SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Human leg

81

Here we show that novel, energy-recycling stairs reduce the amount of work required for humans to both ascend and descend stairs. Our low-power, interactive, and modular steps can be placed on existing staircases, storing energy during stair descent and returning that energy to the user during stair ascent. Energy is recycled through event-triggered latching and unlatching of passive springs without the use of powered actuators. When ascending the energy-recycling stairs, naive users generated 17.4 ± 6.9% less positive work with their leading legs compared to conventional stairs, with the knee joint positive work reduced by 37.7 ± 10.5%. Users also generated 21.9 ± 17.8% less negative work with their trailing legs during stair descent, with ankle joint negative work reduced by 26.0 ± 15.9%. Our low-power energy-recycling stairs have the potential to assist people with mobility impairments during stair negotiation on existing staircases.

Concepts: Human anatomy, Human leg, Joint, Knee, Joints, Stairway, Energy, Potential energy

60

Sthenurine kangaroos (Marsupialia, Diprotodontia, Macropodoidea) were an extinct subfamily within the family Macropodidae (kangaroos and rat-kangaroos). These “short-faced browsers” first appeared in the middle Miocene, and radiated in the Plio-Pleistocene into a diversity of mostly large-bodied forms, more robust than extant forms in their build. The largest (Procoptodon goliah) had an estimated body mass of 240 kg, almost three times the size of the largest living kangaroos, and there is speculation whether a kangaroo of this size would be biomechanically capable of hopping locomotion. Previously described aspects of sthenurine anatomy (specialized forelimbs, rigid lumbar spine) would limit their ability to perform the characteristic kangaroo pentapedal walking (using the tail as a fifth limb), an essential gait at slower speeds as slow hopping is energetically unfeasible. Analysis of limb bone measurements of sthenurines in comparison with extant macropodoids shows a number of anatomical differences, especially in the large species. The scaling of long bone robusticity indicates that sthenurines are following the “normal” allometric trend for macropodoids, while the large extant kangaroos are relatively gracile. Other morphological differences are indicative of adaptations for a novel type of locomotor behavior in sthenurines: they lacked many specialized features for rapid hopping, and they also had anatomy indicative of supporting their body with an upright trunk (e.g., dorsally tipped ischiae), and of supporting their weight on one leg at a time (e.g., larger hips and knees, stabilized ankle joint). We propose that sthenurines adopted a bipedal striding gait (a gait occasionally observed in extant tree-kangaroos): in the smaller and earlier forms, this gait may have been employed as an alternative to pentapedal locomotion at slower speeds, while in the larger Pleistocene forms this gait may have enabled them to evolve to body sizes where hopping was no longer a feasible form of more rapid locomotion.

Concepts: Kangaroo, Anatomy, Foot, Walking, Locomotion, Marsupial, Human leg, Human anatomy

39

A 29-year-old woman presented to the spine clinic with pain in her right leg, accompanied by paresthesia. MRI of the lumbar spine revealed a lumbar disk herniation resulting in substantial spinal stenosis and nerve-root compression.

Concepts: Human leg, Surgery, Spinal stenosis, The Spine, Neurology, Lumbar vertebrae, Vertebral column, Spinal disc herniation

31

Regeneration is a complex and dynamic process, mobilizing diverse cell types and remodelling tissues over long time periods. Tracking cell fate and behaviour during regeneration in active adult animals is especially challenging. Here, we establish continuous live imaging of leg regeneration at single-cell resolution in the crustacean Parhyale hawaiensis. By live recordings encompassing the first 4-5 days after amputation, we capture the cellular events that contribute to wound closure and morphogenesis of regenerating legs with unprecedented resolution and temporal detail. Using these recordings we are able to track cell lineages, to generate fate maps of the blastema and to identify the progenitors of regenerated epidermis. We find that there are no specialized stem cells for the epidermis. Most epidermal cells in the distal part of the leg stump proliferate, acquire new positional values and contribute to new segments in the regenerating leg.

Concepts: Blastema, Cell, Human leg, Regeneration, Cellular differentiation, Developmental biology

29

The purpose of the study was to examine the effects of a resistance exercise program on soccer kick biomechanics. Twenty male amateur soccer players were divided in the Experimental (EG) and the Control (CG) group, each consisting of ten players. The EG followed a 10-week resistance exercise program mainly for the lower limb muscles. Maximal instep kick kinematics, electromyography and ground reaction forces (GRFs) as well as maximum isometric leg strength were recorded before and after training. A two-way analysis of variance showed significantly higher ball speed values only for the EG (26.14 ± 1.17 m/sec versus 27.59 ± 1.49 m/sec before and after training, respectively), while no significant differences were observed for the CG. The EG showed a decline in joint angular velocities and an increase in biceps femoris EMG of the swinging leg during the backswing phase followed by a significant increase in segmental and joint velocities and muscle activation of the same leg during the forward swing phase (P < 0.05). The EG also showed significantly higher vertical GRFs and rectus femoris and gastrocnemius activation of the support leg (P < 0.05). Similarly, maximum and explosive isometric force significantly increased after training only for the EG (P < 0.05). These results suggest that increases in soccer kicking performance after a 10-week resistance training program were accompanied by increases in maximum strength as well as an altered soccer kick movement pattern, characterized by a more explosive backward - forward swinging movement and higher muscle activation during the final kicking phase.

Concepts: Exercise, Ground reaction force, Human leg, Football, Strength training, Isometric exercise, Electromyography, Muscle

28

Endovascular therapy (ET) is the treatment of choice for critical limb ischemia (CLI) and tibial arteries disease (TAD) in focal lesions with restorable run-off; ankle and foot bypass (BPG) is indicated in patients unfit for ET with foot or ankle arteries suitable for surgery. The aim of this study was to evaluate limb salvage (LS), primary patency (PP) and survival (S) of patients underwent BPG in the era of ET for TAD and to define the correlated prognostic factors.

Concepts: Human leg, Ischemia, Medical terms, Foot, Medicine

28

To evaluate the effectiveness of low-intensity pulsed ultrasound (LIPUS) for the improvement of lower limb bone stress injuries in a civilian population.

Concepts: Civilian, Human leg, Randomized controlled trial

28

Background  “Tender cutaneous nodules of the legs” is a common manifestation in dermatology. Histopathological investigation is usually required for this condition, because clinical data are frequently insufficient to make a definite diagnosis. Objective  To identify and analyze the causes of patients presenting with tender leg nodules and to reveal clinical clues that could help to differentiate causes. Materials and methods  The medical records and histopathological slides of patients presenting with tender cutaneous nodules of the legs between January 2005 and December 2007 were retrospectively reviewed. Results  Of the total of 154 patients, 122 (79.2%) were female. Definite diagnoses were categorized into four groups: inflammation (84.4%); infection (5.8%); tumor (6.5%); and nonspecific (3.2%). The most common cause in the inflammation group was erythema nodosum. The infections found were Acremonium spp., Penicillium sp., Mycobacterium abscessus, Mycobacterium fortuitum and Mycobacterium leprae. The tumors included leiomyoma, leukemia cutis, and lymphomas. Clinical data that correlated with and could be used as clues for the inflammation group were female sex (P = 0.03, OR 6.43) and lower leg involvement (P = 0.03, OR 7.14). Limitations  The retrospective manner of this study is a limitation. Conclusion  Various inflammatory conditions, infections, and tumors can present as tender cutaneous nodules of the legs. Female sex and lower leg involvement were clinical data that could be used as clues for the diagnoses in the inflammation group. However, histopathological investigation is still crucial to determine a definite diagnosis in patients presenting with tender cutaneous nodules of the legs.

Concepts: Leprosy, Mycobacterium leprae, Infection, Mycobacterium, Erythema nodosum, Human leg, Cancer, Inflammation

28

The purpose of this study was to describe the effects of lower limb positioning and shoe conditions on stability levels of selected single leg ballet poses performed in demi-pointe position. Fourteen female non-professional ballet dancers (mean age of 18.4±2.8 years and mean body mass index of 21.5±2.8kg/m) who had practiced ballet for at least seven years, without any musculoskeletal impairment volunteered to participate in this study. A capacitive pressure platform allowed for the assessment of center of pressure variables related to the execution of three single leg ballet poses in demi pointé position: attitude devant, attitude derriére, and attitude a la second. Peak pressures, contact areas, COP oscillation areas, anterior-posterior and medio-lateral COP oscillations and velocities were compared between two shoe conditions (barefoot versus slippers) and among the different poses. Barefoot performances produced more stable poses with significantly higher plantar contact areas, smaller COP oscillation areas and smaller anterior-posterior COP oscillations. COP oscillation areas, anterior-posterior COP oscillations and medio-lateral COP velocities indicated that attitude a la second is the least challenging and attitude derriére the most challenging pose.

Concepts: Ballet, Positioning, Pressure, Oscillation, Performance, Human leg, Mass, Body mass index

28

Hypertrophy of abductor hallucis muscle is one of the reported causes of compression of tibial nerve branches in foot, resulting in tarsal tunnel syndrome. In this study, we dissected the foot (including the sole) of 120 lower limbs in 60 human cadavers (45 males and 15 females), aged between 45 and 70 years to analyze the possible impact of abductor hallucis muscle in compression neuropathy of tibial nerve branches. We identified five areas in foot, where tibial nerve branches could be compressed by abductor hallucis. Our findings regarding three of these areas were substantiated by clinical evidence from ultrasonography of ankle and sole region, conducted in the affected foot of 120 patients (82 males and 38 females), aged between 42 and 75 years, who were referred for evaluation of pain and/or swelling in medial side of ankle joint with or without associated heel and/or sole pain. We also assessed whether estimation of parameters for the muscle size could identify patients at risk of having nerve compression due to abductor hallucis muscle hypertrophy. The interclass correlation coefficient for dorso-planter thickness of abductor hallucis muscle was 0.84 (95% CI, 0.63-0.92) and that of medio-lateral width was 0.78 (95% CI, 0.62-0.88) in the imaging study, suggesting both are reliable parameters of the muscle size. Receiver operating characteristic curve analysis showed, if ultrasonographic estimation of dorso-plantar thickness is >12.8 mm and medio-lateral width > 30.66 mm in patients with symptoms of nerve compression in foot, abductor hallucis muscle hypertrophy associated compression neuropathy may be suspected. Clin. Anat., 2012. © 2012 Wiley Periodicals, Inc.

Concepts: Calcaneus, Tibial nerve, Receiver operating characteristic, Human anatomy, Lateral plantar nerve, Ankle, Human leg, Foot