Motor unit firing rates during slow and fast contractions in boys and men

• Published in: European journal of applied physiology 2024-10, Vol.124 (10), p.2965-2979
• Main Authors: Woods, Stacey, McKiel, Andrew, Herda, Trent, Klentrou, Panagiota, Holmes, Michael, Gabriel, David, Falk, Bareket
• Format: Article
• Language: English
• Subjects: Action potential; Action Potentials - physiology; Adult; Biomedical and Life Sciences; Biomedicine; Children & youth; Decomposition; Electromyography; Electromyography - methods; Firing rate; Habituation; Human Physiology; Humans; Isometric; Isometric Contraction - physiology; Male; Motor Neurons - physiology; Muscle contraction; Muscle Contraction - physiology; Muscle function; Muscle, Skeletal - physiology; Occupational Medicine/Industrial Medicine; Original Article; Physiology; Sports Medicine; Torque; Variance analysis; Wrist; Young Adult
• ISSN: 1439-6319; 1439-6327; 1439-6327
• DOI: 10.1007/s00421-024-05500-8

Background Motor unit (MU) activation during maximal contractions is lower in children compared with adults. Among adults, discrete MU activation differs, depending on the rate of contraction. We investigated the effect of contraction rate on discrete MU activation in boys and men. Methods Following a habituation session, 14 boys and 20 men completed two experimental sessions for knee extension and wrist flexion, in random order. Maximal voluntary isometric torque (MVIC) was determined before completing trapezoidal isometric contractions (70%MVIC) at low (10%MVIC/s) and high (35%MVIC/s) contraction rates. Surface electromyography was captured from the vastus lateralis (VL) and flexor carpi radialis (FCR) and decomposed into individual MU action potential (MUAP) trains. Results In both groups and muscles, the initial MU firing rate (MUFR) was greater ( p