Stretch-shortening cycle during plantar flexion in young and elderly women and men

The stretch-shortening cycle (SSC) is a combination of eccentric and concentric muscle actions. The purpose of the study was to compare the SSC of four different groups comprising a total of 29 women and 30 men, divided according to sex and age (i.e. 20–40 years and 70–85 years). A KIN-COM dynamometer was used for strength measurements of the plantar flexion of the right foot. An electromyogram (EMG) from the gastroenemius muscle was recorded simultaneously. Maximal voluntary concentric muscle actions at 120° · s^–1 and 240° · s^–1 with and without prior eccentric muscle actions were performed. Average torque values of the range of motion between 90° and 99° of the ankle joint were extracted. All four groups were significantly stronger at 120° · s^–1 than at 240° · s^–1 for pure concentric actions. The average torque values of the concentric phases in the SSC movement were significantly higher than the torque values for pure concentric actions in all four groups and at both velocities. The EMG was significantly lower or unchanged in the SSC movement compared to a pure concentric action in all groups. A larger percentage increase in torque with prior eccentric action was found in young women compared to young men at both velocities. Our results suggested that the enhanced performance was even more marked when a concentric action was preceded by an eccentric action in the young women than in the young men, probably due to better utilization of elastic forces, but we could not demonstrate any age-related differences in enhanced performance with SSC.     

The impact of increased femoral antetorsion on gait deviations in healthy adolescents

Increased femoral antetorsion leads to several gait deviations, and amongst others, an increased knee flexion was reported in mid and terminal stance. Therefore, the purpose of this retrospective study was to identify gait deviations caused by increased femoral antetorsion and to perform subgroup analyses based on sagittal knee kinematics. Patients with isolated, CT confirmed increased femoral antetorsion (n = 42) and age-matched typically developing children (TDC, n = 17) were included in this study. Patients were referred to gait analysis because of gait abnormalities going along with an increased femoral antetorsion ≥30°. Kinematic and kinetic data were recorded during 3D gait analysis and three valid gait cycles were analyzed. Principal component (PC) analysis was used to achieve data transformation. A linear mixed model was used to estimate the group effect of PC-scores of retained PCs explaining 90% of the cumulative variance. Group effects of PC-scores revealed that patients walked with more flexed hips and greater anterior pelvic tilt throughout the gait cycle. Knee flexion was increased in patients during mid and terminal stance. Increased frontal plane knee and hip joint moments were found for patients compared to TDC. Furthermore, dividing patients into two subgroups based on their sagittal knee kinematics showed that kinematic gait deviations were more pronounced in patients with higher femoral antetorsion, while deviations in joint moments were more pronounced in patients with lower femoral antetorsion. Increased femoral antetorsion showed alterations in all lower limb joints and may be not only a cosmetic problem. Therefore, 3D gait analysis should be used for clinical management and operative treatment should be considered depending on severity of gait deviations.     

CPM结合早期康复训练在儿童肘部骨折术后肘关节功能障碍的康复疗效

目的:探讨CPM结合早期康复训练对儿童肘部骨折术后肘关节功能恢复临床疗效。方法:选取我院2015年12月~2017年2月期间骨科收治的儿童肘部骨折患者122例为研究对象,根据患者术后康复模式的不同将其分成了研究组(给予CPM结合早期康复训练)和对照组(给予早期康复训练),每组各61例。对两组患儿治疗前后的肘关节功能评分结果和综合疗效进行观察和比较。结果:(1)治疗后,研究组患儿的各项肘关节功能评分均明显优于对照组,且差异具有统计学意义;(2)治疗后优良率组间比较,研究组高于对照组,且差异具有统计学意义。结论:CPM结合早期康复训练能够有效的促进儿童肘部骨折术后肘关节功能恢复,是临床实际中的理想选择之一。     

Control of the Elbow Extensor Muscles in Slow Targeted Extensions of the Arm in Humans

Relations between the kinematic parameters of slow (non-ballistic) targeted extension movements in the elbow joint of humans and characteristics of the movement-related EMG activity in the two heads of the m. triceps brachii were analyzed. Test movements were performed under conditions of application of non-inertional external loadings directed toward flexion. It was shown that the movement-related EMG activity of the elbow extensors, similarly to what was observed in the flexors at flexion movements with the same parameters, demonstrates a complex structure and includes dynamic and stationary phases. In the former phase, in turn, initial and main components can be differentiated. The rising edge and decay of the main component of the dynamic extensor EMG phase could be approximated by exponential functions; this component was never split into a few subcomponents. Dependences between the amplitudes of m. triceps brachii EMG phases and the amplitude of the movement (or external loading) were, as a rule, nonlinear but monotonic. An increase in the test movement velocity led to an increase in the rate of rise of the rising edge of the dynamic EMG phase, while an increment in the amplitude was less significant. Under the used test conditions, the activity of the elbow extensors was usually accompanied by some coactivation of the antagonists (m. biceps brachii). It is concluded that motor commands coming to the elbow extensors at performance of the extension test movements differ from motor commands to the flexors at analogous flexion test movements by a simpler structure and more tonic pattern. Biomechanical specificities of fixation of the mentioned muscle groups to the arm bones (stability of the moment for application of the extensor force under conditions of changing the joint angle vs variable moment of the flexor force) are considered one of the main reasons for such specificity of the patterns of the extensor and flexor motor commands.     

Intrarater reliability and agreement of linear encoder derived heel-rise endurance test outcome measures in healthy adults

A linear encoder measuring vertical displacement during the heel-rise endurance test (HRET) enables the assessment of work and maximum height in addition to the traditional repetitions measure. We aimed to compare the test-retest reliability and agreement of these three outcome measures. Thirty-eight healthy participants (20 females, 18 males) performed the HRET on two occasions separated by a minimum of seven days. Reliability was assessed by the intraclass correlation coefficient (ICC) and agreement by a range of measures including the standard error of measurement (SEM), coefficient of variation (CV), and 95% limits of agreement (LoA). Reliability for repetitions (ICC = 0.77 (0.66, 0.85)) was equivalent to work (ICC = 0.84 (95% CI 0.76, 0.89)) and maximum height (ICC = 0.85 (0.77, 0.90)). Agreement for repetitions (SEM = 6.7 (5.8, 7.9); CV = 13.9% (11.9, 16.8%); LoA = −1.9 ± 37.2%) was equivalent to work (SEM = 419 J (361, 499 J); CV = 13.1% (11.2, 15.8%); LoA = 0.1 ± 34.8%) with maximum height superior (SEM = 0.8 cm (0.6, 1.0 cm); CV = 6.6% (5.7, 7.9%); LoA = 1.3 ± 17.1%). Work and maximum height demonstrated acceptable reliability and agreement that was at least equivalent to the traditional repetitions measure.     

Extrapolation of an empirical elbow muscle co-activation relationship to a novel task set: implications for predictions of individual muscle demands

Biomechanical optimisation models applying efficiency-based objective functions often underestimate antagonist contributions. Previous work has quantified an empirical co-activation relationship in the elbow musculature, demonstrating that implementing this relationship as a constraint in an elbow muscle force prediction model improves muscle force predictions. The current study evaluated this modified model by extrapolating the co-activation relationship to 36 novel isometric unilateral, right-handed exertions, including those requiring greater intensity of effort and performed in different postures. Surface electromyography was recorded from the elbow flexors and extensors. Novel extrapolative co-activation relationships were developed and used as constraints in a muscle force prediction model. Model predictions using both constraints were compared with empirical biophysical data. Predictions by the modified model were more consistent with biophysical data than those by the original model for the novel exertions. Novel co-activation relationships did not further enhance predictions when compared with the previous relationship, suggesting that extrapolation of the previous relationship is feasible.     

Ligament fibre recruitment at the human ankle joint complex in passive flexion

Knowledge of ligament fibre recruitment at the human ankle joint complex is a fundamental prerequisite for analysing mobility and stability. Previous experimental and modelling studies have shown that ankle motion must be guided by fibres within the calcaneofibular and tibiocalcaneal ligaments, which remain approximately isometric during passive flexion. The purpose of this study was to identify these fibres.

Three below-knee amputated specimens were analysed during passive flexion with combined radiostereometry for bone pose estimation and 3D digitisation for ligament attachment area identification. A procedure based on singular value decomposition enabled matching bone pose with digitised data and therefore reconstructing position in space of ligament attachment areas in each joint position. Eleven ordered fibres, connecting corresponding points on origin and insertion curves, were modelled for each of the following ligaments: posterior talofibular, calcaneofibular, anterior talofibular, posterior tibiotalar, tibiocalcaneal, and anterior tibiotalar.

The measured changes in length for the ligament fibres revealed patterns of tightening and slackening. The most anterior fibre of the calcaneofibular and the medio-anterior fibre of the tibiocalcaneal ligament exhibited the most isometric behaviour, as well as the most posterior fibre of the anterior talofibular ligament. Fibres within the calcaneofibular ligament remain parallel in the transverse plane, while those within the tibiocalcaneal ligament become almost parallel in joint neutral position. For both these ligaments, fibres maintain their relative inclination in the sagittal plane throughout the passive flexion range.

The observed significant change in both shape and orientation of the ankle ligaments suggest that this knowledge is fundamental for future mechanical analysis of their response to external forces.     

Orcadian Rhythm in the Torque Developed by Elbow Flexors During Isometric Contraction Effect of Sampling Schedules

Time-dependent changes in elbow flexion torque have been documented according to two different sampling schedules. Seven physical education students took part in the first series of experiments, and 7 other similar subjects in the second. In both sets of experiments, the subjects performed isometric contractions: maximal and submaximal at 90° in the first experiments and maximal at different angular positions in the second. After a 30-minute rest period, the torque developed was measured at 00:00, 06:00, 09:00, 12:00, 15:00, 18:00, and 21:00h on the day of the experiment. These subjects remained in the laboratory for 24h. In the second series of experiments, the torque developed was measured at 01:00, 05:00, 09:00, 13:00, 17:00, and 21:00h over the subsequent 6 days with only one test session per day. In this case, there was an interval of 20h between two successive test sessions. In the first experiment, a significant time-of-day effect was observed for the torque of the elbow flexors under isometric conditions with an acrophase at 17:58h. The 24h normalized mean score was 92.85% with an amplitude of 7.63% of the daily mean. In the second series of experiments, there was evidence of a circadian rhythm in the torque developed by the elbow flexors at every angle position, especially at 90°, the angle investigated in the first set of experiments. The peak torque was calculated to have occurred at 17:55h. The amplitude of the rhythm was equal to 6.99% of the daily mean. There were no statistically significant differences in the characteristics of the circadian rhythm observed between the two experimental designs. We concluded that an experiment extending over several days could be employed to evaluate circadian rhythms in muscular activity reliably. (Chronobiology International, 14(3), 287–294, 1997)     

Morphology and evolution of the wing bullae in South American Leptophlebiidae (Ephemeroptera)

Insects were the first animals to take to the skies, and have been flying for over 320 million years. The order Ephemeroptera is, or at least is part of, the most early-diverging lineage of extant winged insects. The extant species present a very short adult life span, mainly dedicated to reproduction and dispersal of eggs. Mating and egg-laying behavior depend on flight. Wings are structures to fly and as such face a number of physical and physiological challenges. The convex curvature along the anterior–posterior axis of the wing generates a camber that must be carefully regulated. One of the most interesting ways of wing bending is provided by the bullae, which have been defined as short sections of flexible chitin, where the flexion lines cross veins. Although the bullae have been frequently used as taxonomic characters, there is no study focused on their morphology, although their prevalence on the wings of mayflies strongly suggests a role in flight. In order to identify evolutionary trends of these structures within Ephemeroptera, we constructed a matrix with comparative anatomy data of the bullae from whole mounts of the wings of 300 specimens belonging to 70 species of several mayfly families, as well as scanning microscopy samples of selected specimens. We also surveyed the number of bullae and their distribution in the wings of the different species within the South American Leptophlebiidae clade. We optimized the characters onto the latest published phylogeny for Leptophlebiidae.     

Antibody elbow angles are influenced by their light chain class

We have examined the elbow angles for 365 different Fab fragments, and observe that Fabs with lambda light chains have adopted a wider range of elbow angles than their kappa chain counterparts, and that the lambda light chain Fabs are frequently found with very large (>195 degrees ) elbow angles. This apparent hyperflexibility of lambda chain Fabs may be due to an insertion in their switch region, which is one residue longer than in kappa chains, with glycine occurring most frequently at the insertion position. A new, web-based computer program that was used to calculate the Fab elbow angles is described.