10-rep-max is a form of Submaximal testing used in place where a 1RM is inappropriate, such as a bicep curl or calf extension, our 10RM is approximately 75% of our 1RM, so if for example our bench press 1RM is 200lbs our 10RM is around 150lbs depending on our level of muscular conditioning.
A light warm up of 10-15 reps is recommended before proceeding to heavier weights, roughly 50% of the expected resistance or load.
After the warmup set, the weight should be increased by roughly 25% and a set of 8-10 should be performed.
Following this set we should be able to estimate our 10-rep max, if we can only perform 8 reps then the weight should be lowered, usually in 5% increments, and a two-minute rest should be taken before attempting a lighter weight.
If we can perform more than 10 reps the weight should be increased, usually in 5% increments, and a two-minute rest period should be taken before attempting a heavier weight.
Repeat this process until a true 10-rep max is found, then to find your estimated 1RM use the following formula:
10RM ÷ 0.75 ≈ 1RM
Ex.
85lbs ÷ 0.75 ≈ 113.5lbs
135lbs ÷ 0.75 ≈ 180lbs