The Monday Memo
August 7, 2017 PITT DPT STUDENTS
WHAT IS MOBILITY?
Charles R. Badawy SPT, CSCS, USAW
This term is thrown around constantly, but do we really know what it means? Some see it as a measure of the amount of range-of-motion (ROM) available at a joint, others imply a stability component. This indecision is an issue and the term must be clearly defined if it’s to be used properly.
To start, we need to address a few things. You see, there are principles at play concerning how “Mobility” is typically used. I think it’s important to bring them to attention in order to enhance our understanding of the term.
I think we can clearly understand that the term mobility at a basic level has to do with joint function. I like to believe people are well intentioned and genuinely use this term to help patients. They’re using it as an attribute. As a way to describe joint movement. Are there other well defined terms that would help us?
- Range of Motion: Refers to the distance and direction a joint can move, measured in degrees in the field of physical therapy. There are two types to concern us with, although a third exists
- Passive ROM (PROM)
- Active ROM (AROM)
- Flexibility: Refers to the ability to move a joint or series of joints through a full, non-restricted, injury, and pain-free ROM.
Flexibility helps us further break down PROM. Flexibility applies to any human joint, where PROM can refer to any mechanical system. Flexibility depends on the following factors: Joint ROM, Muscle Extensibility, & Neuromuscular control.
JOINT ROM, MUSCLE EXTENSIBILITY (ME) & NEUROMUSCULAR (NM) CONTROL
- Joint ROM: In essence, PROM describes Joint ROM, the degrees of rotation allowed by the bony articulations, so what do the other two terms mean?
- ME: A measure of the effect of muscles that cross the joint on the ROM available at the bony articulations. Is it highly extensible, giving it the ability to lengthen and allow for great joint movement? Or not? This applies a muscular layer to our current description of PROM or Joint ROM.
Muscle extensibility has a passive effect, which is where the nervous system comes into play.
- NM Control: The nervous system gives us our greatest gift, the ability to move. The nervous system has an affect on the muscular components of a joint, and applies an active component to the bony articulations. It is a measure of our AROM.
The nervous system processes information taken in through various receptors throughout the body and provides instructions to the muscles to contract a certain way. The end goal being: stability. A system can be referred to as being inherently stable when homeostasis, or the ability to maintain neutral position, is adequate to restore previous function. This poses the question, “What is stable?”
“WHAT IS STABLE?”
When it comes strictly to bony articulations, stable is a position where the bony structures are balanced against the effects of gravity. As the bones change positions and the forces applied to them change, our bodies depend on two factors to help us maintain stability, or this position of balance.
- Active Restraints: Structures that produce and apply force to a joint.
- Passive Restraints: Structures that don’t inherently produce force, but limit joint ROM due to their structure. Things like ligaments, bony architecture, etc.
You see, neuromuscular control affects these active restraints. When we run, forces are applied to the system that must be counteracted. The active restraints perform the bulk of the work here and the nervous system must be effective enough to accomplish a given task
The term neuromuscular control has huge implications on our understanding of mobility, in that it demands further information from those who utter it. Are we talking about the active mobility or passive mobility of a joint?
- If we’re discussing the passive mobility of a joint, we’ve truly only discussing the extensibility of the soft tissue and bony architecture. We’re discussing the passive restraints.
- If we’re talking about the active mobility of a joint, we are discussing nervous system function. How effective it is in processing information and modulating muscular force application. We’re discussing neuromuscular control.
SO WHAT’S OUR TAKEAWAY HERE?
Does the term even have a purpose? I’d argue that we already have defined attributes of joint function. If the definitions laid out in this article are to be accepted, the following statements can be made:
- Active mobility and neuromuscular control are synonymous.
- Passive mobility is simply a measure of tissue extensibility and bony architecture.
I’ve thrown around the term “mobility” countless times, but I’m trying to be more judicious in the way I communicate. These reflections show me that there may be more appropriate ways to describe joint function when talking to clients/patients.
At the end of the day, when attempting to create a therapeutic effect or change in performance, it’s important to understand the limiting factor: Should we be focusing on improving neuromuscular control, tissue extensibility, or bony architecture? The answer should greatly influence our method of intervention.