I may have slept through this lecture in PT school, but early on in my career I often mix balance and proprioception into the same definition or would at least train them the same. Although my first job involved the rehabilitation and training of high level athletes, the implementation of balance and proprioception often overlapped. In hindsight, the reality is that most high level athletes get better with rest and some moderately skilled manual and exercise treatment. Not to say that the treatments weren't skilled, but the vast majority of injuries progressed with very similar treatments.
But with time and experience, it was those intermediate, competitive athletes that would see failures; at least never return play how they considered their pre-morbid level. Often the return to play would involved continued muscle spasm or that low grade ache that, while not preventing them from competing, would yield hesitation or decreased performance. Re-evaluation would demonstrate normal ROM, strength and functional movement screen. It was at this time that I delved back into what I may have been missing and how I could clean this up. And I noticed that I was ignoring that differences between balance and proprioception. Especially in head, neck and shoulder injuries.
Proprioception involves that conscious AND unconscious understanding of a joints position in space, movement, and force sense. It is processed at all levels of the CNS and is integrated with other body systems like the vestibular, visual and somatosenory systems. Mechanoreceptors are specialized nerve endings that process this sensory information and convert this input into action potentials to be sent to CNS for processing. According to Proske and Gandevia, 2012, the most important source of proprioception is considered to come from the muscle spindles found in skeletal muscle. The suboccipital muscles have a high density of muscle spindles, thought to reflect the exceptional coordination role in head and eye movement control. Proprioception is also important after movement has occurred for a comparison of intended movement vs actual achieved movement. This comparison is vital for motor learning to occur by updating the internal forward planning model of motor commands.
Proprioception can be altered or impaired by several factors. Pain, fatigue, joint effusion on the capsule, and trauma to structures all can change our proprioceptive awareness and thereby changing the motor control pattern in which our body systems work together to be most effective. Disturbed feedback, feedforwrad, regulation of muscle stiffness, postural stability in balance, visual acuity, and joint stabilization can all be affected with changes to the body's proprioception.
Despite the substantial importance of proprioception for body function, most clinics have a paucity of tools to accurately assess proprioception.
Several research articles have stated that exercise augments proprioception via activation of muscle spindles. I'm sure this is why so many of my athletes would succeed early on in my career. Exercise would naturally retrain the proprioceptive losses from injury and body awareness would return without specific re-training. But various exercises activate receptors at specific levels of the CNS that can differ between individuals. Thus leaving some patients without the proper training to re-educate their proprioception. If not properly re-educated, the body may continue to interpret certain inputs as a threat and produce abnormal responses.
This is where I enjoy using the Motion Guidance device. Both for clinical assessment of how people like to move as well, interpretation of if that movement (or lack of) is abnormal or necessary, and visual feedback for the patient immediately as they are moving. Many of my patients present in clinic without being able to reproduce their primary symptom that may warrant them to be in my office anyway. What is left is an educated guess on what movement patterns, weakness, overload, environment, etc may be contributing to their pain. The Motion Guidance device allows me to see a piece of what might be contributing to their pain more accurately that with the naked eye. And helps bridge the gap between the novice and expert clinician. It gives clinicians an extra clinical assessment tool for proprioception, preferred movement patterns, and development of motor learning. This is most evident in the use of laser feedback regarding Joint Position Sense. Chen and Treleaven in 2013 researched the use of a laser to determine accurate JPS in whiplash patients and it was found to be reliable and valid (1). Simple observations of errors on a target determined whether the subject had altered cervical proprioception. Balke found similar alterations in changes for proprioception of the unstable shoulder in 2011(2) . Hande et al also found knee JPS loss was correlated with both quadriceps eccentric and concentric strength among patients with PFPS (3) .
Perhaps the most valuable aspect of attempting to define and objectively measure proprioception is ultimately how we see, or don't see the body move. Having the ability to accurately determine a preferred motor pattern or attempt to correct a faulty one comes down to proprioception. If the patient can't feel it, they won't change it. There are biofeedback tools that are available to clinicians to improve the learning curve, such as the Motion Guidance device (insert hyperlink and video), Dynamic Movement Assessment, or clinicians can use garments, tactile cues or mirrors to assist in understanding an individuals propriocepetion. But these tools are only extremely valuable if the information or data collection yields learning by the patient. The old saying of “you can lead a horse to water, but you can't make it drink” really applies to this scenario.
As “movement science specialists”, the sports and healthcare professionals involved in rehabilitation MUST be able to understand and diagnosed movement. But it goes further. It is imperative to convert this information into lay terms that the patient can use to interpret what is necessary to create change in their movement. This change, whether addressing JPS, weakness, FMP, tissue overload, etc, is what needs to be owned, understood and acknowledged by the patient. This is all effecting proprioception! Otherwise, change will not happen. If the patient can't feel it, they won't change it! One of our job as rehabilitation professionals is to help our patients learn.
Eric M. Dinkins PT, MSPT, OCS, Cert. MT, CMP, MCTA