Motor point heatmap guide for neuromuscular electrical stimulation of the quadriceps muscle

Purpose: To create an anatomical chart that indicates the probability of finding a motor point (MP) in different areas of the quadriceps muscle. Methods: On 31 healthy adults, the individual anatomy of the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) was determined using ultrasound. Thereafter, a 3 Hz neuromuscular electrical stimulation (NMES) MP-search with a MP-pen was performed. The thigh anatomy was normalized and divided into 112 (8x14) 3x3cm areas, and the probability of finding a MP in the different areas was calculated to create a MP heat-map. Results: The heat-map displayed the two best 3x3cm areas, over VL and VM respectively, each with a probability greater than 50% of finding a MP and a higher probability compared to all other areas (p <.05). RF exhibited two areas with a 29% probability of finding a MP. A higher number of MPs on the quadriceps, mean (+/- SD) 9.4 +/- 1, was in regression analysis found to be significantly associated with two independent factors higher physical activity level and lower body fat (R-2 = 0.42, p=<.0001). Conclusion: Large inter-individual variations in location, and number of MPs were found, but the heat-map displayed areas with higher probability of finding a MP and can be used to facilitate NMES-application.