A few years back I did a test400 only. FOR ME, the next few days after injection was quite painful. Felt like a killer deep bruise in the muscle. For that reason, I would only inject the test in my glutes because it was a bigger muscle, and the pain was alot more bearable and I was able to function more efficiently with lifting and everyday life......except for walking lol. I tried a couple of times in my delts, and that was death for me. Couldnt brush my teeth, lifts was hard and surfing was near impossible. Keep in mind I have a pretty high tolerance to pain.