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25 pages, 28890 KiB

Open AccessArticle

Antagonistic Feedback Control of Muscle Length Changes for Efficient Involuntary Posture Stabilization

by Masami Iwamoto, Noritoshi Atsumi and Daichi Kato

Biomimetics 2024, 9(10), 618; https://doi.org/10.3390/biomimetics9100618 - 11 Oct 2024

Viewed by 1381

Simultaneous and cooperative muscle activation results in involuntary posture stabilization in vertebrates. However, the mechanism through which more muscles than joints contribute to this stabilization remains unclear. We developed a computational human body model with 949 muscle action lines and 22 joints and examined muscle activation patterns for stabilizing right upper or lower extremity motions at a neutral body posture (NBP) under gravity using actor–critic reinforcement learning (ACRL). Two feedback control models (FCM), muscle length change (FCM–ML) and joint angle differences, were applied to ACRL with a normalized Gaussian network (ACRL–NGN) or deep deterministic policy gradient. Our findings indicate that among the six control methods, ACRL–NGN with FCM–ML, utilizing solely antagonistic feedback control of muscle length change without relying on synergy pattern control or categorizing muscles as flexors, extensors, agonists, or synergists, achieved the most efficient involuntary NBP stabilization. This finding suggests that vertebrate muscles are fundamentally controlled without categorization of muscles for targeted joint motion and are involuntarily controlled to achieve the NBP, which is the most comfortable posture under gravity. Thus, ACRL–NGN with FCM–ML is suitable for controlling humanoid muscles and enables the development of a comfortable seat design. Full article

(This article belongs to the Special Issue Computer-Aided Biomimetics: 2nd Edition)

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17 pages, 5746 KiB

Open AccessArticle

Motor Overflow during Reaching in Infancy: Quantification of Limb Movement Using Inertial Motion Units

by Agata Kozioł, David López Pérez, Zuzanna Laudańska, Anna Malinowska-Korczak, Karolina Babis, Oleksandra Mykhailova, Hana D’Souza and Przemysław Tomalski

Sensors 2023, 23(5), 2653; https://doi.org/10.3390/s23052653 - 28 Feb 2023

Viewed by 2726

Abstract

Early in life, infants exhibit motor overflow, which can be defined as the generation of involuntary movements accompanying purposeful actions. We present the results of a quantitative study exploring motor overflow in 4-month-old infants. This is the first study quantifying motor overflow with high accuracy and precision provided by Inertial Motion Units. The study aimed to investigate the motor activity across the non-acting limbs during goal-directed action. To this end, we used wearable motion trackers to measure infant motor activity during a baby-gym task designed to capture overflow during reaching movements. The analysis was conducted on the subsample of participants (n = 20), who performed at least four reaches during the task. A series of Granger causality tests revealed that the activity differed depending on the non-acting limb and the type of the reaching movement. Importantly, on average, the non-acting arm preceded the activation of the acting arm. In contrast, the activity of the acting arm was followed by the activation of the legs. This may be caused by their distinct purposes in supporting postural stability and efficiency of movement execution. Finally, our findings demonstrate the utility of wearable motion trackers for precise measurement of infant movement dynamics. Full article

(This article belongs to the Special Issue Wearable Sensors for Gait, Human Motion Analysis and Health Monitoring)

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13 pages, 918 KiB

Open AccessReview

Effects of Exercise on Skeletal Muscle Pathophysiology in Huntington’s Disease

by Bruno Trovato, Benedetta Magrì, Alessandro Castorina, Grazia Maugeri, Velia D’Agata and Giuseppe Musumeci

J. Funct. Morphol. Kinesiol. 2022, 7(2), 40; https://doi.org/10.3390/jfmk7020040 - 11 May 2022

Cited by 10 | Viewed by 4608

Abstract

Huntington’s disease (HD) is a rare, hereditary, and progressive neurodegenerative disease, characterized by involuntary choreatic movements with cognitive and behavioral disturbances. In order to mitigate impairments in motor function, physical exercise was integrated in HD rehabilitative interventions, showing to be a powerful tool to ameliorate the quality of life of HD-affected patients. This review aims to describe the effects of physical exercise on HD-related skeletal muscle disorders in both murine and human models. We performed a literature search using PubMed, Scopus, and Web of Science databases on the role of physical activity in mouse models of HD and human patients. Fifteen publications fulfilled the criteria and were included in the review. Studies performed on mouse models showed a controversial role played by exercise, whereas in HD-affected patients, physical activity appeared to have positive effects on gait, motor function, UHDMRS scale, cognitive function, quality of life, postural stability, total body mass, fatty acid oxidative capacity, and VO2 max. Physical activity seems to be feasible, safe, and effective for HD patients. However, further studies with longer follow-up and larger cohorts of patients will be needed to draw firm conclusions on the positive effects of exercise for HD patients. Full article

(This article belongs to the Special Issue Exercise and Neurodegenerative Disease 2.0)

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