Coordination of Locomotion with Voluntary Movements in Humans

Abstract

Muscle activity occurring during human locomotion can be accounted for by five basic temporal activation patterns in a variety of locomotion conditions. Here, we examined how these activation patterns interact with muscle activity required for a voluntary movement. Subjects produced a voluntary movement during locomotion, and we examined the resulting kinematics, kinetics, and EMG activity in 16 -31 ipsilateral limb and trunk muscles during the tasks. There were four voluntary tasks added to overground walking (ϳ5 km/h) in which subjects kicked a ball, stepped over an obstacle, or reached down and grasped an object on the floor (weight support on either the right or the left foot). Statistical analyses of EMG waveforms showed that the five basic locomotion patterns were invariantly present in each task, although they could be differently weighted across muscles, suggesting a characteristic locomotion timing of muscle activations. We also observed a separate activation that was timed to the voluntary task. The coordination of locomotion with the voluntary task was accomplished by combining activation timings that were associated separately with the voluntary task and locomotion. Activation associated with the voluntary tasks was either synchronous with the timing for locomotion or had additional activations not represented in the basic locomotion timing. We propose that this superposition of an invariant locomotion timing pattern with a voluntary activation timing may be consistent with the proposal suggesting that compound movements are produced through a superposition of motor programs.

Analysis of muscle synergies and activation–deactivation patterns in subjects with anterior cruciate ligament deficiency during walking

“…It is believed that the number of synergies used by a human being when walking is between 4 and 6 (Allen and Neptune, 2012;Clark et al, 2010;De Groote et al, 2014;Ivanenko et al, 2005Ivanenko et al, , 2004Oliveira et al, 2014). The Variance Accounted For (VAF) between the reconstructed and the original signals is evaluated to select the proper number of modules to be used when factorizing the signals.…”

“…It is reported that there are similarities in the muscle synergies when performing the same movement across subjects. Several authors reported muscle synergies when walking (Clark et al, 2010;Dominici et al, 2011;Ivanenko et al, 2004;Neptune et al, 2009;Oliveira et al, 2014), walking with perturbations (Ivanenko et al, 2005) or performing other tasks (Rugy et al, 2013). Clark et al (2010) applied the muscle synergy analysis in post-stroke injured subjects.…”

Multi-muscle synergies in an unusual postural task: quick shear force production

“…The notion of multi-muscle synergies has been invoked in many studies of postural tasks (Krishnamoorthy et al 2003a(Krishnamoorthy et al ,b, 2004Ivanenko et al 2005Ivanenko et al , 2006 ; Ting and Macpherson 2005;Wang et al 2005Wang et al , 2006Torres-Oviedo et al 2006;Danna-Dos-Santos et al 2007) as a means of reducing (but not eliminating) the notorious redundancy of the multi-muscle system (cf. Bernstein 1967).…”

“…At the lower level, muscles form groups, within which their levels of activation co-vary across a wide range of tasks. Such groups have been referred to as muscle modes (M-modes, Krishnamoorthy et al 2003a,b) or muscle synergies (Ivanenko et al 2004(Ivanenko et al , 2005(Ivanenko et al , 2006Ting and Macpherson 2005;Torres-Oviedo and Ting 2007;Saltiel et al 2001;D'Avela et al 2005). At the upper level, the M-modes are considered as the elemental variables, and their co-variation is organized in a task-specific manner to stabilize an important performance variable.…”

Learning effects on muscle modes and multi-mode postural synergies

“…The coordination of the many muscles involved in standing has been viewed as an example of muscle synergies, large groups of muscles united by a common motor goal (Bernstein 1967;Ivanenko et al 2004Ivanenko et al , 2005Ting and Macpherson 2005).…”