Aquatic and terrestrial takeoffs require different hindlimb kinematics and muscle function in mallard ducks.

Mallard ducks are capable of performing a wide range of behaviors including nearly vertical takeoffs from both terrestrial and aquatic habitats. The hindlimb plays a key role during takeoffs from both media. However, because force generation differs in water versus on land, hindlimb kinematics and muscle function are likely modulated between these environments. Specifically, we hypothesize that hindlimb joint motion and muscle shortening are faster during aquatic takeoffs, but greater hindlimb muscle forces are generated during terrestrial takeoffs. In this study, we examined the hindlimb kinematics and in vivo contractile function of the lateral gastrocnemius (LG), a major ankle extensor and knee flexor, during takeoffs from water versus land in mallard ducks. In contrast to our hypothesis, we observed no change in ankle angular velocity between media. However, the hip and metatarsophalangeal joints underwent large excursions during terrestrial takeoffs but exhibited almost no motion during aquatic takeoffs. The knee extended during terrestrial takeoffs but flexed during aquatic takeoffs. Correspondingly, LG fascicle shortening strain, shortening velocity and pennation angle change were greater during aquatic takeoffs than during terrestrial takeoffs because of the differences in knee motion. Nevertheless, we observed no significant differences in LG stress or work, but did see an increase in muscle power output during aquatic takeoffs. Because differences in the physical properties of aquatic and terrestrial media require differing hindlimb kinematics and muscle function, animals such as mallards may be challenged to tune their muscle properties for movement across differing environments.

Re-innovation of split lateral gastrocnemius muscle flap for complicated proximal tibia open fracture: Case report.

INTRODUCTION AND IMPORTANCE: Maintaining mobility and hence the productivity of individuals depends on the preservation of lower limb integrity. Increasing violence, mainly triggered by weapons, inversely impacts limb functionality, and the resulting wounds require proper care. CASE PRESENTATION: A 47-year-old African man without any previous medical conditions experienced an injury to his right leg from a high-speed accident, resulting in an open fracture in the upper third of the tibia with missing tissue. At first, he received care from orthopedic surgeons and had debridement done along with the use of an external fixation device to stabilize his limb. Two weeks later, he was referred to the plastic surgery unit and was preparing for urgent surgery. A split lateral gastrocnemius muscle flap was used to reconstruct him after a surgical debridement. CLINICAL DISCUSSION: Proximal leg trauma can be managed successfully by rearrangement of local tissue, resulting in a perfect outcome with less donor site morbidity and a long, complex surgery compared to free tissue transfer. Gastrocnemius muscle or myocutaneous flap, is a gold standard for proximal leg trauma, mainly when a cavity exists, and it is able to create satisfactory reconstruction. CONCLUSION: The split lateral gastrocnemius muscle flap is an effective modification of the flap, resulting in greater surface area coverage, less bulk and shape distortion, and reliable blood supply. Furthermore, it is easy to harvest and apply, deferring the need for step-curve microsurgical procedures.

3-D Ultrasonographic Quantification of Hand and Calf Muscle Volume: Statistical Shape Modeling Approach.

Accurate acquisition and segmentation of muscles are essential in 3-D freehand ultrasonography (US) to estimate in vivo muscle volume, but the source of segmentation inaccuracy in shape variation has never been the focus. This study was aimed at investigating reliability of 3-D US in the acquisition and segmentation for muscle volume of two muscles of different sizes and in identifying a primary source of measurement difference. The lateral gastrocnemius and flexor pollicis brevis of 12 healthy adults were assessed using freehand 3-D US scans. The motion-tracking data of the probe were synchronized with the B-mode ultrasound scan to reconstruct 3-D muscle volume. Statistical shape modeling was used to provide a spatial segmentation volume difference that further explains the variation around segmentation repeatability. The absolute difference of the flexor pollicis brevis was 3.5 percentage points greater than that for the lateral gastrocnemius. The highest measurement differences were observed when for inter-acquirer analysis. Statistical shape modeling revealed that the primary segmentation volume differences were at the muscle ends and edges, where the muscle interfaces with the surrounding muscles. Three-dimensional US is a reliable tool in the clinical setting, but care must be taken to ensure that acquisition and segmentation are consistent, particularly in a small muscle that interfaces with tendons and other soft tissues.

Comparison of the relative muscle volume of triceps surae among sprinters, runners, and untrained participants.

Muscle hypertrophy is considered more prominent in fast-twitch than in slow-twitch muscles. This leads to the hypothesis that the relative muscle volume of the medial gastrocnemius (MG) and lateral gastrocnemius (LG) becomes larger than that of the soleus (SOL) in highly trained participants because MG and LG include more fast-twitch muscles than SOL. Thus, we compared relative muscle volume among highly trained sprinters, long-distance runners, and untrained participants to examine whether the above hypothesis is correct. Magnetic resonance imaging was used to calculate the muscle volume of MG, LG, and SOL from 126 participants. The total muscle volume of the three muscles and the relative muscle volume of each muscle with respect to the total muscle volume were calculated. The total muscle volume was significantly larger in the sprinters than in the long-distance runners and untrained participants. The relative muscle volume of MG was significantly larger in the sprinters than in the long-distance runners and untrained participants and that of SOL was significantly smaller in the sprinters than in the long-distance runners and untrained participants. These results indicate that the relative muscle volume can vary among participants, possibly due to fiber type-dependent muscle hypertrophy.

Could Ankle Muscle Activation be Used as a Simple Measure of Balance Exercise Intensity?

Few, if any, studies have reported the effects of intensity of balance exercise for balance training and rehabilitation. The aim of the present study was to find a relative measure of intensity of balance exercise. On this basis, we analysed ankle muscle activation in the sagittal plane with increasing difficulty for a one leg stance on a T-board. Ten adults (7 men, 24.1 ± 3.5 years; 3 women, 30.6 ± 5.8 years) performed 3 trials on a T-board within 6 randomly assigned stability levels. T-board swaying velocities in the sagittal plane were manipulated to attain different stability levels (conditions). Concurrently, angular distance of the T-board and active balance time (i.e., percentage of a total time balancing) under each condition were measured. Surface electromyography from the tibialis anterior, gastrocnemius and soleus were monitored during one leg stance. The surface electromyography amplitude in the time domain was quantified using the root-mean-square values. Significant effect of stability levels on angular distance (F5,45 = 3.4; p = 0.01) and velocity of the T-board (F5,45 = 4.6; p = 0.002) were obtained. Active balance time decreased by ∼15% (p = 0.001) from the maximal to the minimal stability conditions. The graded level of balance board stability conditions did not generate significantly higher root-mean-square values in any muscles and hence could not be used as a relative measure of intensity of balance exercise. These findings imply that there could be a plateau in difficulty of balance exercise for enhancement of ankle muscle activity.

[Reconstruction of the donor area of distally based sural flap with relaying lateral gastrocnemius artery perforator propeller flap].

Objective: To investigate the clinical application of relaying lateral gastrocnemius artery perforator flap in reconstruction of the donor defect after distally sural flap transferring. Methods: Between January 2014 and January 2016, 12 cases with foot and ankle defects were treated. There were 10 males and 2 females with an average age of 23.4 years (mean, 14-52 years). The injury was caused by motorcycle accident in 7 cases and traffic accident in 5 cases. The injury located at left limb in 7 cases and right limb in 5 cases. The size of soft tissue ranged from 10 cm×4 cm to 12 cm×6 cm. The disease duration was 2-84 hours (mean, 26.2 hours). The foot and ankle defects were reconstructed by distally sural flaps, then the flap donor sites were reconstructed with relaying lateral gastrocnemius artery perforator flap at the same stage. The size of distally sural flap ranged from 11 cm×5 cm to 13 cm×7 cm. The size of relaying flap ranged from 7 cm×4 cm to 10 cm×6 cm. Results: All flaps survived uneventfully. All recipient sites and donor sites healed smoothly. No vascular crisis, wound dehiscence, or evident swelling occurred. All patients were followed up 6-14 months (mean, 12.4 months) with satisfied esthetic and functional results in recipient and donor sites. There were only linear scar on the donor sites. The color and contour was satisfying, the function of calf and foot were not affected. Conclusion: The relaying lateral gastrocnemius artery perforator flap combined with distally sural flap is an idea choice to reconstruct foot and ankle defect, which can avoid donor site skin grafting, minimize donor site morbidity.

Regionalizing muscle activity causes changes to the magnitude and direction of the force from whole muscles-a modeling study.

Skeletal muscle can contain neuromuscular compartments that are spatially distinct regions that can receive relatively independent levels of activation. This study tested how the magnitude and direction of the force developed by a whole muscle would change when the muscle activity was regionalized within the muscle. A 3D finite element model of a muscle with its bounding aponeurosis was developed for the lateral gastrocnemius, and isometric contractions were simulated for a series of conditions with either a uniform activation pattern, or regionally distinct activation patterns: in all cases the mean activation from all fibers within the muscle reached 10%. The models showed emergent features of the fiber geometry that matched physiological characteristics: with fibers shortening, rotating to greater pennation, adopting curved trajectories in 3D and changes in the thickness and width of the muscle belly. Simulations were repeated for muscle with compliant, normal and stiff aponeurosis and the aponeurosis stiffness affected the changes to the fiber geometry and the resultant muscle force. Changing the regionalization of the activity resulted to changes in the magnitude, direction and center of the force vector from the whole muscle. Regionalizing the muscle activity resulted in greater muscle force than the simulation with uniform activity across the muscle belly. The study shows how the force from a muscle depends on the complex interactions between the muscle fibers and connective tissues and the region of muscle that is active.

Redistribution of Kv2.1 ion channels on spinal motoneurons following peripheral nerve injury.

Pathophysiological responses to peripheral nerve injury include alterations in the activity, intrinsic membrane properties and excitability of spinal neurons. The intrinsic excitability of α-motoneurons is controlled in part by the expression, regulation, and distribution of membrane-bound ion channels. Ion channels, such as Kv2.1 and SK, which underlie delayed rectifier potassium currents and afterhyperpolarization respectively, are localized in high-density clusters at specific postsynaptic sites (Deardorff et al., 2013; Muennich and Fyffe, 2004). Previous work has indicated that Kv2.1 channel clustering and kinetics are regulated by a variety of stimuli including ischemia, hypoxia, neuromodulator action and increased activity. Regulation occurs via channel dephosphorylation leading to both declustering and alterations in channel kinetics, thus normalizing activity (Misonou et al., 2004; Misonou et al., 2005; Misonou et al., 2008; Mohapatra et al., 2009; Park et al., 2006). Here we demonstrate using immunohistochemistry that peripheral nerve injury is also sufficient to alter the surface distribution of Kv2.1 channels on motoneurons. The dynamic changes in channel localization include a rapid progressive decline in cluster size, beginning immediately after axotomy, and reaching maximum within one week. With reinnervation, the organization and size of Kv2.1 clusters do not fully recover. However, in the absence of reinnervation Kv2.1 cluster sizes fully recover. Moreover, unilateral peripheral nerve injury evokes parallel, but smaller effects bilaterally. These results suggest that homeostatic regulation of motoneuron Kv2.1 membrane distribution after axon injury is largely independent of axon reinnervation.

Enhanced sympathetic activity in mice with brown adipose tissue transplantation (transBATation).

Brown adipose tissue (BAT) burns calories to produce heat, and is thus relevant to energy balance. Interscapular BAT (IBAT) of donor mice was transplanted into recipient mice (transBATation). To test whether transBATation counteracts high-fat diet (HFD)-induced obesity, some sham-operated and recipient mice were fed a HFD (HFD-sham, HFD-trans) while others remained on a standard chow (chow-sham, chow-trans). HFD-trans mice had lower body weight and fat and greater energy expenditure, but similar caloric intake compared with HFD-sham mice. We hypothesized that HFD-trans mice had elevated sympathetic activity compared with HFD-sham mice, contributing to increased energy expenditure and fuel mobilization. This was supported by findings that HFD-trans mice had greater energy expenditure during a norepinephrine challenge test and higher core temperatures after cold exposure than did HFD-sham mice, implicating enhanced whole-body metabolic response and elevated sympathetic activity. Additionally, transBATation selectively increased sympathetic drive to some, but not all, white adipose tissue depots and skeletal muscles, as well as the endogenous IBAT, heart, and liver. Collectively, transBATation confers resistance to HFD-induced obesity via increase in whole-body sympathetic activity, and differential activation of sympathetic drive to some of the tissues involved in energy expenditure and fuel mobilization.