Choosing the Right Weight
Strength training guidelines often refer to your “one-rep max,” or “1RM” – the heaviest weight that you can lift once for any given exercise. The American College of Sports Medicine suggests that beginners work with weights that are 60 to 70 percent of 1RM for 8 to 12 repetitions; using less than 50 percent of 1RM may not stimulate any muscle growth.
But how do you determine 1RM? For most people trying to lift the heaviest weight possible is an unnecessary injury risk. Instead, use trial and error to find a weight that has you reaching “failure” near the end of your final set. If you plan three sets of 10 reps and you successfully complete them, increase the weight slightly next time so that you’re unable to complete the final one or two reps. New research by Stuart Phillips at McMaster University suggests that reaching failure is the most important factor in building muscle – even more important than how heavy the weights are or how many reps you do. His study found that volunteers lifting at 30 percent 1RM synthesized just as much muscle protein as volunteers lifting at 90 percent 1RM, as long as they lifted to failure.
The take-home: don’t worry too much about one-rep max, but choose a weight so that you reach failure, or at least come very close.