title: Neuromuscular performance of maximal voluntary explosive concentric contractions is influenced by angular acceleration.
abstract: Torque production during maximal voluntary explosive contractions is considered to be a functionally more relevant neuromuscular measure than steady-state torque, but little is known about accelerated concentric contractions. This study investigated torque, muscle activity, and fascicle behavior during isometric and fast concentric contractions of quadriceps femoris. Ten participants performed maximal voluntary explosive isometric, isovelocity, and additional concentric knee extensions at angular accelerations ranging from 700 to 4000° s-2that resulted in an angular velocity of 300° s-1at 40° knee flexion. Concentric torque at 40° knee flexion was corrected for inertia, and the corresponding isometric torque was matched to the time when the target knee angle of 40° was reached during concentric contractions. Electromyography of quadriceps femoris and hamstrings and ultrasound of vastus lateralis were measured to determine muscle activity, fascicle length, and fascicle velocity (FV). The faster the acceleration, the more torque was produced during concentric contractions at 40° knee flexion, which was accompanied by a reduction in FV. In comparison with isometric conditions, concentric quadriceps muscle activity was increased and torque during accelerations ≥3000° s-2equaled the time-matched isometric torque. Our results provide novel evidence that acceleration influences torque production during maximal voluntary explosive concentric contractions. This is suggested to be due to series elasticity and reduced force depression.
authors.affiliation: Human Movement Science, Faculty of Sport Science, Ruhr-University Bochum, Bochum, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Hahn
authors.affiliation: Human Movement Science, Faculty of Sport Science, Ruhr-University Bochum, Bochum, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Bakenecker
authors.affiliation: Human Movement Science, Faculty of Sport Science, Ruhr-University Bochum, Bochum, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Zinke
mesh_terms: D000054:Acceleration; D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D052097:Quadriceps Muscle / Q000502:physiology*; D019415:Torque
keywords: angular acceleration; concentric contraction; explosive torque production; fascicle velocity; neural activation; rate of force development; residual force depression; series elasticity