Filipe O. Barroso

Shared muscle synergies in human walking and cycling

The motor system may rely on a modular organization (muscle synergies activated in time) to execute different tasks. We investigated the common control features of walking and cycling in healthy humans from the perspective of muscle synergies. Three hypotheses were tested: 1) muscle synergies extracted from walking trials are similar to those extracted during cycling; 2) muscle synergies extracted from one of these motor tasks can be used to mathematically reconstruct the electromyographic (EMG) patterns of the other task; 3) muscle synergies of cycling can result from merging synergies of walking. A secondary objective was to identify the speed (and cadence) at which higher similarities emerged. EMG activity from eight muscles of the dominant leg was recorded in eight healthy subjects during walking and cycling at four matched cadences. A factorization technique [nonnegative matrix factorization (NNMF)] was applied to extract individual muscle synergy vectors and the respective activation coefficients behind the global muscular activity of each condition. Results corroborated hypotheses 2 and 3, showing that 1) four synergies from walking and cycling can successfully explain most of the EMG variability of cycling and walking, respectively, and 2) two of four synergies from walking appear to merge together to reconstruct one individual synergy of cycling, with best reconstruction values found for higher speeds. Direct comparison of the muscle synergy vectors of walking and the muscle synergy vectors of cycling (hypothesis 1) produced moderated values of similarity. This study provides supporting evidence for the hypothesis that cycling and walking share common neuromuscular mechanisms.

Effects of robotic guidance on the coordination of locomotion

BackgroundFunctional integration of motor activity patterns enables the production of coordinated movements, such as walking. The activation of muscles by weightened summation of activation signals has been demonstrated to represent the spatiotemporal components that determine motor behavior during walking. Exoskeleton robotic devices are now often used in the rehabilitation practice to assist physical therapy of individuals with neurological disorders. These devices are used to promote motor recovery by providing guidance force to the patients. The guidance should in principle lead to a muscle coordination similar to physiological human walking. However, the influence of robotic devices on locomotor patterns needs still to be characterized. The aim of this study was to analyze the effect of force guidance and gait speed on the modular organization of walking in a group of eight healthy subjects.MethodA group of healthy subjects walked on a treadmill with and without robotic aiding at speeds of 1.5, 2.0 and 2.5 Km/h. The guidance force was varied between 20%, 40%, 70% and 100% level of assistance. EMG recordings were obtained from seven leg muscles of the dominant leg and kinematic and kinetic features of the knee and hip joints were extracted.ResultsFour motor modules were sufficient to represent the variety of behavioral goals demanded during robotic guidance, with similar relationships between muscle patterns and biomechanical parameters across subjects, confirming that the low-dimensional and impulsive control of human walking is maintained using robotic force guidance. The conditions of guidance force and speed that maintained correct and incorrect (not natural) modular control were identified.ConclusionIn neurologically intact subjects robotic-guided walking at various force guidance and speed levels does not alter the basic locomotor control and timing. This allows the design of robotic-aided rehabilitation strategies aimed at the modulation of motor modules, which are altered in stroke.

Muscle Synergies in Cycling after Incomplete Spinal Cord Injury: Correlation with Clinical Measures of Motor Function and Spasticity

Background: After incomplete spinal cord injury (iSCI), patients suffer important sensorimotor impairments, such as abnormal locomotion patterns and spasticity. Complementary to current clinical diagnostic procedures, the analysis of muscle synergies has emerged as a promising tool to study muscle coordination, which plays a major role in the control of multi-limb functional movements. Objective: Based on recent findings suggesting that walking and cycling share similar synergistic control, the analysis of muscle synergies during cycling might be explored as an early descriptor of gait-related impaired control. This idea was split into the following two hypotheses: (a) iSCI patients present a synergistic control of muscles during cycling; (b) muscle synergies outcomes extracted during cycling correlate with clinical measurements of gait performance and/or spasticity. Methods: Electromyographic (EMG) activity of 13 unilateral lower limb muscles was recorded in a group of 10 healthy individuals and 10 iSCI subjects during cycling at four different cadences. A non-negative matrix factorization (NNMF) algorithm was applied to identify synergistic components (i.e., activation coefficients and muscle synergy vectors). Reconstruction goodness scores (VAF and r2) were used to evaluate the ability of a given number of synergies to reconstruct the EMG signals. A set of metrics based on the similarity between pathologic and healthy synergies were correlated with clinical scales of gait performance and spasticity. Results: iSCI patients preserved a synergistic control of muscles during cycling. The similarity with the healthy reference was consistent with the degree of the impairment, i.e., less impaired patients showed higher similarities with the healthy reference. There was a strong correlation between reconstruction goodness scores at 42 rpm and motor performance scales (TUG, 10-m test and WISCI II). On the other hand, the similarity between the healthy and affected synergies presented correlation with some spasticity symptoms measured by Penn, Modified Ashworth and SCATS scales. Conclusion: Overall, the results of this study support the hypothesis that the analysis of muscle synergies during cycling can provide detailed quantitative assessment of functional motor impairments and symptoms of spasticity caused by abnormal spatiotemporal muscle co-activation following iSCI.

How can the land managers and his multi-stakeholder network at the farm level influence the multifunctional transitions pathways?

The changing role of agriculture is at the core of transition pathways in many rural areas. Productivism, post-productivism and multifunctionality have been targeted towards a possible conceptualization of the transition happening in rural areas. The factors of change, including productivist and post-productivist trends, are combined in various ways and have gone in quite diverse directions and intensities, in individual regions and localities. Even, in the same holding, productivist and post-productivist strategies can coexist spatially, temporally, structurally, leading to a higher complexity in changing patterns. In south Portugal extensive landscapes, dominated by traditionally managed agro-forestry systems under a fuzzy land use pattern, multifunctionality at the farm level is indeed conducted by different stakeholders whose interests may or not converge: a multifunctional land management may indeed incorporate post-productivist and productivist agents. These stakeholders act under different levels of decision, management and use, reflecting a particular land management dynamic, in which different interests may exist, from commercial production to a variety of other functions (hunting, bee-keeping, subsistence farming, etc.), influencing management at the farm level and its supposed transition trajectory. This multi-stakeholder dynamic is composed by a main land-manager (the one who takes the main decisions), secondary land-managers (land-managers under the rules of the main land-manager), workers and users (locals or outsiders), as also hybrid situations can occur. Each of these can influence the land management in different ways as their interest and action within the holding may vary differently and therefore reflect more or less multifunctional systems, and also a different situation in a spectrum that goes from productivism to postproductivism. The goal of the proposed presentation is to show the evidence of productivist and non-productivist strategies linked with multifunctional transitions in place, which are the land managers types in place, their attitudes and behaviors and how each of the land manager types behave regarding the multi-stakeholders network but also to describe the multi-stakeholder relations at the farm level and the consequences regarding multifunctional transitions happening in place.

Review on Tremor Suppression Using Afferent Electrical Stimulation

Pathological tremor is the most prevalent movement disorder and affects daily living activities. Research on tremor suppression over the past five years suggest that transcutaneous stimulation below the motor threshold (also known as afferent or sensory stimulation) has a powerful inhibitory effect on the descending supraspinal tremorogenic input by means of spinal interneurons. The aim of this study was to review the most recent and promising strategies to suppress tremor using afferent electrical stimulation in two main pathologies: Essential Tremor (ET) and Parkinson’s Disease (PD). Five studies were retrieved from PubMed database. Most of these studies reported at least 40% of tremor reduction during afferent stimulation and one article reported a suppression effect five minutes after stopping the stimulation. More research on how to maximize the suppression lasting effect as a therapeutic tool is required.

Emerging Techniques for Assessment of Sensorimotor Impairments after Spinal Cord Injury

Gait function can be altered after incomplete spinal cord (iSCI) lesions. Muscular weakness, co‐activation of antagonist muscles, and altered muscle mechanics are likely to provoke abnormal gait and postural movements. Functional scales are available for assessment of functional walking in SCI patients, such as walking index for spinal cord injury (WISCI II), timed up and go (TUG) test, 10‐meter walk test (10MWT), and 6‐ minute walk test (6MWT). Novel metrics for a more detailed comprehension of neuromuscular control in terms of degree of voluntary motor control have been recently proposed. This section describes novel techniques based on muscle synergy and frequency domain analysis of electromyographic signals. Such techniques are illustrated as potential tools for assessment of motor function after SCI with experi‐ mental data and a case study describing a diagnostic scenario. This chapter presents a discussion of the current status of the emerging metrics for assessment of sensorimo‐ tor impairments. Conclusions are given with respect to the availability of enriched information about neuromuscular behavior between functional tasks (walking and pedalling) and the potential relevance of these new techniques to improve the efficacy of treatment to improve locomotion after iSCI.

Modular Control of Gait in Incomplete Spinal Cord Injury: Preliminary Results

Muscles synergies, or motor modules, are thought to be the building blocks of motor control in vertebrates. In human walking, experimental finding demonstrated that 4 to 5 synergies can explain most of the variability of electromyographic activity of lower limb muscles. How is modular control affected in neurologically injured patients is still object of investigation. In this paper we present preliminary experimental findings on the modular control of walking in three incomplete spinal cord injury (SCI) patients. Results show that the impulsive and synergistic control of muscles is preserved in these patients, and that the basic features are in general similar to the healthy modular control, as described in the literature. Relevant differences in timing recruitment of muscle synergies are associated to large deviations in spatiotemporal parameters, supporting the functional meaning of muscle synergies.

Chapter 23: The Multifunctional Landscape of Marvão, central Portugal: Can high valued non commodity functions support the maintenance of small scale farm landscapes in the periphery of Europe?

The landscape of Marvao is unique, in that it still combines two components of traditional Mediterranean agricultural landscapes: large estates with silvopastoral areas of montado in the north, on slopes with poor soils, extensively managed, mainly for cattle grazing; and a small scale mosaic landscape in the south, in the large fertile valleys, on small properties owned and cultivated mostly by elderly farmers, with a variety of crops and uses, and surrounded by forests, with scrub on the slopes. The result is a distinctive, contrasting landscape, whose striking character relates to its diversity, the intensity of use in the valleys, and the remarkable small town of Marvao, which is currently a candidate for UNESCO World Heritage status. Nowadays, this landscape is valued mostly for aesthetic, cultural and recreational purposes, but it is nevertheless undergoing change. Keywords: cultural landscape; fertile valleys; Marvao landscape; UNESCO World Heritage status