Limb Position Research Articles

Heteronymous feedback from quadriceps onto soleus is influenced by limb loading and task context.

Heteronymous reflexes from quadriceps can increase and/or decrease soleus activity; yet few studies have examined factors influencing reflex strength. This study examined the independent influence of limb loading, posture, and task context on heteronymous feedback from quadriceps onto soleus. The influence of limb loading and posture was determined by comparing femoral nerve elicited heteronymous excitation and inhibition of soleus in a semi-recumbent position with and without 50% body weight limb loading and while standing with back support (n = 16). Task context was examined by comparing heteronymous reflex magnitudes while standing with back support to maintaining an unsupported squat posture which requires tonic soleus activity to maintain the posture (n = 12). Heteronymous inhibition decreased by 20% with limb loading in both semi-recumbent and standing postures, while excitation remained unchanged suggesting that limb loading, rather than postural orientation, independently modulates heteronymous inhibition. Inhibition decreased by 50% and excitation by 90% when maintaining the squat posture compared to supported standing, The pronounced suppression of both excitation and inhibition during the squat is considered a task-appropriate reflex modulation that aids in maintaining the posture. The results of this study highlight an important modulatory influence of limb loading afferents and task context on heteronymous reflex circuits.

Upper Crossed Syndrome and Scapulae Upper-Trapping: A Mesotherapy Protocol in Cervicoscapulobrachial Pain-The 8:1 Block.

Upper Crossed Syndrome (UCS), described by Vladimir Janda, is characterized by postural changes involving the cervical spine and trunk, leading to biomechanical limitations and cervicoscapulobrachial pain. This study proposes a mesotherapy protocol, termed the 8:1 block, to address cervicoscapulobrachialgia by targeting the scapulae and associated musculature. The scapula, central to shoulder girdle kinematics, often exhibits dyskinesis and muscular imbalances, notably the pattern referred to as scapular upper trapping (SUT). SUT involves scapular elevation, medial rotation, and shoulder protraction, contributing to cervicobrachial pain. The protocol includes a comprehensive assessment of muscle tone changes and biomechanical considerations, highlighting the importance of the scapula in upper limb movement and posture. Key anatomical changes involve tightened upper trapezius, levator scapulae, and pectoralis minor muscles, with weakened middle trapezius and serratus anterior. The mesotherapy approach targets these imbalances through specific injection points to alleviate muscle tension and correct postural deviations. Case studies from our clinic demonstrate the protocol's effectiveness in reducing pain and restoring scapular biomechanics. Patients reported significant improvements in pain relief and functional outcomes, underscoring the clinical utility of the 8:1 block in treating cervicoscapulobrachialgia. This protocol offers a feasible, cost-effective intervention that enhances the efficacy of traditional therapeutic exercises by addressing underlying muscular and biomechanical dysfunctions. In conclusion, the 8:1 block mesotherapy protocol provides a novel approach to managing cervicoscapulobrachial pain by focusing on scapular biomechanics and muscle tension. Further studies are needed to validate these findings and refine the protocol for broader clinical application.

Key point trajectory prediction method of human stochastic posture falls

ABSTRACT The human body will show very complex and diversified posture changes in the process of falling, including body posture, limb position, angle and movement trajectory, etc. The coordinates of the key points of the model are mapped to the three-dimensional space to form a three-dimensional model and obtain the three-dimensional coordinates of the key points; The construction decomposition method is used to calculate the rotation matrix of each key point, and the rotation matrix is solved to obtain the angular displacement data of the key points on different degrees of freedom. The method of curve fitting combined with the weight distribution kernel function based on self-organizing mapping theory is used to obtain the motion trajectory prediction equation of the human body falling in different degrees of freedom at random positions in three-dimensional space, determine the key point trajectory of human random fall behaviour. The experimental results show that the mapped 3D model is consistent with the real human body structure. This method can accurately determine whether the human body falls or squats randomly, and the prediction results of the key points of the human fall are consistent with the actions of the human body after the fall.

Human Muscle Inspired Anisotropic and Dynamic Metal Ion-Coordinated Mechanically Robust, Stretchable and Swelling-Resistant Hydrogels for Underwater Motion Sensing and Flexible Supercapacitor Application.

Mechanically robust and anisotropic conductive hydrogels have emerged as crucial components in the field of flexible electronic devices, since they possess high mechanical properties and intelligent sensing capabilities. However, the hydrogels often swell on exposure to aqueous medium because of their hydrophilicity, which compromises their mechanical properties. Additionally, the hydrogels' isotropic polymeric networks demonstrate isotropic ion transport, which significantly diminishes the sensing capabilities of electrical devices based on hydrogels. These factors greatly limit their use in flexible and wearable sensors. In this study, we have developed poly(acrylamide-co-maleic acid-co-butyl acrylate) based anisotropic hydrogels by prestretching and drying, followed by ionic cross-linking to fix the alignment. The anisotropic arrangement of the polymer network resulted in significant improvements in mechanical performance and electrical conductivity along the prestretching direction. This anisotropic hydrogel combines hydrophobic and metal ion-ligand interactions, enhancing the maximum tensile strength up to 11 MPa along the prestretching direction, about 3 times higher than in the perpendicular direction. The optimized 200% prestretched hydrogel exhibited high tensile strength (7 MPa), flexibility (fracture strain 370%), high toughness (16 MJ m-3) and antiswelling behavior in water (equilibrium swelling ratio 2% after 15 days). alongside higher conductivity (3 times higher) and strain sensing ability (4 times higher gauge factor) along the prestretching direction. The hydrogel demonstrated efficient and stable underwater sensing for underwater communication and to monitor human limb position and movement. The anisotropic hydrogel electrolyte-based flexible supercapacitor exhibited 117 Fg-1 specific capacitance at 0.5 Ag-1, and maximum energy density 5.85 Whkg-1, significantly higher than the corresponding values for the isotropic hydrogel-based device (88 F g-1 and 4.4 Whkg-1, respectively). This hydrogel mimics the structural design of unidirectionally oriented muscle fibers, showing better direction dependent functional properties than the corresponding isotropic hydrogel. The anti-swelling ability and retention of mechanical and conductive properties of these hydrogels in aqueous environment suggest long-term usage capability of these functional materials.

Effect of Soft Knee Brace on Shank Movement in Running

Background: Soft knee braces are used for the protection and treatment of knee injuries in light-intensity activities of daily life. Soft knee braces have several functions, such as stabilizing and supporting the lower limb posture. However, previous studies did not investigate the effects of a soft knee brace on the lower limbs during vigorous-intensity activities. Aims: The objective of this study was to investigate the effect of a soft knee brace on the physical load and stability of the lower limb during running as a vigorous-intensity activity. Methods: Participants were asked to run with or without a soft knee brace, and lower-limb movements during running were measured using an inertial sensor on the shank. Results: The result showed that soft knee brace significantly reduced the magnitude and mediolateral standard deviation of shank acceleration. Conclusion: The results of this study indicate the possibility that wearing a soft knee brace can improve the physical load and stability of the lower limbs during running.

Functional outcome of mirror therapy versus task oriented training on hand function in children with unilateral cerebral palsy

Background. Unilateral cerebral palsy (UCP) is a kind of spastic cerebral palsy which is characterized by atypical posture of upper limb, poor eye-hand coordination, and reduced hand skills. These symptoms can restrict a child’s ability to engage in life activities. Purpose. To compare the effectiveness of mirror therapy as well as task-oriented training on hand functions improvement among UCP children. Methods. Sixty children suffering from UCP were randomly allocated into three equal groups. A schemed physical therapy protocol was utilized to the control, mirror therapy (MT), and task-oriented training (TOT) groups. The protocols of mirror therapy and task-oriented training were administered to MT and TOT groups respectively. Assessments of upper extremity skills, hand dexterity, wrist extension range of motion, along with overall grip strength were conducted at baseline and after intervention using the Quality of Upper Extremity Skills Test (QUEST), Box and Block Test (BBT), universal goniometer, as well as pneumatic squeeze handheld dynamometer respectively. Throughout a total of twelve consecutive weeks, the intervention session was held three days a week. Results. The change amount in all measured hand outcomes were significantly improved following the intervention in all three groups, with the TOT group showing a larger significant effect. Conclusion. Task-oriented training had superior impact than mirror therapy in enhancing hand functions among children having UCP.

Late acquisition of erect hindlimb posture and function in the forerunners of therian mammals.

The evolutionary transition from early synapsids to therian mammals involved profound reorganization in locomotor anatomy and function, centered around a shift from "sprawled" to "erect" limb postures. When and how this functional shift was accomplished has remained difficult to decipher from the fossil record alone. Through biomechanical modeling of hindlimb force-generating performance in eight exemplar fossil synapsids, we demonstrate that the erect locomotor regime typifying modern therians did not evolve until just before crown Theria. Modeling also identifies a transient phase of increased performance in therapsids and early cynodonts, before crown mammals. Further, quantifying the global actions of major hip muscle groups indicates a protracted juxtaposition of functional redeployment and conservatism, highlighting the intricate interplay between anatomical reorganization and function across postural transitions. We infer a complex history of synapsid locomotor evolution and suggest that major evolutionary transitions between contrasting locomotor behaviors may follow highly nonlinear trajectories.

Effect of limb position change on capsaicin-evoked pain: Evidence of interplays between the vascular and nociceptive systems?

This experiment aimed at confirming our incidental observation that, when capsaicin is applied on the volar forearm, raising the arm to a vertical position leads to a dramatic increase in capsaicin-evoked pain and to explore possible underlying mechanisms. Twenty healthy volunteers received a 2% capsaicin patch on one forearm and a vehicle patch on the other. Patches were kept in place for 60 min. The perception caused by the patch was assessed repeatedly before, during and after patch application, both with the arm in horizontal resting position and raised vertically. In addition, capsaicin-induced secondary hyperalgesia was assessed using mechanical pinprick stimuli. Half of the participants were seated upright while the other half were lying supine, to assess whether the effect of limb position on capsaicin-evoked pain was due to gravity. After a few minutes of patch application, raising the capsaicin-treated arm (but not the vehicle-treated arm) led to a strong increase of the pain experienced at the patch. This effect of raising the arm did not differ between participants in the supine and seated groups and is therefore likely related to the position of the arm relative to the ground rather than to the body. Mechanical secondary hyperalgesia and the arm raising effect were strongly decorrelated at the last time point after patch removal, indicating different underlying mechanisms. Our results indicate that capsaicin-evoked pain can be strongly modulated by limb posture and that this effect may be caused by an interplay between vascular and nociceptive systems. Capsaicin-evoked pain can be strongly modulated by limb posture and this effect may be caused by an interplay between vascular and nociceptive systems.

Correlation between physical activity and anthropometric measurements among children and adolescents

ObjectivesThe purpose of this study was to measure the association between the level of physical activity and sedentary conditions with anthropometric measurements of children and adolescents. MethodsThis cross-sectional descriptive study consisted of a convenience sample of 400 children and adolescents from public schools in Itapevi-SP, Brazil. The Physical Activity Checklist Interview or LAF “Lista de Atividades Físicas” in a Brazilian version, was administered in a face-to-face interview on a school day and allowed assessment of sedentary behavior and physical activity on the previous day. Anthropometric measurements included body weight, sex, age, and lower limb posture. The participants were photographed in the frontal and sagittal planes, and the photos were analyzed using postural assessment software (PAS/SAPO). Pearson's tests were applied to analyze correlations. ResultsChildren and adolescents show a greater tendency toward valgus knees with increasing body mass (r = ‒0.33). On average, girls have a larger Q angle. Ankles are less likely to become valgus with increasing age and mass (r = ‒0.18 and ‒0.23, respectively). The horizontal alignment of the pelvis is mostly in anteversion with a significant increase with age (r = 0.27) and a slight increase with mass (r = 0.15). The knee and ankle tend to be less hyperextended and more dorsiflexed from the age of 10, with no correlation with the other variables. It was not possible to observe a clear relationship between the time spent in physical activity and sedentary behavior and the postural angles mentioned above. ConclusionAlthough correlations were found between age, sex and body mass, and postural angles, notably pelvis alignment, Q angle, knee, ankle, sex, and body weight, there was no correlation between the time spent in physical activity, sedentary behavior, and lower limb posture.

Beyond balance: The role of the Vestibular system in action recognition

BackgroundAction recognition is a fundamental aspect of human interaction. This process is mediated by the activation of shared sensorimotor representations during action execution and observation. Although complex movements involving balance or head and trunk rotations require vestibular signals for effective execution, their role in the recognition of others' actions is still unknown. ObjectiveTo investigate the causal involvement of the vestibular system in the discrimination of actions performed by others and whether this is influenced by motor familiarity. MethodsIn a single-blind design involving 25 healthy participants, Galvanic Vestibular Stimulation (GVS) was administered during an Action Discrimination Task (ADT), in which videos of actions categorized as vestibular/non-vestibular and familiar/unfamiliar were presented. Following each video, participants were required to identify the climax of the previously viewed action between two image options, using a two-alternative forced choice paradigm. The ADT was performed in active and sham GVS conditions, with left or right anodal montages. Response Times (RTs), Accuracy, and subjective motor familiarity were recorded for each action category. ResultsIn sham GVS condition, an overall familiarity effect was observed, where RTs for familiar actions were faster than RTs for unfamiliar ones, regardless of vestibular engagement (p < .001; ηp2 = .80). Conversely, under active GVS, a selective interference of the identification of vestibular familiar actions was observed compared to sham. Specifically, GVS prolonged RTs for recognizing familiar vestibular actions (p = .004, d = .59) while concurrently enhancing visual sensitivity (d’) for the same actions (p = .03, r = .21). ConclusionThese findings demonstrate the contribution of the vestibular system to action recognition. GVS disrupted the sensorimotor representation of vestibular actions and led to increased reliance on an alternative processing system focused on visual analysis of limb positions. This dissociation provides valuable insights for future investigations into the complex relationship between vestibular signals and cognitive processes involved in action identification, essential for developing innovative GVS interventions, particularly for individuals with sensorimotor or vestibular disorders.

The Mcgregor Pedicled Groin Flap for Hand Skin Defects

The groin flap is a surgical method used to cover soft tissue defects in the hand and forearm, such as wounds, traumatic amputations, degloving injuries, burns, burn scar release, and tumor excision. It is effective in covering extensive and intricate defects, such as wounds, traumatic amputations, degloving injuries, burns, burn scar release, and tumor excision. The procedure involves a remote autoplasty supported by the vascular territory of the superficial iliac circumflex artery. The flap's boundaries are defined using the "2 fingers width" criterion, and the flap is raised from lateral to medial, transferring subcutaneous tissue while keeping it above the fascia. The flap is closed using drain suction, and the patient is allowed to walk on the 5th day after surgery. Effective preoperative planning is essential for preventing the creation of too big or too tiny flaps and ensuring the fabrication of appropriate tubing to avoid complications. The McGregor groin flap is a commonly used technique for hand deformity reconstruction due to its extended pedicle and quick execution. It is adaptable, repeatable, and can be performed by less-experienced surgeons without microsurgery expertise. The flap covers significant tissue loss with pliable tissue, making it suitable for joints. It can cover abnormalities on the back or palm, and can be used for early wrist and hand rehabilitation. However, it has drawbacks, such as shoulder stiffness in older patients, discomfort during the upper limb positioning, and the need for multiple phases. Despite these, the groin flap remains relevant in the age of microsurgery and can be improved with technical modifications.

Local muscle pressure stimulates the principal receptors for proprioception

Proprioception plays a crucial role in motor coordination and self-perception. Muscle spindles are the principal receptors for proprioception. They are believed to encode muscle stretch and signal limb position and velocity. Here, we applied percutaneous pressure to a small area of extensor muscles at the forearm while recording spindle afferent responses, skeletal muscle activity, and hand kinematics. Three levels of sustained pressure were applied on the spindle-bearing muscle when the hand was relaxed and immobile ("isometric" condition) and when the participant's hand moved rhythmically at the wrist. As hypothesized to occur due to compression of the spindle capsule, we show that muscle pressure is an "adequate" stimulus for human spindles in isometric conditions and that pressure enhances spindle responses during stretch. Interestingly, release of sustained pressure in isometric conditions lowered spindle firing below baseline rates. Our findings urge a re-evaluation of muscle proprioception in sensorimotor function and various neuromuscular pathologies.

Classification of upper limb spasticity patterns in patients with multiple sclerosis: a pilot observational study.

The aim of this study was to provide a classification of the upper limb patterns in patients with upper limb spasticity due to multiple sclerosis. Pilot observational study. Twenty-five adult patients with multiple sclerosis suffering from upper limb spasticity who underwent one segmental (i.e., proximal and distal upper limb) botulinum toxin treatment cycle were recruited. Patients remained in a sitting position during the evaluation. Upper limb spasticity postures (i.e., postural attitude of a single joint/anatomical region) were evaluated and recorded for the shoulder (adducted/internally rotated), elbow (flexed/extended), forearm (pronated/supinated/neutral), wrist (flexed/extended/neutral) and hand (fingers flexed/thumb in palm). On the basis of the clinical observations, 6patterns (i.e., sets of limb postures) of upper limb spasticity have been described according to the postures of the shoulder, elbow, forearm, and wrist. The patterns of upper limb spasticity in patients with multiple sclerosis described by this pilot study do not completely overlap with those observed in patients with post-stroke spasticity. This further supports the need to consider the features of spasticity related to its aetiology in order to manage patients appropriately.

Abnormal lower limb posture recognition based on spatial gait feature dynamic threshold detection

Lower limb rehabilitation training often involves the use of assistive standing devices. However, elderly individuals frequently experience reduced exercise effectiveness or suffer muscle injuries when utilizing these devices. The ability to recognize abnormal lower limb postures can significantly enhance training efficiency and minimize the risk of injury. To address this, we propose a model based on dynamic threshold detection of spatial gait features to identify such abnormal postures. A human-assisted standing rehabilitation device platform was developed to build a lower limb gait depth dataset. RGB data is employed for keypoint detection, enabling the establishment of a 3D lower limb posture recognition model that extracts gait, time, spatial features, and keypoints. The predicted joint angles, stride length, and step frequency demonstrate errors of 4 %, 8 %, and 1.3 %, respectively, with an average confidence of 0.95 for 3D key points. We employed the WOA-BP neural network to develop a dynamic threshold algorithm based on gait features and propose a model for recognizing abnormal postures. Compared to other models, our model achieves a 96 % accuracy rate in recognizing abnormal postures, with a recall rate of 83 % and an F1 score of 90 %. ROC curve analysis and AUC values reveal that the WOA-BP algorithm performs farthest from the pure chance line, with the highest AUC value of 0.89, indicating its superior performance over other models. Experimental results demonstrate that this model possesses a strong capability in recognizing abnormal lower limb postures, encouraging patients to correct these postures, thereby reducing muscle injuries and improving exercise effectiveness.

Different sensory information is used for state estimation when stationary or moving.

The accurate estimation of limb state is necessary for movement planning and execution. While state estimation requires both feedforward and feedback information, we focus here on the latter. Prior literature has shown that integrating visual and proprioceptive feedback improves estimates of static limb position. However, differences in visual and proprioceptive feedback delays suggest that multisensory integration could be disadvantageous when the limb is moving. We formalized this hypothesis by modeling feedback-based state estimation using the longstanding maximum likelihood estimation model of multisensory integration, which we updated to account for sensory delays. Our model predicted that the benefit of multisensory integration was largely lost when the limb was passively moving. We tested this hypothesis in a series of experiments in human subjects that compared the degree of interference created by discrepant visual or proprioceptive feedback when estimating limb position either statically at the end of the movement or dynamically at movement midpoint. In the static case, we observed significant interference: discrepant feedback in one modality systematically biased sensory estimates based on the other modality. However, no interference was seen in the dynamic case: participants could ignore sensory feedback from one modality and accurately reproduce the motion indicated by the other modality. Together, these findings suggest that the sensory feedback used to compute a state estimate differs depending on whether the limb is stationary or moving. While the former may tend toward multimodal integration, the latter is more likely to be based on feedback from a single sensory modality.Significance statement The estimation of limb state involves feedforward and feedback information. While estimation based on feedback has been well studied when the limb is stationary, it is unknown if similar sensory processing supports limb position estimates when moving. Using a computational model and behavioral experiments, we show that feedback-based state estimation may involve multisensory integration in the static case, but it is likely based on a single modality when the limb is moving. We suggest that this difference may stem from visual and proprioceptive feedback delays.

Effective shape of ball-and-socket prosthesis in restoring range of thumb motion for total thumb carpometacarpal joint arthroplasty: three-dimensional motion analysis

PurposeTotal joint arthroplasty (TJA) has often been used to treat thumb carpometacarpal (CMC) osteoarthritis (OA). However, guidelines for the CMC prosthesis shape remain unclear. This study aimed to identify the effective shape of a ball-and-socket prosthesis in restoring the range of thumb motion after TJA.MethodsThe participants were 10 healthy young adult men (22–32 years; 26.8 ± 3.57 [mean ± SD]). CT scans were performed in eight static limb positions during abduction and flexion. We defined three design variables (offset R, height H, and neck rotation angle Φ) as the variables that determine the basic shape of the ball-and-socket prosthesis. The ideal values of these design variables were examined based on the results of a 3D motion analysis, which evaluated the change in the posture of the first metacarpal (r, h, and φ corresponding to R, H, and Φ, respectively) relative to the center of rotation (COR) during abduction and flexion. We also simulated the effect of these design variables on the range of thumb motion after TJA using 3D CAD.ResultsWe found that the values of r and h averaged over all limb positions were 6.92 ± 1.60 mm and 51.02 ± 1.67 mm, respectively, showing that these values remained constant regardless of limb position. In contrast, φ changed significantly. The simulation results indicated that Φ affected the range of thumb motion after TJA, and Φ = 0° relatively reproduced all limb positions compared to other values.ConclusionOur results suggested that the desirable values of R and H were the average of r and h over several limb positions and that Φ = 0° was effective in restoring the range of thumb motion after TJA. Our results will provide surgeons with new guidelines for selecting a prosthesis.

Unravelling Influence Factors in Pattern Recognition Myoelectric Control Systems: The Impact of Limb Positions and Electrode Shifts.

Pattern recognition (PR)-based myoelectric control systems can naturally provide multifunctional and intuitive control of upper limb prostheses and restore lost limb function, but understanding their robustness remains an open scientific question. This study investigates how limb positions and electrode shifts-two factors that have been suggested to cause classification deterioration-affect classifiers' performance by quantifying changes in the class distribution using each factor as a class and computing the repeatability and modified separability indices. Ten intact-limb participants took part in the study. Linear discriminant analysis (LDA) was used as the classifier. The results confirmed previous studies that limb positions and electrode shifts deteriorate classification performance (14-21% decrease) with no difference between factors (p > 0.05). When considering limb positions and electrode shifts as classes, we could classify them with an accuracy of 96.13 ± 1.44% and 65.40 ± 8.23% for single and all motions, respectively. Testing on five amputees corroborated the above findings. We have demonstrated that each factor introduces changes in the feature space that are statistically new class instances. Thus, the feature space contains two statistically classifiable clusters when the same motion is collected in two different limb positions or electrode shifts. Our results are a step forward in understanding PR schemes' challenges for myoelectric control of prostheses and further validation needs be conducted on more amputee-related datasets.

Limb Position Influences Peripheral Arterial Stiffness Reduction with Reactive Hyperemia

The mechanism behind the acute reduction in peripheral arterial stiffness with reactive hyperemia is presumed to be flow-mediated; however, this has not been clearly demonstrated. We hypothesized that a larger reactive hyperemia magnitude would result in a greater reduction in peripheral arterial stiffness. Fourteen healthy young adults (5 females, 25 ± 5 yrs, mean ± SD) underwent reactive hyperemia with a rapid-release cuff on the upper arm inflated to 220 mmHg for 5 min: once with the arm positioned ~ 50ο above heart level and once with the arm positioned ~ 50ο below heart level. Brachial-radial pulse wave velocity (PWV) was measured with tonometers over brachial and radial arteries before cuff inflation and at 5, 15, and 30 min after release. Brachial blood flow was monitored with doppler ultrasound. At 5 min after reactive hyperemia, both the absolute (2.31 ± 1.22 vs 1.19 ± 1.19 m/sec, p = 0.007) and relative (24% vs 15%; p = 0.043) changes in brachial to radial PWV were greater with the arm below the heart compared to above the heart. The peak brachial blood flow was higher when the arm was below the heart compared to above the heart (477 ±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document} 145 vs 369 ±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document} 137 ml/min; p < 0.001). Reactive hyperemia acutely reduced peripheral arterial stiffness above and below heart level, with a greater decrease observed when the arm was positioned below the heart. These results demonstrate the contribution of conduit artery blood flow to the reduction of peripheral arterial stiffness after reactive hyperemia.

Comparison of the Effects of a Roller Massager Intervention on the Rectus Femoris Between Lengthened and Slack Positions.

Kasahara, K, Konrad, A, Murakami, Y, Thomas, E, and Nakamura, M. Comparison of the effects of a roller massager intervention on the rectus femoris between lengthened and slack positions. J Strength Cond Res 38(11): 1879-1884, 2024-A roller massager (RM) is a type of foam rolling device, which previous studies have shown to be effective for acutely decreasing tissue hardness and increasing range of motion (ROM). However, these effects may differ with the RM intervention position (i.e., knee flexion or knee extension). Therefore, this study aimed to compare the acute effects of an RM intervention on the rectus femoris (RF) in the knee flexed and extended positions. The subjects were 14 healthy male college students (age, 22.6 ± 0.8 years). The RF of the dominant leg was tested. Three conditions were compared: a control condition with no intervention (CON), an RM intervention in knee extension (i.e., RM_extension), and a RM intervention in knee flexion (i.e., RM_flexion). The measurements were tissue hardness in the proximal (TH_pro), middle (TH_mid), and distal (TH_dis) portions of the RF, knee flexion ROM, pain pressure threshold (PPT), maximal voluntary isometric contraction (MVC-ISO) torque, and maximal voluntary concentric contraction (MVC-CON) torque in the RF before and immediately after the intervention. There were significant interaction effects of TH_mid and knee flexion ROM. Both RM_extension and RM_flexion conditions showed a significant ( p < 0.01) decrease in TH_mid and an increase in knee flexion ROM, but there were no significant differences between conditions. There was a main effect for TH_pro and PPT ( p < 0.05) but no significant interaction effect or main effect for TH_dis, MVC-ISO torque, and MVC-CON torque. The results showed that the RM intervention can effectively decrease tissue hardness and increase ROM, regardless of limb position (i.e., knee extension or flexion).

Different sensory information is used for state estimation when stationary or moving.

The accurate estimation of limb state is necessary for movement planning and execution. While state estimation requires both feedforward and feedback information, we focus here on the latter. Prior literature has shown that integrating visual and proprioceptive feedback improves estimates of static limb position. However, differences in visual and proprioceptive feedback delays suggest that multisensory integration could be disadvantageous when the limb is moving. We formalized this hypothesis by modeling feedback-based state estimation using the longstanding maximum likelihood estimation model of multisensory integration, which we updated to account for sensory delays. Our model predicted that the benefit of multisensory integration was largely lost when the limb was passively moving. We tested this hypothesis in a series of experiments in human subjects that compared the degree of interference created by discrepant visual or proprioceptive feedback when estimating limb position either statically at the end of the movement or dynamically at movement midpoint. In the static case, we observed significant interference: discrepant feedback in one modality systematically biased sensory estimates based on the other modality. However, no interference was seen in the dynamic case: participants could ignore sensory feedback from one modality and accurately reproduce the motion indicated by the other modality. Together, these findings suggest that the sensory feedback used to compute a state estimate differs depending on whether the limb is stationary or moving. While the former may tend toward multimodal integration, the latter is more likely to be based on feedback from a single sensory modality.