The quadrupedal walking gait of the olive baboon, Papio anubis: an exploratory study integrating kinematics and EMG.

Primates exhibit unusual quadrupedal features (e.g. diagonal gaits, compliant walk) compared with other quadrupedal mammals. Their origin and diversification in arboreal habitats have certainly shaped the mechanics of their walking pattern to meet the functional requirements necessary for balance control in unstable and discontinuous environments. In turn, the requirements for mechanical stability probably conflict with mechanical energy exchange. In order to investigate these aspects, we conducted an integrative study on quadrupedal walking in the olive baboon (Papio anubis) at the Primatology station of the CNRS in France. Based on kinematics, we describe the centre of mass mechanics of the normal quadrupedal gait performed on the ground, as well as in different gait and substrate contexts. In addition, we studied the muscular activity of six hindlimb muscles using non-invasive surface probes. Our results show that baboons can rely on an inverted pendulum-like exchange of energy (57% on average, with a maximal observed value of 84%) when walking slowly (<0.9 m s-1) with a tight limb phase (∼55%) on the ground using diagonal sequence gaits. In this context, the muscular activity is similar to that of other quadrupedal mammals, thus reflecting the primary functions of the muscles for limb movement and support. In contrast, walking on a suspended branch generates kinematic and muscular adjustments to ensure better control and to maintain stability. Finally, walking using the lateral sequence gait increases muscular effort and reduces the potential for high recovery rates. The present exploratory study thus supports the assumption that primates are able to make use of an inverted pendulum mechanism on the ground using a diagonal walking gait, yet a different footfall pattern and substrate appear to influence muscular effort and efficiency.

Effect of botulinum toxin injection on length and force of the rectus femoris and triceps surae muscles during locomotion in patients with chronic hemiparesis (FOLOTOX).

BACKGROUND: After stroke, spasticity of the rectus femoris (RF) and triceps surae (TS) muscles frequently alters the gait pattern. Knee flexion and ankle dorsiflexion in swing are often reduced, respectively called Stiff Knee Gait (SKG) and equinus. A preliminary uncontrolled study suggested that botulinum toxin type A (BTX-A) injections could improve muscle length and force generated during gait, improving inter-segmental coordination. The aim of this randomised controlled study is thus to evaluate changes in the length of the RF and TS muscles during gait 1 month after either BTX-A or placebo injection in patients with chronic stroke, SKG and spastic equinus. The secondary aims are to evaluate peak length and peak force generated during gait, as well inter-segmental coordination assessed using the continuous relative phase method initially described by Barela et al. in patients with stroke. METHODS: This is a prospective, three-centre, randomised, placebo-controlled, triple blind study over 3 months with 4 visits. Forty patients will be included. During visits V1, V3 and V4, length and force generated by RF and TS during gait will be assessed using musculoskeletal models (MSM). Muscle force will also be assessed using an isokinetic dynamometer. Inter segmental coordination will be evaluated using 3D gait analysis and functional tests will be performed. During V2, patients will receive either an injection of BTX-A in the RF and TS muscles or a placebo injection of saline solution. DISCUSSION: We expect an increase in peak length and a decrease in peak force generated by the RF and TS muscles in the BTX-A group 1 month post injection. Moreover, we expect these parameters to be more improved in the BTX-A than the Control group. This is the first study to assess these parameters in a randomised, controlled trial using instrumented methods (isokinetic evaluation and 3D gait analysis). The results should help to improve understanding of the mechanism(s) underlying improvements in inter-segmental coordination that have been found in many previous uncontrolled studies. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01821573 , First received: March 27, 2013 Last updated: September 14, 2016 Last verified: September 2016 Other Study ID Numbers: P110136 AOM11223.

A single session of anodal transcranial direct current stimulation applied over the affected primary motor cortex does not alter gait parameters in chronic stroke survivors.

OBJECTIVES: The excitability of some neural circuits involved in walking and affected in individuals with chronic stroke can be modulated during and/or immediately after anodal transcranial direct current stimulation (a-tDCS). This study was designed to investigate the effects of a-tDCS during and immediately after application on leg muscle activity during gait, and on spatiotemporal and kinematic gait parameters in patients with chronic stroke. METHODS: This study was randomized, sham-controlled and double-blinded with a cross-over design and included 24 individuals with chronic stroke. Each participant underwent one 30-minute session each of effective a-tDCS at 2mA and sham tDCS. In both sessions, the anode was placed over the leg motor cortex of the affected hemisphere and the cathode over the contralateral orbit. Six gait trials were performed before, during and immediately after each effective/sham tDCS session. Electromyographic activity of leg muscles, as well as spatiotemporal (e.g. gait speed) and kinematic (e.g. peak knee flexion and ankle dorsiflexion in the swing phase of gait) gait parameters were recorded. Genotyping for the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism was undertaken since this gene may influence motor skill learning and the effects of tDCS. RESULTS: No significant effects of a-tDCS on gait parameters were found either for the total group or for the Val66Met (N=10) and Val66Val (N=14) subgroups. CONCLUSION: A single session of a-tDCS delivered to the leg motor cortex did not immediately improve gait parameters in individuals with chronic stroke, regardless of their BDNF genotype.