Motor Points: An Excerpt From Matt Callison’s Upcoming Book
You can access Callison’s expertise and published content in Unified Practice’s reference library. Callison is also an avid Unified Practice user and recently shared his insight on the best way to use the software for diagnostic strategies and charting techniques.
Now we’re thrilled to share this guest blog post, which is an excerpt from the soon to be released textbook by Callison: Sports Medicine Acupuncture: An Integrated Approach Combining Sports Medicine and Traditional Chinese Medicine. The pre-sale book date will be July 15th and the release date will be in mid-October.
Motor Points: An Excerpt
The quest to find the optimal location on which to use electricity in the muscle tissue for diagnosis and treatment has been ongoing for well over a century. Between 1850-1930, Duchenne de Boulogne, Jean-Martin Charcot and Joseph Babinski were some of the first pioneers in neurological medicine to use electricity on muscles to better understand and treat motor coordination and neuromuscular disease processes. (1) As technology has advanced over the years, Western biomedical research on muscle motor points has also evolved since the 1930’s and has rapidly increased in the past 25 years.
The electrophysiological definition of a muscle motor point is still not universally agreed upon and finding precise motor point locations has proven to be an ongoing challenge. (2) In fact, between researchers, the number of motor points per muscle varied between subjects, where some individuals have predictable muscle motor point locations, while other subjects did not have the same motor point location at all. (3-5)
This confusion is due in part to the various definitions of a motor point. The motor point has been described as the zone of innervation, which in turn can be defined as either where the motor nerve first pierces the muscle belly, also known as the motor nerve entry point (MEP), or where the terminal end of the motor nerve is located at the motor-end plate (also known as the intramuscular motor point). (6-8) When examining muscle motor points in cadaver dissection, there is usually one primary MEP in each muscle. If there are htwo or more, a frequent occurrence in the tibialis anterior muscle (see video), one MEP is usually more reactive to surface electrode stimulation than the other due to the higher quantity of motor and sensory nerve fibers. Once the motor nerve has entered the muscle, in most cases it will bifurcate with one branch that travels in a proximal direction and the other nerve branch that goes in a distal direction. These proximal and distal branches of the motor nerve traverse across the intramuscular spaces until the nerve eventually meets its terminal end at the motor end-plates, which is the location that some refer to as the intramuscular motor point. (9-10)
The motor nerve at the MEP is usually larger in diameter and carries a greater quantity of motor and sensory fibers than after the nerve bifurcates in the intramuscular tissue. Although proximal and distal intramuscular motor points can be nearby or a fair distance away from the MEP, research indicates that the MEP, located between the intramuscular motor points, is where the motor nerve endings are most densely populated. The farther the motor nerve travels through the intramuscular tissue, the thinner the nerve becomes.
Based on the author’s examinations of nerve topography and motor point locations from over 20 years of cadaver dissections, there are marked variations in locations from specimen to specimen of where the motor nerve branches off the primary nerve to eventually enter the muscle at the MEP. For example, the author has seen variability in the location where the motor nerve branches off the ulnar nerve to innervate the flexor carpi ulnaris, which has a motor point location of 3-4 cun distal from SI 8 (xiaohai). In certain specimens, a very short collateral branch splits from the nearby ulnar nerve very close to the motor point location and travels at a 70˚-80˚ angle to go directly into the muscle motor point. In other specimens, the motor nerve branch can split from the ulnar nerve 1-1.5 inches proximal to the motor point location and travel alongside the ulnar nerve until it enters the MEP. In other words, there may be differences in where the motor nerve branches off the primary nerve but the MEP is generally at the same location from specimen to specimen. In addition, the size of the motor nerve that enters the muscle tissue does not seem to be based on the size or sex of the individual. For example, a collateral branch of the median nerve that enters the pronator teres muscle in a 5-foot tall woman can be twice the size as the same nerve of a 6-foot tall man.
Finding motor point locations of large diameter motor nerve entry points, those that have the greatest clinical impact when needled, has been a long process. The passion and desire to continue this research has not waned for the author because matching anatomical findings with TCM acupuncture theory and its applications continue to fascinate him.
- Clarac, F., Massion, J., & Smith, A. M. (2009). Duchenne, Charcot and Babinski, three neurologists of La Salpetrière Hospital, and their contribution to concepts of the central organization of motor synergy. Journal of Physiology-Paris, 103(6), 361-376.
- An, X. C., Lee, J. H., Im, S., Lee, M. S., Hwang, K., Kim, H. W., Han, S. H. (2010). Anatomic localization of motor entry points and intramuscular nerve endings in the hamstring muscles. Surgical and radiologic anatomy, 32(6), 529-537.
- Behringer, M., Franz, A., McCourt, M., Mester, J. (2014). Motor point map of upper body muscles. European journal of applied physiology, 114(8), 1605-1617.
- Moon, J. Y., Hwang, T. S., Sim, S. J., Chun, S. I., & Kim, M. (2012). Surface mapping of motor points in biceps brachii muscle. Annals of rehabilitation medicine, 36(2), 187.
- Wang, Z. J., Xing, Y. L., Gao, X., Hu, X. Y., Zhang, L., Li, J., Robinson, N. (2015). Motor entry point acupuncture compared with the standard acupuncture for treatment of shoulder abduction dysfunction after stroke: A randomized clinical trial. European Journal of Integrative Medicine, (7), 26.
- Lee, J. H., Kim, H. W., Im, S., An, X., Lee, M. S., Lee, U. Y., & Han, S. H. (2010). Localization of motor entry points and terminal intramuscular nerve endings of the musculocutaneous nerve to biceps and brachialis muscles. Surgical and radiologic anatomy, 32(3), 213-220.
- Hwang, K., Jin, S., Hwang, S. H., Lee, K. M., & Han, S. H. (2007). Location of nerve entry points of flexor digitorum profundus. Surgical and Radiologic Anatomy, 29(8), 617-621.
- Lee, J. H. (2010). Surgical and radiologic anatomy, 32(3), 213-220.
- An, X. C., (2010) Surg Radiol Anat 32:529–537
- Botter, A., Oprandi, G., Lanfranco, F., Allasia, S., Maffiuletti, N. A., Minetto, M. A. (2011). Atlas of the muscle motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning. European journal of applied physiology, 111(10), 2461.