When you start to work with clients who haven’t done resistance training before you’ll soon discover that finding the right weights for them to start with is almost entirely trial and error.
You’ll train people who surprise themselves (and you) with how much they can lift as well as others who look much stronger than they actually are and will need to start out on lighter weights.
First of all, safety is key when finding the right weights to start with; if you’re training someone who’s never worked with free weights before then you may want to use very light weights with them for the first session whilst they get used to performing the moves correctly. (Also, if you push them too hard in their first session they may ache so much in the following days that they won’t want to come back.)
However, for a client with some experience of free weights, or who you’ve already done at least one session with, it’s a good idea to establish what weights they should be using for each move early on, so you can ensure that they work at a level that challenges them and then build upon that in future sessions. And a good way to do this is to use the 12-15 System.
The 12-15 System
The 12-15 System is a method of progressive overload that allows you to gradually and safely increase the amount lifted in a move without increasing it too quickly and risking injury.
The way the 12-15 System works is that you stay within the 12-15 rep range, meaning you aim to perform no fewer than 12 reps and no more than 15 reps within a set.
You will have to use trial and error to find starting weights during the first session, over several sets if necessary, but should end up with weights that the client can perform between 12 and 15 reps with.
Ideally, the first session should have allowed you to find weights that the client can use for at least 12 reps, but if they’re not quite able to do that then you can stay on the chosen weights until they can, or reduce them.
After that you should aim to increase the reps gradually over subsequent sessions; this could be by increasing the reps by one per week, but could also happen more quickly or more slowly. Either way, the idea is to slowly and safely increase the reps until 15 can be performed, after which the weights should be increased at the next session and the reps taken back to 12.
The system is then continued with until 15 reps can be performed with the new weight, before the weight is again increased and the reps taken back to 12.
The 12-15 System is a good way to build up muscular endurance with a new client, by performing the moves slowly and under control, and can later be used to work towards hypertrophy, by performing the moves with an explosive lifting phase and a slower lowering phase (though it should be noted that the higher rep range makes it less suited to pure strength training, where a smaller rep range combined with a higher weight is preferred).
Functional Fitness PTS 