I have been doing a lot of cubing in the past several days, mainly because of break. Today, for example, I did an average of 5 on my partially modded 6x6 and started an average of 5 on 7x7, amongst many other cubes and things. However, during my third 7x7 solve, I began to feel "jolts" down my arm. They felt very similar to small amounts of electricity. Needless to say, I stopped (after the solve, haha). Has anyone else experienced these?