Reduce Muscle Fatigue Research Articles

6′-sialyllactose prevents dexamethasone-induced muscle atrophy by controlling the muscle protein degradation pathway

Sarcopenia is associated with various geriatric diseases, such as gait disorders, falls, malnutrition, and osteoporosis. Accordingly, interest in the prevention and treatment of sarcopenia has grown over the years. The human milk oligosaccharide (HMO) 6′-sialyllactose (6′-SL) is known to improve exercise performance, reduce muscle fatigue, and improve GNE myopathy; however, its effect on sarcopenia has not yet been reported. In this study, we aimed to investigate the efficacy of 6′-SL in dexamethasone-induced muscle atrophy, which is a widely used model for the study of sarcopenia. The effects of 6′-SL on differentiated C2C12 skeletal muscle cells and on mice were examined by treatment with 6′-SL in the presence or absence of dexamethasone. 6′-SL was found to inhibit the dexamethasone-induced decrease of MHC expression, as well as to prevent reduction in the number, length, and width of myotubes. Furthermore, the dexamethasone-induced upregulation of myostatin, muscle RING-finger protein-1 (MuRF1), and atrogin-1 were also inhibited by 6′-SL treatment. In mice, intraperitoneal administration of dexamethasone caused decreases in muscle fiber diameter, muscle weight, and exercise performance, most of which were significantly inhibited by oral treatment with 6′-SL. Therefore, utilization of 6′-SL could contribute to the prevention and treatment of muscle atrophy and sarcopenia.

Metabolic characteristics of ischaemic preconditioning induced performance improvement in Taekwondo athletes using LC‒MS/MS-based plasma metabolomics.

In recent years, ischemic preconditioning (IPC) has garnered significant attention in sports research. While IPC has demonstrated positive effects in high-intensity sports such as judo and swimming, its potential benefits for enhancing the performance of Taekwondo athletes have not been extensively studied. This study aimed to investigate the effects of IPC on taekwondo performance and to observe the metabolic characteristics associated with enhancing sports performance via LC‒MS/MS-based plasma metabolomics. Seventeen participants underwent the repeated frequency speed of kick test (FSKT) after IPC, along with pre- and post-exercise plasma metabolite analysis. Differential abundance metabolite analysis, enriched pathway analysis, and weighted gene coexpression network analysis (WGNCA) were employed to delve into metabolic characteristics. The findings highlighted a significant enhancement in FSKT performance in the experimental group. Metabolomic analysis revealed 109 differentially abundant metabolites, including Dl-lactate, hypoxanthine, acetylcarnitine, and acetylsalicylic acid. Enriched pathway analysis revealed pathways such as pentose and glucuronic acid interconversion, ascorbic acid and aldonic acid metabolism, the pentose phosphate pathway (PPP), and the Warburg effect. In conclusion, IPC can significantly increase the specific athletic abilities of Taekwondo athletes, with enhancements linked to anaerobic metabolism, PPP utilization, the Warburg effect for energy production, redox system stability, reduced muscle fatigue, and pain alleviation.

Eicosapentaenoic Acid and Medium-Chain Triacylglycerol Structured Lipid Supplementation Improves Muscular Endurance Exercise Performance and Reduces Muscle Fatigue in Young Healthy Male

Objective Structured lipids containing medium-chain fatty acids, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) from fish oil (EPA/MCT) and it improve overall endurance. However, their effects on local muscle endurance remain unclear. This study aimed to investigate the effects of EPA/MCT intake on muscle endurance during leg extension exercises and subsequent muscle fatigue. Methods This 8-week, placebo-controlled, randomized, double-blind parallel-group trial involved 20 healthy young men. Subjects were randomly assigned to an EPA/MCT group (10 subjects) and a placebo group (PL group, 10 subjects). They consumed 4560 mg of the test food daily for 8 wk before an exercise intervention. The EPA/MCT supplement contained 600 mg of EPA, 260 mg of DHA, and 1890 mg of MCT (1110 mg of octanoic acid and 780 mg of decanoic acid). After the 8-week intervention, the subjects performed four sets of leg extension exercises at 40% of their body weight until exhaustion. The number of repetitions per set and the total repetitions across the four sets served as indicators of muscle endurance. Isometric maximum voluntary contraction (MVC), range of motion, circumference, muscle thickness, echo intensity, and muscle stiffness were measured before and after exercise to assess muscle fatigue. Results There was no difference between the groups in the number of repetitions for sets 1–4 or in the total number of repetitions during the leg extension exercise. In the EPA/MCT group, a significant negative correlation was observed between the increase in the blood EPA/AA ratio and the rate of decrease in the number of repetitions. Additionally, the decrease in MVC after exercise was significantly smaller in the EPA/MCT group than in the PL group. Conclusion Our study results suggest that an 8-week intake of EPA/MCT can increase the blood EPA/AA ratio and improve muscle endurance performance. Additionally, EPA/MCT intake reduces muscle fatigue after exercise.

Using nonlinear dynamics analysis to evaluate time response of cupping therapy with different intervention timings on reducing muscle fatigue.

Cupping therapy has been indicated effective in reducing muscle fatigue after 24h based on the spectral analyses of surface electromyography (sEMG). However, there is no sufficient evidence showing changes of sEMG nonlinear indexes at more time points after cupping therapy. Furthermore, it is unclear whether the intervention timings of cupping therapy affect the recovery from muscle fatigue. The purpose of this study was to use the sEMG nonlinear analysis to assess the difference of time response of cupping therapy between different intervention timings after muscle fatigue. This randomized controlled trial recruited 26 healthy volunteers. Cupping therapy (-300mmHg pressure for 5min by the 45mm-diameter cup) was applied before (i.e., pre-condition) or after (i.e., post-condition) muscle fatigue induced by performing repeated biceps curls at 75% of the 10 repetitions of maximum (RM) on the non-dominant upper extremity. Subjects were randomly allocated to the pre-condition group or the post-condition group. The sEMG signals during the maximal voluntary isometric contractions (MVC) of the biceps were recorded at four time points (i.e., baseline; post 1: immediate after cupping-fatigue/fatigue-cupping interventions; post 2: 3h after cupping-fatigue/fatigue-cupping interventions; post 3: 6h after cupping-fatigue/fatigue-cupping interventions). Two nonlinear sEMG indexes (sample entropy, SampEn; and percent determinism based on recurrence quantification analysis, %DET) were used to evaluate the recovery from exercise-introduced muscle fatigue. The Friedman test followed by the Nemenyi test and the Mann-Whitney U test were applied in statistics. The SampEn and %DET change rate did not show any significant differences at four time points in the pre-condition group. However, there were significant delayed effects instead of immediate effects on improving muscle fatigue in the post-condition group (SampEn change rate: baseline 0.0000 ± 0.0000 vs. post 2 0.1105 ± 0.2253, p < 0.05; baseline 0.0000 ± 0.0000 vs. post 3 0.0627 ± 0.4665, p < 0.05; post 1-0.0321 ± 0.2668 vs. post 3 0.0627 ± 0.4665, p < 0.05; and %DET change rate: baseline 0.0000 ± 0.0000 vs. post 2-0.1240 ± 0.1357, p < 0.01; baseline 0.0000 ± 0.0000 vs. post 3 0.0704 ± 0.6495, p < 0.05; post 1 0.0700 ± 0.3819 vs. post 3 0.0704 ± 0.6495, p < 0.05). Moreover, the SampEn change rate of the post-condition group (0.1105 ± 0.2253) was significantly higher than that of the pre-condition group (0.0006 ± 0.0634, p < 0.05) at the post 2 time point. No more significant between-groups difference was found in this study. This is the first study demonstrating that both the pre-condition and post-condition of cupping therapy are useful for reducing muscle fatigue. The post-condition cupping therapy can e ffectively alleviate exercise-induced muscle fatigue and there is a significant delayed effect, especially 3h after the interventions. Although the pre-condition cupping therapy can not significantly enhance muscle manifestations, it can recover muscles into a non-fatigued state.

Stroke-induced excess in capillarization relative to oxidative capacity in rats is muscle specific.

Stroke is not only associated with muscle weakness, but also associated with reduced muscle fatigue resistance and reduced desaturation during exercise that may be caused by a reduced oxidative capacity and/or microvasculature. Therefore, the objective of the present study was to determine the effects of stroke on muscle mass, fiber size and shape, capillarization and oxidative capacity of the rat m. extensor carpi radialis (ECR) and m. flexor carpi ulnaris (FCU) after a photothrombotic stroke in the forelimb region of the primary sensorimotor cortex. The main observation of the present study was that 4 weeks after induction of stroke there were no significant changes in muscle fiber size and shape. Although there was no significant capillary rarefaction, there was some evidence for remodeling of the capillary bed as reflected by a reduced heterogeneity of capillary spacing (p = 0.006) that may result in improved muscle oxygenation. In the ECR, but not in the FCU, this was accompanied by reduction in muscle fiber oxidative capacity as reflected by reduced optical density of sections stained for succinate dehydrogenase (p = 0.013). The reduced oxidative capacity and absence of significant capillary rarefaction resulted in a capillary to fiber ratio per unit of oxidative capacity that was higher after stroke in the ECR (p = 0.01), but not in the FCU. This suggests that at least during the early stages, stroke is not necessarily accompanied by muscle fiber atrophy, and that stroke-induced reductions in oxidative capacity resulting in relative excess of capillarization are muscle specific.

Fatigue Alleviation by Low-Level Laser Preexposure in Ischemic Neuromuscular Electrical Stimulation.

Despite its susceptibility to muscle fatigue, combined neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) are effective regimens for managing muscle atrophy when traditional resistance exercises are not feasible. This study investigated the potential of low-level laser therapy (LLLT) in reducing muscle fatigue after the application of combined NMES and BFR. Thirty-six healthy adults were divided into control and LLLT groups. The LLLT group received 60 J of 850-nm wavelength LLLT before a training program of combined NMES and BFR of the nondominant extensor carpi radialis longus (ECRL). The control group followed the same protocol but received sham laser therapy. Assessments included maximal voluntary contraction, ECRL mechanical properties, and isometric force tracking for wrist extension. The LLLT group exhibited a smaller normalized difference in maximal voluntary contraction decrement (-4.01 ± 4.88%) than the control group (-23.85 ± 7.12%) ( P < 0.001). The LLLT group demonstrated a smaller decrease in muscle stiffness of the ECRL compared with the control group, characterized by the smaller normalized changes in frequency ( P = 0.002), stiffness ( P = 0.002), and relaxation measures ( P = 0.011) of mechanical oscillation waves. Unlike the control group, the LLLT group exhibited a smaller posttest increase in force fluctuations during force tracking ( P = 0.014), linked to the predominant recruitment of low-threshold MU ( P < 0.001) without fatigue-related increases in the discharge variability of high-threshold MU ( P > 0.05). LLLT preexposure reduces fatigue after combined NMES and BFR, preserving force generation, muscle stiffness, and force scaling. The functional benefits are achieved through fatigue-resistant activation strategies of motor unit recruitment and rate coding.

Limosilactobacillus reuteri ID-D01 improves exercise performance and reduces muscle fatigue in C57BL/6 mice through regulation of oxidative capacity

The objective of this study was to evaluate the influence of the Limosilactobacillus reuteri ID-D01 (ID-D01) lactic acid bacteria probiotic on exercise performance and muscle fatigue in C57BL/6 mice. ID-D01 improved exercise endurance by extending treadmill running time and forced swimming duration. Moreover, mice treated with ID-D01 exhibited increased quadriceps muscle tissue weight, suggesting a potential for enhancing muscle growth. Serum analysis showed decreased muscle fatigue markers, and lower levels of lactate, and ammonia, indicating reduced exercise-induced fatigue. ID-D01 also affected intramuscular factors such as citrate synthase and glycogen. Notably, citrate synthase levels increased, indicating improved aerobic capacity, while intramuscular glycogen decreased. ID-D01 decreased reactive oxygen species and increased antioxidant enzymes SOD2 and catalase, in muscle tissue. This study identifies the potential of ID-D01 to improve exercise performance and relieve muscle fatigue. Further, it provides a rationale for the development of ID-D01-based functional supplements for individuals who are physically active.

A Wearable Upper Limb Exoskeleton System and Intelligent Control Strategy.

Heavy lifting operations frequently lead to upper limb muscle fatigue and injury. In order to reduce muscle fatigue, auxiliary force for upper limbs can be provided. This paper presents the development and evaluation of a wearable upper limb exoskeleton (ULE) robot system. A flexible cable transmits auxiliary torque and is connected to the upper limb by bypassing the shoulder. Based on the K-nearest neighbors (KNN) algorithm and integrated fuzzy PID control strategy, the ULE identifies the handling posture and provides accurate active auxiliary force automatically. Overall, it has the quality of being light and easy to wear. In unassisted mode, the wearer's upper limbs minimally affect the range of movement. The KNN algorithm uses multi-dimensional motion information collected by the sensor, and the test accuracy is 94.59%. Brachioradialis muscle (BM), triceps brachii (TB), and biceps brachii (BB) electromyogram (EMG) signals were evaluated by 5 kg, 10 kg, and 15 kg weight conditions for five subjects, respectively, during lifting, holding, and squatting. Compared with the ULE without assistance and with assistance, the average peak values of EMG signals of BM, TB, and BB were reduced by 19-30% during the whole handling process, which verified that the developed ULE could provide practical assistance under different load conditions.

Vertical climbing in free-ranging bonobos: An exploratory study integrating locomotor performance and substrate compliance.

Ecological factors and body size shape animal movement and adaptation. Large primates such as bonobos excel in navigating the demanding substrates of arboreal habitats. However, current approaches lack comprehensive assessment of climbing performance in free-ranging individuals, limiting our understanding of locomotor adaptations. This study aims to explore climbing performance in free-ranging bonobos and how substrate properties affect their behavior. We collected data on the climbing performance of habituated bonobos, Pan paniscus, in the Bolobo Territory, Democratic Republic of Congo. We analyzed 46 climbing bouts (12 ascents, 34 descents) while moving on vertical substrates of varying diameter and compliance levels. This study assessed the average speed, peak acceleration, resting postures, and transitions between climbing and other locomotor modes. During climbing sequences and transitions, bonobos mitigate speed variations. They also exhibit regular pauses during climbing and show higher speeds during descent in contrast to their ascent. Regarding the influence of substrate properties, bonobos exhibit higher speed when ascending on thin and slightly flexible substrates, while they appear to achieve higher speeds when descending on large and stiff substrates, by using a "fire-pole slide" submode. Bonobos demonstrate remarkable abilities for negotiating vertical substrates and substrate properties influence their performance. Our results support the idea that bonobos adopt a behavioral strategy that aligns with the notion of minimizing costs. Overall, the adoption of high velocities and the use of low-cost resting postures may reduce muscle fatigue. These aspects could represent important targets of selection to ensure ecological efficiency in bonobos.

A Data-Driven Design Framework for Structural Optimization to Enhance Wearing Adaptability of Prosthetic Hands.

Prosthetic hands have significant potential to restore the manipulative capabilities and self-confidence of amputees and enhance their quality of life. However, incompatibility between prosthetic devices and residual limbs can lead to secondary injuries such as skin pressure ulcers and restricted joint motion, contributing to a high prosthesis abandonment rate. To address these challenges, this study introduces a data-driven design framework (D3Frame) utilizing a multi-index optimization method. By incorporating motion/ pressure data, as well as clinical criteria such as pain threshold/ tolerance, from various anatomical sites on the residual limbs of amputees, this framework aims to optimize the structural design of the prosthetic socket, including the Antecubital Channel (AC), Lateral Epicondylar Region Contour (LC), Medial Epicondylar Region Contour (MC), Olecranon Region Contour (OC), Lateral Flexor/ Extensor Region (LR), and Medial Flexor/ Extensor Region (MR). Experiments on five forearm amputees verified the improved adaptability of the optimized socket compared to traditional sockets under three load conditions. The experimental results revealed a modest score enhancement on standard clinical scales and reduced muscle fatigue levels. Specifically, the percent effort of muscles and slope value of mean/ median frequency decreased by 19%, 70%, and 99% on average, respectively, and the average values of mean/ median frequency in the motion cycle both increased by approximately 5%. The proposed D3Frame in this study was applied to optimize the structural aspects of designated regions of the prosthetic socket, offering the potential to aid prosthetists in prosthesis design and, consequently, augmenting the adaptability of prosthetic devices.

Breaking the Fatigue Cycle: Investigating the Effect of Work-Rest Schedules on Muscle Fatigue in Material Handling Jobs.

Muscle fatigue has proven to be a main factor in developing work-related musculoskeletal disorders. Taking small breaks or performing stretching routines during a work shift might reduce workers' fatigue. Therefore, our objective was to explore how breaks and/or a stretching routine during a work shift could impact muscle fatigue and body kinematics that might subsequently impact the risk of work-related musculoskeletal disorder (WMSD) risk during material handling jobs. We investigated muscle fatigue during a repetitive task performed without breaks, with breaks, and with a stretching routine during breaks. Muscle fatigue was detected using muscle activity (electromyography) and a validated kinematic score measured by wearable sensors. We observed a significant reduction in muscle fatigue between the different work-rest schedules (p < 0.01). Also, no significant difference was observed between the productivity of the three schedules. Based on these objective kinematic assessments, we concluded that taking small breaks during a work shift can significantly reduce muscle fatigue and potentially reduce its consequent risk of work-related musculoskeletal disorders without negatively affecting productivity.

Effect of Lactobacillus plantarum PS128 on neuromuscular efficiency after a half-marathon

Introduction:Lactobacillus plantarum PS128 (PS128) could be considered an antioxidant supplement to reduce muscle fatigue and improve exercise capacity recovery after vigorous exercise.Purpose: The purpose of this study is to investigate the effect of PS128 on muscle fatigue and electromyography (EMG) activity after a half-marathon (HM).Methods: The experimental design used a repeated-measures design with a double-blind approach. The participants either took two capsules of PS128 for 4 weeks as the PS128 group (PSG, n = 8) or took two capsules of a placebo for 4 weeks as the placebo group (PLG, n = 8) to ensure counterbalancing. The time points of the maximal voluntary isometric contraction (MVIC) and EMG activity test were set before probiotics were taken (baseline), 48 h before HM (Pre), and immediately at 0 h, 3 h, 24 h, 48 h, 72 h, and 96 h after HM.Results: EMG activity included median power frequency (MDF), integrated EMG (iEMG), and neuromuscular efficiency (peak torque/iEMG). The MVICs of knee extensors, analyzed by using an isokinetic dynamometer, showed a decrease from the Pre to 0 h (p = 0.0001), 3 h (p &amp;lt; 0.0001), 24 h (p &amp;lt; 0.0001), 48 h (p &amp;lt; 0.0001), 72 h (p = 0.0002), and 96 h (p = 0.0408) time points in the PLG. Sidak’s multiple comparisons tests showed that the PLG was significantly lower than the PSG at 0 h (p = 0.0173), 3 h (p &amp;lt; 0.0001), 24 h (p &amp;lt; 0.0001), 48 h (p &amp;lt; 0.0001), 72 h (p &amp;lt; 0.0001), and 96 h (p = 0.0004) time points. The MDF of vastus medialis oblique (VMO) in the PLG was significantly decreased 24 h after HM and significantly lower than that in the PSG at all times points after HM. The iEMG of VMO in the PLG was significantly decreased 48 h after HM and significantly lower than that in the PSG at 0 h, 3 h, 24 h, 48 h, and 72 h after HM.Conclusion: The PS128 supplementation may prevent the decrease in MDF, iEMG, and peak torque after vigorous exercise. Recreational runners may consider implementing a probiotic supplementation regimen as a potential strategy to mitigate muscle fatigue following HM.

Verification of Industrial Worker Walking Efficiency with Wearable Hip Exoskeleton

In highly mobile workplaces, wearable walking-assistant devices reduce muscle fatigue in workers’ lower extremities and increase energy efficiency. In our study, we verify this following the development of an ultralight wearable hip exoskeleton for industrial workers. Ten healthy male adults participated in this study, and their muscle activity, muscle fatigue, and energy expenditure were compared with and without a device while walking on a treadmill and going up stairs. While walking on a treadmill with the assistive device, muscle fatigue in the gastrocnemius decreased by 79.5%, and oxygen uptake and energy expenditure per minute decreased by 7.9% and 7.4%, respectively. While climbing stairs with the assistive device, muscle fatigue of the tibialis anterior decreased by 83.5%, average muscle activity of the rectus femoris, semitendinosus, and gastrocnemius muscles decreased significantly, and oxygen uptake and energy expenditure decreased by 14% and 12.9% per minute, respectively. We confirm that an ultralight wearable hip exoskeleton helps the wearer reduce lower-limb muscle fatigue and use metabolic energy more efficiently. The results of this study are intended as basic data to expand the use of ultralight wearable hip exoskeletons at industrial sites and to improve device performance.

Impact of task variation and microbreaks on muscle fatigue at seated and standing postures.

Prolonged and sustained work posture among computer users is one of the main factors that contributes to musculoskeletal discomfort. Rest-break interventions such as task variation and microbreaks may help prevent muscle fatigue and work-related musculoskeletal disorder. We aimed to investigate the effects of task variation and microbreaks at seated and standing workstations on forearm muscle activity, namely extensor digitorum communis, extensor carpi ulnaris, flexor digitorum superficialis, and flexor carpi ulnaris; mouse operation force (vertical compression force); mouse operation parameters; and perceived body discomfort during mouse operation. Twelve healthy right-handed young adults were recruited (male: n = 7, 21.6±1.4 years; female: n = 5, 21.4±1.7 years). Participants performed three blocks of computer tasks (computer mouse operation and typing) in both seated and standing postures with each block lasting for 30 min. Surface electromyography (EMG) of the forearm muscles and operation force were monitored during computer mouse operation. Body discomfort rating was recorded at the end of each block. With simulated task variation and microbreaks, work posture and work time showed no significant difference with EMG amplitude and mouse operation force. Task variation and microbreaks could be of benefit to computer users by reducing muscle fatigue during long hours of computer work at both seated and standing workstations.

Beta-alanine supplementation and improvement of performance in swimming and water polo: a systematic review

Beta-alanine is a non-essential amino acid that is naturally produced by the human body and used by many athletes and practitioners of physical activity to reduce muscle fatigue and to increase performance in high performance exercises. As a precursor of intramuscular carnosine, it has been shown to reduce the hydrogen ions that cause muscle fatigue during exercise in sports such as swimming and water polo. Objective: To evaluate various beta-alanine supplementation protocols in swimmers and water polo players and their effects on performance. Materials and methods: This study is a systematic review of various beta-alanine supplementation protocols used in exercises involving water polo and high-performance swimming, from searches on the Pubmed, SCIELO and RBNE platforms. Articles in English and Portuguese were included, which were evaluated on the basis of methods and parameters specific to swimming and water polo. Results: The review found that beta-alanine supplementation protocols varied according to the studies and their objectives. However, beta-alanine supplementation was shown to be effective in improving times, reducing blood lactate and increasing strength. Conclusion: Supplementation with beta-alanine generates a possible beneficial effect on swimmers and water polo players by fostering improvements in time, reduction of blood lactate and strength, all of which can positively influence the results of competitions and championships. The best protocols are those that administered a dose greater than or equal to 4.8g per day for, at least, four weeks.

Pharmacological NF-κB inhibition decreases cisplatin chemoresistance in muscle-invasive bladder cancer and reduces cisplatin-induced toxicities.

Most patients with muscle-invasive bladder cancer (MIBC) are not cured with platinum chemotherapy. Up-regulation of nuclear factor kappa light-chain enhancer of activated B cells (NF-κB) is a major mechanism underlying chemoresistance, suggesting that its pharmacological inhibition may increase platinum efficacy. NF-κB signaling was investigated in two patient cohorts. The Cancer Genome Atlas (TCGA) was used to correlate NF-κB signaling and patient survival. The efficacy of cisplatin plus the NF-κB inhibitor dimethylaminoparthenolide (DMAPT) versus cisplatin or DMAPT alone was tested in vitro. Xenografted and immunocompetent MIBC mouse models were studied in vivo. Platinum-naive claudin-low MIBC showed constitutive NF-κB signaling and this was associated with reduced disease-specific survival in TCGA patients. Chemotherapy up-regulated NF-κB signaling and chemoresistance-associated genes, including SPHK1, PLAUR, and SERPINE1. In mice, DMAPT significantly improved the efficacy of cisplatin in both models. The combination preserved body weight, renal function, and morphology, reduced musclefatigue and IL-6 serum levels, and did not aggravate immuno-hematological toxicity compared with cisplatin alone. These data provide a rationale for combining NF-κB inhibition with platinum-based chemotherapy and conducting a clinical trial in MIBC patients.

Closed-Loop FES Control of a Hybrid Exoskeleton during Sit-to-Stand Exercises: Concept and First Evaluation

Rehabilitation of paralysis caused by a stroke or a spinal cord injury remains a complex and time-consuming task. This work proposes a hybrid exoskeleton approach combining a traditional exoskeleton and functional electrical stimulation (FES) as a promising method in rehabilitation. However, hybrid exoskeletons with a closed-loop FES control strategy are functionally challenging to achieve and have not been reported often. Therefore, this study aimed to investigate a powered lower-limb exoskeleton with a closed-loop FES control for Sit-to-Stand (STS) movements. A body motion capture system was applied to record precise hip and knee trajectories of references for establishing the human model. A closed-loop control strategy with allocation factors is proposed featuring a two-layer cascaded proportional–integral–derivative (PID) controller for both FES and exoskeleton control. Experiments were performed on two participants to examine the feasibility of the hybrid exoskeleton and the closed-loop FES control. Both open- and closed-loop FES control showed the desired performance with a relatively low root-mean-squared error (max 1.3∘ in open-loop and max 4.1∘ in closed-loop) in hip and knee trajectories. Notably, the closed-loop FES control strategy can achieve the same performance with nearly 60% of the electrical power input compared to the open-loop control, which reduced muscle fatigue and improved robustness during the training. This study provides novel insights into body motion capture application and proposes a closed-loop FES control for hybrid exoskeletons.

Synchronous Generation of Electrical and Cellular Energies via Body-Mediated Energy Transfer: Inevitable Electric Field Concentration

The effect of body-mediated energy transfer and harvesting on biological tissues has not been considered yet. We demonstrate through clinical protocols that body-mediated energy harvesting concentrates inevitable and local electric fields in biological tissues, which reduces muscle fatigue (6.4%, P-value = 0.020). The waveform (AC and DC) and intensity (∼3000 mV/mm) of these electric fields can be adjusted by controlling several variables (grounding method, external resistance, charging capacitor) depending on the purpose (usefulness, energy strength) without using any additional battery or wiring. Moreover, the harvested energy can be used to operate small electronic devices semipermanently. These findings indicate that body-mediated energy harvesting is a promising solution for powering wearable technologies and as a noninvasive treatment for harvesting energy and stimulating biological tissues synchronously.

A Portable Soft Exosuit to Assist Stair Climbing with Hip Flexion

Soft exosuits are an emerging class of robots that have been shown to significantly reduce the metabolic cost of daily human movement. However, most soft exosuits are currently being studied for walking and running, and relatively minor research has been carried out on exosuits for stair climbing. Numerous exoskeletons used for stair climbing have a more rigid structure and are heavier, which may result in a greater force required by the wearer to overcome the weight from the exoskeleton when ascending stairs, which can result in metabolic costs. As a result, a reduction in rigid structures can reduce the weight of the exoskeleton and further reduce metabolic costs during stair climbing. In this paper, a waist-wearable soft exosuit was designed that assists hip flexion to aid stair climbing in older adults, in order to demonstrate the importance of choosing to assist hip flexion during stair climbing. An admittance delayed feedback control method was also proposed to use the angular information measured by the IMUs to enable the exosuit to adapt to different staircases. Metabolic experiments have shown that people who use soft exosuits have an average decrease of 6.9% in metabolism when they climb stairs than those who do not. The muscle fatigue experiments demonstrated a reduction in muscle fatigue of approximately 9.35%, 38.75% and 9.65% for the rectus femoris, lateral femoris and gastrocnemius muscles, respectively, when compared to cases without the soft exosuit. The results show that assisted hip flexion during stair climbing is a reasonable approach to effectively reduce metabolic consumption and muscle fatigue.

Stiffness optimization based on muscle fatigue and muscle synergy for passive waist assistive exoskeleton

PurposeThis paper aims to optimize the stiffness coefficient of the elastic element for a passive waist assistive exoskeleton (WAE). There is a tradeoff between stiffness coefficient of elastic element of the exoskeleton and work efficiency of the wearer, because elastic element affects original bending motion of the wearer and the force requirement of erector spinae is compensated by the other muscles. However, there is no accepted conclusion on how to determine the proper stiffness coefficient, especially with respected to the effort of groups of muscles, not only erector spinae.Design/methodology/approachIn this study, a consumption indicator based on muscle fatigue of seven muscles is proposed and a Bayesian-based human-in-the-loop optimization approach is adopted to optimize the stiffness coefficient. Pneumatic artificial muscles are used to replace the mechanical elastic part to adjust the assistive force automatically. The proposed optimization method is verified by the way of load-lifting experiments with three different conditions: without exoskeleton, with fixed air pressure and with optimized air pressure. Six subjects participated in the experiment and each experiment is performed in different day.FindingsCompared with No-Exo condition and static assistance condition, the parameter-optimized waist exoskeleton averagely reduces muscle fatigue of the six subjects by 45.30 ± 29.14% and 30.94 ± 30.29%, respectively. The experimental results indicate that the proposed method is effective to reduce muscle fatigue during stoop lifting task.Originality/valueThis paper provides a novel cost function construction method based on muscle fatigue and muscle synergy for passive WAE stiffness optimization.