Motor unit firing patterns of lower leg muscles during isometric plantar flexion with flexed knee joint position

• Published in: Journal of electromyography and kinesiology 2022-12, Vol.67, p.102720-102720, Article 102720
• Main Authors: Kunugi, Shun, Holobar, Aleš, Kodera, Tsutomu, Toyoda, Heishiro, Watanabe, Kohei
• Format: Article
• Language: English
• Subjects: Electromyography; EMG; Flexed knee joint; Humans; Isometric contraction; Isometric Contraction - physiology; Knee Joint - physiology; Leg - physiology; Motor unit; Muscle, Skeletal - physiology; Torque; Torque-dependent change
• ISSN: 1050-6411; 1873-5711
• DOI: 10.1016/j.jelekin.2022.102720

The ankle flexor and extensor muscles are essential for pedal movements associated with car driving. Neuromuscular activation of lower leg muscles is influenced by the posture during a given task, such as the flexed knee joint angle during car driving. This study aimed to investigate the influence of flexion of the knee joint on recruitment threshold-dependent motor unit activity in lower leg muscles during isometric contraction. Twenty healthy participants performed plantar flexor and dorsiflexor isometric ramp contractions at 30 % of the maximal voluntary contraction (MVC) with extended (0°) and flexed (130°) knee joint angles. High-density surface electromyograms were recorded from medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) muscles and decomposed to extract individual motor units. The torque-dependent change (Δpps /Δ%MVC) of the motor unit activity of MG (recruited at 15 %MVC) and SOL (recruited at 5 %MVC) muscles was higher with a flexed compared with an extended knee joint (p