Training muscles to become stronger

Welcome to the first of a series of online lectures on different aspects of sports injuries and rehabilitation. I hope they help you to manage and understand your rehabilitation.

It is generally accepted that a muscle worked close to its force-generating capacity will increase in strength.

The important point is that strength improvements are generally governed by the intensity (level of tension placed on a muscle) of overload and not by the specific type of exercise used to apply that overload.

Certain methods of exercise lend themselves to a precise and systematic overload application. Progressive resistance weight training, isometric training and isokinetic training are three common exercise systems used for training muscles to become stronger.

These systems rely on three types of muscle action: Concentric, Eccentric and Isometric.

• Concentric: the muscle shortens, and joint movement occurs as tension develops, eg dumbbell curl.

• Eccentric: the muscle lengthens whilst developing tension, eg lowering the dumbbell down slowly against the force of gravity

• Isometric: the muscle attempts to shorten but cannot overcome the external resistance, eg pushing against a wall

Progressive resistance weight training

The technique of progressive resistance is a practical application of the overload principle. (You first need to know your repetition maximum (RM) which is 10 repetitions of your maximum weight without resting. The variable is the weight of the weight). The method involves three sets of exercise each consisting of 10 repetitions, the first done with half of your RM, the second with three quarters of your RM and third with your full RM. Obviously as strength improves the RM needs to be increased.

Isometric strength training

Isometric exercise is effective for providing muscle overload and improving strength, though it may be of limited use for sports training. Isometric strength is highly specific, a muscle trained isometrically demonstrates improved strength when the muscle acts isometrically and particularly at the joint angle used. The isometric method does seem to provide benefits during muscle testing and rehabilitation. Isometrically trained muscle is stronger when measured isometrically, whereas the dynamically-trained muscle is stronger when measured during resistance activities requiring movement.

Isokinetic resistance training

Isokinetic resistance training attempts to combine the features of both isometrics and weight training to provide muscle overload at a preset constant speed throughout the full range of motion. A main limitation of weight lifting exercise is that the force generated by the muscles is not at maximum through all phases of movement. With an isokinetically loaded muscle the desired speed of movement occurs immediately when force is applied, and the muscle is able to generate peak power throughout the range of motion.

In summary, it appears that all methods work but if you wish to train for a particular sport some approaches are likely to be better than others. Furthermore, it does not matter how the resistance is applied which allows you to have variety within your workout to increase strength.

I hope you have enjoyed this very condensed look at muscle strength training, the February lecture will look at running injuries, prevention and treatment as some of you look forward to marathon. If you have any questions about this lecture or would like me to cover a specific topic in this short series email physio@joeshotboltphysiotherapy.co.uk