what symptoms can result from excess free radicals in the muscles?

If you imagine a muscle cell as the wild west, you can can consider free radicals as outlaws. Free radicals are unstable molecules with unpaired electrons. For a molecule to regain its stability it needs an electron. In the wild west, electrons don't come cheap and the only way our rouge free radical can obtain one is to steal it from another molecule. Not only are free radicals outlaws, they are also zombies. Free radicals rob stagecoach drivers like Black Bart and turn other molecules into free radicals like zombies. An unsavory situation in the wild west indeed.

This process culminates in a chain reaction. Free radicals roam, relatively unchecked by the authorities, raping and pillaging, decapitating lawmen to feast on their quivering brains and causing cattle stampedes in their free time. This, as you would expect, results in a disruption of normal muscle cell activity. To understand the symptoms, we need to understand what free radicals do in a strictly chemical sense: oxidize.

Oxidation is the reaction free radicals create. Although this process is damaging to our muscle cells, it is essential to life as we know it. Two of the most common occurrences of oxidation are rust and fire. Oxidation can be halted by, the only chemical with an obvious name, an Antioxidant. Commonly known to researchers as SuperJesus.

Antioxidants halt the destructive chain reaction by supplying free radicals with an electron. The difference between a molecule of an antioxidant and a normal molecule is that after restoring a rampaging outlaw zombie to its normal stable state, it remains stable itself. Hence its scientific name. SuperJesus can combat hordes of zombies with the strength of an omnipotent man in tights by sacrificing itself and forgiving the free radicals for their sin. Still, the antioxidant remains the archetype that all molecules aspire to emulate.

As for the observable symptoms of free radicals in muscles, one can infer, through the flawless system of logic, that your muscles will simultaneously rust and burst into flames.