The repetition max is the amount of times you can lift a specific weight until you reach muscular failure. Sometimes strength coaches or personal trainers will have athletes find their repetition max with a lift instead of doing a 1 rep maximum lift in order to test strength. You can find an approximate 1 rep max by using this chart:
|Reps||% 1 RM|
As an example, if you can squat 100 pounds 9 times, look in the chart to see what percentage of your 1 rep max that is. The chart says that if you can do 9 reps, 100 pounds is 76% of your 1 rep max. So divide 100 by .76 and you get 131 pounds. That is your estimated 1 rep max! You can use this to track your progress, or just see how strong you are.