Hi I was wondering if ne one could help me!!

I'm writting a short review on how i propose to do a meta analysis on the effect of alkalising agents on sports performance. There are a number of variables namely: age, **** doseage, alkalising agent used, then the studies have used many different ways of recording data such as blood pH levels, blood lactate levels etc. I am really confused and dont know where to start!. Which statisics would I use and why?,
Thank you to any one who may help!

Flic***