Passive range of motion is most commonly used in a therapy setting to look for asymmetries between sides. Asymmetrical passive ROM can provide information about the current structural and/or neurological conditions affecting a joint and its surrounding muscles. In many cases passive ranges are beyond the range of motion achieved in most loaded training motions. Asymmetries and significantly reduced passive range of motion are usually the result of an injury or chronic issue that has led to a neurological adaptation to restrict motion.
Active range of motion is the best predictor of what the maximum trainable range of motion could be. The closer your trainable ROM to your active ROM, the more likely you have good balance of strength, stability, and neuromuscular coordination of a movement. In addition, having an active range of motion that is close to your passive ROM (provided it’s symmetrical) is also a positive indicator of good neuromuscular function.
It is normal though that the active ROM will always be a little less than the passive, because in an active state you are creating compressive and co-contraction forces around the joint. The reality is, it would not be ideal if we were taking our joints into the structural limits under load anyway. That would be incredibly inefficient in most cases from a force production standpoint, and drastically more prone to injury. When functioning properly, our neuromuscular system is not going to take us to structural end ranges.
When measuring the lengthened portion of a movement actively, you are contracting the antagonist muscles and your brain is regulating how far that antagonist can pull the target tissue into a stretch before it determines the integrity of the joint/tissues has reached its limit, and then it does not allow you to shorten that antagonist any further. So the active ROM is in a sense the maximum range that your body currently has good neuromuscular control over.
Doing light exercises with the goal of improving neuromuscular function to open up more range may be beneficial. But when using training loads meant to drive a physiological stimulus, you should stay within the active ROM.
We know trainable range of motion should not exceed active ROM, but that doesn’t mean it will be the full active ROM. Remember the factor in trainable ROM is load. As soon as load starts to exceed the threshold of the prime movers or any of the stabilizers, the motion will begin to be altered if it is continued. This may or may not be an acceptable alteration.
In the squatting example mentioned in the early part of the article, where if the knee extensor threshold is met, the squat may become more hip dominant. In some cases a person may still be able to achieve full ROM if their body segments and mobility allow them to still hit depth in just a more hip dominant squat, which may still be ok if the goal was not significant quadricep bias. If the goal was to train more of the hip musculature this also may be fine. However in the case where you were trying to target the quads, and the load now causes loss of ROM at the knee, you are possibly decreasing the effectiveness of the exercise and increasing non specific stress by just adding load. Or in the case after adding load you have to round at the low back in order to get the range of motion of the knee, you are exceeding the trainable ROM for the load being used.
Whether you use joint versus isolated muscle range of motion to guide your training should depend on your goal. Are you training a muscle or a motion? If you are training a motion, it may not be isolated to a specific muscle, but you should still make note of the primary force producers and their specific ROM. This can help you improve your technique for better overall performance if you can make the motion align better and stay within the range of the major force producers.
If your goal is a local physiological stimulus for a muscle, then isolated muscle ROM should be your guide. Remember this is path of motion specific, so you need to understand your functional anatomy. Utilizing the correct path and range of motion for a specific tissue will increase the magnitude and duration of tension and metabolic work in that specific tissue. The amount of stimulus change as you deviate from these paths of motion will vary quite a bit across different muscles, joints, and exercises.
For example, the two gastrocnemius bellies and the soleus have slightly different paths of motion, but because they are very similar and the joint is fairly simple, you are going to achieve some degree of stimulus in all of the during any plantarflexion exercise. So as long as you are training close to failure, you may get sufficient stimulus in all of them. That doesn’t mean it can’t be more isolated or optimal by being more specific with your path and range, but in this case there is a higher tolerance to inaccuracy while still achieving a training stimulus.
Now if we take a more complex joint like the shoulder that has a lot of motion, it is very easy to significantly lose stimulus in the target muscle by going outside its specific path or range. For example performing a rowing or pulling movement with too wide of an arm path can drastically shift the force demands from the lats to the upper back and rear delt muscles. The lats may still be doing some work, but no longer enough to produce the stimulus needed for positive adaptations. Looking deeper, the lats have 3 divisions, and each of those has a specific path and range of motion. So if you are trying to bring up a specific portion of that muscle, you will get much better results using the specific path and range for the respective division.
When it comes to physique based goals, there is a tremendous amount of efficacy and efficiency gained by training in isolated muscle ROM. Unfortunately most people do not understand anatomy or biomechanics well enough to assess their ROM and improve their technique. Even more unfortunate is the misinformation out there that leads people to believe that increased range of motion of any kind is better. This leads to people focusing on motions that aren’t in the joints or tissues they are targeting and in some cases aren’t even occurring in the body. They may be focused on implement range of motion (how far a bar/handle etc is moving). You will often see these people going through huge total body motions simply to create motion in the implement and often not even approaching the full trainable ROM of the target tissue. The irony is that these people are often training their target tissues through less ROM, while blindly thinking more ROM = better. You will often find individuals that train in this nature require the use of momentum and/or high reps in many motions to “feel” them properly. If you can not achieve a targeted stimulus in a controlled or high intensity (low rep) condition, it is likely because your path/range of motion is not specific enough and the movement is reaching task failure before you can achieve significant local stimulus. If you are doing motions that are targeted, you can create isolated stimuli at higher intensities, which opens up the programming playbook more and leads to greater results and happier joints.