Simplifying the One Rep Max Equation - FITNESS INSTITUTE

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Simplifying the One Rep Max Equation

Written by admin

January 2, 2020

Fitness Testing | News

Determining and testing One Repetition Maximum (1RM), which is the amount of weight you can lift only once, helps to work out specific load settings when designing effective strength training programs….

Knowing your 1RM also helps with knowing how effective and efficient your training routine is over time and assesses the progress you are making…..
You can use 1RM testing to get an idea of maximal force production within a specific muscle group.
These results are useful in determining starting intensities for resistance exercises. 1 RM may be determined by trial and error or indirectly by using sub-maximal loads at less than 10 repetitions and applying an equation to estimate 1RM.
Some examples of movement suitable for 1RM tests are: Bench Press, Squats, Deadlifts and Lat Pulldown.

To help explain how to work out the %1RM, we asked Fitness Institute Trainer and Assessor, Boris Bojanovic…

How do you measure intensity of resistance exercise?

So %1RM means the percentage of the weight you can only lift once before you fail and try again.
Let’s say you tested your deadlift with 100kg on the bar.
You tried 2 reps, failed on the second one (i.e. you got it half way up to your knees but as hard as you pulled you couldn’t make it budge, so you dropped it).
Your 1RM on the deadlift would be 100kg.

Using %1RM charts: 

If you wanted a challenging weight for 5 reps, you would consult this really handy table at and see 100kg would be around 85-87% 1RM so you would use 85-87kg and lift it 5 times, but if you tried a 6th rep you would fail.
Because it was a maximum effort, if you wanted to repeat another set after a rest you probably wouldn’t be able to recover to repeat it (i.e. your muscles don’t have the energy and your nerves are depleted).
You would need to rest 24-48hr and you would come back stronger – so if you wanted to repeat sets of 5, you should probably choose a weight 5-10% less than the %1RM for 5 reps – meaning 75-80%1RM.
With that in mind, 6-8 reps would be somewhere between 75-85 %1RM.
Taking 5-10% off that, something like 70-80% 1RM for 6-8 reps is what you would program.
If we use the table at, it will look like this:
Brycki, Matt (1998), A Practical Guide to Strength Training, McGraw Hill 
Baechle TR, Earle RW, Wathen D (2000). Essentials of Strength Training and Conditioning, 2: 395 – 425. 
dos Remedios R (2007) Men’s Health Power Training Training, Rodale Inc 23.   
You can find more information and examples on the Top End Sport website.