As part of an online competition I want to perfom 1RM on all of my lifts (squat, bench press, over head press, bent over rows, dead lift). I do not know what my current 1RM is and would like to find out in a safe way. How can I do this safely?
You should have a general idea of what you should be able to do based on the training you've done to date. If you haven't trained long enough to have an idea, I highly recommend waiting a bit. This will help you plan your warm ups.
Estimating 1RM Based on Longer Sets
For a ball park estimate of what you would be good for, use the formula below:
I would use your current maximum work set you've done to plug in to the numbers. So if you are doing Starting Strength, and your highest squat was 225lbs for 5 reps your estimated 1RM will be about 255lbs. Just note that the higher the number of reps you use for this estimate, the less accurate the formula becomes.
I recommend this method if you are figuring out what to plug in to a program that uses percentages. I also recommend this method if you are a beginner. Work up to your heaviest set of 3 or 5, or pick a weight you know you can lift repeatedly and go for the maximum reps.
Actually Testing 1RM
Testing your 1RM requires preparation to do it safely.
When preparing for a competition, you have 3 attempts. Most recommendations I have seen are close to these percentages of your target max: 85%, 93%, 100%. (I've also seen 90%, 95%, 97%). The idea is that the first attempt should be something you can easily do for a triple. The second attempt increases your total for the day, and the last attempt is going for a Personal Record (PR). This is the approach I now use. If I hit all three attempts, I don't try for a fourth.
NOTE: Here is a huge reason to use safeties and not rely on a spotter:
At the weight the power lifter was lifting, it would be unreasonable to expect the spotters to be able to do much with it, even if their hands remained under the bar the entire time.