Full Range of Motion vs Effective Range of Motion - By David Klein

The aim of this post is to explain the importance of performing exercises through an Effective Range of Motion and also to define exactly what is the required range of motion for a muscle action. The required effective range of motion will vary from one muscle action to another and thus one exercise to another.

The goal of this post is to understand the difference between Full Range of Motion (FROM) and “Effective Range of Motion” (EROM). For too long the importance of Full Range of Motion has been evaded, and when mentioned, generalised without taking a closer examination of this fundamentally crucial concept. Very few people have successfully published a guide to performing a full range of motion exercise but performing it with care and consideration for “Effective Muscle Torque” “Moment Arms” and their implications on safety. Yes too much ROM can be a bad thing when applied in a practical setting.

Effective Range of Motion…

So let’s start with why you should focus on Full and Effective Range of Motion in your workouts.

1) The main factor would be the flexibility of the muscle/s in question.

The most effective way of increasing flexibility in a muscle… say, the hamstring, for example, is to contract it’s antagonist (opposing muscle), in this example the quadriceps. When you contract the quadricep the hamstring must lengthen in response. When you fully contract the quadricep you fully lengthen the hamstring, you engage it in a full and complete stretch.

2) Although muscle fibre engagement is dictated by the level of intensity of effort, by carrying out a maximal excursion (subject to caveat we will get to shortly) you can be sure to maximise a contraction and tap into as many muscle fibres as possible if you start from a position of extension and reach a position of peak contraction.

3) If you focus on the Effective Range of Motion (EROM) you are by default ensuring maximal stimulus and maximal safety. Necessities of efficient exercise.

The Caveat…

Now, in order to ensure a constant stimulus which is needed to ensure we are continually spiking intensity and making the variables easier to accurately measure and safer we need to ensure:

  1. We Avoid zero Moment Arm. This is the point in a movement when the load is above the axis of the movement (think of standing above the hinging point (Fulcrum) of a see-saw or at the point of full extension when the weight is just hanging. There is no load at these moments and this constitutes as a rest during our set which we must avoid for intensity and accuracy of measurement purposes.
  1. We do not load the muscles in positions of extreme extension. I.E be careful not to go to deep into the stretching phase (eccentric phase) of the movement, certain joints like the shoulder do not have a “knee-cap” so one must be extremely careful when performing an exercise such as a dumb bell fly. Mainly because the resistance from such an exercise does not include variable resistance which factors in the strength curve and varies the resistance in differing phases of the movement. A machine like vintage Nautilus, MedX or RenX machines do have varying resistance so if you’re using such machines you needn’t worry. But when using a free weight we tend to start in a position of “lock out” the problem here, (and this is an inherent problem with free weights) is that when one starts in the strongest position the weight gets heavier because the moment arm increases (think of now walking along that see-saw away from the axis) the weight is now as heavy in the strongest position as it is in the weakest position. Combined with the needed high levels of fatigue this can prove dangerous.

The solution…

The solution is to avoid Zero moment arm in some full flexion exercises, so stop just short of the lock-out, ensure that the muscle is loaded at all times and when lowering the weight ensure you stop just short of zero moment arm in full extension. You will place less stress on the tendons whilst continually increasing intensity.

Also be sure that you continually travel the same distance in your Effective Range of Motion. As you fatigue your natural instinct will be to reduce the range of the muscle excursion and thus reduce the intensity in order to offer some respite. Always travel the same distance from the beginning of a set to the end of a set.

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