We all know (or should know) resistance training is a great way to increase your lean muscle mass, metabolism, strength, endurance, and bone density. Everyone should do at least some resistance training no matter what their lifestyle, goals, health, or fitness level. All resistance training exercises are not created alike however and you need to know what types of exercises you should perform for your goals. Resistance training exercises are generally divided into two categories: Isolation and Compound Exercises. This post is on the former and I will be posting shortly on Compound Exercises.
Isolation exercises are those that involve focusing on a single muscle or small muscle group. These exercises typically involve movement at a single joint and therefore will use less muscles than an exercise involving movement at multiple joints. Isolation exercises include crunches, bicep curls, tricep extensions, calf raises, leg extensions, leg curls, wrist curls, and other similar exercises and variations. In my opinion, there are only 3 reasons to utilize isolation exercises. The first one is for injury prevention or rehabilitation. Sometimes it can be very useful to perform isolation exercises to minimize joint involvement in an area that has injury, tightness, or weakness. The second reason is for building muscle mass. Isolation exercises have been used by bodybuilders to achieve gains in muscle mass at the expense of functionality and stability. Since less core muscles or stabilizers are required, the targeted muscle or muscle group will be doing all of the work and therefore will adapt to the increased stress by growing larger and stronger.
The third reason, which I include in my rationale for doing nearly any exercise at least once in awhile, is for the sake of variety. This isn't just variety to make the workout fun or more interesting, but because it will help to prevent your body from adapting to the same exercises and workouts. If you continue to do the same exercises (even the most efficient ones), your body will get less out of it in terms of muscle stimulation, metabolism, or hormonal response. To give a simplified example, everyone agrees that squats are more important than leg extensions. That doesn't mean that leg extensions have no place in a workout.
I think that if somebody is doing several total body workouts per week, they can incorporate at least a few isolation exercises to hit on lagging muscles or muscle groups. I would prefer them to be done towards the end of the workout as "burn-out" sets instead of making them the main focus of the workout. If you are looking to bulk-up and put on muscle mass, isolation exercises will have more use to you (although compound exercises should still be the main course of your workouts, as you will see in my next post).