I’ve always heard that you get stronger from lifting weights by damaging the muscle slightly when lifting and when your body repairs it, it builds it back better and therefore you get stronger. I also know that you don’t grow new muscles fibers when you lift weights and get bigger, but your muscle fibers actually get bigger (hypertrophy).
Now, I’m taking an anatomy class at the moment and I know about stuff like thick microfilaments, thin microfilaments, H bands, T tubules, myosin, and actin. I’m wondering if someone could explain to me in more detail what happens when you lifts weights and how you actually get stronger.
It’s been way too long since I studies this and research may have changed since then. You can produce new muscle fibers in addition to increasing the size of existing ones. I think it is something along the lines of two mechanisms for muscle size and strength. One is that the larger muscle cell split and give rise to additional fibers (hyperplasia). The other means can cause hypertrophy or hyperplasia. When you exercise and have muscular injury, satellite cells are activated and they reproduce or split to form immature muscle cells called myoblasts. These new cells can ban together to form new muscle cells and fibers or they can latch on to existing muscle cells and make the fibers larger.
Has to do with motor units and recruitment.
When you lift, you tear the Z lines in a fiber. As weight increases or you do more reps, more z lines are torn and eventually you will recruit more fibers in the muscle into action. These are already existing fibers so strength gain happens first before size increases. Eventually the fibers you have aren’t enough so you grow more - hypertrophy.
I’ve always heard that you get stronger from lifting weights by damaging the muscle slightly when lifting and when your body repairs it, it builds it back better and therefore you get stronger. I also know that you don’t grow new muscles fibers when you lift weights and get bigger, but your muscle fibers actually get bigger (hypertrophy).
Now, I’m taking an anatomy class at the moment and I know about stuff like thick microfilaments, thin microfilaments, H bands, T tubules, myosin, and actin. I’m wondering if someone could explain to me in more detail what happens when you lifts weights and how you actually get stronger.
Thanks.
Muscle gets stronger because you add more myosin and actin proteins to existing muscle fibers, so more cross-bridges exist to produce force. In humans this accounts for almost all increases in the force-producing capacity of muscle because we do not add muscle fibers to any appreciably degree, if at all.
Stressing a muscle with high forces leads to activation of pathways that increase protein synthesis rates and thereby a net increase in the amount of myosin/actin present in muscle fibers.
Wayne's answer is closest to the mark of how your skeletal muscle adapts to strength training, at least according to my understanding.
As tigerchik points out, lifting weights damages the muscle fibers themselves. In addition to z-line damage, there is also damage to the filament architecture of the muscle fiber (how the myosin proteins interact with the actin proteins) as well as sarcolemma damage (the lipid membrane of the fiber). Damage to the sarcolemma results in calcium leakage which is required for proper muscle function and is a signal that the muscle fiber is damaged.
To clear up some confusion here: The primary response to strength training is hypertrophy (increase in size of existing muscle fibers), not hyperplasia (increase in number of muscle fibers). The number of muscle fibers you have in a given muscle is more or less set during fetal development and what you have at birth is pretty much it. All the muscle development throughout postnatal life is due to hypertrophy.
One additional thing that Tigerchick alluded to…some gains in strength with resistance training occur before hypertrophy occurs this intial gain in strength is due to improved neuromuscular recruitment motor units.
One additional thing that Tigerchick alluded to…some gains in strength with resistance training occur before hypertrophy occurs this intial gain in strength is due to improved neuromuscular recruitment motor units.
I was referring to a muscle getting stronger per se. In a person there are neural adaptations that lead to increased strength before any significant hypertrophy can even be measured. I’m not sure how well we can parse out what those neural adaptations are, whether they are are improved “recruitement”, increased coordination or stabilization or likely a combination of those factors and others we are not considering.