How strong are you? Estimating your one rep max is one way (and perhaps the safest way) to find out.
Whether you are trying to build muscle or burn fat, on many workout plans, you often see percentages. What do those percentages mean? Believe it or not, that is the amount of weight you should use during that set for that exercise in order to build muscle or burn fat.
What is that you say? How does a percentage tell you how much weight to use when burning fat or building muscle? That number represents the percentage of your 1 rep max (1RM) that you should be using.
Your 1RM represents the amount of weight you can lift using maximum effort exactly one time. When you hear someone ask, "How much do you bench?" they are asking specifically what is the maximum amount of weight you can bench press.
You will often hear someone talk about "maxing out" when considering testing his or her single rep max. Of course, it is not always feasible or safe to "max out." You can easily injure yourself when testing your muscular limits. So how do you find out what your 1 rep max is without the risk?
Fortunately, there are a few formulas that can give us pretty good estimates of your max based on the number of repetitions you can do at a weight you are comfortable lifting.
1RM = ((Number of Reps / 30) + 1) x Weight Used
For example, if you were to lift 185 pounds 6 times, you calculate your one rep max as follows:
1RM = ((6 reps / 30) + 1) x 185 pounds
1RM = (0.2 + 1) x 185 pounds
1RM = 1.2 x 185 pounds
1RM = 222 pounds
1RM = Weight Used / (1.0278 - (0.0278 x Number of Reps))
Using the example above,
1RM = 185 pounds / (1.0278 - (0.0278 x 6 reps))
1RM = 185 pounds / (1.0278 - 0.1668)
1RM = 185 pounds / 0.861
1RM = 215 pounds
Method 3 (aka "Brzycki Formula"):
1RM = (Weight Used) x 36 / (37 - Number of Reps)
Again, using our example of lifting 185 pound for 6 repetitions:
1RM = 185 pounds x 36 / (37 - 6 reps)
1RM = 185 pounds x 36 / 31
1RM = 6660 / 31
1RM = 215 pounds
As you can see, Methods 2 and 3 give very similar results, while Method 1 provides a slightly higher estimate. This is an important reminder than any formula based calculation is an estimate.
Because it is an estimate, percentage calculations for workouts may be off slightly. Use your best judgment, and if you have trouble completing a set at the calculated weight, make a slight adjustment for future sets.
Once you know your 1RM, you can use the percentages found on workout plans to determine approximately how much weight you should use for each set of that exercise.
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