I have to take a two week break from my Stronglifts program, and I won't have access to the gym or any weights. On the break I will be doing occasional body weight workouts, but for the most part I am going to be inactive.
When resuming the program after two weeks of inactivity can I just come back where I left off, or should I deload 10-20% from my last workout?
Deload. Significantly. 10% at a minimum, more likely 20% for such a significant break.
I tried to start back where I had left off after a one-week break, and it messed up my progress significantly in the short and long term.
Think of it this way: say you started with a 1RM of 135, and squatted, say, 95x5x5. By squatting increasingly heavy weights you improved your 1RM to 170, and are squatting 140x5x5. It's hard, but not at your limit. It probably isn't even your 5x5 limit. If someone held a gun to your head, you could probably make that last workout ten pounds heavier. You keep a little bit up your sleeve so that you can keep adding weight to the bar every workout for several months.
After two weeks, in the best case your 1RM will drop to something like 150. Doing sets of 5 across at 135 or 140 might be possible, but it will be a dramatically different experience. Your form will suffer and you might hurt yourself. Worse, you'll then try to increase the weight five pounds in the next workout, whereas you've only improved your 1RM by two or three pounds. By working too close to your 1RM, you've shortened the amount of time you can keep linearly adding weight.
It's much better to deload to, say, 115 or 120. Give your body the opportunity to restart the progression and you'll decrease your chance of getting hurt, and it will turn out better in the long run.
