Speed-dependent modulation of phase variations on a step-by-step basis and its impact on the consistency of interlimb coordination during quadrupedal locomotion in intact adult cats

Abstract

Frigon A, D'Angelo G, Thibaudier Y, Hurteau MF, Telonio A, Kuczynski V, Dambreville C. Speed-dependent modulation of phase variations on a step-by-step basis and its impact on the consistency of interlimb coordination during quadrupedal locomotion in intact adult cats. J Neurophysiol 111: 1885-1902, 2014. First published February 12, 2014 doi:10.1152/jn.00524.2013.-It is well established that stance duration changes more than swing duration for a given change in cycle duration. Small variations in cycle duration are also observed at any given speed on a step-by-step basis. To evaluate the step-bystep effect of speed on phase variations, we measured the slopes of the linear regressions between the phases (i.e., stance, swing) and cycle duration during individual episodes at different treadmill speeds in five adult cats. We also determined the pattern of dominance, defined as the phase that varies most with cycle duration. We found a significant effect of speed on hindlimb phase variations, with significant differences observed between the slowest speed of 0.3 m/s compared with faster speeds. Moreover, although patterns of phase dominance were primarily stance/extensor dominated at the slowest speeds, as speed increased the patterns were increasingly categorized as covarying, whereby both stance/extensor and swing/flexor phases changed in approximately equal proportion with cycle duration. Speed significantly affected the relative duration of support periods as well as interlimb phasing between homolateral and diagonal pairs of limbs but not between homologous pairs of limbs. Speed also significantly affected the consistency of interlimb coordination on a step-by-step basis, being less consistent at the slowest speed of 0.3 m/s compared with faster speeds. We found a strong linear relationship between hindlimb phase variations and the consistency of interlimb coordination. Therefore, results show that phase variations on a step-by-step basis are modulated by speed, which appears to influence the consistency of interlimb coordination. locomotion; speed; phase variations; interlimb coordination DURING OVERGROUND OR TREADMILL locomotion, the cycle can be broadly divided into stance and swing phases. Numerous studies have shown that cycle duration is reduced as speed increases, which is accomplished primarily by a reduction in the duration of the stance phase, while the duration of the swing phase is much less affected (reviewed in Frigon 2012;Gossard et al. 2011). This can be demonstrated by plotting the durations of the stance and swing phases as a function of cycle duration and measuring the slopes of the linear regressions (Halbertsma 1983). In most terrestrial walking species, including insects, birds, rodents, reptiles, dogs, cats, macaques, and humans, the slope of the regression between the stance phase and cycle duration (r STA ) is steeper than the slope of the regression between the swing phase and cycle duration (r SW ) (Arshavskii et al.

Modulation of phase durations, phase variations, and temporal coordination of the four limbs during quadrupedal split-belt locomotion in intact adult cats

“…Six adult cats (2 males, 4 females) weighing between 3.5 and 6.0 kg were used. Five of these cats were used in other studies (Frigon et al , 2014Thibaudier et al 2013) to provide answers to other scientific questions. This is part of our effort to maximize the scientific output of each animal.…”

“…This is part of our effort to maximize the scientific output of each animal. Kinematic data from five of the six cats were obtained after surgical implantation of electrodes for electromyography (Frigon et al , 2014. However, the surgical procedures are not described in detail here as the present report does not refer further to electromyography.…”

“…During a normalized cycle, here defined from successive right hindlimb contacts, there are normally eight different time periods that can be determined on the basis of the pattern of limb supports (Frigon et al 2014;Gray 1968;Hildebrand 1989;Wetzel and Stuart 1976). Individual support periods were calculated for each locomotor episode and expressed as a percentage of cycle duration (Frigon et al 2014).…”

“…Individual support periods were calculated for each locomotor episode and expressed as a percentage of cycle duration (Frigon et al 2014). In quadrupeds, coordinated behavior must be realized for six different limb pairings: 1) homologous coupling between the left (LF) and right (RF) forelimbs and 2) between the left (LH) and right (RH) hindlimbs; 3) homolateral coupling between LF and LH and 4) between RF and RH; and 5) diagonal coupling between RH and LF and 6) between LH and RF.…”

“…In quadrupeds, coordinated behavior must be realized for six different limb pairings: 1) homologous coupling between the left (LF) and right (RF) forelimbs and 2) between the left (LH) and right (RH) hindlimbs; 3) homolateral coupling between LF and LH and 4) between RF and RH; and 5) diagonal coupling between RH and LF and 6) between LH and RF. Phase intervals were calculated by measuring the absolute interval of time between contacts of two limbs and expressed as a function of cycle duration (English 1979;English and Lennard 1982;Frigon et al 2014;Orsal et al 1990). Phase intervals were then expressed in degrees to illustrate their continuous nature and possible distributions (English and Lennard 1982).…”