A 1:1 locomotion–respiration entrainment is observed in galloping quadrupeds, and is thought to improve running economy. However, this has not been tested directly in animals, as animals cannot voluntarily disrupt this entrainment. The purpose of this study was to evaluate metabolic economy in a human gait involving all four limbs, cross-country skiing, in natural entrainment and forced nonentrainment. Nine elite cross-country skiers roller skied at constant speed using the 2-skate technique. In the first and last conditions, athletes used the natural entrained breathing pattern: inhaling with arm recovery and exhaling with arm propulsion, and in the second condition, the athletes disentrained their breathing pattern. The rate of oxygen uptake (VO2) and metabolic rate (MR) were measured via expired gas analysis. Propulsive forces were measured with instrumented skis and poles. VO2 and MR increased by 4% and 5% respectively when skiers used the disentrained compared with the entrained breathing pattern. There were no differences in ski or pole forces or in timing of the gait cycle between conditions. We conclude that breathing entrainment reduces metabolic cost of cross-country skiing by approximately 4%. Further, this reduction is likely a result of the entrainment rather than alterations in gait mechanics.
Kevin Boldt, Anthony Killick and Walter Herzog
Dylan C. Perry, Christopher C. Moore, Colleen J. Sands, Elroy J. Aguiar, Zachary R. Gould, Catrine Tudor-Locke and Scott W. Ducharme
approach for communicating ambulatory PA intensity guidelines and improving health. 4 One method for prescribing cadence recommendations involves instructing individuals to synchronize or entrain their foot strikes to rhythmic auditory cues (RAC). 6 , 7 The RAC take advantage of existing intimate neural
Betteco J. de Boer, C. (Lieke) E. Peper, Arne Ridderikhoff and Peter J. Beek
In the current study, we examined whether coupling influences resulting from unintended afference-based phase entrainment are affected by movement amplitude as such or by the amplitude relation between the limbs. We assessed entrainment strength by studying how passive movements of the contralateral hand influenced unimanual coordination with a metronome. Results showed that amplitude as such did not affect entrainment strength, whereas the amplitude relation between the hands did. Larger amplitudes of the passive hand relative to the active hand resulted in stronger entrainment. This dependence on relative amplitude implies that entrainment strength is not only based on the intensity of afferent signals generated in the entraining limb but also on the susceptibility of the entrained limb to these signals.
Anat V. Lubetzky, Daphna Harel, Helene Darmanin and Ken Perlin
information may lead to loss of balance (LOB) with changes in the environment (e.g., darkness and rapidly moving vehicles). The sensory weighting theory has been supported in multiple studies utilizing an entrainment (i.e., moving along with a stimulus) paradigm. Specifically, Jeka’s group has demonstrated
Jeff A. Nessler, Gerald Kephart, Jason Cowell and Charles J. De Leone
Studying spontaneous synchronization of stepping as two individuals walk on side-by-side treadmills may be useful for understanding the control of bipedal locomotion and may have implications for gait rehabilitation. Existing data suggest that this behavior is related to differences in leg length, walkway slope, and overground speed between partners, and might be promoted by altering these variables. This idea was evaluated here as 24 pairs of subjects stepped on side-by-side treadmills under several conditions of relative speed and slope. Overall, pairings that demonstrated very little spontaneous synchronization with the same treadmill speed and slope exhibited significant increases in this behavior when one treadmill was manipulated. Conversely, pairings that demonstrated a tendency to synchronize under normal conditions exhibited significant decreases in this behavior when either treadmill was altered.
Emma L. Sweeney, Daniel J. Peart, Irene Kyza, Thomas Harkes, Jason G. Ellis and Ian H. Walshe
SRE). All experimental conditions were separated by at least 1 week to prevent carryover effects ( van Leeuwen et al., 2010 ), but no more than 3 weeks. Throughout the study, participants slept at home. Experimental trials were preceded by a 1-week entraining period, in which participants were asked
Nancy Getchell, Susan McMenamin and Jill Whitall
This study examines gross motor coordination in children with and without learning disabilities using a dynamical systems perspective. In a dual motor task paradigm (walk/clap, gallop/clap), we measured and compared frequency and phase locking and consistency within and across trials in 12 children with learning disabilities and 12 age-matched typically developing children. In the walk/clap condition, groups differed in consistency and in entrainment (increased frequency of 4 limb coupling) over short-term practice. In the gallop/clap condition, groups differed in consistency; neither group showed entrainment. Comparisons within the LD group of participants with and without diagnosed visual-motor problems showed differences in classification, consistency, and entrainment. These results suggest that gross motor coordination tasks provide information about as well as a novel opportunity for early identification of learning disabilities.
Simon Wang and Stuart M. McGill
Spine stability is ensured through isometric coactivation of the torso muscles; however, these same muscles are used cyclically to assist ventilation. Our objective was to investigate this apparent paradoxical role (isometric contraction for stability or rhythmic contraction for ventilation) of some selected torso muscles that are involved in both ventilation and support of the spine. Eight, asymptomatic, male subjects provided data on low back moments, motion, muscle activation, and hand force. These data were input to an anatomically detailed, biologically driven model from which spine load and a lumbar spine stability index was obtained. Results revealed that subjects entrained their torso stabilization muscles to breathe during demanding ventilation tasks. Increases in lung volume and back extensor muscle activation coincided with increases in spine stability, whereas declines in spine stability were observed during periods of low lung inflation volume and simultaneously low levels of torso muscle activation. As a case study, aberrant ventilation motor patterns (poor muscle entrainment), seen in one subject, compromised spine stability. Those interested in rehabilitation of patients with lung compromise and concomitant back troubles would be assisted with knowledge of the mechanical links between ventilation during tasks that impose spine loading.
Kimberly B. Harbst, Jo-Anne C. Lazarus and Jill Whitall
The purpose of this study was to investigate how children and adults control bimanual activities with the influence of kinematic variables minimized. Force and timing measures were analyzed in self-paced, isometric bimanual pinch tasks performed by 6-, 8-, 10-, 12-year-old, and adult subjects. Subjects (n = 84) performed four tasks (inphase symmetrical, antiphase reciprocal, inphase asymmetrical force-right high, inphase asymmetrical force-left high) cycling between low levels (10-30%) of maximal volitional force during three 15-s trials. Bimanual tasks requiring similar activation between the hands were performed more accurately, more quickly, and with less force and timing variability than tasks requiring different actions and/or levels of force to be produced simultaneously. Evidence of force entrainment between the hands was exhibited when force direction (increasing vs. decreasing) was similar between hands but greater relative force was required of the left hand. Lower accuracy and greater variability resulted when controlled decrement of force was required to reach the lower force targets as opposed to the upper force targets which required subjects to increase force. Subjects in the two youngest age groups exhibited lower force accuracy and greater force and timing variability relative to older children and adults. Twelve-year-old subjects approximated adults' performance in all variables.
Arthur D. Kuo
A simple pendulum model is used to study how feedforward and feedback can be combined to control rhythmic limb movements. I show that a purely feedforward central pattern generator (CPG) is highly sensitive to unexpected disturbances. Pure feedback control analogous to reflex pathways can compensate for disturbances but is sensitive to imperfect sensors. I demonstrate that for systems subject to both unexpected disturbances and sensor noise, a combination of feedforward and feedback can improve performance. This combination is achieved by using a state estimation interpretation, in which a neural oscillator acts as an internal model of limb motion that predicts the state of the limb, and by using alpha-gamma coactivation or its equivalent to generate a sensory error signal that is fed back to entrain the neural oscillator. Such a hybrid feedforward/feedback system can optimally compensate for both disturbances and sensor noise, yet it can also produce fictive locomotion when sensory output is removed, as is observed biologically. CPG behavior arises due to the interaction of the internal model and a feedback control that uses the predicted state. I propose an interpretation of the neural oscillator as a filter for processing sensory information rather than as a generator of commands.