Reliability of In Vivo Creatine-Weighted Chemical Exchange Saturation Transfer (CrCEST) MRI in Calf Skeletal Muscle of Healthy Volunteers at 3 T.

BACKGROUND: Skeletal muscle mitochondrial oxidative phosphorylation (mtOXPHOS) is important for ATP generation and its dysfunction leads to exercise intolerance. Phosphorus magnetic resonance spectroscopy (31P-MRS) is a useful, noninvasive technique for mtOXPHOS assessment but has limitations. Creatine-weighted chemical exchange saturation transfer (CrCEST) MRI is a potential alternative to assess muscle bioenergetics. PURPOSE: To evaluate the interscan repeatability, intra- and interobserver reproducibility of CrCEST during mild plantar flexion exercise. STUDY TYPE: Retrospective. SUBJECTS: Twenty healthy volunteers (age 37.6 ± 12.4 years, 11 females). FIELD STRENGTH/SEQUENCE: 3 T/CEST imaging using gradient echo readout. ASSESSMENT: τCrCEST (postexercise Cr recovery time) was assessed in two scans for each participant, following mild plantar flexion exercises targeting the medial gastrocnemius (MG), lateral gastrocnemius (LG), and soleus (Sol) muscles. Three observers measured τCrCEST for interobserver reproducibility. Three readings by one observer were used to measure intraobserver reproducibility. Two scans were used for within-participant interscan repeatability. STATISTICAL TESTS: Paired t tests, intraclass correlation coefficient (ICC), and Pearson correlation were conducted. Bland-Altman plots were used to analyze the interobserver variability. A P-value of 0.05 was considered statistically significant. RESULTS: There was excellent intra- (ICC ∈ 0.94 - 0.98 $$ \in \left[0.94-0.98\right] $$ ) and interobserver (ICC ∈ 0.9 - 0.98 $$ \in \left[0.9-0.98\right] $$ ) reproducibility, with moderate interscan repeatability for τCrCEST in LG and MG (ICC ∈ 0.54 - 0.74 $$ \in \left[0.54-0.74\right] $$ ) and poor-to-moderate interscan repeatability in Sol (ICC ∈ 0.24 - 0.53 $$ \in \left[0.24-0.53\right] $$ ). Excellent interobserver reproducibility was confirmed by Bland-Altman plots (fixed bias P-value ∈ 0.08 - 0.87 $$ \in \left[0.08-0.87\right] $$ ). DATA CONCLUSION: CrCEST MRI shows promise in assessing muscle bioenergetics by evaluating τCrCEST during mild plantar flexion exercise with reasonable reliability, particularly in LG and MG. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY: Stage 1.

Motoneuron persistent inward current contribution to increased torque responses to wide-pulse high-frequency neuromuscular electrical stimulation.

PURPOSE: To assess the effect of a remote handgrip contraction during wide-pulse high-frequency (WPHF) neuromuscular electrical stimulation (NMES) on the magnitude of extra torque, progressive increase in torque during stimulation, and estimates of the persistent inward current (PIC) contribution to motoneuron firing in the plantar flexors. METHODS: Ten participants performed triangular shaped contractions to 20% of maximal plantar flexion torque before and after WPHF NMES with and without a handgrip contraction, and control conditions. Extra torque, the relative difference between the initial and final torque during stimulation, and sustained electromyographic (EMG) activity were assessed. High-density EMG was recorded during triangular shaped contractions to calculate ∆F, an estimate of PIC contribution to motoneuron firing, and its variation before vs after the intervention referred to as ∆F change score. RESULTS: While extra torque was not significantly increased with remote contraction (WPHF + remote) vs WPHF (+ 37 ± 63%, p = 0.112), sustained EMG activity was higher in this condition than WPHF (+ 3.9 ± 4.3% MVC EMG, p = 0.017). Moreover, ∆F was greater (+ 0.35 ± 0.30 Hz) with WPHF + remote than control (+ 0.03 ± 0.1 Hz, p = 0.028). A positive correlation was found between ∆F change score and extra torque in the WPHF + remote (r = 0.862, p = 0.006). DISCUSSION: The findings suggest that the addition of remote muscle contraction to WPHF NMES enhances the central contribution to torque production, which may be related to an increased PIC contribution to motoneuron firing. Gaining a better understanding of these mechanisms should enable NMES intervention optimization in clinical and rehabilitation settings, improving neuromuscular function in clinical populations.

Association of the rate of torque development and joint angle with passive muscle stiffness.

PURPOSE: The purpose of this study was to statistically compare the rate of torque development normalized by maximal strength (relative RTD) across ankle angles. Additionally, this study was aimed at exploring the correlation coefficients between relative RTD and passive stiffness of the medial gastrocnemius (MG) at different ankle angles. METHODS: Twenty-two healthy men and women (age: 31 ± 4 years) performed randomly-ordered explosive isometric plantar flexions at plantarflexed (15°), neutral (0°), and dorsiflexed (- 15°) angles; relative RTD comprised the slope of the time-torque curve normalized to maximal torque. The shear wave velocity (SWV; index of stiffness) of the MG at rest was measured at each angle using ultrasound shear wave elastography. RESULTS: The relative RTD was greater at 15° than - 15° for 0-50, 0-100, and 0-150 ms time-windows and at 15° than 0° for the 0-150 ms time-window (P < 0.05), although peak torque was lower at 15° than 0° and - 15° (P < 0.05). The relative RTD for the 0-50 ms time-window correlated with SWV at - 15° (rs = 0.475, P < 0.05), but not at 15º and 0º. Furthermore, the correlation coefficient of RTD for the 0-100 ms time-window with SWV was significantly greater at - 15° (rs = 0.420) than 0 ° (rs = - 0.109). CONCLUSIONS: A greater relative RTD occurs at plantarflexed angles (i.e., the ascending limb of the force-length curve) in the triceps surae, and relative RTD is strongly related to passive MG stiffness at dorsiflexed angles (i.e., longer muscle lengths).

The effects of using heel protectors on the prevention of heel pressure injuries and plantar flexion contractures.

BACKGROUND: Immobilization in the intensive care unit can lead to pressure injuries and plantar flexion contractures. AIM: This study was conducted to evaluate the effectiveness of heel protectors applied for the prevention of heel pressure injuries and plantar flexion contractures in intensive care units. METHODOLOGY: This study was conducted as a randomized controlled trial in two adult intensive care units of a teaching and research hospital. The study sample consisted of 84 patients admitted to intensive care units between January 2022 and December 2022. Patients who had been in the intensive care unit for at least 5 days, scored 16 or less on the Braden Pressure Ulcer Risk Assessment Scale and scored 4 or more on the Ramsey Sedation Scale, were included in the study. Heel protector boots were applied to the heels of the patients in the intervention group, while standard positioning with a pillow and ROM exercises were continued in the control group. A sociodemographic data form, the Ramsey Sedation Scale and the Braden Pressure Ulcer Risk Assessment Scale were used to collect data. While pressure injuries were evaluated with the International NPUAP-EPUAP Pressure Ulcer Classification System, goniometric measurements were made to evaluate joint ROM. RESULTS: In the intervention group, heel pressure injuries did not develop during the study, whereas five patients in the control group developed heel pressure injuries. The risk of pressure injury development that was seen in the control group was 1.7 times higher compared with the risk for the intervention group (log 95% CI: 0.91-2.59). There were significant differences between the right foot (99%; F = 99.229; p = .000) and left foot (99%; F = 100.519; p = .000) in range of motion measurement values of the patients in the intervention group according to the measurement times. According to the results of the multiple comparison test (Bonferroni) performed to determine the range of motion measurement periods showing significant differences, it was observed that each measurement for both feet yielded lower results than the previous measurement (seven measurements from day 1 to day 13). CONCLUSION: The use of heel protector boots was found to be effective in preventing the development of heel pressure injuries and plantar flexion contractures in intensive care unit patients. RELEVANCE FOR CLINICAL PRACTICE: This study provides evidence that intensive care nurses can use heel protector boots to prevent the development of heel pressure injuries and plantar flexion contractures.

Repeatability assessment for simultaneous measurement of arterial blood flow, venous oxygen saturation, and muscle perfusion following dynamic exercise.

The purpose of the present study was to demonstrate a new sequence and determine the repeatability of simultaneous dynamic measurements of blood flow, venous oxygen saturation (SvO2 ), and relative perfusion (change from resting perfusion) in calf muscle during recovery from plantar flexion exercise. The feasibility of near simultaneous measurement of bio-energetic parameters was also demonstrated. A sequence was developed to simultaneously measure arterial blood flow using flow-encoded projection, SvO2 using susceptibility-based oximetry, and relative perfusion using arterial spin labeling in combination with dynamic plantar flexion exercise. The parameters were determined at rest and during recovery from single leg plantar flexion exercise. Test-retest repeatability was analyzed using Bland-Altman analysis and intraclass correlation coefficients (ICC). The mitochondrial capacity of skeletal muscle was also measured immediately afterwards with dynamic phosphorus magnetic resonance spectroscopy. Eight healthy subjects participated in the study for test-retest repeatability. Popliteal artery blood flow at rest was 1.79 ± 0.58 ml/s and increased to 11.18 ± 3.02 ml/s immediately after exercise. Popliteal vein SvO2 decreased to 45.93% ± 6.5% from a resting value of 70.46% ± 4.76% following exercise. Relative perfusion (change from rest value) was 51.83 ± 15.00 ml/100 g/min at the cessation of exercise. The recovery of blood flow and SvO2 was modeled as a single exponential with time constants of 38.03 ± 6.91 and 71.19 ± 14.53 s, respectively. All the measured parameters exhibited good repeatability with ICC ranging from 0.8 to 0.95. Bioenergetics measurements were within normal range, demonstrating the feasibility of near simultaneous measurement of hemodynamic and energetic parameters. Clinical feasibility was assessed with Barth syndrome patients, demonstrating reduced oxygen extraction from the blood and reduced mitochondrial oxidative capacity compared with healthy controls. The proposed protocol allows rapid imaging of multiple parameters in skeletal muscle that might be affected in disease.

Effect of relaxation time on hysteresis of human tendon in vivo.

OBJECTIVES: The purpose of this study was to investigate the effect of relaxation time on tendon hysteresis. METHODS: Subjects exerted isometric plantar flexion torque from rest to maximal voluntary isometric contractions within around 0.5 s, followed by relaxation with six different times (0.3, 0.5, 0.7, 1, 3, and 5 s). During each trial, tendon elongation in the medial gastrocnemius muscle was measured by ultrasonography. The area within the exerted torque-tendon elongation loop, as a percentage of the area beneath the curve during ascending phase, was calculated as tendon hysteresis. RESULTS: Between the 0.3 and 1 s relaxation time conditions, the hysteresis values were significantly greater for the shorter relaxation time conditions (except between the 0.5 and 0.7 s conditions). In contrast, no significant differences in tendon hysteresis were found between 1 and 5 s of relaxation time conditions. Furthermore, the relationship between relaxation time and tendon hysteresis showed a significantly negative correlation under 1 s or less of relaxation time, but no significant correlation was observed under conditions of 1 s or more. CONCLUSION: These results suggest that relaxation time greatly affects tendon hysteresis under condition that relaxation time was less than 1 s.

Iatrogenic Flexion-Related Classic Metaphyseal Lesion of the Distal Tibia: Three Cases.

BACKGROUND: Classic metaphyseal lesions (CMLs) should raise concern for nonaccidental trauma. However, iatrogenic causes for CMLs have increasingly been described and warrant close consideration. Increasing the clinical understanding of CML mechanics and their relation to often routine medical procedures will enhance provider awareness and expand the differential diagnosis when these otherwise highly concerning injuries are identified. CASE REPORTS: We describe three clinical cases where suspected iatrogenic dorsiflexion or plantar flexion resulted in an isolated distal tibia CML. Respectively, we present heel-stick testing and i.v. line placement as clinical correlates of these two mechanisms. Although prior reports have aimed to describe iatrogenic CML etiologies, they have not focused on dorsiflexion or plantar flexion as predominant mechanisms of injury. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians are critical to the surveillance and identification of nonaccidental trauma. Given that children oftentimes present to the emergency department with subtle yet concerning signs of maltreatment, an emergency physician must be aware of the potential causes of injury as well as the recommended response. Although avoiding missed cases of abuse and improving the detection of injuries is crucial for child health and well-being, failing to consider or recognize alternative explanations could also have serious implications for a child and their caregivers.

Examination and reliability of measuring muscle strength of ankle plantar flexion with knee extended.

[Purpose] A hand-held dynamometer (HHD) is less expensive than the isokinetic muscle strength measurement device, and research using HHD is gradually increasing. However, measurement is performed only at a low muscle strength level at which the heel does not take off or heel detachment occurs; therefore, fixation of the foot becomes a problem. This study aimed to determine the validation of measuring ankle plantar flexion strength (with the knee extended) using HHD. [Participants and Methods] Twenty healthy adults (14 males and 6 females) participated in this study. The chair used in this study was for swallowing videofluorography, which was fixed to a wall bar by the belt. The sensor was located at the third metatarsal head. After warming up, the participants sat in a long sitting position on the chair. We conducted the test two times. We used intraclass correlation coefficient (ICC) and Bland-Altman analysis to assess reliability. [Results] The ICC(1, 1) and ICC(2, 1) results were all greater than 0.9. No fixed and proportional errors were present. [Conclusion] The measurement method of this study was both intra- and inter-examiner reliabilities, which were high, and we suggest that sufficient clinical application is possible.

Association between effective neural drive to the triceps surae and fluctuations in plantar-flexion torque during submaximal isometric contractions.

NEW FINDINGS: What is the central question of this study? What is the association between the fluctuations in various estimates of effective neural drive to the triceps surae muscles and fluctuations in net plantar-flexion torque during steady submaximal contractions? What is the main finding and its importance? The fluctuations in estimates of effective neural drive to the triceps surae were moderately correlated with fluctuations in net torque at light and moderate plantar-flexion torques. Significant variability was observed in the association between neural drive and torque across participants, trials, short epochs of individual contractions and varying motor unit number. ABSTRACT: The influence of effective neural drive on low-frequency fluctuations in torque during steady contractions can be estimated from the cumulative spike train (CST) or first principal component (FPC) of smoothed motor unit discharge rates obtained with high-density electromyography. However, the association between these estimates of total neural drive to synergist muscles and the fluctuations in net torque has not been investigated. We exposed the variability and compared the correlations between estimates of effective neural drive to the triceps surae muscles and fluctuations in plantar-flexion torque during steady contractions at 10% and 35% of maximal voluntary contraction (MVC) torque. Both neural drive estimates were moderately correlated with torque (CST, 0.55 ± 0.14; FPC, 0.58 ± 0.16) and highly correlated with one another (0.81 ± 0.1) during the 30-s steady contractions. There was substantial variability in cross-correlation values across participants, trials, and the 1- and 5-s epochs of single contractions. Moreover, epoch duration significantly influenced cross-correlation values. Motor unit number was weakly associated with cross-correlation strength at 35% MVC (marginal R2 0.09-0.11; all P < 2.2 × 10-5 ), but not at 10% MVC (all P > 0.37). Approximately, one-fifth of the variance in the coefficient of variation (CV) for torque was explained by CV for the CST estimate of the neural drive (P = 6.6 × 10-13 , R2  = 0.21). Estimates of total neural drive to the synergistic triceps surae muscles obtained by pooling motor unit discharge times were moderately correlated with fluctuations in net plantar-flexion torque.

Test-retest reliability of isometric ankle plantar flexion strength measurement performed by a hand-held dynamometer considering fixation: examination of healthy young participants.

[Purpose] This study aimed to investigate the test-retest reliability of isometric ankle plantar flexion strength measurements performed by a hand-held dynamometer (HHD) using two belts and a newly devised fixation plate. [Participants and Methods] The participants were 83 healthy individuals (female, n=31; male, n=52) with an average age of 20 years. An HHD (µTas F-1) sensor was fixed using two belts and a newly developed metal device to the measurement site on the dominant foot of a participant who was in a sitting position. Measurements were performed twice for each participant. [Results] The average value was 65.6 kgf (bodyweight ratio, 127.3%) for female and 88.0 kgf (136.9%) for male participants. The intraclass correlation coefficients of the two measurements were 0.915 for female and 0.938 for male participants. The minimum detectable change at 95% was 10.1 kgf (12.1% of the average value) for female and 12.1 kgf (15.4%) for male participants. [Conclusion] The test-retest reliability of measuring the ankle plantar flexion strength performed by an HHD using a belt and plate is high. Therefore, the increase or decrease in muscle strength should be judged based on the minimal detectable change with 95% confidence.

Correlation between ankle plantar flexion strength and degree of body sway.

[Purpose] The purpose of this study is to consider the correlation between ankle plantar flexion strength and degree of body sway. [Participants and Methods] Twenty-one healthy adult males were targeted. A handheld dynamometer was used to measure ankle plantar flexion strength. The Body Pressure Measurement System was used to measure the degree of body sway. Lastly, correlation between ankle plantar flexion strength and degree of body sway was considered. [Results] A negative correlation was observed between ankle plantar flexion strength and degree of body sway. [Conclusion] Regarding ankle plantar flexion strength and degree of body sway, results of a consideration using a handheld dynamometer and Body Pressure Measurement System were the same as that of previous studies using large equipment.

Recovery kinetics of creatine in mild plantar flexion exercise using 3D creatine CEST imaging at 7 Tesla.

PURPOSE: Two-dimensional creatine CEST (2D-CrCEST), with a slice thickness of 10-20 mm and temporal resolution (τRes ) of about 30 seconds, has previously been shown to capture the creatine-recovery kinetics in healthy controls and in patients with abnormal creatine-kinase kinetics following the mild plantar flexion exercise. Since the distribution of disease burden may vary across the muscle length for many musculoskeletal disorders, there is a need to increase coverage in the slice-encoding direction. Here, we demonstrate the feasibility of 3D-CrCEST with τRes of about 30 seconds, and propose an improved voxel-wise B1+ -calibration approach for CrCEST. METHODS: The current 7T study with enrollment of 5 volunteers involved collecting the baseline CrCEST imaging for the first 2 minutes, followed by 2 minutes of plantar flexion exercise and then 8 minutes of postexercise CrCEST imaging, to detect the temporal evolution of creatine concentration following exercise. RESULTS: Very good repeatability of 3D-CrCEST findings for activated muscle groups on an intraday and interday basis was established, with coefficient of variance of creatine recovery constants (τCr ) being 7%-15.7%, 7.5%, and 5.8% for lateral gastrocnemius, medial gastrocnemius, and peroneus longus, respectively. We also established a good intraday and interday scan repeatability for 3D-CrCEST and also showed good correspondence between τCr measurements using 2D-CrCEST and 3D-CrCEST acquisitions. CONCLUSION: In this study, we demonstrated for the first time the feasibility and the repeatability of the 3D-CrCEST method in calf muscle with improved B1+ correction to measure creatine-recovery kinetics within a large 3D volume of calf muscle.

Attenuated spontaneous postural sway enhances diastolic blood pressure during quiet standing.

PURPOSE: Spontaneous postural sway during quiet standing has been considered a simple output error of postural control. However, as postural sway and inherent body orientation evoke compensatory activity of the plantar flexors, they might contribute to blood circulation under gravitational stress via the muscle pump. Hence, the present study employed an external support device to attenuate the plantar flexor activity in supported standing (SS), to experimentally identify its physiological impact on blood circulation. METHODS: Eight healthy young subjects performed two 5-min quiet standing trials (i.e., normal standing (NS) and SS), and the beat-to-beat interval (RRI) and blood pressure (BP) were compared between trials. We confirmed that postural sway and corresponding plantar flexor activity, quantified by the anteroposterior displacement of the foot center of pressure and lower back position with respect to the wall, and by the amplitude of electromyography and mechanomyography, respectively, were attenuated in SS, while mean body orientation angle and relative position of the BP sensor were comparable to NS. RESULTS: The 5-min averages of diastolic BP and mean arterial pressure during SS were significantly higher than during NS, while RRI and systolic BP did not change. These could be interpreted as an increase in peripheral vascular resistance; meanwhile, in NS, this effect was replaced by the muscle pump of the plantar flexors. CONCLUSION: The muscle contractions related to spontaneous postural sway and body orientation produce substantial physiological impact on blood circulation during quiet standing.

Sex differences in heel pad stiffness during in vivo loading and unloading.

Due to conflicting data from previous studies a new methodological approach to evaluate heel pad stiffness and soft tissue deformation has been developed. The purpose of this study was to compare heel pad (HP) stiffness in both limbs between males and females during a dynamic unloading and loading activity. Ten males and 10 females volunteered to perform three dynamic trials to unload and load the HP. The dynamic protocol consisted of three continuous phases: foot flat (baseline phase), bilateral heel raise (unloading phase) and foot flat (loading phase) with each phase lasting two seconds. Six retroreflective markers (3 mm) were attached to the skin of the left and right heels using a customised marker set. Three-dimensional motion analysis cameras synchronised with force plates collected the kinematic and kinetic data throughout the trials. Three-way repeated measures ANOVA together with a Bonferroni post hoc test were applied to the stiffness and marker displacement datasets. On average, HP stiffness was higher in males than females during the loading and unloading phases. ANOVA results revealed no significant differences for the stiffness and displacement outputs with respect to sex, sidedness or phase interactions (p > .05) in the X, Y and Z directions. Irrespective of direction, there were significant differences in stiffness between the baseline and unloading conditions (p < .001) but no significant differences between the baseline and loaded conditions (p = 1.000). Post hoc analyses for the marker displacement showed significant differences between phases for the X and Z directions (p < .032) but no significant differences in the Y direction (p > .116). Finally, females portrayed lower levels of mean HP stiffness whereas males had stiffer heels particularly in the vertical direction (Z) when the HP was both unloaded and loaded. High HP stiffness values and very small marker displacements could be valuable indicators for the risk of pathological foot conditions.

Impaired knee extension muscle strength in adolescents but not in children with Fontan circulation.

INTRODUCTION: Impaired isometric muscle strength was previously reported in adults with Fontan circulation. However, it is unclear if this impairment is present in children and adolescents with Fontan circulation. We investigated isometric muscle strength of the lower limb in patients (6-18 years) with Fontan circulation in comparison with healthy controls. METHOD: In this cross-sectional study, 43 patients (6-18 years) with Fontan circulation and 43 age- and sex-matched controls were included. Isometric knee extension and plantar flexion muscle strength were assessed using dynamometry (Newton, N). Lean mass of the legs was assessed with dual-energy X-ray absorptiometry. Analyses were performed on group level (n = 43), and for subgroups that included children aged 6-12 years (n = 18) and adolescents aged 13-18 years (n = 25). RESULTS: On group level, the patients with Fontan circulation had impaired isometric knee extension strength in comparison with the controls (p = 0.03). In subgroup analyses, impaired isometric knee extension strength was present in the adolescents (p = 0.009) but not in the children groups. For plantar flexion, there was no difference between patients and controls. There was no difference in lean mass between patients and controls (9.6 ± 4.3 kg vs. 10.8 ± 5.6 kg, p = 0.31). However, the lean mass was highly correlated to isometric knee extension strength (patients r = 0.89, controls r = 0.96, p < 0.001) and isometric plantar flexion strength (patients r = 0.7, controls r = 0.81, p < 0.001). CONCLUSION: The finding of impaired isometric knee extension muscle strength in adolescents (13-18 years) with Fontan circulation and no corresponding impairment in the children group (6-12 years) could imply that isometric muscle strength gets more impaired with age.

Nerve dysfunction leads to muscle morphological abnormalities in chronic inflammatory demyelinating polyneuropathy assessed by MRI.

Neuropathic features of chronic inflammatory demyelinating polyneuropathy (CIDP) have been well documented, however very little is known about the implication of this neuropathy on skeletal muscle, and whether nerve lesions in CIDP lead to uniform disruptions in skeletal muscles. In this study, we assessed the triceps surae complex, using magnetic resonance imaging (MRI) in a group (n = 10) of CIDP patients compared with a healthy age-matched control group (n = 9). MRI (T1 and T2) of the leg musculature as well as plantar flexion strength measurements were obtained from both groups. CIDP patients compared with controls had ∼28% lower plantar flexion strength and ∼19% less total muscle volume (T1) of the triceps surae. When strength was normalized to fat corrected triceps surae volume CIDP patients were ∼30% weaker than controls. Relaxation times from the T2 scans were significantly longer in CIDP with the soleus, medial head of gastrocnemius and lateral head of gastrocnemius showing ∼37%, ∼38% and ∼26% longer relaxation times, respectively. CIDP patients were significantly weaker compared to controls and despite normalizing strength to total triceps surae contractile tissue volume this difference remained. CIDP patients had significantly longer T2 times, reflecting increased noncontractile tissue infiltration. These results indicate reduced muscle quantity and quality as a result of alterations in axonal function. Furthermore, when present study results are considered together with a prior report on the anterior compartment (Gilmore et al. 2016, Muscle Nerve 3:413-420), it is clear that both anterior and posterior leg compartments are affected similarly in CIDP despite different terminal nerve innervation and functional properties. Clin. Anat. 32:77-84, 2019. © 2019 Wiley Periodicals, Inc.

Exercise-induced calf muscle hyperemia: quantitative mapping with low-dose dynamic contrast enhanced magnetic resonance imaging.

Peripheral artery disease (PAD) in the lower extremities often leads to intermittent claudication. In the present study, we proposed a low-dose DCE MRI protocol for quantifying calf muscle perfusion stimulated with plantar flexion and multiple new metrics for interpreting perfusion maps, including the ratio of gastrocnemius over soleus perfusion (G/S; for assessing the vascular redistribution between the two muscles) and muscle perfusion normalized by whole body perfusion (for quantifying the muscle's active hyperemia). Twenty-eight human subjects participated in this Institutional Review Board-approved study, with 10 healthy subjects ( group A) for assessing interday reproducibility and 8 healthy subjects ( group B) for exploring the relationship between plantar-flexion load and induced muscle perfusion. In a pilot group of five elderly healthy subjects and five patients with PAD ( group C), we proposed a protocol that measured perfusion for a low-intensity exercise and for an exhaustion exercise in a single MRI session. In group A, perfusion estimates for calf muscles were highly reproducible, with correlation coefficients of 0.90-0.93. In group B, gastrocnemius perfusion increased linearly with the exercise workload ( P < 0.05). With the low-intensity exercise, patients with PAD in group C showed substantially lower gastrocnemius perfusion compared with elderly healthy subjects [43.4 (SD 23.5) vs. 106.7 (SD 73.2) ml·min-1·100 g-1]. With exhaustion exercise, G/S [1.0 (SD 0.4)] for patients with PAD was lower than both its low-intensity level [1.9 (SD 1.3)] and the level in elderly healthy subjects [2.7 (SD 2.1)]. In conclusion, the proposed MRI protocol and the new metrics are feasible for quantifying exercise-induced muscle hyperemia, a promising functional test of PAD. NEW & NOTEWORTHY To quantitatively map exercise-induced hyperemia in calf muscles, we proposed a high-resolution MRI method shown to be highly reproducible and sensitive to exercise load. With the use of low contrast, it is feasible to measure calf muscle hyperemia for both low-intensity and exhaustion exercises in a single MRI session. The newly proposed metrics for interpreting perfusion maps are promising for quantifying intermuscle vascular redistribution or a muscle's active hyperemia.

Closing the Wearable Gap-Part II: Sensor Orientation and Placement for Foot and Ankle Joint Kinematic Measurements.

The linearity of soft robotic sensors (SRS) was recently validated for movement angle assessment using a rigid body structure that accurately depicted critical movements of the foot-ankle complex. The purpose of this study was to continue the validation of SRS for joint angle movement capture on 10 participants (five male and five female) performing ankle movements in a non-weight bearing, high-seated, sitting position. The four basic ankle movements-plantar flexion (PF), dorsiflexion (DF), inversion (INV), and eversion (EVR)-were assessed individually in order to select good placement and orientation configurations (POCs) for four SRS positioned to capture each movement type. PF, INV, and EVR each had three POCs identified based on bony landmarks of the foot and ankle while the DF location was only tested for one POC. Each participant wore a specialized compression sock where the SRS could be consistently tested from all POCs for each participant. The movement data collected from each sensor was then compared against 3D motion capture data. R-squared and root-mean-squared error averages were used to assess relative and absolute measures of fit to motion capture output. Participant robustness, opposing movements, and gender were also used to identify good SRS POC placement for foot-ankle movement capture.

Ankle Strength Deficits in a Cohort of College Athletes With Chronic Ankle Instability.

CONTEXT: Lateral ankle sprains commonly occur in an athletic population and can lead to chronic ankle instability. OBJECTIVE: To compare ankle strength measurements in athletes who have mechanical laxity and report functional instability after a history of unilateral ankle sprains. DESIGN: Retrospective cohort. SETTING: Athletic Training Research Lab. PARTICIPANTS: A total of 165 National Collegiate Athletic Association Division I athletes, 97 males and 68 females, with history of unilateral ankle sprains participated. MAIN OUTCOME MEASURES: Functional ankle instability was determined by Cumberland Ankle Instability Tool scores and mechanical ankle instability by the participant having both anterior and inversion/eversion laxity. Peak torque strength measures, concentric and eccentric, in 2 velocities were measured. RESULTS: Of the 165 participants, 24 subjects had both anterior and inversion/eversion laxity and 74 self-reported functional ankle instability on their injured ankle. The mechanical ankle instability group presented with significantly lower plantar flexion concentric strength at 30°/s (139.7 [43.7] N·m) (P = .01) and eversion concentric strength at 120°/s (14.8 [5.3] N·m) (P = .03) than the contralateral, uninjured ankle (166.3 [56.8] N·m, 17.4 [6.2] N·m, respectively). CONCLUSION: College athletes who present with mechanical laxity on a previously injured ankle exhibit plantar flexion and eversion strength deficits between ankles.

Estimation of the ankle power during the terminal stance of gait using an inertial sensor.

[Purpose] The purpose of this study was to develop an assessment tool that reflects the ankle function during the terminal stance of gait using an inertial sensor. [Participants and Methods] Thirteen healthy males (20 limbs) participated in this study. All the participants were required to perform five straight-line walking trials along a 10-m level walkway. During the terminal stance phase, both the anterior-posterior and vertical accelerations were measured with an inertial sensor mounted on the fibular head. The Pythagorean theorem was used to calculate the acceleration vector. A three-dimensional gait analysis system was used for movement data acquisition. All statistical analyses were performed using IBM SPSS Statistics 24.0 for Windows. [Results] Results were obtained using the following multiple regression equation for the estimation of ankle plantar flexion power: Estimated Ankle Power=-4.689 + 0.269 × vertical acceleration + 0.104 × body weight. [Conclusion] Our novel method for gait analysis using an inertial sensor can assess the ankle power during the terminal stance phase of gait.