic. This doesn't allow the fiber to be repaired, instead it's broken down within its cell membrane and then regeneration occurs meaning a completely new fiber is grown. Essentially this means that too much muscle damage during a training session can actually cause muscle loss (at least until a new fiber is grown to replace the old fiber which isn't a super fast process). Studies have shown this to be the case by taking a group of untrained people, hammering their biceps with five or so sets taken beyond failure (forced reps) and then finding a reduction in muscle mass a couple of weeks after the session.

Trained people experience the repeated bout effect which is a mechanism that protects against future muscle damage from similar exercise. You'll notice this if you have an extended break from training and then come back and hit it hard from the off - the muscle soreness after the first session will be horrific but the soreness will be far less after each subsequent session. Whilst this is generally beneficial it could also cause some problems because there are times where increasing levels of muscle damage could be beneficial for future muscle growth which I will get to.

So just to recap the first point of this article; it seems that mechanical tension is the primary driver of muscle growth and muscle damage is just a by product of achieving optimal mechanical tension. In other words it doesn't seem muscle damage itself is providing a hypertrophy stimulus it just so happens to occur when trying to stimulate the mechanisms that do provide a muscle hypertrophy stimulus. This tells us that finding ways to maximise mechanical tension whilst simultaneously minimising muscle damage will allow us to achieve the optimal hypertrophy stimulus and will reduce the time it takes to recover between sessions.

There is a theory that muscle damage could be useful when looking at maximising muscle growth over the long term, and for advanced lifters who are at a point where muscle growth has become a very slow process. This is tied into the myonuclear domain theory which is basically the theory that each myonucleus can 'control' a certain volume of the contents of a muscle fiber. Our muscle fibers have many myonucleus' (myonuclei) which are kind of command centres of the muscle cell and control the rate of muscle protein synthesis. So essentially there's a finite volume of muscle that can be built per myonucleus and to build more muscle we need more myonuclei which we obtain via satellite cells. After exercise that involves high levels of muscle damage (enough for some fibers to become necrotic) this is where we get the donation of nuclei from the satellite cells to our muscles.

If this theory holds water (which it certainly seems to) then increasing training stress to really drive up muscle soreness in the days after training seems like a pretty sound method for increasing muscle growth for more advanced lifters who've hit a plateau. In less advanced lifters who haven't maxed out their muscular potential in regards to their number of myonuclei then it makes a great deal of sense to minimise muscle damage from training.

The cool thing about myonuclei is that they stick around for a long time, even if you stop training. How long they stay is debatable but the research suggests at least six months and often much longer with the exception of nerve damage and complete muscle inactivity. This means that if you've not trained much during the covid lockdown and you get back on it when the gyms reopen you'll gain back any lost muscle tissue far easier than when you built it initially. You may also take this into account during periods of fat loss. If you happen to be a little too aggressive with the calorie deficit and end up losing some muscle those myonuclei will still be there making it very easy to regain any lost muscle when you're back in a calorie surplus.

In summary don't chase really high levels of muscle soreness as a primary goal, some degree of muscle soreness isn't a bad thing (it's just a sign that you stressed the muscle) but constant high levels of soreness probably aren't ideal in most circumstances. Taking a hammer to my quads will certainly cause a lot of muscle damage and soreness but that doesn't mean it's going to set in motion processes that stop me from looking like I'm riding a chicken. For more advanced lifters who've found their muscle gains have really slowed down I think phases of doing the opposite and pushing hard for more soreness due to high levels of damage could be very worthwhile. The problem that comes with this is navigating injuries due to the greater stress however I think this can be largely managed by good training programming.