One rep max (1RM) is the maximum amount of weight an individual can lift during a single exercise. It is an abbreviation for one repetition maximum. This weight limit is often used to determine someone's total maximum body strength.
An individual will typically be able to perform one rep max for different exercises, at different weights. For example, one person may only be able to lift 50 lbs (22.7 kg) one time during a single bicep curl. That same person may then be able to lift 200 lbs (90.9 kg), once, during a barbell lift.
There are a variety of one rep max calculators available on the Internet. These use the maximum number of repetitions an individual can perform during a single exercise, at one established weight, to determine the maximum weight he can lift for one repetition. Each exercise should be evaluated separately. The calculator is meant to be used as a suggested starting weight only, and this amount can be adjusted as needed by the athlete.
This formula may also be worked in reverse. If someone already knows his own one rep max number for an exercise, he can use that number to calculate how many repetitions can be performed at a lower weight setting. That lower number of repetitions is known as a percentage of 1RM. This terminology is frequently found in exercise training guides.
Knowing the one rep max for various exercises can help an individual determine his overall exercise goals. Different parts of the body respond at varying levels of the one rep max percentage. When an athlete lifts 100% of his 1RM, he is generating neurological responses across the body to increase overall strength. When that number is lowered to between 65% and 75%, the body responds metabolically and increases muscle size instead of strength. With this information in mind, an individual can create a workout regimen that targets his own personal goals, whether that is to become stronger or to build larger muscles.
One rep max is often used in strength competitions to determine a winner. The three most common exercises performed during such competitions are the bench press, the back squat, and the deadlift. Each exercise typically involves the barbell, however, some competitions may also make use of dumbbells and kettlebells. These exercises are believed to target the three main muscle groups of the body, providing an overall reflection of total body strength.