This article is an excerpt on Muscle Motor Points from the soon to be released textbook Sports Medicine Acupuncture: An Integrated Approach to Combining Sports Medicine with Traditional Chinese Medicine by Matt Callison, L.Ac. Book publication is coming October 25, 2019.
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.1 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.2-4
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).5-7 The motor point has also been defined as the cutaneous point, located on the skin above the MEP. Researchers agree that this cutaneous point has the lowest resistance to electrical conductivity in the entire muscle.8-9 The cutaneous point is popularly used for detecting motor point locations with a surface electrode device, although there is a notable lack of consistency from person to person when using this location technique. The thickness and hydration of the subcutaneous layer significantly impacts the effectiveness of the electrical stimulation and detectability of the cutaneous locations of muscle motor points.10
There is a high likelihood that the MEP can be found in the central aspect of the muscle, which is the location that provides the best advantage for neuro-mechanical efficiency to affect the entire muscle.11 When examining muscle motor points in cadaver dissection, there is usually one primary MEP in each muscle. If there are two or more, a frequent occurrence in the pectoralis major muscle (sternal fibers), 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 travels 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.12-13 The MEP and the intramuscular motor points are both considered to innervate the muscle tissue.
Based on the author’s examinations of nerve topography and motor point locations from over 20 years of cadaver dissections, it is safe to say that there are similar and predictable trajectories for the large nerves that traverse the extremities (sciatic, ulnar, etc.). However, 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 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. These types of disparities may be attributable to anthropometric differences or they may be adaptations to the individual’s health and activity level.
Motor Point Locations & TCM Theory
In many Western-based research articles on motor point locations, the measurements are specified through the use of X and Y coordinates that are based on anatomical landmarks. While this can be an efficient way to locate a point, this type of mapping doesn’t offer any additional insights. TCM practitioners have the advantage of a comprehensive system of inter-connected acupuncture points that are categorized and classified in many different ways, including the traditional names of the acupuncture points themselves. This gives the TCM practitioner not only an easy and practical way to find motor points using cun measurements, but in certain cases, especially when a motor point and acupuncture point share the same location, the acupuncture point names or their classifications can provide additional clinical information that enables a more comprehensive, holistic treatment.
For example, the primary motor point for the external oblique shares the same location as LIV 13 (zhangmen). This motor point has a profound effect on correcting pelvic rotations, but if we look at its TCM categorization, we’ll remember that this point is not only the front-mu point of the Spleen, but also a meeting point of the Liver and Gallbladder channels. Front-mu points are known as “alarm” points, which display ashi tenderness when the corresponding organ is not functioning properly. Knowing crossing points of particular channels is useful to understand because of the point’s influence on those particular channels and organs. So, if the external oblique motor point is tender, the practitioner can understand that not only does the muscle need to be regulated, but there is also a high probability that the patient has some manner of Spleen disharmony that may be related to a Liver/Gallbladder disharmony. There is even the potential that the muscle dysfunction and pelvic rotation is physically affecting the Spleen’s ability to function. This is the type of integrative information that practitioners can gain from remembering some of the basics of TCM theory.
In another example where point nomenclature provides additional information, the peroneus tertius motor point shares the same location as an extra point called naoqing, meaning “Brain’s clearing.” This point is not only useful for musculoskeletal injuries (ankle sprain or foot-over-pronation for example) but by paying attention to the point’s name and its traditional functions, the TCM practitioner understands that it also has a remarkable ability as a distal point to help with lassitude, amnesia and vertigo.
In addition to the decades of the author’s testing, refining and clinical use, motor point locations can definitely vary and finding the most consistent 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 continues to fascinate him.
Matt Callison, has been licensed and practicing in California since 1992. Mr. Callison is the president of AcuSport Education and of the Sports Medicine Acupuncture Certification Program founded in 2007.
- 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.
- An, X. C., (2010) Surg Radiol Anat 32:529–537
- 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.
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- Coers C., A.L. Woolf. The Innervation of Muscle. Oxford: Blackwell Scientific Publications, 1959. 3-5.
- Nordander C, Willner J, Hansson GA, Larsson B, Unge J, GranquistL, Skerfving S (2003) Influence of the subcutaneous fat layer, as measured by ultrasound, skinfold calipers and BMI, on the EMG amplitude. Eur J Appl Physiol 89:514–519.
- Seidel, P.M.P., Seidel, G.K., and B.M. Gans. “Precise Localization of the Motor Nerve Branches to the Hamstring Muscles: An Aid to the Conduct of Neurolytic Procedures.” Arch Phys Med Rehabil 77 (1996) : 1157-1160.
- Lee, J. H., Surgical and radiologic anatomy, 32(3), 213-220. (2010).
- An, X. C., (2010) Surg Radiol Anat 32:529–537