I will be clear right away: unstable strength exercise cannot and will not lead to the stimulation of as much muscle growth as stable variations of the movements. The decrease in force production will prevent maximum motor unit recruitment. As a result, using unstable variations of weight lifting exercise makes very little sense.
The main use of unstable training is to increase CNS activity. To "wake-up" the nervous system, so to speak. The nervous system will have to work harder to maintain proper stability during the movement. So when you perform an unstable movement, you better prepare the nervous system to perform optimally during regular lifting exercises: the CNS will be potentiated by the unstable training and this will lead to greater motor unit activation during the subsequent lifting drills.
So, the correct application of unstable exercise when muscle growth is the main concern is as a CNS activator. As such, it should be performed before a stable exercise with the same movement structure or muscle involvement (e.g. push-ups with the hands on a swiss ball before moving on to DB bench press). This can be done either as a superset (one set of unstable exercise, no rest, one set of stable exercise) in alternate fashion (one set of unstable exercise, brief rest period, one set of stable exercise) or as a separate drill within a workout. In the later case, the unstable exercise should be used at the beginning of the workout. However, the best option for maximum muscle growth stimulation seems to be either to superset or alternate both type of exercise.
You don't have to use an unstable exercise for every body part or movement structure, but it can be a good tool to use for a stubborn muscle group. A stubborn muscle is often as such because of a lack of activation from the CNS so using an unstable exercise could help solve that problem.
Also note that to be "unstable" an exercise doesn't necessarily have to be performed on an unstable surface. Simply reducing the base of support (e.g. lunges on your toes, singleleg squat, single leg Romanian deadlift, etc.) can also do the trick.
Was this article helpful?
The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.