Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: Andres on 13/12/2008 19:31:22
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Andres asked the Naked Scientists:
Dear Scientists,
after some exercise, what goes on inside our bodies, so that after some hours or after a good night sleep, your muscles feel sore. I have heard many explanations, but you are the experts, so please save me from my ignorance.
Thank you
Andres
What do you think?
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There could be a number of possible reasons/causes. Basically aching muscles results from fatigue.
Your muscle can strain and/or tear if they are stretched abnormally. It may not function properly, so there may be a loss of movement of a limb or joint, making movement sore when you try to move it too much.
Stiff muscles can result after exercise that we are not used to. The stiffness comes from fluid that has not drained away efficiently during exercise.
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I thought I'd re-light this topic, because I was about to start a new one with pretty much the same subject.
I've recently started exercisng again and discovering muscles I wasn't aware of, and it struck me as odd that in order to improve our health and fitness, we have to inflict pain on ourselves which is usually associated with damaged tissue.
I was wondering whether in order for muscles to grow stronger, the exercise is actually causing damage to the muscles which then react by healing with reinforcements? Kind of like the idea that a broken bone will knit stronger than it was before it broke.
Any recent ideas?
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I think a lot of the pain is lactic acid. I have recently upped my exercise (50 km per day on my bike), my thighs are permanently sore; from mildly stiff to screaming lactic acid build up. But I have made it to "the runners high" the exerciser's endorphins level - I get a real kick from exercise. Its a reward, combined with pain to limit the risk being taken to receive the reward. If lactic acid build up was not painful I would push my 25km ride to and from work to the limit.
At present I am not really that out of breath and heartrate is raised but not extreme - without that lactic acid warning sign I would push till I was breathing hard, heart racing etc. (because its fun and I get the runner's high) and I would start seriously damaging my muscles (and more likely my knees). Like so many things in the body, the self-balancing systems are very well tuned - you can in extremis end up damaging your muscles through exercise but it is much more likely to get a strain through no warming up, or to do your joints in.
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Exercise makes muscles achy for several reasons. One is that muscles are bundles of ATP-powered molecular machines that use energy to do work. As such, the protein moving parts eventually clap out and need to be replaced. A bout of unaccustomed exercise causes discomfort because it causes overloading of the untrained muscle and damage above normal wear-and-tear levels. The result is mild inflammation as the immune system moves in to clear up the mess and enact repair.
But exercise-induced pain isn't just down to muscles. The other tissues that are involved in movements - tendons, ligaments and connective tissues around joints - are also traumatised (and subsequently strengthened) by exercise. Again, unaccustomed exercise can cause damage to the tissue, releasing inflammatory mediators that cause pain and recruit the immune system to help clear up and repair the injury.
I speak from some experience: I've been digging a very long trench to lay some electrical cables. The action of swinging a pickaxe means I have rediscovered in the process a number of muscles I forgot I had...
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I've heard that our muscles are made up of fibers, and after doing a hard workout, the fibers needs time to get healed, so this may cause soreness or other muscular problems.