I was working out with my two cousins and one of them was barely getting back into the groove of working out for about two months or so. And this guy always wanted go heavy and do his one rep max for the bench press, and since he has spotters now, he can finally do it.
However, it seemed like this guy did not need that much of a warm up, which is not very wise because you can really mess up your joints and body if you lift heavy too often without warm up. In fact, with proper warm up, you should be able to lift more.
Before performing it, the warm-up for the one rep max is absolutely crucial. It is absolutely crucial for you to warm up your muscles and neuromuscular system before lifting that heavy load.
BUT DO NOT warm-up so much that your muscles are exhausted and you drop the huge load and crack your ribs! That will decrease your one rep max. For the average person, about 5-7 total warm-up sets are probably optimal and more than that may start to exhaust your muscles.
Now I know everyone is different, so here is how your warm-up typically looks like. The first set should feel very easy, about ten easy reps or so just to get your juices flowing.
After that, the next 2 through 3 sets should be about 5 reps, a little more resistance, but gradually increasing the weight. Again, you are different and so is everyone else so you will have to determine what is right for you.
And then gradually increase the weight for only one rep without overtiring your muscles for another 3 sets until you reach the maximal. Again, there is no set amount of weight you need to increase it by, you or an experienced coach should be the judge and have some strong spotters. Preferably one on each side if you lift REAL heavy!
According to the book Baechle TR, Earle RW. 2000. Essentials of Strength Training and Conditioning 2nd Ed. Champaign, IL: Human Kinetics., here is a safe, proper, and rough generalization of determining your one rep max.
If you can lift a certain amount of weight, lets say 10 times maximum with good form. You multiply that weight by a factor of 1.33. So if you can lift 225 pounds ten times with good form, you multiply 225 pounds by 1.33 and voila! your max should be around 299.25 pounds.
8 times maximum, multiply your load by 1.25; 5 times maximum, multiply your load by 1.15; 3 times maximum, multiply your load by 1.08. Again, this is just a generalization. Ultimately it’s going to be you and your coach who will determine what you can and can’t lift.