Is the heaviest weight you can lift if you give it your maximum effort for 1 rep.
Example: If you can complete 1 rep of a chest press with 20 lbs that is your 1RM. Each Phase will use a different percentage of your 1 rep max. See each separate card for the appropriate weight to be used.
You don’t need to determine your 1RM for every exercise. You will be able to lift more with a large muscle like your chest versus a smaller muscle like your bicep or tricep so consider the size of the muscle involved before picking up a weight.
Remember to warm up your muscles before attempting to identify your 1RM. Begin with a weight you know you can lift (5 or 10 lbs) and increase that by 2-5 lbs increments until you reach your 1RM. You may want to have a spotter with you for at least a bench chest press.
I would recommend determining your 1 rep max for a chest press on a bench as your chest is a large muscle and can lift more; however, feel free to determine your 1 RM for your chest, back, shoulder, tricep, bicep and legs.
Example: For Phase 1 use 50-75% of your 1 RM. If your 1 RM for your chest is 20 lbs then use 10-15 lbs weights for your chest exercises (50% of 20 = 10 and 75% of 20 = 15.) Check each Phase Title card before beginning a new phase as each uses a different percentage of your 1 rep max.