After recording the data for five repeated trials, you should calculate the average of the five values and report that average in your lab report.

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully