Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands

Abstract

Blake OM, Wakeling JM. Muscle coordination limits efficiency and power output of human limb movement under a wide range of mechanical demands. J Neurophysiol 114: 3283-3295, 2015. First published October 7, 2015 doi:10.1152/jn.00765.2015.-This study investigated the influence of cycle frequency and workload on muscle coordination and the ensuing relationship with mechanical efficiency and power output of human limb movement. Eleven trained cyclists completed an array of cycle frequency (cadence)-power output conditions while excitation from 10 leg muscles and power output were recorded. Mechanical efficiency was maximized at increasing cadences for increasing power outputs and corresponded to muscle coordination and muscle fiber type recruitment that minimized both the total muscle excitation across all muscles and the ineffective pedal forces. Also, maximum efficiency was characterized by muscle coordination at the top and bottom of the pedal cycle and progressive excitation through the uniarticulate knee, hip, and ankle muscles. Inefficiencies were characterized by excessive excitation of biarticulate muscles and larger duty cycles. Power output and efficiency were limited by the duration of muscle excitation beyond a critical cadence (120 -140 rpm), with larger duty cycles and disproportionate increases in muscle excitation suggesting deteriorating muscle coordination and limitations of the activation-deactivation capabilities. Most muscles displayed systematic phase shifts of the muscle excitation relative to the pedal cycle that were dependent on cadence and, to a lesser extent, power output. Phase shifts were different for each muscle, thereby altering their mechanical contribution to the pedaling action. This study shows that muscle coordination is a key determinant of mechanical efficiency and power output of limb movement across a wide range of mechanical demands and that the excitation and coordination of the muscles is limited at very high cycle frequencies. electromyography; excitation; power output; cadence; cycling; motor control HUMAN LIMB MOVEMENT IS ACHIEVED through interactions between the neuromuscular and skeletal systems. Movement performance is commonly measured by the resultant mechanical efficiency (ratio of mechanical power output to metabolic power) and power output, both of which are significantly influenced by the coordinated excitation of individual muscles and the coordination of that excitation between muscles Dorel et al. 2012;Samozino et al. 2007;Wakeling et al. 2010). Therefore, investigating movement performance requires a comprehensive understanding of how the individual muscle excitations and the coordination between muscles (muscle coordination) change in response to the demands.Mechanical demands such as workload and movement velocity can be uncoupled during cycling (Wakeling et al. 2006;Wakeling and Horn 2009), making it an appropriate model to investigate the effects of mechanical demands on individual muscle excitation and muscle coordination and the resultant performan...

The effect of action observation and motor imagery combinations on upper limb kinematics and EMG during dart‐throwing

“…48 Furthermore, the increased efficiency of movement by the combined groups suggests reduced muscle excitation, coordination of muscular fibers, and a reduction in the mechanical demand that occurs during the execution of a refined motor program. 49 In the current study, there was a significant reduction in EMG activity in the bicep producing a concentric muscular contraction from flexion to point of release and triceps brachii muscles producing also concentric muscular contraction from flexion to extension within both AOMI groups, corroborating with research showing a reduction in EMG activity with skill development and execution. 22,50 Taken as a whole, we believe that reduced muscular activity may be explained by two, well-established theoretical notions: psychoneuromuscular theory 51 and the central explanation.…”

“…The reductions observed in EMG activity in the agonist muscles producing concentric muscular contractions are indicative of more expert like motor control characterized in maximum efficiency of movement and could be underpinned by the recruitment of fewer motor units recruited . Furthermore, the increased efficiency of movement by the combined groups suggests reduced muscle excitation, coordination of muscular fibers, and a reduction in the mechanical demand that occurs during the execution of a refined motor program . In the current study, there was a significant reduction in EMG activity in the bicep producing a concentric muscular contraction from flexion to point of release and triceps brachii muscles producing also concentric muscular contraction from flexion to extension within both AOMI groups, corroborating with research showing a reduction in EMG activity with skill development and execution .…”

Evaluation of Pedaling Skill Based on Muscle Synergy in Lower Extremities during Pedaling Exercise

“…10,11 From the above we concluded that muscle synergies acquired by CNS through motor learning provide useful knowledge to explain pedaling techniques. Particularly, Blake et al (2015) 12 confirmed that muscle coordination is an important factor in improving exercise efficiency, and we concluded that pedaling techniques and proficiency can be quantified using the concept of muscle synergy.…”

Quantifying Achilles tendon force in vivo from ultrasound images

“…On the left limb, bipolar Ag/AgCl surface EMG electrodes (10mm diameter, 21mm spacing; Norotrode; Myotronics, Kent, USA) were placed over the mid-bellies of the MG, LG, SOL, tibialis anterior (TA), and six other muscles (not reported here). EMG signals were preamplified (gain 1000), band-pass filtered (bandwidth 10–500Hz; Biovision, Wehrheim, Germany), and sampled at 2000Hz as described elsewhere (e.g., Wakeling and Horn, 2009; Blake and Wakeling, 2015). …”