{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,1]],"date-time":"2026-08-01T16:41:29Z","timestamp":1785602489847,"version":"3.56.0"},"reference-count":51,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2023,9,29]],"date-time":"2023-09-29T00:00:00Z","timestamp":1695945600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University of Rwanda, the Regional Centre of Excellence for Biomedical Engineering and E-Health (UR-CEBE)"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Neuromuscular electrical stimulation plays a pivotal role in rehabilitating muscle function among individuals with neurological impairment. However, there remains uncertainty regarding whether the muscle\u2019s response to electrical excitation is affected by forearm posture, joint angle, or a combination of both factors. This study aimed to investigate the effects of forearm postures and elbow joint angles on the muscle torque and MMG signals. Measurements of the torque around the elbow and MMG of the biceps brachii (BB) muscle were conducted in 36 healthy subjects (age, 22.24 \u00b1 2.94 years; height, 172 \u00b1 0.5 cm; and weight, 67.01 \u00b1 7.22 kg) using an in-house elbow flexion testbed and neuromuscular electrical stimulation (NMES) of the BB muscle. The BB muscle was stimulated while the forearm was positioned in the neutral, pronation, or supination positions. The elbow was flexed at angles of 10\u00b0, 30\u00b0, 60\u00b0, and 90\u00b0. The study analyzed the impact of the forearm posture(s) and elbow joint angle(s) on the root-mean-square value of the torque (TQRMS). Subsequently, various MMG parameters, such as the root-mean-square value (MMGRMS), the mean power frequency (MMGMPF), and the median frequency (MMGMDF), were analyzed along the longitudinal, lateral, and transverse axes of the BB muscle fibers. The test\u2013retest interclass correlation coefficient (ICC21) for the torque and MMG ranged from 0.522 to 0.828. Repeated-measure ANOVAs showed that the forearm posture and elbow flexion angle significantly influenced the TQRMS (p &lt; 0.05). Similarly, the MMGRMS, MMGMPF, and MMGMDF showed significant differences among all the postures and angles (p &lt; 0.05). However, the combined main effect of the forearm posture and elbow joint angle was insignificant along the longitudinal axis (p &gt; 0.05). The study also found that the MMGRMS and TQRMS increased with increases in the joint angle from 10\u00b0 to 60\u00b0 and decreased at greater angles. However, during this investigation, the MMGMPF and MMGMDF exhibited a consistent decrease in response to increases in the joint angle for the lateral and transverse axes of the BB muscle. These findings suggest that the muscle contraction evoked by NMES may be influenced by the interplay between actin and myosin filaments, which are responsible for muscle contraction and are, in turn, influenced by the muscle length. Because restoring the function of limbs is a common goal in rehabilitation services, the use of MMG in the development of methods that may enable the real-time tracking of exact muscle dimensional changes and activation levels is imperative.<\/jats:p>","DOI":"10.3390\/s23198165","type":"journal-article","created":{"date-parts":[[2023,9,29]],"date-time":"2023-09-29T07:42:08Z","timestamp":1695973328000},"page":"8165","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":8,"title":["Effect of Forearm Postures and Elbow Joint Angles on Elbow Flexion Torque and Mechanomyography in Neuromuscular Electrical Stimulation of the Biceps Brachii"],"prefix":"10.3390","volume":"23","author":[{"given":"Raphael","family":"Uwamahoro","sequence":"first","affiliation":[{"name":"Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer, Universiti Teknikal Malaysia Melaka, Durian Tunggal 76100, Melaka, Malaysia"},{"name":"Regional Centre of Excellence in Biomedical Engineering and e-Health, University of Rwanda, Kigali P.O. Box 4285, Rwanda"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kenneth","family":"Sundaraj","sequence":"additional","affiliation":[{"name":"Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer, Universiti Teknikal Malaysia Melaka, Durian Tunggal 76100, Melaka, Malaysia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Farah Shahnaz","family":"Feroz","sequence":"additional","affiliation":[{"name":"Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer, Universiti Teknikal Malaysia Melaka, Durian Tunggal 76100, Melaka, Malaysia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,9,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Akima, H., Maeda, H., Koike, T., and Ishida, K. (2021). Effect of elbow joint angles on electromyographic activity versus force relationships of synergistic muscles of the triceps brachii. PLoS ONE, 16.","DOI":"10.1371\/journal.pone.0252644"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"904","DOI":"10.1109\/TNSRE.2018.2807762","article-title":"Influence of Elbow Flexion and Stimulation Site on Neuromuscular Electrical Stimulation of the Biceps Brachii","volume":"26","author":"Gonzalez","year":"2018","journal-title":"IEEE Trans. Neural Syst. Rehabil. Eng."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"164","DOI":"10.1016\/j.jneumeth.2005.05.013","article-title":"Mechanomyographic response to transcranial magnetic stimulation from biceps brachii and during transcutaneous electrical nerve stimulation on extensor carpi radialis","volume":"149","author":"Reza","year":"2005","journal-title":"J. Neurosci. Methods"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2499","DOI":"10.1109\/JSEN.2013.2255982","article-title":"Mechanomyography sensor development, related signal processing, and applications: A systematic review","volume":"13","author":"Islam","year":"2013","journal-title":"IEEE Sens. J."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"691","DOI":"10.1016\/j.clinbiomech.2014.04.003","article-title":"Mechanomyography and muscle function assessment: A review of current state and prospects","volume":"29","author":"Ibitoye","year":"2014","journal-title":"Clin. Biomech."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1016\/j.medengphy.2016.05.012","article-title":"Torque and mechanomyogram relationships during electrically evoked isometric quadriceps contractions in persons with spinal cord injury","volume":"38","author":"Ibitoye","year":"2016","journal-title":"Med. Eng. Phys."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Kleiber, T., Kunz, L., and Disselhorst-Klug, C. (2015). Muscular coordination of biceps brachii and brachioradialis in elbow flexion with respect to hand position. Front. Physiol., 6.","DOI":"10.3389\/fphys.2015.00215"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"413","DOI":"10.1152\/jn.00620.2018","article-title":"Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures","volume":"122","author":"Forman","year":"2019","journal-title":"J. Neurophysiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"19","DOI":"10.1007\/s004210000321","article-title":"Mechanomyogram and force relationship during voluntary isometric ramp contractions of the biceps brachii muscle","volume":"84","author":"Akataki","year":"2001","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Uwamahoro, R., Sundaraj, K., and Subramaniam, I.D. (2021). Assessment of muscle activity using electrical stimulation and mechanomyography: A systematic review. Biomed. Eng. Online, 20.","DOI":"10.1186\/s12938-020-00840-w"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1521","DOI":"10.1007\/s00421-022-04949-9","article-title":"Knee extensor force production and discomfort during neuromuscular electrical stimulation of quadriceps with and without gluteal muscle co-stimulation","volume":"122","author":"Flodin","year":"2022","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Uwamahoro, R., Sundaraj, K., and Subramaniam, I.D. (2019, January 19\u201322). Analysis of upper limb rehabilitation using muscle mechanics: Current and future perspectives using Mechanomyography signals. Proceedings of the 12th Biomedical Engineering International Conference, Ubon Ratchathani, Thailand.","DOI":"10.1109\/BMEiCON47515.2019.8990250"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1347","DOI":"10.1080\/02640410903165093","article-title":"Acute passive stretching in a previously fatigued muscle: Electrical and mechanical response during tetanic stimulation","volume":"27","author":"Esposito","year":"2009","journal-title":"J. Sports Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"342","DOI":"10.1109\/86.867876","article-title":"The relationship between electrical stimulus and joint torque: A dynamic model","volume":"8","author":"Ferrarin","year":"2000","journal-title":"IEEE Trans. Rehabil. Eng."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1002\/mus.20328","article-title":"Influence of knee joint angle on muscle properties of paralyzed and nonparalyzed human knee extensors","volume":"32","author":"Gerrits","year":"2005","journal-title":"Muscle Nerve"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"451","DOI":"10.1016\/S1050-6411(03)00058-0","article-title":"Mechanomyographic and electromyographic responses of the triceps surae during maximal voluntary contractions","volume":"13","author":"Miyamoto","year":"2003","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Islam, M.A., Sundaraj, K., Ahmad, R.B., and Ahamed, N.U. (2013). Mechanomyogram for Muscle Function Assessment: A Review. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0058902"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1191","DOI":"10.1109\/TBME.2007.909538","article-title":"Continuous monitoring of sonomyography, electromyography and torque generated by normal upper arm muscles during isometric contraction: Sonomyography assessment for arm muscles","volume":"55","author":"Shi","year":"2008","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.jelekin.2005.12.002","article-title":"Does the frequency content of the surface mechanomyographic signal reflect motor unit firing rates? A brief review","volume":"17","author":"Beck","year":"2007","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Gobbo, M., Maffiuletti, N.A., Orizio, C., and Minetto, M.A. (2014). Muscle motor point identification is essential for optimizing neuromuscular electrical stimulation use. J. Neuroeng. Rehabil., 11.","DOI":"10.1186\/1743-0003-11-17"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/j.jneumeth.2006.05.018","article-title":"Spatial and force dependency of mechanomyographic signal features","volume":"158","author":"Madeleine","year":"2006","journal-title":"J. Neurosci. Methods"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Lei, K.F., Cheng, S.C., Lee, M.Y., and Lin, W.Y. (2013). Measurement and estimation of muscle contraction strength using mechanomyography based on artificial neural network algorithm. Biomed. Eng. Singap., 25.","DOI":"10.4015\/S1016237213500208"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1007\/s00421-005-1359-7","article-title":"Effect of joint angle on mechanomyographic amplitude during unfused and fused tetani in the human biceps brachii muscle","volume":"95","author":"Miyamoto","year":"2005","journal-title":"Eur. J. Appl. Physiol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"419","DOI":"10.1152\/japplphysiol.00385.2020","article-title":"Universal spectral profile, and dynamic evolution of muscle activation","volume":"129","author":"Rizzo","year":"2020","journal-title":"J. Appl. Physiol."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Talib, I., Sundaraj, K., and Lam, C.K. (2019). Association of anthropometric parameters with amplitude and crosstalk of mechanomyographic signals during forearm flexion, pronation, and supination torque tasks. Sci. Rep., 9.","DOI":"10.1038\/s41598-019-52536-4"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1016\/j.bbe.2015.02.002","article-title":"Verification of the functionality of device for monitoring human tremor","volume":"35","author":"Szumilas","year":"2015","journal-title":"Biocybern. Biomed. Eng."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"473","DOI":"10.1007\/s12541-016-0059-z","article-title":"Fatigue analysis of the quadriceps femoris muscle based on mechanomyography","volume":"17","author":"Shin","year":"2016","journal-title":"Int. J. Precis. Eng. Manuf."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1016\/j.jelekin.2019.02.002","article-title":"Test-retest reliability of elbow flexor contraction characteristics with tensiomyography for different elbow joint angles","volume":"45","author":"Latella","year":"2019","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Ortega, D.G., Housh, T.J., Smith, R.W., Arnett, J.E., Neltner, T.J., Anders, J.P.V., Schmidt, R.J., and Johnson, G.O. (2023). Fatiguing Joint Angle Does Not Influence Torque and Neuromuscular Responses Following Sustained, Isometric Forearm Flexion Tasks Anchored to Perceptual Intensity in Men. J. Funct. Morphol. Kinesiol., 8.","DOI":"10.3390\/jfmk8030114"},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Paillard, T. (2018). Training based on electrical stimulation superimposed onto voluntary contraction would be relevant only as part of submaximal contractions in healthy subjects. Front. Physiol., 9.","DOI":"10.3389\/fphys.2018.01428"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"760","DOI":"10.1016\/j.jelekin.2007.03.006","article-title":"Effect of elbow joint angle on force\u2013EMG relationships in human elbow flexor and extensor muscles","volume":"18","author":"Doheny","year":"2008","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Nunes, J.P., Jacinto, J.L., Ribeiro, A.S., Mayhew, J.L., Nakamura, M., Capel, D.M., Santos, L.R., Santos, L., Cyrino, E.S., and Aguiar, A.F. (2020). Placing greater torque at shorter or longer muscle lengths? Effects of cable vs. barbell preacher curl training on muscular strength and hypertrophy in young adults. Int. J. Environ. Res. Public Health, 17.","DOI":"10.3390\/ijerph17165859"},{"key":"ref_33","first-page":"125","article-title":"The effect of elbow angle on the isometric strength and endurance of the elbow flexors in men and women","volume":"9","author":"Petrofsky","year":"1980","journal-title":"J. Hum. Ergol."},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Hou, J., Sun, Y., Sun, L., Pan, B., Huang, Z., Wu, J., and Zhang, Z. (2016). A pilot study of individual muscle force prediction during elbow flexion and extension in the neurorehabilitation field. Sensors, 16.","DOI":"10.3390\/s16122018"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1500","DOI":"10.1152\/jappl.1988.64.4.1500","article-title":"Myoelectrical and mechanical changes linked to length specificity during isometric training","volume":"64","author":"Maton","year":"1988","journal-title":"J. Appl. Physiol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"384","DOI":"10.1590\/1517-3151.0541","article-title":"Advances and perspectives of mechanomyography","volume":"30","author":"Krueger","year":"2014","journal-title":"Rev. Bras. Eng. Biomed."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1111\/j.1600-0838.2005.00450.x","article-title":"Effects of isometric training at different knee angles on the muscle\u2013tendon complex in vivo","volume":"16","author":"Kubo","year":"2006","journal-title":"Scand. J. Med. Sci. Sports"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"144","DOI":"10.1016\/j.jelekin.2005.06.010","article-title":"Innervation zone shift with changes in joint angle in the brachial biceps","volume":"16","author":"Martin","year":"2006","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"767","DOI":"10.1016\/j.clinbiomech.2014.06.003","article-title":"Effects of involuntary eccentric contraction training by neuromuscular electrical stimulation on the enhancement of muscle strength","volume":"29","author":"Son","year":"2014","journal-title":"Clin. Biomech."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1016\/j.jelekin.2018.10.003","article-title":"Static hand posture classification based on the biceps brachii muscle synergy features","volume":"43","author":"He","year":"2018","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_41","unstructured":"Talib, I., Sundaraj, K., Lam, C.K., and Sundaraj, K. (2018). A systematic review of muscle activity assessment of the biceps brachii muscle using mechanomyography. J. Musculoskelet. Neuronal Interact., 18."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2046","DOI":"10.1016\/j.clinph.2014.02.007","article-title":"Corticomotor excitability of arm muscles modulates according to static position and orientation of the upper limb","volume":"125","author":"Mogk","year":"2014","journal-title":"Clin. Neurophysiol."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"769","DOI":"10.1016\/S0006-3495(87)83403-3","article-title":"Acoustic signals from frog skeletal muscle","volume":"51","author":"Barry","year":"1987","journal-title":"Biophys. J."},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Beck, T.W., Housh, T.J., Cramer, J.T., Weir, J.P., Johnson, G.O., Coburn, J.W., Malek, M.H., and Mielke, M. (2005). Mechanomyographic amplitude and frequency responses during dynamic muscle actions: A comprehensive review. Biomed. Eng. Online, 4.","DOI":"10.1186\/1475-925X-4-67"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"3126","DOI":"10.1152\/jn.00537.2005","article-title":"Change in muscle fascicle length influences the recruitment and discharge rate of motor units during isometric contractions","volume":"94","author":"Pasquet","year":"2005","journal-title":"J. Neurophysiol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"775","DOI":"10.1016\/S0006-3495(87)83404-5","article-title":"The Mechanism of Low-Frequency Sound Production in Muscle","volume":"51","author":"Frangioni","year":"1987","journal-title":"Biophys. J."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1056","DOI":"10.1016\/j.jelekin.2011.08.011","article-title":"Spectral properties of electromyographic and mechanomyographic signals during dynamic concentric and eccentric contractions of the human biceps brachii muscle","volume":"21","author":"Qi","year":"2011","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1016\/S1050-6411(96)00023-5","article-title":"The Effect of Muscle Length on Electrically Elicited Muscle Vibrations in the In-Situ Cat Soleus Muscle","volume":"7","author":"Vaz","year":"1997","journal-title":"J. Electromyogr. Kinesiol."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1002\/mus.21981","article-title":"Effect of knee position on quadriceps muscle force steadiness and activation strategies","volume":"43","author":"Krishnan","year":"2011","journal-title":"Muscle Nerve"},{"key":"ref_50","first-page":"98","article-title":"Acquiring Expertise in Precision Sport\u2014What Can We Learn from an Elite Snooker Player?","volume":"5","author":"Kong","year":"2021","journal-title":"Muscle Nerve"},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Kim, J., Yang, S., Koo, B., Lee, S., Park, S., Kim, S., Cho, K.H., and Kim, Y. (2022). sEMG-Based Hand Posture Recognition and Visual Feedback Training for the Forearm Amputee. Sensors, 22.","DOI":"10.3390\/s22207984"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/19\/8165\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T21:01:42Z","timestamp":1760130102000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/19\/8165"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,9,29]]},"references-count":51,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2023,10]]}},"alternative-id":["s23198165"],"URL":"https:\/\/doi.org\/10.3390\/s23198165","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,9,29]]}}}