Experiencing an Elongated Limb in Virtual Reality Modifies the Tactile Distance Perception of the Corresponding Real Limb.

In measurement, a reference frame is needed to compare the measured object to something already known. This raises the neuroscientific question of which reference frame is used by humans when exploring the environment. Previous studies suggested that, in touch, the body employed as measuring tool also serves as reference frame. Indeed, an artificial modification of the perceived dimensions of the body changes the tactile perception of external object dimensions. However, it is unknown if such a change in tactile perception would occur when the body schema is modified through the illusion of owning a limb altered in size. Therefore, employing a virtual hand illusion paradigm with an elongated forearm of different lengths, we systematically tested the subjective perception of distance between two points [tactile distance perception (TDP) task] on the corresponding real forearm following the illusion. Thus, the TDP task is used as a proxy to gauge changes in the body schema. Embodiment of the virtual arm was found significantly greater after the synchronous visuotactile stimulation condition compared with the asynchronous one, and the forearm elongation significantly increased the TDP. However, we did not find any link between the visuotactile-induced ownership over the elongated arm and TDP variation, suggesting that vision plays the main role in the modification of the body schema. Additionally, significant effect of elongation found on TDP but not on proprioception suggests that these are affected differently by body schema modifications. These findings confirm the body schema malleability and its role as a reference frame in touch.

Pathomechanics of lumbrical and flexor digitorum profundus muscle tears in climbers: A cadaveric model.

Lumbrical muscles originate on the flexor digitorum profundus (FDP) tendons and, during fist making, they move in the same direction when FDP muscle produces maximal proximal tendon gliding. Injuries of the bipennate lumbricals have been described when a shear force acts between the origins on adjacent tendons of the FDP, as they glide in opposite directions in asymmetric hand postures. Other structures of the deep flexors complex can be affected during this injury mechanism, due to the so-called quadriga effect, which can commonly occur during sport climbing practise. Biomechanical studies are needed to better understand the pathomechanism. A cadaveric study was designed to analyse the effects of load during the fourth lumbrical muscle injury mechanism. The amount of FDP tendon gliding and metacarpophalangeal (MCP) joint flexion of the 5th finger were calculated. Ten fresh-frozen cadaveric specimens (ten non-paired forearms and hands) were used. The specimens were placed on a custom-made loading apparatus. The FDP of the 5th finger was loaded, inducing isolated flexion of the 5th finger, until rupture. The rupture occurred in all specimens, under a load of 11 kg (SD 4.94), at 9.23 mm of proximal tendon gliding (SD 3.55) and at 21.4° (SD 28.91) of MCP joint flexion. Lumbrical muscle detachment from the 4th FDP was observed, from distal to proximal, and changes in FDP tendons at the distal forearm level too. The quadriga effect can lead to injury of the bipennate lumbrical muscles and the deep flexors complex in the hand and forearm.

Neuromechanical Differences between Pronated and Supinated Forearm Positions during Upper-Body Wingate Tests.

Arm-cycling is a versatile exercise modality with applications in both athletic enhancement and rehabilitation, yet the influence of forearm orientation remains understudied. Thus, this study aimed to investigate the impact of forearm position on upper-body arm-cycling Wingate tests. Fourteen adult males (27.3 ± 5.8 years) underwent bilateral assessments of handgrip strength in standing and seated positions, followed by pronated and supinated forward arm-cycling Wingate tests. Electromyography (EMG) was recorded from five upper-extremity muscles, including anterior deltoid, triceps brachii lateral head, biceps brachii, latissimus dorsi, and brachioradialis. Simultaneously, bilateral normal and propulsion forces were measured at the pedal-crank interface. Rate of perceived exertion (RPE), power output, and fatigue index were recorded post-test. The results showed that a pronated forearm position provided significantly (p < 0.05) higher normal and propulsion forces and triceps brachii muscle activation patterns during arm-cycling. No significant difference in RPE was observed between forearm positions (p = 0.17). A positive correlation was found between seated handgrip strength and peak power output during the Wingate test while pronated (dominant: p = 0.01, r = 0.55; non-dominant: p = 0.03, r = 0.49) and supinated (dominant: p = 0.03, r = 0.51; don-dominant: p = 0.04, r = 0.47). Fatigue changed the force and EMG profile during the Wingate test. In conclusion, this study enhances our understanding of forearm position's impact on upper-body Wingate tests. These findings have implications for optimizing training and performance strategies in individuals using arm-cycling for athletic enhancement and rehabilitation.

The effect of self-identified arm dominance on exercising forearm hemodynamics and skeletal muscle desaturation.

The human forearm model is commonly employed in physiological investigations exploring local vascular function and oxygen delivery; however, the effect of arm dominance on exercising forearm hemodynamics and skeletal muscle oxygen saturation (SmO2) in untrained individuals is poorly understood. Therefore, the purpose of this study was to explore the effect of self-identified arm dominance on forearm hemodynamics and SmO2 in untrained individuals during submaximal, non-ischemic forearm exercise. Twenty healthy individuals (23±4 years, 50% female; 80% right-handed) completed three-minute bouts of supine rhythmic (1 second contraction: 2 second relaxation duty cycle) forearm handgrip exercise at both absolute (10kg; 98N) and relative (30% of maximal voluntary contraction) intensities in each forearm. Beat-by-beat measures of forearm blood flow (FBF; ml/min), mean arterial blood pressure (MAP; mmHg) and flexor digitorum superficialis SmO2 (%) were obtained throughout and averaged during the final 30 seconds of rest, exercise, and recovery while forearm vascular conductance was calculated (FVC; ml/min/100mmHg). Data are Δ from rest (mean±SD). Absolute force production did not differ between non-dominant and dominant arms (97±11 vs. 98±13 N, p = 0.606) whereas relative force production in females did (69±24 vs. 82±25 N, p = 0.001). At both exercise intensities, FBFRELAX, FVCRELAX, MAPRELAX, and the time constant tau for FBF and SmO2 were unaffected by arm dominance (all p>0.05). While arm dominance did not influence SmO2 during absolute intensity exercise (p = 0.506), the non-dominant arm in females experienced an attenuated reduction in SmO2 during relative intensity exercise (-14±10 vs. -19±8%, p = 0.026)-though exercise intensity was also reduced (p = 0.001). The present investigation has demonstrated that arm dominance in untrained individuals does not impact forearm hemodynamics or SmO2 during handgrip exercise.

Influence of Blood Flow Restriction on Neuromuscular Function and Fatigue During Forearm Flexion in Men.

ABSTRACT: Montgomery, TR Jr, Olmos, A, Sears, KN, Succi, PJ, Hammer, SM, Bergstrom, HC, Hill, EC, Trevino, MA, and Dinyer-McNeely, TK. Influence of blood flow restriction on neuromuscular function and fatigue during forearm flexion in men. J Strength Cond Res 38(7): e349-e358, 2024-To determine the effects of blood flow restriction (BFR) on the mean firing rate (MFR) and motor unit action potential amplitude (MUAPAMP) vs. recruitment threshold (RT) relationships during fatiguing isometric elbow flexions. Ten men (24.5 ± 4.0 years) performed isometric trapezoidal contractions at 50% maximum voluntary contraction to task failure with or without BFR, on 2 separate days. For BFR, a cuff was inflated to 60% of the pressure required for full brachial artery occlusion at rest. During both visits, surface electromyography was recorded from the biceps brachii of the dominant limb and the signal was decomposed. A paired-samples t test was used to determine the number of repetitions completed between BFR and CON. ANOVAs (repetition [first, last] × condition [BFR, CON]) were used to determine differences in MFR vs. RT and MUAPAMP vs. RT relationships. Subjects completed more repetitions during CON (12 ± 4) than BFR (9 ± 2; p = 0.012). There was no significant interaction (p > 0.05) between the slopes and y-intercepts during the repetition × condition interaction for MUAPAMP vs. MFR. However, there was a main effect of repetition for the slopes of the MUAPAMP vs. RT (p = 0.041) but not the y-intercept (p = 0.964). Post hoc analysis (collapsed across condition) indicated that the slopes of the MUAPAMP vs. RT during the first repetition was less than the last repetition (first: 0.022 ± 0.003 mv/%MVC; last: 0.028 ± 0.004 mv/%MVC; p = 0.041). Blood flow restriction resulted in the same amount of higher threshold MU recruitment in approximately 75% of the repetitions. Furthermore, there was no change in MFR for either condition, even when taken to task failure. Thus, BFR training may create similar MU responses with less total work completed than training without BFR.

Multimodal sensorimotor assessment of hand and forearm asymmetries: a reliability and correlational study.

Background: Effective rehabilitation of upper limb musculoskeletal disorders requires multimodal assessment to guide clinicians' decision-making. Furthermore, a comprehensive assessment must include reliable tests. Nevertheless, the interrelationship among various upper limb tests remains unclear. This study aimed to evaluate the reliability of easily applicable upper extremity assessments, including absolute values and asymmetries of muscle mechanical properties, pressure pain threshold, active range of motion, maximal isometric strength, and manual dexterity. A secondary aim was to explore correlations between different assessment procedures to determine their interrelationship. Methods: Thirty healthy subjects participated in two experimental sessions with 1 week between sessions. Measurements involved using a digital myotonometer, algometer, inclinometer, dynamometer, and the Nine-Hole Peg test. Intraclass correlation coefficients, standard error of the mean, and minimum detectable change were calculated as reliability indicators. Pearson's correlation was used to assess the interrelationship between tests. Results: For the absolute values of the dominant and nondominant sides, reliability was 'good' to 'excellent' for muscle mechanical properties, pressure pain thresholds, active range of motion, maximal isometric strength, and manual dexterity. Similarly, the reliability for asymmetries ranged from 'moderate' to 'excellent' across the same parameters. Faster performance in the second session was consistently found for the Nine-Hole Peg test. No systematic inter-session errors were identified for the values of the asymmetries. No significant correlations were found between tests, indicating test independence. Conclusion: These findings indicate that the sensorimotor battery of tests is reliable, while monitoring asymmetry changes may offer a more conservative approach to effectively tracking recovery of upper extremity injuries.

Hand Gesture Recognition Based on High-Density Myoelectricity in Forearm Flexors in Humans.

Electromyography-based gesture recognition has become a challenging problem in the decoding of fine hand movements. Recent research has focused on improving the accuracy of gesture recognition by increasing the complexity of network models. However, training a complex model necessitates a significant amount of data, thereby escalating both user burden and computational costs. Moreover, owing to the considerable variability of surface electromyography (sEMG) signals across different users, conventional machine learning approaches reliant on a single feature fail to meet the demand for precise gesture recognition tailored to individual users. Therefore, to solve the problems of large computational cost and poor cross-user pattern recognition performance, we propose a feature selection method that combines mutual information, principal component analysis and the Pearson correlation coefficient (MPP). This method can filter out the optimal subset of features that match a specific user while combining with an SVM classifier to accurately and efficiently recognize the user's gesture movements. To validate the effectiveness of the above method, we designed an experiment including five gesture actions. The experimental results show that compared to the classification accuracy obtained using a single feature, we achieved an improvement of about 5% with the optimally selected feature as the input to any of the classifiers. This study provides an effective guarantee for user-specific fine hand movement decoding based on sEMG signals.

Optimal Duration of Cold and Heat Compression for Forearm Muscle Biomechanics in Mixed Martial Arts Athletes: A Comparative Study.

BACKGROUND Cold and heat therapies for recovery in sports are commonly used, including in the mixed martial arts (MMA). The Game Ready (GR) device can be used for local monotherapy with either heat or cold and for contrast therapy. This study aimed to compare the effects of duration of cold and heat compression on biomechanical changes in the forearm muscles of 20 healthy mixed martial arts athletes. MATERIAL AND METHODS Twenty MMA volunteers (26.5±4.5 years old) underwent 3 different phases of the GR: (1) stimulation time 10 min (eGR-10, GR experimental group), (2) 10 min (cGR-10, sham control group) and (3) 20 min (eGR-20, GR experimental group). The following outcomes were assessed: muscle tone (T), stiffness (S), flexibility (E), pressure pain threshold (PPT), microvascular response (PU), and maximum isometric strength (Fmax). All measurements were performed before GR (rest) and after GR stimulation (post). RESULTS Both eGR-10 and eGR-20 significantly improved outcomes T (p<0.001), S (p<0.001), E (p=0.001, and p<0.001, respectively), PPT (p<0.001), PU (p<0.001), and Fmax (p<0.001). Notably, eGR-20 exhibited superior improvements in PU, Fmax, and PPT, with larger effect sizes (p<0.001). While eGR-10 demonstrated more pronounced reductions in T and S (p<0.001), these results underscore the potential for tailored GR therapy durations to optimize specific recovery goals for MMA athletes. CONCLUSIONS GR stimulation affects muscle biomechanical changes, pain threshold, muscle strength, and tissue perfusion. The study results suggest that 10 min of GR stimulation is sufficient to achieve changes that can be used to optimize recovery for MMA athletes.

Tactile Landmarks: the Relative Landmark Location Alters Spatial Distortions.

The influence of landmarks, that is, nearby non-target stimuli, on spatial perception has been shown in multiple ways. These include altered target localization variability near landmarks and systematic spatial distortions of target localizations. Previous studies have mostly been conducted in the visual modality using temporary, artificial landmarks or the tactile modality with persistent landmarks on the body. Thus, it is unclear whether both landmark types produce the same spatial distortions as they were never investigated in the same modality. Addressing this, we used a novel tactile setup to present temporary, artificial landmarks on the forearm and systematically manipulated their location to either be close to a persistent landmark (wrist or elbow) or in between both persistent landmarks at the middle of the forearm. Initial data (Exp. 1 and Exp. 2) suggested systematic differences of temporary landmarks based on their distance from the persistent landmark, possibly indicating different distortions of temporary and persistent landmarks. Subsequent control studies (Exp. 3 and Exp. 4) showed this effect was driven by the relative landmark location within the target distribution. Specifically, landmarks in the middle of the target distribution led to systematic distortions of target localizations toward the landmark, whereas landmarks at the side led to distortions away from the landmark for nearby targets, and toward the landmark with wider distances. Our results indicate that experimental results with temporary landmarks can be generalized to more natural settings with persistent landmarks, and further reveal that the relative landmark location leads to different effects of the pattern of spatial distortions.

Comparison of the forearm rotation restriction capacities of four upper-extremity immobilization methods: there is no difference between single and double sugar tong splinting.

BACKGROUND: The aim of this study was to compare the effects of four different immobilization methods [single sugar tong splint (SSTS), double sugar tong splint (DSTS), short arm cast (SAC), and long arm cast (LAC)] commonly used for restricting forearm rotation in the upper extremity. METHODS: Forty healthy volunteers were included in the study. Dominant extremities were used for measurements. Basal pronation and supination of the forearm were measured with a custom-made goniometer, and the total rotation arc was calculated without any immobilization. Next, the measurements were repeated with the SAC, LAC, SSTS and DSTS. Each measurement was compared to the baseline value, and the percentage of rotation restriction was calculated. RESULTS: The most superior restriction rates were observed for the LAC (p = 0.00). No statistically significant difference was detected between the SSTS and DSTS in terms of the restriction of supination, pronation or the rotation arc (p values, 1.00, 0.18, and 0.50, respectively). Statistically significant differences were not detected between the SAC and the SSTS in any of the three parameters (p values, 0.25; 1.00; 1.00, respectively). When the SAC and DSTS were compared, while there was no significant difference between the two methods in pronation (p = 0.50), a statistically significant difference was detected in supination (p = 0.01) and in the total rotation arc (p = 0.03). CONCLUSION: The LAC provides superior results in restricting forearm rotation. The SAC and SSTS had similar effects on forearm rotation. The DSTS, which contains, in addition to the SSTS, a sugar tong portion above the elbow, does not provide additional rotational stability.

Prediction of Dexterous Finger Forces With Forearm Rotation Using Motoneuron Discharges.

Motor unit (MU) discharge information obtained via electromyogram (EMG) decomposition can be used to decode dexterous multi-finger movement intention for neural-machine interfaces (NMI). However, the variation of the motor unit action potential (MUAP) shape resulted from forearm rotation leads to the decreased performance of EMG decomposition, especially under the real-time condition and then the degradation of motion decoding accuracy. The object of this study was to develop a method to realize the accurate extraction of MU discharge information across forearm pronated/supinated positions in the real-time condition for dexterous multi-finger force prediction. The FastICA-based EMG decomposition technique was used and the proposed method obtained multiple separation vectors for each MU at different forearm positions in the initialization phase. Under the real-time condition, the MU discharge information was extracted adaptively using the separation vector extracted at the nearest forearm position. As comparison, the previous method that utilized a single constant separation vector to extract MU discharges across forearm positions and the conventional method that utilized the EMG amplitude information were also performed. The results showed that the proposed method obtained a significantly better performance compared with the other two methods, manifested in a larger coefficient of determination ( [Formula: see text] and a smaller root mean squared error (RMSE) between the predicted and recorded force. Our results demonstrated the feasibility and the effectiveness of the proposed method to extract MU discharge information during forearm rotation for dexterous force prediction under the real-time conditions. Further development of the proposed method could potentially promote the application of the EMG decomposition technique for continuous dexterous motion decoding in a realistic NMI application scenario.

Impact of repetitive mouse clicking on forearm muscle fatigue and mouse aiming performance.

Exercise induced performance fatigue has been shown to impair many aspects of fine motor function in the distal upper limb. However, most fatiguing protocols do not reflect the conditions experienced with computer use. The purpose of this study was to determine how a prolonged, low-force mouse clicking fatigue protocol impacts performance fatigue of the distal upper limb for gamers and non-gamers. Participants completed a total of 1 h of mouse clicking at 5 clicks per second. Muscle fatigue and performance were intermittently assessed. RMS amplitude increased for the forearm flexors throughout the fatigue protocol. Accuracy decreased following the first bout of clicking and returned to baseline values after 40-min. EDC and ECU displayed the greatest muscle activity while aiming, producing 11.4% and 12.9% of MVC, respectively. These findings indicate that mouse clicking may not result in performance fatigue, however, high levels of extensor activity may explain common injuries among gamers.

The Effects of Anchoring a Fatiguing Forearm Flexion Task to a High vs. Low Rating of Perceived Exertion on Torque and Neuromuscular Responses.

ABSTRACT: Ortega, DG, Housh, TJ, Smith, RW, Arnett, JE, Neltner, TJ, Schmidt, RJ, and Johnson, GO. The effects of anchoring a fatiguing forearm flexion task to a high versus low rating of perceived exertion on torque and neuromuscular responses. J Strength Cond Res 38(5): e219-e225, 2024-This study examined the torque and neuromuscular responses following sustained, isometric, forearm flexion tasks anchored to 2 ratings of perceived exertion (RPE). Nine men (mean ± SD: age = 21.0 ± 2.4 years; height = 179.5 ± 5.1 cm; body mass = 79.6 ± 11.4 kg) completed maximal voluntary isometric contractions (MVIC) before and after sustained, isometric, forearm flexion tasks to failure anchored to RPE = 2 and RPE = 8. The amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) signal were recorded from the biceps brachii. Normalized torque was divided by normalized EMG AMP to calculate neuromuscular efficiency (NME). A dependent t-test was used to assess the mean difference for time to task failure (TTF). Repeated-measures analysis of variances was used to compare mean differences for MVIC and normalized neuromuscular parameters. There was no significant difference in TTF between RPE = 2 and RPE = 8 (p = 0.713). The MVIC decreased from pretest to posttest at RPE = 2 (p = 0.009) and RPE = 8 (p = 0.003), and posttest MVIC at RPE = 8 was less than that at RPE = 2 (p < 0.001). In addition, NME decreased from pretest to posttest (p = 0.008). There was no change in normalized EMG AMP or EMG MPF (p > 0.05). The current findings indicated that torque responses were intensity specific, but TTF and neuromuscular responses were not. Furthermore, normalized EMG AMP and EMG MPF remained unchanged but NME decreased, likely due to peripheral fatigue and excitation-contraction coupling failure. Thus, this study provides information regarding the neuromuscular responses and mechanisms of fatigue associated with tasks anchored to RPE, which adds to the foundational understanding of the relationship between resistance exercise and the perception of fatigue.

Does Exerting Grasps Involve a Finite Set of Muscle Patterns? A Study of Intra- and Intersubject Variability of Forearm sEMG Signals in Seven Grasp Types.

Surface Electromyography (sEMG) signals are widely used as input to control robotic devices, prosthetic limbs, exoskeletons, among other devices, and provide information about someone's intention to perform a particular movement. However, the redundant action of 32 muscles in the forearm and hand means that the neuromotor system can select different combinations of muscular activities to perform the same grasp, and these combinations could differ among subjects, and even among the trials done by the same subject. In this work, 22 healthy subjects performed seven representative grasp types (the most commonly used). sEMG signals were recorded from seven representative forearm spots identified in a previous work. Intra- and intersubject variability are presented by using four sEMG characteristics: muscle activity, zero crossing, enhanced wavelength and enhanced mean absolute value. The results confirmed the presence of both intra- and intersubject variability, which evidences the existence of distinct, yet limited, muscle patterns while executing the same grasp. This work underscores the importance of utilizing diverse combinations of sEMG features or characteristics of various natures, such as time-domain or frequency-domain, and it is the first work to observe the effect of considering different muscular patterns during grasps execution. This approach is applicable for fine-tuning the control settings of current sEMG devices.

Exploratory analysis using machine learning algorithms to predict pinch strength by anthropometric and socio-demographic features.

Objectives. This study examines the role of different machine learning (ML) algorithms to determine which socio-demographic factors and hand-forearm anthropometric dimensions can be used to accurately predict hand function. Methods. The cross-sectional study was conducted with 7119 healthy Iranian participants (3525 males and 3594 females) aged 10-89 years. Seventeen hand-forearm anthropometric dimensions were measured by JEGS digital caliper and a measuring tape. Tip-to-tip, key and three-jaw chuck pinches were measured using a calibrated pinch gauge. Subsequently, 21 features pertinent to socio-demographic factors and hand-forearm anthropometric dimensions were used for classification. Furthermore, 12 well-known classifiers were implemented and evaluated to predict pinches. Results. Among the 21 features considered in this study, hand length, stature, age, thumb length and index finger length were found to be the most relevant and effective components for each of the three pinch predictions. The k-nearest neighbor, adaptive boosting (AdaBoost) and random forest classifiers achieved the highest classification accuracy of 96.75, 86.49 and 84.66% to predict three pinches, respectively. Conclusions. Predicting pinch strength and determining the predictive hand-forearm anthropometric and socio-demographic characteristics using ML may pave the way to designing an enhanced tool handle and reduce common musculoskeletal disorders of the hand.

Associations between ultra-distal forearm bone mineral density and incident fracture in women.

Bone mineral density measured at the ultra-distal forearm site was associated with any fracture, as well as distal radius fracture in women from a longitudinal cohort study. PURPOSE: Femoral neck (BMDhip) and lumbar spine (BMDspine) bone mineral density (BMD) are routinely used to assess fracture risk. More data are needed to understand how ultra-distal forearm BMD (BMDUDforearm) may assist fracture prediction. METHODS: Using a Lunar DPX-L, Geelong Osteoporosis Study women (n = 1026), aged 40-90 years, had BMD measured. Incident low-trauma fractures were radiologically verified. Using Cox proportional hazard models, hazard ratios (HR) were calculated for BMDUDforearm as a continuous variable (expressed as a one-unit decrease in T-score) and a categorical variable (normal/osteopenia/osteoporosis). Areas under receiver operating characteristics (AUROC) curves were calculated. Analyses were conducted for any fracture and distal radius fractures. RESULTS: During 14,270 person-years of follow-up, there were 318 fractures (85 distal radius). In adjusted models, continuous BMDUDforearm was associated with any (HR 1.26;95%CI 1.15-1.39) and distal radius fractures (HR 1.59;95%CI 1.38-1.83). AUROCs for continuous BMDUDforearm, 33% forearm(BMD33%forearm), BMDhip, BMDspine, and FRAX without BMD were similar for any fracture (p > 0.05). For distal radius fracture, the AUROC for BMDUDforearm was higher than other sites and FRAX (p < 0.05). In adjusted models, those with osteoporosis had a higher likelihood of any fracture (HR 2.12; 95%CI 1.50-2.98). For distal radius fractures, both osteopenia and osteoporosis had a higher risk (HR 4.31; 95%CI 2.59-7.15 and 4.81; 95%CI 2.70-8.58). AUROCs for any fracture were similar for categorical BMD at all sites but lower for FRAX (p < 0.05). For distal radius fractures, the AUROC for BMDUDforearm, was higher than other sites and FRAX (p < 0.05). CONCLUSION: Ultra-distal forearm BMD may aid risk assessments for any distal radius fractures.

Are performance and perceived fatigability dependent on the anchor scheme of fatiguing isometric tasks in men?

BACKGROUND: Ratings of perceived exertion (RPE) can be used to regulate exercise intensity. This study examined the effect of anchor scheme on performance fatigability and neuromuscular responses following fatiguing forearm flexion tasks. METHODS: Twelve men (age 20.9±2.2 years; height 179.8±5.3 cm; body mass 80.2±9.9 kg) performed sustained, isometric forearm flexion tasks to failure anchored to RPE=6 (RPEFT) and the torque (TRQFT) that corresponded to RPE=6. Pre-test and post-test maximal voluntary isometric contractions (MVIC) were performed to quantify changes in the amplitude (AMP) and mean power frequency (MPF) of the electromyographic (EMG) and mechanomyographic (MMG) signals. Neuromuscular efficiency (NME) was calculated by dividing normalized torque by normalized EMG AMP. A dependent t-test was used to assess the mean difference for time to task failure (TTF). Repeated measures ANOVAs were used to compare mean differences for performance fatigability and normalized neuromuscular parameters. RESULTS: The RPEFT had a greater TTF than the TRQFT (P<0.001). MVIC and NME decreased from pre-test to post-test following the RPEFT and TRQFT (P<0.05) with no differences between anchor schemes. Following the TRQFT, normalized EMG MPF decreased from pre-test to post-test (P=0.004). Following the RPEFT, normalized MMG MPF increased from pre-test to post-test (P=0.021). There were no changes in normalized EMG AMP or MMG AMP (P>0.05). CONCLUSIONS: These findings indicated anchor scheme-specific neuromuscular responses and TTF, despite no difference in performance fatigability. Furthermore, performance fatigability was likely due to peripheral fatigue (based on normalized EMG MPF and NME) following the TRQFT, but peripheral and central fatigue (based on normalized MMG MPF and NME) following the RPEFT.

In-Vivo Electrical Properties Estimation of Biological Tissues by Means of a Multi-Step Microwave Tomography Approach.

The accurate quantitative estimation of the electromagnetic properties of tissues can serve important diagnostic and therapeutic medical purposes. Quantitative microwave tomography is an imaging modality that can provide maps of the in-vivo electromagnetic properties of the imaged tissues, i.e. both the permittivity and the electric conductivity. A multi-step microwave tomography approach is proposed for the accurate retrieval of such spatial maps of biological tissues. The underlying idea behind the new imaging approach is to progressively add details to the maps in a step-wise fashion starting from single-frequency qualitative reconstructions. Multi-frequency microwave data is utilized strategically in the final stage. The approach results in improved accuracy of the reconstructions compared to inversion of the data in a single step. As a case study, the proposed workflow was tested on an experimental microwave data set collected for the imaging of the human forearm. The human forearm is a good test case as it contains several soft tissues as well as bone, exhibiting a wide range of values for the electrical properties.

Location of the posterior interosseous nerve in relation to common lateral approaches to the elbow.

PURPOSE: The risk of posterior interosseous nerve (PIN) injury during surgical approaches to the lateral elbow varies depending on the chosen approach, level of dissection, and rotational position of the forearm. Previous studies evaluated the trajectory of the PIN in specific surgical applications to reduce iatrogenic nerve injuries. The goal of this study is to examine the location of the PIN using common lateral approaches with varying forearm rotation. METHODS: The Kaplan, extensor digitorum communis (EDC) split, and Kocher approaches were performed on 18 cadaveric upper extremity specimens. Measurements were recorded with a digital caliper from the radiocapitellar (RC) joint and the lateral epicondyle to the point where the PIN crosses the approach in full supination, neutral, and full pronation with the elbow at 90°. The ratio of the nerve's location in relation to the entire length of the radius was also evaluated to account for different-sized specimens. RESULTS: The PIN was not encountered in the Kocher interval. For Kaplan and EDC split, with the forearm in full supination, the mean distance from the lateral epicondyle to the PIN was 52.0 ± 6.1 mm and 59.1 ± 5.5 mm, respectively, and the mean distance from the RC joint to the PIN was 34.7 ± 5.5 mm and 39.3 ± 4.7 mm, respectively; with the forearm in full pronation, the mean distance from the lateral epicondyle to the PIN was 63.3 ± 9.7 mm and 71.4 ± 8.3 mm, respectively, and the mean distance from the RC joint to the PIN was 44.2 ± 7.7 mm and 51.1 ± 8.7 mm, respectively. CONCLUSIONS: The PIN is closer to the lateral epicondyle and RC joint in the Kaplan than EDC split approach and is not encountered during the Kocher approach. The PIN was not encountered within 26 mm from the RC joint and 39 mm from the lateral epicondyle in any approach and forearm position and is generally safe from iatrogenic injury within these distances.

Comparison of finger flexion strength and muscular recovery of male lead sport climbers across climbing classes.

BACKGROUND/OBJECTIVE: The purpose of this study was to compare finger flexor strength (FS), finger flexor muscle recovery (FR), and forearm circumference (FC) across three different climbing classes in male lead sport climbers. METHODS: A total of 37 male lead sport climbers were classified into low (LC), intermediate (IC), and advanced classes (AC) categories according to the International Rock Climbing Research Association (IRCRA) Scale. All participants measured FS three times for both open grip (OG) and crimp grip (CG). Following FS measurement, the FR was observed immediately after the all-out training. The FC was measured twice using an inelastic tape. RESULTS: The FS differed significantly across climbing classes for both grip styles and hands, regardless of dominant hand, with the higher classes showing greater FS (all, p ≤ 0.001). FR was significantly higher in AC compared to IC and LC at 5 min (all, p ≤ 0.001), 10 min (all, p ≤ 0.005) and 15 min (all, p ≤ 0.005). The FC showed significant differences with climbing classes for both forearms. CONCLUSION: Climbing classes are associated with differences in FS, with higher class corresponding to greater FS. Similarly, climbing classes are linked to FR and FC, with higher classes being associated with faster recovery and larger FC.