**One rep maximum** (**one repetition maximum** or **1RM**) in weight training is the maximum amount of weight one can lift in a single repetition for a given exercise. One rep maxima can be used for determining an individual's maximum strength and is the method for determining the winner in events such as powerlifting and weightlifting competitions. One rep maxima can also be used as an upper limit, in order to determine the desired "load" for an exercise (as a percentage of the 1RM).

## Calculating 1RMEdit

Various weight training protocols call for lifting some percentage of the lifter's 1RM. However, many consider the risk of injury when attempting a 1RM to be equal to or higher than when performing multiple rep sets. Therefore, there have been various proposals for ways to calculate an approximation of the 1RM.

There are two common formulas used to calculate the one rep maximum.^{[1]} If $ r $ is the number of repetitions performed and $ w $ is the amount of weight used, then

### Formula 1Edit

$ 1RM = \left [ \left ( \frac{r}{30} \right ) + 1 \right ] \times w $

Note: This formula may be mistyped as it does not work out mathematically. Should you actually test your 1 rep max, and then plug the results into this formula you would get a result that is higher than your 1 rep max. I suggest this modification:

$ 1RM = \left [ \left ( \frac{r-1}{30} \right ) + 1 \right ] \times w $

### Formula 2Edit

This version of the one rep maximum calculation is often referred to as the Brzycki Formula after its creator, Matt Brzycki,^{[2]} and can be written either in terms of integers or decimal approximation:

$ 1RM = w \times \frac {36}{ \left ( 37 - r \right ) } = \frac{w}{ \left [ \frac{37}{36} - \left ( \frac{1}{36} \times r \right ) \right ] } \approx \frac{w}{ \left [ 1.0278 - \left ( 0.0278 \times r \right ) \right ] } $

Both formula 1 and 2 return similar results for 10 repetitions. However, for less than 10 reps, formula 1 returns a slightly higher estimated maximum. For example, if a person can lift 100 pounds on a given exercise for 10 reps, the estimated one rep max would be 133 pounds for both formulae. However, if the person were to complete only 6 reps, then formula 1 would estimate a one rep maximum of approximately 120 pounds, while formula 2 would both return an estimate of approximately 116 pounds.

These types of calculations may not always produce accurate results, but can be used as starting point. The weight can then be changed as needed to perform the number of reps called for by the training protocol.

Several more complex formulae have been proposed which use different coefficients for different rep numbers and sometimes even for different exercises.

One rep maximum calculators are used to *predict* a one rep maximum lift. The degree of accuracy can vary largely depending on the weight training experience and muscular composition of the athlete. Also, most one rep maximum calculators are design for seasoned strength trainers, and those with little experience may find their actual one rep maximum is much lower because their nervous system cannot handle the stress of a high weight. This test should performed with a spotter for reasons of safety.

## See alsoEdit

## External linksEdit

- ↑
*See How Easily You Can Calculate Your One Rep Max.* - ↑ Brzycki, Matt (1998).
*A Practical Approach To Strength Training*. McGraw-Hill. ISBN 1-570-28018-5.

## External linksEdit

- One-Rep Max Estimator with rep ranges, percentages and graphing
- 1 rep max bench press calculator
- ExRx.net: One-rep max calculator
- A 1RM calculator and explanation of several different calculation methods.
- Free: One Repetition Maximum Calculator.
- 1RepMax Calculator providing 24# results
- one rep max calculator in Jess Marunde's web