Interlimb Coordination During Locomotion: What Can be Adapted and Stored?

Abstract

. Interlimb coordination is critically important during bipedal locomotion and often must be adapted to account for varying environmental circumstances. Here we studied adaptation of human interlimb coordination using a split-belt treadmill, where the legs can be made to move at different speeds. Human adults, infants, and spinal cats can alter walking patterns on a split-belt treadmill by prolonging stance and shortening swing on the slower limb and vice versa on the faster limb. It is not known whether other locomotor parameters change or if there is a capacity for storage of a new motor pattern after training. We asked whether adults adapt both intra-and interlimb gait parameters during split-belt walking and show aftereffects from training. Healthy subjects were tested walking with belts tied (baseline), then belts split (adaptation), and again tied (postadaptation). Walking parameters that directly relate to the interlimb relationship changed slowly during adaptation and showed robust aftereffects during postadaptation. These changes paralleled subjective impressions of limping versus no limping. In contrast, parameters calculated from an individual leg changed rapidly to accommodate split-belts and showed no aftereffects. These results suggest some independence of neural control of intra-versus interlimb parameters during walking. They also show that the adult nervous system can adapt and store new interlimb patterns after short bouts of training. The differences in intra-versus interlimb control may be related to the varying complexity of the parameters, task demands, and/or the level of neural control necessary for their adaptation. I N T R O D U C T I O NAnimal locomotor patterns must constantly change to accommodate the demands of a complex world. Walking a perfectly straight line over a smooth, level surface is more commonly an exception (e.g., a roadside sobriety test) than the rule. Therefore, functional locomotion demands that limb movements be flexible enough to accommodate different terrain, speeds, and trajectories. Achieving this flexibility without sacrificing stability is no small feat; it requires continuous modulation of coordination within (intralimb) or between (interlimb) the legs. Interlimb coordination, particularly the maintenance of reciprocal, out of phase motions of the limbs, is particularly critical for stable human (bipedal) walking. As such, different interlimb coordination patterns are used for various forms of locomotion (e.g., walk, run) and for walking in curved trajectories Schieppati 2003, 2004).For example, to walk in a curved path, the relative motion of the legs must change: the outer leg takes a longer step with a shorter stance time, and the inner leg does the opposite (Courtine and Schieppati 2003). However, this is accomplished effortlessly and without obvious asymmetries. Surprisingly, relatively little is known about the adaptability or plasticity of interlimb locomotor coordination patterns (Prokop et al. 1995).The use of a split-belt treadmill, where the belt ...

Short-term ankle motor performance with ankle robotics training in chronic hemiparetic stroke

“…However, those studies differ from ours in that they investigated MA and ML in the leg as a whole and used spatio-temporal gait parameters [9], joint angle-based gait symmetry [10], or muscle electromyogram [8,10] as metrics, whereas here we focused on studying STMA and STML at the HP ankle using position and torque information. Moreover, those studies used nondisabled subject volunteers [8][9][10] or subjects with cerebellar damage [11] but not stroke. Also, none of the authors, except Kao and Ferris [8], investigated short-term (e.g., 48 hours) postadaptation aftereffects (retention), thereby limiting their scope in examining ML at the LL.…”

“…Several studies have explored this topic but mostly in the context of gait [8][9][10][11]. However, those studies differ from ours in that they investigated MA and ML in the leg as a whole and used spatio-temporal gait parameters [9], joint angle-based gait symmetry [10], or muscle electromyogram [8,10] as metrics, whereas here we focused on studying STMA and STML at the HP ankle using position and torque information. Moreover, those studies used nondisabled subject volunteers [8][9][10] or subjects with cerebellar damage [11] but not stroke.…”

“…Thus, strategies that assess and can enhance short-term skill acquisition or retention are of great scientific and practical interest to the motor learning (ML) and rehabilitation community. Prior studies have investigated motor adaptation (MA) and ML under different conditions, e.g., walking on a split-belt treadmill, in both nondisabled subjects [8][9][10] and those with cerebellar damage [11]. These studies show that the uninjured or injured brain can adapt and store new locomotor patterns after short bouts of training; however, whether this is true at the HP ankle is not known.…”

Effects of Gait Variations on Grip Force Coordination During Object Transport

“…This alternative hypothesis is supported by studies showing subjects are remarkably adept at predicting the overall timing of locomotion associated with regularly paced steps using motor imagery (Bakker et al 2007;Decety et al 1989;Papaxanthis et al 2002a). Thus the strength of the grip-inertial force coupling may be determined by the regularity of the walking cycle in a manner similar to the coordination of breathing with walking, running, or other cyclical limb movements (i.e., via entrainment) (Bernasconi et al 1995;Ebert et al 2000;Kohl et al 1981;Rassler and Kohl 2000;Seebauer et al 2003), and a shift from a regular pattern to an irregular one could disrupt this relationship (e.g., Nishino and Hiraga 1991;Prokop et al 1995;Reisman et al 2005).…”

Motor learning in childhood reveals distinct mechanisms for memory retention and re-learning

“…To study motor adaptation in children aged 6 -17 yr, we used a split-belt treadmill that has separate belts for each leg, allowing one belt to move faster than the other (Musselman et al 2011;Vasudevan et al 2011). Split-belt walking creates temporal and spatial asymmetries in one's gait (Reisman et al 2005), necessitating adaptation of the gait pattern. More specifically, it creates asymmetries in step length, spatial coordination (measured by the point of oscillation of each leg, called the center of oscillation), and temporal coordination (measured by the phasing between the legs).…”