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1RM Calculation and Use

September 12, 2010 Print This ArticleShare

Author: Michael Greeves

There is nothing worse than trying to find information on something and being struck by terms that you can’t define and that aren’t defined in the article.  When I came across the term 1RM or the 1 Rep Max, I thought perhaps I would explain it for the people just getting started with strength training.  As you get more involved with strength training you may see directions for doing 12 reps at 20% load, then 12 reps at 40% load and then maybe another set of 5 reps at 70% load.  All of this involves your 1 Rep Max.

The 1 Rep Max is a basic calculation of the weight you would need to lift to only be able to handle one repetition.  There are many calculators online that will help you determine your 1RM, but there is a fairly simple formula that you can use if you aren’t near a computer.  That formula is weight divided by 1.0278 minus (.0278 times # of reps) To figure your 1RM, choose a weight you are sure you can do multiple reps with, say 80 lbs for leg presses.   Then do as many reps as you can without straining, say 10. Now, using the formula, your RM1 for leg presses would be 80/1.0278-(.0278 x 10) = 80/1.0278-.278 = 80/.7498 = 107.  Your leg press 1RM would be 107 lbs.

To achieve whatever goal you have set for yourself in strength training, you will need to incorporate reps, sets, and load.  Load is a percentage of your 1RM.  If you want to strengthen and lose weight you use a lower load with more reps. Your program might include 3 sets of 12 reps at a 50% load.  That would be 3 sets of 12 reps of 54 lbs if we use our leg press numbers.  As that become easier you may go up to 65% load and work back up to the 12 reps.  The maximum load that should be used is usually 85% with only 6-8 reps.  That will build muscle bulk.  Again, your strength training goal will determine your program.

The 1RM formula in strength training should be used with care.  Always base your actual weights and reps on what your body can handle.



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