Limb Muscle Activity Research Articles

The Effects of Unpowered Soft Exoskeletons on Preferred Gait Features and Resonant Walking

Resonant walking with preferred gait features is a self-optimized consequence of long-term human locomotion. Minimal energy expenditure can be achieved in this resonant condition. This unpowered multi-joint soft exoskeleton is designed to test whether: (1) there is an obvious improvement in preferred speed and other gait features; (2) resonant walking still exists with exoskeleton assistance. Healthy participants (N = 7) were asked to perform the following trials: (1) walking at 1.25 m/s without assistance (normal condition); (2) walking at 1.25 m/s with assistance (general condition); (3) walking at preferred speed with assistance (preferred condition); (4) walking at the speed in trial (3) without assistance (comparison condition). Participants walked at the preferred frequency and ±10% of it. An average 21% increase in preferred speed was observed. The U-shaped oxygen consumption and lower limb muscle activity curve with the minimum at preferred frequency indicated that the resonant condition existed under the preferred condition. Average metabolic reductions of 4.53% and 7.65% were found in the preferred condition compared to the general and comparison condition, respectively. These results demonstrate that the resonant condition in assisted walking could benefit energy expenditure and provide a new perspective for exoskeleton design and evaluation.

Virtual Neuromuscular Control for Robotic Ankle Exoskeleton Standing Balance

The exoskeleton is often regarded as a tool for rehabilitation and assistance of human movement. The control schemes were conventionally implemented by developing accurate physical and kinematic models, which often lack robustness to external variational disturbing forces. This paper presents a virtual neuromuscular control for robotic ankle exoskeleton standing balance. The robustness of the proposed method was improved by applying a specific virtual neuromuscular model to estimate the desired ankle torques for ankle exoskeleton standing balance control. In specialty, the proposed control method has two key components, including musculoskeletal mechanics and neural control. A simple version of the ankle exoskeleton was designed, and three sets of comparative experiments were carried out. The experimentation results demonstrated that the proposed virtual neuromuscular control could effectively reduce the wearer’s lower limb muscle activation, and improve the robustness of the different external disturbances.

Left-Right Locomotor Coordination in Human Neonates.

Terrestrial locomotion requires coordinated bilateral activation of limb muscles, with left-right alternation in walking or running, and synchronous activation in hopping or skipping. The neural mechanisms involved in interlimb coordination at birth are well known in different mammalian species, but less so in humans. Here, 46 neonates (of either sex) performed bilateral and unilateral stepping with one leg blocked in different positions. By recording EMG activities of lower-limb muscles, we observed episodes of left-right alternating or synchronous coordination. In most cases, the frequency of EMG oscillations during sequences of consecutive steps was approximately similar between the two sides, but in some cases it was considerably different, with episodes of 2:1 interlimb coordination and episodes of activity deletions on the blocked side. Hip position of the blocked limb significantly affected ipsilateral, but not contralateral, muscle activities. Thus, hip extension backward engaged hip flexor muscle, and hip flexion engaged hip extensors. Moreover, the sudden release of the blocked limb in the posterior position elicited the immediate initiation of the swing phase of the limb, with hip flexion and a burst of an ankle flexor muscle. Extensor muscles showed load responses at midstance. The variable interlimb coordination and its incomplete sensory modulation suggest that the neonatal locomotor networks do not operate in the same manner as in mature locomotion, also because of the limited cortical control at birth. These neonatal mechanisms share many properties with spinal mammalian preparations (i.e., independent pattern generators for each limb, and for flexor and extensor muscles, load, and hip position feedback).SIGNIFICANCE STATEMENT Bilateral coupling and reciprocal activation of flexor and extensor burst generators represent the fundamental mechanisms used by mammalian limbed locomotion. Considerable progress has been made in deciphering the early development of the spinal networks and left-right coordination in different mammals, but less is known about human newborns. We compared bilateral and unilateral stepping in human neonates, where cortical control is still underdeveloped. We found neonatal mechanisms that share many properties with spinal mammalian preparations (i.e., independent pattern generators for each limb, the independent generators for flexor and extensor muscles, load, and hip-position feedback. The variable interlimb coordination and its incomplete sensory modulation suggest that the human neonatal locomotor networks do not operate in the same manner as in mature locomotion.

Portable Electromyogram-sensitive System for Assessment of Fear of Fall: Relevance of Gait Phases for Post-Stroke Patients.

Post-stroke patients often suffer from gait deficits along with Fear of Fall (FoF) that adversely affect their ambulation. The FoF has been reported to be negatively correlated with one's performance in daily life. Clinical scales, e.g., Falls Efficacy Scale are often used to assess one's FoF. Though powerful, it can suffer from subjectivity. Thus, it is important to have reliable assessment of FoF. Motivated by this, we used one's lower limb muscle activation during specific gait phases to assess one's FoF. For this, we developed a portable electromyogram-sensitive system that can synchronously measure one's muscle activation along with gait phases. We conducted an experimental study with post-stroke patients and age-matched healthy controls who walked under Dual-Task condition. We investigated the lower limb muscle (Gastrocnemius Lateralis (GM) and Tibialis Anterior (TA)) activation during Loading Response, Terminal Stance and Initial Swing phases of gait, associated with slips contributing to FoF. Results show that our system could quantify the disparity (∆) in muscle activation between the affected and unaffected sides of patients (∆ = ∼84% during Loading response for both GM and TA, ~32%for GM during Terminal Stance and TA during Initial Swing) which was considerably higher than that between dominant and non-dominant sides of healthy controls. This might infer reduced dynamic stability of patients leading to their FoF. Also, muscle activation could classify patients from healthy controls with 90% accuracy during Loading Response and Initial Swing phases with clinical relevance in diagnostics and monitoring rehabilitation outcomes. Clinical Relevance- This study indicated that our system has potential to be utilized as a tool for diagnostic and monitoring rehabilitation outcomes as it can quantify the residual muscle ability of the post-stroke patients during gait.

Reliability and Variability of Lower Limb Muscle Activation as Indicators of Familiarity to Submaximal Eccentric Cycling.

Submaximal eccentric (ECC) cycling exercise is commonly used in research studies. No previous study has specified the required time naïve participants take to familiarize with submaximal ECC cycling. Therefore, we designed this study to determine whether critical indicators of cycling reliability and variability stabilize during 15 min of submaximal, semi-recumbent ECC cycling (ECC cycling). Twenty-two participants, aged between 18–51 years, volunteered to complete a single experimental session. Each participant completed three peak eccentric torque protocol (PETP) tests, nine countermovement jumps and 15 min of submaximal (i.e., 10% peak power output produced during the PETP tests) ECC cycling. Muscle activation patterns were recorded from six muscles (rectus femoris, RF; vastus lateralis, VL; vastus medialis, VM; soleus, SOL; medial gastrocnemius, GM; tibialis anterior, TA), during prescribed-intensity ECC cycling, using electromyography (EMG). Minute-to-minute changes in the reliability and variability of EMG patterns were examined using intra-class correlation coefficient (ICC) and variance ratios (VR). Differences between target and actual power output were also used as an indicator of familiarization. Activation patterns for 4/6 muscles (RF, VL, VM and GM) became more consistent over the session, the RF, VL and VM increasing from moderate (ICC = 0.5–0.75) to good (ICC = 0.75–0.9) reliability by the 11th minute of cycling and the GM good reliability from the 1st minute (ICC = 0.79, ICC range = 0.70–0.88). Low variability (VR ≤ 0.40) was maintained for VL, VM and GM from the 8th, 8th and 1st minutes, respectively. We also observed a significant decrease in the difference between actual and target power output (χ2 14 = 30.895, p = 0.006, W = 0.105), expressed primarily between the 2nd and 3rd minute of cycling (Z = -2.677, p = 0.007). Indicators of familiarization during ECC cycling, including deviations from target power output levels and the reliability and variability of muscle activation patterns stabilized within 15 min of cycling. Based upon this data, it would be reasonable for future studies to allocate ∼ 15 min to familiarize naïve participants with a submaximal ECC cycling protocol.

Immediate effect of weight load on lower limb muscle activity and gait ability in patients with incomplete spinal cord injury during walker gait training

Objective Walkers are actively used to improve gait ability in patients with incomplete spinal cord injury (ISCI). This study aimed to investigate the immediate effect of weight load during walker gait training on lower limb muscle activity and gait ability in patients with ISCI using a dependence feedback walker (DFW). Design A single group cross-sectional design. Setting Local rehabilitation hospital. Participants Fourteen patients with ISCI (62.00 years, Onset duration: 20.57months). Interventions The DFW was used to measure the change in lower limb muscle activity and gait ability on walker dependence during the 20-meter walk. Based on the initial measurement of walker dependence, three levels of walker dependence threshold were set (100%, 60%, and 20%). If the weight loaded on the walker exceeded the three threshold levels of walker dependence, auditory and visual feedback was generated. Outcome Measures During the 20-meter walk, changes in both lower limb muscle activity (rectus femoris, biceps femoris, medial gastrocnemius, tibialis anterior, and gluteus medius) and gait ability (velocity, cadence, and single-limb support phase) were measured by surface electromyography and 3-axis accelerometer. Results The increase in lower limb muscle activation and improvement of gait ability were greater during 20% walker dependence gait training than during 100% walker dependence gait training (P < 0.05). Conclusion Reduction of walker dependence by extrinsic feedback generated via DFW during walker gait training may lead to increased lower limb muscle activity and improved gait. These results could be useful for successful self-gait training and improving walking independence in patients with ISCI.

Evaluation of Upper Limb Muscle Activation Using Musculoskeletal Model with Wearable Assistive Device.

In recent years, wearable assistive device has been used to support upper arm movement training for rehabilitation purposes. A wearable assistive device could affect the muscle output during motor tasks to support upper limb disorder rehabilitation training. However, the investigation of muscle activity with the given assistive force is not widely investigated. In this study, the evaluation of upper limb muscle activities using musculoskeletal simulation systems with the developed wearable cable-driven assistive device has been carried out. An experimental protocol consisting of a series of motions was executed with five healthy subjects. Muscle activation on the brachioradialis, biceps, and triceps muscles was measured by using surface electromyography (EMG) and analyzed. The simulations with a musculoskeletal model to estimate muscle output with and without a wearable assistive device were performed for three tasks. An assistive upper arm device was integrated into the musculoskeletal model, and the desired assistive force is translated to the arm joint along with a tendon routing structure. Assisting movement by the wearable device was evaluated by measuring muscle activation with-assist and without-assist conditions. The results show that the use of the wearable assistive device can effectively assist in arm movement. Comparisons of measured EMG muscle data and the musculoskeletal model revealed that muscle force was generated throughout the arm. The integrated musculoskeletal model results show that muscle force values for two primary muscles (biceps and brachioradialis) were reduced during the simulated task when wearing the assistive device. These results are congruent with expectations, with the assistive device that supports the upper limb movement, providing practical assistance. The results highlight the importance of evaluating muscle output for the developed wearable assistive device to support the assistive movement. Lastly, the musculoskeletal simulation system could reduce the resource-intensive, and time consumed with the experimental testing could be achieved.

Effects of Whole-Body Vibration Training with Different Body Positions and Amplitudes on Lower Limb Muscle Activity in Middle-Aged and Older Women

PurposeThe present study was designed to investigate the electromyographic (EMG) response in leg muscles to whole-body vibration while using different body positions and vibration amplitudes.Methods:An experimental study with repeated measures design involved a group of community-dwelling middle-aged and older women (n = 15; mean age=60.8 ± 4.18 years). Muscle activity of the gluteus maximus (GM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and gastrocnemius (GS) was measured by surface electromyography, which participants were performing three different body positions during three WBV amplitudes. The body positions included static semi-squat, static semi-squat with elastic band loading, and dynamic semi-squat. Vibration stimuli tested were 0 mm, 2 mm, and 4 mm amplitude and 30 Hz frequencies. And the maximum accelerations produced by vibration stimuli with amplitudes of 2 mm and 4 mm are approximately 1.83 g and 3.17 g.Results:Significantly greater muscle activity was recorded in VL, BF, and GS. When WBV was applied to training, compared with the same training without WBV (P < .05). There were significant main effects of body positions on EMGrms for the GM, RF, and VM (P < .05). Compared to static semi-squat, static semi-squat with elastic band significantly increased the EMGrms of GM, and dynamic semi-squat significantly increased the EMGrms of GM, RF and VM (P < .05). And there were significant main effects of amplitudes on EMGrms for the GM, RF, and VM (P < .05). The EMGrms of the VL, BF, and GS at 4 mm were significantly higher than 0 mm, and the EMGrms of the VL and BF at 4 mm were significantly higher than 2 mm. There was no significant body interaction between body positions and amplitudes (P > .05).Conclusions:The EMG amplitudes of most leg muscles tested were significantly greater during WBV exposure than in the no-WBV condition. The dynamic semi-squat 4 mm whole-body vibration training is recommended for middle-aged and older women to improve lower limb muscle strength and function.

Prediction of leg muscle activities from arm muscle activities in arm and leg cycling.

Functional electrical stimulation (FES) driven leg cycling is usually controlled by previously established stimulation patterns. We investigated the potential utilization of a particular computational method for controlling electrical stimulation of lower limb muscles by real-time electromyography (EMG) signals of arm muscles during hybrid arm and leg cycling. In hybrid arm and leg cycling, arm cranking is performed voluntarily, while leg cycling is driven by FES. In this study, we investigate arm and leg cycling movements of able-bodied persons when both arm and leg cycling is performed voluntarily without FES. We present a neural network-based model in which the input of the neural network is given by a time series of upper limb muscle activities (EMG), and the output provides potential lower limb muscle activities. The particular neural network was a nonlinear autoregressive exogen (NARX) neural network. The measured EMG signals of the lower limb muscles were compared to the signals that were predicted by the neural network. The neural network was trained with data recorded from four participants. Our preliminary results show notable differences between the predicted and the experimentally measured lower limb muscle activities. The prediction was good only for 60% of the movement time. We conclude that-while including arm cycling in the movement-simpler control modalities or further consideration of applying machine-learning techniques has to be taken into account to improve voluntary upper limb-controlled FES assisted leg cycling.

Whole Body Vibration on the Neuromuscular Performance of Elderls: Randomized Controlled Trial

Objective The main purpose of this study was to evaluate the effects of exercising on a vibratory platform on older adults’ lower limb performance, muscle activation and balance. Design A total of 44 volunteers exercised on a vibratory platform. For half of them (random assignment), the platform vibrated at 40 Hz with 4 mm displacements and for the other half, the platform was off. Lower limb isokinetic performance, neuromuscular activity and balance were assessed before and after exercise protocol. Results A significant increase was observed in 3 of the 4 dynamometric variables evaluated along with increased soleus muscle activation, with no difference between the groups. Conclusion Squatting exercises had immediate effects on neuromuscular performance, muscle activation and balance. However, whole body vibration did not magnify the effects of squatting exercises on older adults. Clinical Trials NCT03356418.

Attenuation of Muscle Damage, Structural Abnormalities, and Physical Activity in Respiratory and Limb Muscles following Treatment with Rucaparib in Lung Cancer Cachexia Mice.

Simple SummaryMuscle wasting and cachexia are common in patients with cancer. Several mechanisms underlie muscle physiological and structural alterations in cancer-induced cachexia. Poly (ADPribose) polymerases (PARPs) are involved in muscle metabolism and in cancer. Selective inhibitors of PARP activity improve muscle function and structure. This study sought to investigate whether rucaparib (PARP inhibitor) may attenuate muscle damage in a mouse model of lung-cancer-induced cachexia. Rucaparib was administered to cancer-cachectic mice. Physiological and biological parameters were determined in the respiratory and limb muscles of the animals. In cancer cachexia mice compared to non-cachexia controls, body weight and body weight gain, muscle weight, limb strength, physical activity, and muscle fiber size significantly declined, while levels of PARP activity, plasma troponin I, muscle damage, and proteolytic and autophagy markers increased. Treatment with rucaparib elicited a significant improvement in body weight gain, tumor size and weight, physical activity, muscle damage, troponin I, and proteolytic and autophagy levels.Overactivation of poly (ADPribose) polymerases (PARPs) is involved in cancer-induced cachexia. We hypothesized that the PARP inhibitor rucaparib may improve muscle mass and reduce damage in cancer cachexia mice. In mouse diaphragm and gastrocnemius (LP07 lung adenocarcinoma) treated with PARP inhibitor (rucaparib,150 mg/kg body weight/24 h for 20 days) and in non-tumor control animals, body, muscle, and tumor weights; tumor area; limb muscle strength; physical activity; muscle structural abnormalities, damage, and phenotype; PARP activity; and proteolytic and autophagy markers were quantified. In cancer cachexia mice compared to non-cachexia controls, body weight and body weight gain, muscle weight, limb strength, physical activity, and muscle fiber size significantly declined, while levels of PARP activity, plasma troponin I, muscle damage, and proteolytic and autophagy markers increased. Treatment with the PARP inhibitor rucaparib elicited a significant improvement in body weight gain, tumor size and weight, physical activity, muscle damage, troponin I, and proteolytic and autophagy levels. PARP pharmacological inhibition did not exert any significant improvements in muscle weight, fiber size, or limb muscle strength. Treatment with rucaparib, however, improved muscle damage and structural abnormalities and physical activity in cancer cachexia mice. These findings suggest that rucaparib exerts its beneficial effects on cancer cachexia performance through the restoration of muscle structure.

Effects of Noisy Galvanic Vestibular Stimulation on the Muscle Activity and Joint Movements in Different Standing Postures Conditions.

ObjectiveNoisy galvanic vestibular stimulation (nGVS) is an effective method for stabilizing posture; however, little is known regarding the detailed muscle activity and joint movement in the standing posture. This study aimed to clarify the changes in the lower limb muscle activity and joint angular velocity by nGVS intervention using the simultaneous assessment method of inertial measurement units and surface electromyography (EMG).MethodsSeventeen healthy participants were assessed for their physical responses under four conditions (standing on a firm surface with eyes-open/eyes-closed, and a foam surface with eyes-open/eyes-closed) without stimulation (baseline) and with stimulation (sham or nGVS). Noise stimuli were applied for 30 s at a level below the perceptual threshold. The body control response was evaluated using EMG activity and angular velocity of the lower limbs.ResultRegarding the change from baseline for each parameter, there was a significant interactive effect of EMG activity in the muscle type × intervention and EMG activity and angular velocity in the condition × intervention. Post hoc analysis revealed that the angular velocity was significantly decreased in the abduction-adduction direction in the standing on a foam surface with eyes-closed condition compared to that with eyes-open in the nGVS intervention.ConclusionOur results suggest that nGVS altered physical responses in different standing postural conditions. The present study is exploratory and therefore the evidence should be investigated in future studies specifically target those muscle activities and joint motion parameters.

Hardware Circuits Design and Performance Evaluation of a Soft Lower Limb Exoskeleton.

Soft lower limb exoskeletons (LLEs) are wearable devices that have good potential in walking rehabilitation and augmentation. While a few studies focused on the structure design and assistance force optimization of the soft LLEs, rarely work has been conducted on the hardware circuits design. The main purpose of this work is to present a new soft LLE for walking efficiency improvement and introduce its hardware circuits design. A soft LLE for hip flexion assistance and a hardware circuits system with scalability were proposed. To assess the efficacy of the soft LLE, the experimental tests that evaluate the sensor data acquisition, force tracking performance, lower limb muscle activity and metabolic cost were conducted. The time error in the peak assistance force was just 1%. The reduction in the normalized root-mean-square EMG of the rectus femoris was 7.1%. The net metabolic cost in exoskeleton on condition was reduced by 7.8% relative to walking with no exoskeleton. The results show that the designed hardware circuits can be applied to the soft LLE and the soft LLE is able to improve walking efficiency of wearers.

Sex influence on muscle synergies in a ballistic force-velocity test during the delayed recovery phase after a graded endurance run

The acute and delayed phases of the functional recovery pattern after running exercise have been studied mainly in men. However, it seems that women are less fatigable and/or recover faster than men, at least when tested in isometric condition. After a 20 km graded running race, the influence of sex on the delayed phase of recovery at 2–4 days was studied using a horizontal ballistic force-velocity test. Nine female and height male recreational runners performed maximal concentric push-offs at four load levels a week before the race (PRE), 2 and 4 days (D2 and D4) later. Ground reaction forces and surface electromyographic (EMG) activity from 8 major lower limb muscles were recorded. For each session, the mechanical force-velocity-power profile (i.e. theoretical maximal values of force (F¯ 0), velocity (V¯ 0), and power (P¯ max)) was computed. Mean EMG activity of each recorded muscle and muscle synergies (three for both men and women) were extracted. Independently of the testing sessions, men and women differed regarding the solicitation of the bi-articular thigh muscles (medial hamstring muscles and rectus femoris). At mid-push-off, female made use of more evenly distributed lower limb muscle activities than men. No fatigue effect was found for both sexes when looking at the mean ground reaction forces. However, the force-velocity profile varied by sex throughout the recovery: only men showed a decrease of both V¯ 0 (p < 0.05) and P¯ max (p < 0.01) at D2 compared to PRE. Vastus medialis activity was reduced for both men and women up to D4, but only male synergies were impacted at D2: the center of activity of the first and second synergies was reached later. This study suggests that women could recover earlier in a dynamic multi-joint task and that sex-specific organization of muscle synergies may have contributed to their different recovery times after such a race.

Brain and muscle activation patterns during postural control affect static postural control

BackgroundPrevious studies have reported existence of coordinated brain and muscle activity patterns that affect postural control. However, differences in these activity patterns that affect postural control are still unclear. The purpose of this study was to clarify brain and muscle activity pattern affecting postural control. Research questionDoes the difference in brain and muscle activity patterns during postural control affect postural control ability? MethodNineteen healthy men (mean age: 24.8 ± 4.1 years, height: 171.8 ± 5.5 cm, and weight: 63.5 ± 12.5 kg) performed a postural control task on a balance board, and their brain and muscle activities and body sway during the task were measured using functional near-infrared spectroscopy, surface electromyography, and three-dimensional accelerometry. Hierarchical cluster analysis was conducted to extract subgroups based on brain and muscle activities and postural control, and correlation analysis was performed to investigate the relationship between brain activity, muscle activity, and postural control. ResultsTwo subgroups were found. Subgroup 1 (n = 9) showed higher brain activity in the supplementary motor area (p = 0.04), primary motor cortex (p = 0.04) and stable postural control in the mediolateral (p < 0.01) planes, and subgroup 2 (n = 10) showed higher muscle activity in the tibialis anterior (p < 0.01), a higher shank muscles co-contraction (p = 0.02) and unstable postural control. Furthermore, the supplementary motor area activity is negatively correlated with body sway of mediolateral plane (r = −0.51, p = 0.02), and tibialis anterior activity is positively correlated with body sway on the mediolateral plane (r = 0.62, p = 0.004). SignificanceHigher brain activity in motor-related areas, lower activity in the lower limb muscles and lower co-contraction of shank muscles were observed in stable postural control. These results will facilitate the planning of new rehabilitation methods for improving postural control ability.

Comparison of Lower Limb Muscle Activation Patterns in Different Foot Structures using Voluntary Response Index: A Study Protocol

Background: Structural foot disorders can widely contribute to lower limb musculoskeletal conditions. Some researchers consider them the origin of overuse injuries in lower limbs. Although their effects on electrical activities of intrinsic and extrinsic foot muscles are well-established, their impact on other lower limb muscle groups are yet to be clarified.&#x0D; Objectives: This study aims to identify the activation patterns of lower limb muscle groups in various foot structures.&#x0D; Materials and Methods: In this case control study, 45 asymptomatic male and female subjects with different foot structures (pronated, supinated, and normal) will be selected using non-random sampling. The electrical activities of the gluteus medius, vastus lateralis and medialis, biceps femoris, semitendinosus, and lateral and medial gastrocnemius muscles will be examined during a jump-landing task. Voluntary response index, including magnitude and similarity index, will be subsequently calculated.&#x0D; Discussion: While several studies have evaluated the activation of lower limb muscles in different foot structures, they have solely focused on foot muscles. In contrast, the present study will assess activation patterns of the global lower limb muscles using the voluntary response index.

Temporal differences in the myoelectric activity of lower limb muscles during rearfoot and forefoot running: A statistical parametric mapping approach

The aim of this study was to apply statistical parametric mapping (SPM) to compare temporal changes in EMG amplitude between rearfoot (RF) and forefoot (FF) running techniques. Eleven recreational runners ran on a treadmill at a self-selected speed, once using a RF strike pattern and once using a FF strike pattern (randomized order). The myoelectric activity of five lower limb muscles [rectus femoris (RFe), biceps femoris (BF), tibialis anterior (TA), medial and lateral gastrocnemius (MG and LG)] was evaluated, using bipolar electromyography (EMG). EMG data from the RF and FF running techniques was then processed and posteriorly compared with SPM, dividing the analysis of the running cycle into stance and swing phases. The MG and LG muscles showed higher activation during FF running at the beginning of the stance phase and at the end of the swing phase. During the end of the swing phase the TA muscle’s EMG amplitude was higher, when the RF running technique was used. A higher level of co-activation between the gastrocnemius and TA muscles was observed at the end of the swing phase during RF running. The myoelectric behaviour of the RFe and BF muscles was similar during both running techniques. These findings highlight the importance of SPM for the accurate assessment of differences in muscle activity during running and strongly suggest that these two running techniques predominately reflect adjustments of the leg and not the thigh muscles.

Providing physical relief for nurses by collaborative robotics

Manual patient handling is one of the most significant challenges leading to musculoskeletal burden among healthcare workers. Traditional working techniques could be enhanced by innovations that can be individually adapted to the physical capacity of nurses. We evaluated the use of a robotic system providing physical relief by collaboratively assisting nurses in manual patient handling tasks. By quantifying kinetic and muscle activity data, it was possible to distinguish two kinds of movement patterns. Highly asymmetric postures and movements corresponded to distinct extremes in lower limb and spine muscle activity data. The use of collaborative robotics significantly reduced maximum force exertion in the caregiving process by up to 51%. Lateral flexion and torsion of the trunk were reduced by up to 54% and 87%, respectively, leading to a significant reduction in mean spine muscle activity of up to 55%. These findings indicate the feasibility of collaborative robot-assisted patient handling and emphasize the need for future individual intervention programs to prevent physical burden in care.

The impacts of surgical mask in young healthy subjects on cardiopulmonary function and muscle performance: a randomized crossover trial

ObjectiveTo explore the impacts of surgical mask in normal subjects on cardiopulmonary function and muscle performance under different motor load and gender differences.DesignRandomized crossover trial.SettingThe Fifth Affiliated Hospital of Guangzhou Medical University, June 16th to December 30th, 2020.ParticipantsThirty-one college students (age: male 21.27 ± 1.22 years; female 21.31 ± 0.79 years) were recruited and randomly allocated in two groups.InterventionsGroup 1 first received CPET in the mask-on condition followed by 48 h of washout, and then received CPET in the mask-off condition. Group 2 first received CPET in the mask-off condition followed by 48 h of washout, then received CPET in the mask-on condition. The sEMG data were simultaneously collected.Main outcome measuresThe primary outcome was maximum oxygen uptake (VO2 max) from CPET, which was performed on a cycle ergometer—this is the most important parameter associated with an individual’s physical conditioning. The secondary parameters included parameters reflecting exercise tolerance and heart function (oxygen uptake, anaerobic valve, maximum oxygen pulse, heart rate reserve), parameters reflecting ventilation function (respiration reserve, ventilation volume, tidal volume, breathing frequency), parameters reflecting gas exchange (end-tidal oxygen and carbon dioxide partial pressure, oxygen equivalent, carbon dioxide equivalent, and the relationship between dead space and tidal volume) and parameters reflecting skeletal muscle function [oxygen uptake, anaerobic valve, work efficiency, and EMG parameters including root mean square (RMS)].ResultsComparing the mask-on and mask-off condition, wearing surgical mask had some negative effects on VO2/kg (peak) and ventilation (peak) in both male and female health subjects [VO2/kg (peak): 28.65 ± 3.53 vs 33.22 ± 4.31 (P = 0.001) and 22.54 ± 3.87 vs 26.61 ± 4.03 (P < 0.001) ml/min/kg in male and female respectively; ventilation (peak): 71.59 ± 16.83 vs 82.02 ± 17.01 (P = 0.015) and 42.46 ± 10.09 vs 53.95 ± 10.33 (P < 0.001) liter in male and female respectively], although, based on self-rated scales, there was no difference in subjective feelings when comparing the mask-off and mask-on condition. Wearing surgical masks showed greater lower limb muscle activity just in male subjects [mean RMS of vastus medialis (load): 65.36 ± 15.15 vs 76.46 ± 19.04 μV, P = 0.031]. Moreover, wearing surgical masks produced a greater decrease in △tidal volume (VTpeak) during intensive exercises phase in male subjects than in female [male − 0.80 ± 0.15 vs female − 0.62 ± 0.11 l P = 0.001].ConclusionsWearing medical/surgical mask showed a negative impact on the ventilation function in young healthy subjects during CPET, especially in high-intensity phase. Moreover, some negative effects were found both in ventilation and lower limb muscle actives in male young subjects during mask-on condition. Future studies should focus on the subjects with cardiopulmonary diseases to explore the effect of wearing mask.Trial registrationChinese Clinical Trial Registry (ChiCTR2000033449).

Robotic upright stand trainer (RobUST) and postural control in individuals with spinal cord injury

Context/objective: Assessed feasibility and potential effectiveness of using a novel robotic upright stand trainer (RobUST) to deliver postural perturbations or provide assistance-as-needed at the trunk while individuals with spinal cord injury (SCI) performed stable standing and self-initiated trunk movements. These tasks were assessed with research participants’ hands on handlebars for self-balance assistance (hands on) and with hands off (free hands). Design: Proof of concept study. Participants: Four individuals with motor complete (n = 3) or incomplete (n = 1) SCI who were not able to achieve independent standing and presented a neurological lesion level ranging from cervical 4 to thoracic 2. Outcome measures: Ground reaction forces, trunk displacement, and electromyography activity of trunk and lower limb muscles. Results: Research participants received continuous pelvic assistance via RobUST, and manual trainer assistance at the knees to maintain standing. Participants were able to attempt all tasks. Free hands trunk perturbations resulted in greater load bearing-related sensory information (73% ipsilateral vertical loading), trunk displacement (57%), and muscle activation compared to hands on. Similarly, free hands stable standing with RobUST assistance-as-needed resulted in 8.5% larger bodyweight bearing, 112% larger trunk movement velocity, and higher trunk muscles activation compared to standing with hands on. Self-initiated trunk movements controlled by hands on showed 116% greater trunk displacement, 10% greater vertical ground reaction force, and greater ankle muscle activation compared to free hands. Conclusion: RobUST established a safe and challenging standing environment for individuals with SCI and has the potential to improve training paradigms and assessments of standing postural control.