Once upon a time, somewhere along the way, someone came up with the magic number for reps in a weight lifting set. A set of 10 or 12 or 15 reps in set is considered key….and this ideal number may be ruining your gains.
The idea of a 12-rep set stemmed from studies that your time under tension (how long a muscle is under strain during a set) is surpassed at 45 seconds and gets closer to 60 seconds in a set. Your tempo in your performance should be considered more important and valued higher than your reps. Your tempo should be enough to elicit hypertrophy (the growth and increase of the size of muscle cells) and the main goal is to prolong the eccentric contraction (or negative) on the way down in your lift (i.e. 1-2 second contraction on the way up and 3-5 second contraction on the way down).
Our fixation on the 3 sets of 12 (or 10 or 15) is killing our gains because is does not reflect on the study of how we got to the “magic number”, but instead, focuses solely on the “magic number”.
Most people, when weight lifting, instinctively start out with a weight that is comfortable in order to ensure they have the energy to get through all reps. What would be more beneficial to muscle growth (or hypertrophy) is to start with a heavier weight and lift to failure. If this means you max out at 8 or 11 reps, then so be it. Focus on the time and effort you are putting into a rep and not on the number of reps in a set – and on your time under tension – and watch your gains increase.