If you want to save time in the gym but also increase your size and strength then doing back-to-back (or double) exercises is a must.
In order to succeed at this technique you need to do three sets in succession, focusing on the same body part, with no rest. For example, a set of front squats is followed immediately by one leg of extensions, then another set of squats.
This technique works because by back to backing your exercises you are training the different components of each muscle group within opposing active ranges of motion. This allows the muscle to be strong in the following exercise because its fibres haven't already been worked in that range. Front squats, for example, primarily work the quads in the bent knee position, while the leg extensions work the quads in the straight knee position. This method means you can work continuously on the same muscle group and completely fatigue absolutely all its fibres, which triggers muscle growth.
To get the best results you should adopt this back-to-back exercise method for one week every month. It will give your training shakeup without burning you out.
It is thought that this doubles training concept was introduced to the world of bodybuilding in the 1970s by professional bodybuilder and wrestling coach Don Ross. Don Ross -who performed under the names "Ripper Savage" and " the Bronx Barbarian" - found that the key to building a bigger muscles was to recruit as many muscle fibres as possible, which led him to create and adopt this method.