During my senior year of college I had a swimming class instructor (who was in his 80s and in amazing physical shape) that touted Lysine tablets almost every class. His theory was that 500 mg a day would do wonders for most athletes. He said most of us didn't get enough through our diet.
I have done some Google searching and it sounds like there may be some truth to this. Supposedly helps with rebuilding muscle tissue and recovery. Thoughts? Experiences?

I don't know about lysine specifically. I just read the label on my whey protein container. It says it has 2.25g of lysine in every 30g serving. You're probably a lot better off getting a balanced protein profile than taking some specific amino tab. I use at least 30g of whey every day, so that's almost 5 times as much lysine as your swim instructor was saying.

As far a muscle goes I've only ever heard of people using BCAA (branched chain amino acid) supplements. The reputable ones seem to contain a particular ratio of leucine, isoleucine, and valine. Haven't ever heard of people using lysine.

People who go crazy with protein ideas really need to take in introductory biology class. Should be around $100 at their local community college. As long as you eat a balanced diet, and get around 40 or so grams a day, maybe 50 if you're body building, you'll be fine. Excess calcium leads to pissing out the calcium from your bones.

So for a semi-active cyclist taking in about 2500 calories per day, you are recommending that protein make up 6.4% to 8% of their intake? Fascinating...

Is this really what you meant to say?

Interesting stuff.
Currently, I do not take any supplements whatsoever but apparently Lysine can help prevent and heal cold sores (which I get from time to time) so maybe I'll try 500 mg a day and see what happens.
Thanks all.

40-50 grams a day is incorrect. Do your own research and you will find that the actual number is much higher. That is barely at the RDA.

I always thought I heard protien was to be around 2 grams/lb. of body weight....or did I hear that wrong?

Depends on who you talk to.
On one hand you have the protein naysayers who think we can subsist on barely any protein. On the other we have the 2 grams a day per lb of bodyweight bodybuilders.
I played around and decided to stick with 1 gram per lb of bodyweight and am happy with the results.
I was at 40 grams a day and would wake up in the morning throbbing. My fitness gains were stalling as well. An increase to 150 grams a day has resulted in barely being sore at the end of a training cycle and a decent performance improvement.

Most people throw around 1g/lb of body weight. The research suggests that for a hard-training strength athlete the requirements may go as high as 0.7-0.8g/lb, but anything more does not give extra muscle-building effect. However, protein is a very thermogenic macronutrient (burns calories to digest it) and also increases satiety. So eating more of it has other benefits.