Dog Forelimb Research Articles

Effects of jump height on forelimb landing forces in border collies.

The objective of this study was to evaluate the effects of jump height on the landing forces of dogs. Client-owned Border Collies experienced in agility competition, n = 9. The study involved client owned border collies with the same AKC standard jump height of 20 inches and preferred height of 16 inches. Standard height is based upon the height of the dog at the withers, with preferred height referred to as reduction in jump height by one level due to injury or age. An AKC regulation bar jump was placed over a previously validated pressure sensitive walkway (PSW). The peak force (%BW) and peak contact pressure (kPa) of the leading and trailing forelimbs were evaluated for all dogs. There was no significant difference in landing force between the two jump heights for either peak force as a percentage of body weight or peak contact pressure when evaluated in both leading and trailing forelimbs. Our findings demonstrated no significant difference in active landing forces of peak contact pressure and peak force on the forelimbs of dogs when jumping at a standard jump height vs. a preferred jump height when controlling for velocity in dogs performing a single running bar jump. These results suggest that the recommendation of decreasing jump height for older animals or injured animals may not provide a significant decrease in the impact on the forelimbs. It is likely that other factors contribute to the total forelimb kinematics picture during competition. Veterinarians and trainers should consider additional ways to decrease impact for canine athletes as they recover from injury.

Comparative characteristics of local anesthetics in brachial plexus block for surgery in dogs

The objective of this study was to compare three different local anesthetics in terms of duration and effectiveness of block development in brachial plexus block for osteosynthesis of radius with plate in dogs. The blockade was received a electroneurostimulation-guided Stimuplex HNS 12 with SENSe function by B. Brown for all group. 15 dogs of smallest breeds were divided into three random groups: in the first, 2% lidocaine solution was used as anesthesia; in the second bupivacaine 0.5%, in the third ropivacaine 0.5%. The time to development and the duration of the local block were assessed with a pinch method in several areas. The fastest development of a complete limb block was observed in group 1, which took an average of 7-10 minutes. The development of a complete block in the 2nd group exceeded three times, and in the 3rd - twice, the anesthetic indicators of the 1st group. All patients from group 1 were immediately injected with analgesics after surgery to relieve postoperative pain. The duration of the blockade of the third group was significantly shorter than in the second group, however, the motor block in the second group was significantly longer than in the 3rd group, patients experienced pain, but the motor function of the distal limb has not yet recovered. Thus, ropivacaine, by its properties, is the drug of choice for brachial plexus blockade for periosteal osteosynthesis of the forelimb in dogs and can be used for surgeries longer than 80 minutes.

Comparative anatomy of selected bones of forelimb of local Mongrelian Dog (Canis lupus familiaris) in Sokoto, Nigeria

This research was conducted over period of 3 months with the aim of studying Age related changes of selected bones of forelimb (Scapula, Humerus, Radius and Ulna) in Local Mongrelian Dog (Canis lupus familiaris). The study entails biometrical and gross observations on the bones. The sample bones were acquired from the experimental animals of comparative anatomy in the department. The bones were categorized into various age groups for the research. The length, width, diameter and circumference of the samples (scapula, humerus, radius and ulna bones) were determined for all the groups. The shape, size, color, location, position and relation of each segment of the samples at various stages of development were determined. The differences across the age groups of different samples were observed and recorded. Based on the research result, it was concluded that, the biometric and morphometry data was found to be increasing with advancement of age. A baseline data was established with the view to enhance learning.

Radiographic and Biochemical Evaluations of Postnatal Development of Bones of the Forelimb in Nigerian Indigenous Dogs.

Bone is a hard and resilient tissue structure that provides mechanical support for the body of an organism. This study was aimed to evaluate the radiographical and biochemical changes during postnatal bone development of forelimbs in Nigerian indigenous puppies from 2-week-old to 24-week-old. Six (6) Nigerian indigenous puppies were chemically restrained using chlorpromazine at 2 mg/kg I.M. and positioned using ropes and sandbags for mediolateral and craniocaudal views of bones of the forelimbs. At 2-week-old, radiographic evaluation of bones of the forelimbs were undertaken and continued bi-weekly up to 24-week-old. Serum samples were analysed from 4-week-old to 24-week-old at four weeks’ interval for mineral (electrolytes) using colometric method for calcium and phosphorus and flame photometry method for sodium and potassium. At 2-week-old, there was an ill-defined radiopaque secondary ossification centre at the proximal epiphysis and a small ovoid radiopaque structure at the distal epiphysis of the humerus. There was not any sign of secondary ossification centre at proximal and distal epiphyses of both radius and ulna. There was the presence of a small radiopaque (ill-defined) accessory carpal. 1st to 5th metacarpals were present together with the proximal, middle and distal phalanges of all digits except the 1st digit that has proximal and distal phalanges. From 20-week-old, fully developed carpals and bony structures were observed through 24-week-old where the commencement of fusion of apophyses of olecranon (proximal epiphysis of ulna) at the centre and acrophyses of metacarpals and phalanges. The mean values (mean ± SEM) from serum biochemistry of calcium, phosphate, sodium and potassium in mmol/L from this study were within the normal limits throughout the study. Conclusively, the complementary information from calcium, phosphate, sodium and potassium in this study showed that these elements are within the normal limit that suggests normal bone development during the study period, which stressed the importance of the knowledge on serial changes of bone development which could be useful in clinical practice.

Comparison of Simultaneous Measurements of Forelimb and Hindlimb Systolic Blood Pressure in Conscious Dogs

Blood pressure is commonly measured in veterinary medicine. Previous studies have used indirect measurements to compare the forelimb and hindlimb blood pressure in dogs, and yielded contradictory results. Notably in these studies, the measurement of both limbs was not performed simultaneously. In this study, Doppler ultrasonography was used to measure systolic arterial pressure (SAP) and pulse rate (PR) simultaneously on the median palmar artery of forelimb and the medial plantar artery of hindlimb in 108 conscious dogs. The optimal cuff size was selected using 30-40% of the limb circumference. The SAP of forelimb and hindlimb were 149.5 ± 28.5 mm Hg and 152.3 ± 31.1 mm Hg. The PR of forelimb and hindlimb were 113.9 ± 31.7 beats per minute (bpm) and 113.1 ± 31.2 bpm, respectively. The SAP and PR of the forelimb and hindlimb correlated significantly (Pearson R2 = 0.696, P < .001; Pearson R2 = 0.966, P < .001). There was no significant difference in SAP and PR between the forelimb and hindlimb (P = .1; P = .184). There was no significant difference in the SAP and PR of the forelimb and hindlimb using Doppler device measurement in conscious dogs. Both sites of blood pressure measurement could be adequate for analyzing trends in blood pressure.

Limb dynamics in agility jumps of beginner and advanced dogs.

A considerable body of work has examined the dynamics of different dog gaits, but there are no studies that have focused on limb dynamics in jumping. Jumping is an essential part of dog agility, a dog sport in which handlers direct their dogs through an obstacle course in a limited time. We hypothesized that limb parameters like limb length and stiffness indicate the skill level of dogs. We analyzed global limb parameters in jumping for 10 advanced and 10 beginner dogs. In experiments, we collected 3D kinematics and ground reaction forces during dog jumping at high forward speeds. Our results revealed general strategies of limb control in jumping and highlighted differences between advanced and beginner dogs. In take-off, the spatially leading forelimb was 75% (P<0.001) stiffer than the trailing forelimb. In landing, the trailing forelimb was 14% stiffer (P<0.001) than the leading forelimb. This indicates a strut-like action of the forelimbs to achieve jumping height in take-off and to transfer vertical velocity into horizontal velocity in landing (with switching roles of the forelimbs). During landing, the more (24%) compliant forelimbs of beginner dogs (P=0.005) resulted in 17% (P=0.017) higher limb compression during the stance phase. This was associated with a larger amount of eccentric muscle contraction, which might in turn explain the soft tissue injuries that frequently occur in the shoulder region of beginner dogs. For all limbs, limb length at toe-off was greater for advanced dogs. Hence, limb length and stiffness might be used as objective measures of skill.

Comparison of vertical force redistribution in the pads of dogs with elbow osteoarthritis and healthy dogs

Kinetic analyses are becoming increasingly important for biomechanical research in veterinary medicine and as a diagnostic tool for orthopaedic examinations in dogs. Such analysis enables accurate evaluation of the vertical force distribution (VFD) in canine paw pads. The aim of this study was to assess peak vertical force (PFz) as a percent of total force (%TF), vertical impulse (IFz, %TF) and time of occurrence of PFz (TPFz) as a percent of the stance phase (%SP) in the pads of all four limbs in 23 dogs with osteoarthritis in the elbow joint and 22 healthy dogs. Dogs walked over a pressure plate, and the pads were divided into four quadrants for VFD analysis. For statistical analysis, a general linear model was used to examine the difference in VFD between both groups, between fore- and hindlimbs, between body sides, and between medial/lateral and cranial/caudal quadrants.Lame dogs had lower PFz in the lame forelimb than in other limbs and transferred their weight to the caudal quadrants of the contralateral forelimb and the caudomedial quadrant of both hindlimbs. IFz was also lower in the affected forelimb and was compensated through higher loading of the caudal quadrants of the contralateral forelimb, the caudomedial quadrants of both hindlimbs and the caudolateral quadrant of the contralateral hindlimb. TPFz (%SP) occurred later in both forelimbs of the lame dogs than in those of healthy dogs. The analysis of force distribution over the paw quadrants can be used for further biomechanical studies of dogs with orthopaedic and neurological diseases.

A STUDY OF USING ABORTED BOVINE FETAL SKIN AND SKIN ALLOGRAFT FOR REPAIRING CRITICAL SKIN DEFECT IN DOGS

The present study was designed to compare the potential repair efficacy of using either skin xenograft or allograft on the treatment of induced skin defects. The study was conducted on twelve stray dogs. Their weight and age ranges were 12-18 kg and 10-15 months, respectively. Animals were randomly allocated into two equal groups. In the first group, a 10 cm of full-thickness skin piece was harvested aseptically from a 4-month-aborted fetus. Along with, in the experimental animals, comparable skin defects were created at the lateral aspect of the forelimb. The grafts were fixed firmly to the wound bed by suturing. In the second group, the skin grafts (10 cm) were harvested from the lower abdomen of dogs and were firmly fixed over induced wounded beds at the forelimb of other dogs. In the first group, a few days postoperatively, the operative site demonstrated dryness, scar tissue formations, delayed wound healing, and local inflammation. However, after one-month post-surgery, there was a separation of the grafted tissue from the wound bed and signs of tissue rejection. In first group, histopathological examination revealed extensive infiltration of the inflammatory cells and separation of the grafted tissue from the subdermal layer. In the second group, the repaired site exhibited inflammatory signs and skin ulcers during the first postoperative week. After one month of the operation, formations of granulation tissue and restoration of normal skin coloration without hair formation were revealed on the allograft site. Complete skin healing and union of the graft with the recipient host were determined after two months of surgery. Histopathological examination demonstrated fibrocystic hyperplasia of the grafted tissue one month post-operatively, while deposition of collagen fibers was the main feature at the second month. In conclusion, unlike using of skin from the aborted bovine fetuses, the study specified the successful outcomes of using skin allograft in tissue repairing in dogs.

Three-dimensional inverse dynamics of the forelimb of Beagles at a walk and trot.

OBJECTIVE To perform 3-D inverse dynamics analysis of the entire forelimb of healthy dogs during a walk and trot. ANIMALS 5 healthy adult Beagles. PROCEDURES The left forelimb of each dog was instrumented with 19 anatomic markers. X-ray fluoroscopy was used to optimize marker positions and perform scientific rotoscoping for 1 dog. Inverse dynamics were computed for each dog during a walk and trot on the basis of data obtained from an infrared motion-capture system and instrumented quad-band treadmill. Morphometric data were obtained from a virtual reconstruction of the left forelimb generated from a CT scan of the same dog that underwent scientific rotoscoping. RESULTS Segmental angles, torque, and power patterns were described for the scapula, humerus, ulna, and carpus segments in body frame. For the scapula and humerus, the kinematics and dynamics determined from fluoroscopy-based data varied substantially from those determined from the marker-based data. The dominant action of scapular rotation for forelimb kinematics was confirmed. Directional changes in the torque and power patterns for each segment were fairly consistent between the 2 gaits, but the amplitude of those changes was often greater at a trot than at a walk. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that control of the forelimb joints of dogs is similar for both a walk and trot. Rotation of the forelimb around its longitudinal axis and motion of the scapula should be reconsidered in the evaluation of musculoskeletal diseases, especially before and after treatment or rehabilitation.

679. Efficient Reconstitution of a 7kb Therapeutic Mini-Dystrophin Gene in Duchenne Muscular Dystrophy Dog Muscle

Duchenne muscular dystrophy (DMD) is a devastating muscle wasting disease caused by mutations in the dystrophin gene. Restoring dystrophin expression by adeno-associated virus mediated gene therapy holds great promise as a mutation-independent therapy for all DMD patients. The full-length dystrophin cDNA (≈11 kb) is far beyond the 5 kb packaging capacity of a single AAV vector. Consequently, truncated micro- and mini-dystrophin genes have been used. The micro- and mini-dystrophin genes encode ≈30% and ≈50% of the full-length dystrophin coding sequence, respectively. Mini-dystrophin is expected to provide better protection than micro-dystrophin. We have previously shown that dual AAV vectors can efficiently express a 6 to 8-kb mini-dystrophin in mdx mice. Dual AAV-mediated mini-dystrophin gene therapy significantly ameliorated histopathology and improved muscle function in mdx mice, a mouse model of DMD. To translate this promising therapy to large mammals, here we evaluated the reconstitution of a 7-kb minigene in the canine model of DMD by local injection. We engineered a pair of dual-AAV vectors to express a 7-kb canine codon-optimized ΔH2-R15 mini-dystrophin gene. For easy detection, a flag-tag and a GFP gene were fused to the N-terminal and C-terminal ends, respectively. To determine whether dual AAV vectors can lead to efficient mini-dystrophin expression, we co-delivered both vectors to the extensor carpi ulnaris muscle in the forelimb of DMD dogs at a dose of 2×013 vg particles/vector/muscle. Two months after gene transfer we evaluated transduction efficiency and observed successful expression of mini-dystrophin from the dual-AAV vectors. All flag-tag positive myofibers were also positive for minidystrophin, GFP and dystrophin-associated glycoprotein complex proteins. Importantly, mini-dystrophin gene therapy also reduced muscle force loss under the stress of repeated cycles of eccentric contraction. These results establish the proof-of-concept for mini-dystrophin gene therapy in dystrophic muscles of large mammals.

Antipruritic application of ovocystatin in atopic dermatitis in dogs - preliminary study

Abstract The study was an attempt to determine the possibilities of using ovocystatin, a component of a new generation product of natural origin, in local therapy of atopic dermatitis in dogs by suppressing pruritus during illness. Chicken egg cystatin was used locally in the interdigital spaces of forelimbs of dogs used in the experiment. The degree of pruritus and clinical changes in the animals were defined using CADESI-03 scale before and after the beginning of the experiment. The results obtained proved that ovocystatin may be used as a substance suppressing pruritus in atopic dermatitis.

Correction of Biapical Radial Deformities by Use of Bi‐Level Hinged Circular External Fixation and Distraction Osteogenesis in 13 Dogs

To describe clinical, radiographic, and computed tomographic (CT) assessment of biapical deformities of the radius in dogs and evaluate the effectiveness of their management by use of bilevel hinged circular external fixation frames. Prospective, non-randomized cohort study. Dogs (N = 26: 13 with 14 limbs operated, 13 controls). CT scans of the forelimbs were performed and CT-based polymer replicas prepared. Rotation within the elbow joint, varus of the proximal portion of the radius, radial torsion, valgus of the distal portion of the radius, procurvatum, and rotation within the carpal joint were measured on radiographs, on polymer replicas, and on CT scans. Bilevel hinged circular external fixation frames were assembled on polymer replicas and identical frames were placed on dogs. Torsion was corrected acutely and angulation was corrected progressively. Functional outcome was assessed subjectively. Buckling was present preoperatively in operated limbs. Mean (± SD) varus of the proximal portion of the radius was 36 ± 8°, valgus of the distal portion of the radius was 32 ± 5°, external radial torsion was 35 ± 6°, procurvatum was 41 ± 10°, and medial translation was 44 ± 11 mm. Treatment duration was 80 ± 24 days. Buckling was not observed after surgery. Lameness scores improved in all dogs (P < .001). The forelimbs of dogs with severe biapical radial deformities buckle and have increased radial head rotation and radial torsion. Biapical radial deformities can be managed with proximal and distal radial osteotomies and bilevel hinged circular external fixation.

Exercises in canine physical rehabilitation: range of motion of the forelimb during stair and ramp ascent

To evaluate overall joint range of motion of the forelimb in healthy dogs ascending stairs compared with incline slope walking. Normal canine forelimb kinematics (range of motion, flexion and extension) were compared during ascent of stairs or a ramp, and compared to unimpeded trotting on a flat surface. Eight adult dogs with no evidence of orthopaedic or neurological lameness were assessed using a 2-dimensional kinematic system as they walked up a custom built ramp and stairs. In healthy dogs, ramp and stair ascent consistently had greater range of motion compared to trotting on a flat surface, and ramp ascent had significantly greater range of motion compared to stair ascent (P<0·05). Shoulder flexion and extension, elbow extension and carpal flexion were all significantly greater while ascending the ramp compared to stairs. Shoulder extension on the flat was significantly greater than while ascending stairs. When planning physical rehabilitation exercises following injury to the forelimb, stair and ramp ascent may be considered, as both augment range of motion of joints. Ramp ascent provides the greatest increase in range of motion of forelimb joints.

Thiolated Carboxymethyl-Hyaluronic-Acid-Based Biomaterials Enhance Wound Healing in Rats, Dogs, and Horses

The progression of wound healing is a complicated but well-known process involving many factors, yet there are few products on the market that enhance and accelerate wound healing. This is particularly problematic in veterinary medicine where multiple species must be treated and large animals heal slower, oftentimes with complicating factors such as the development of exuberant granulation tissue. In this study a crosslinked-hyaluronic-acid (HA-) based biomaterial was used to treat wounds on multiple species: rats, dogs, and horses. The base molecule, thiolated carboxymethyl HA, was first found to increase keratinocyte proliferation in vitro. Crosslinked gels and films were then both found to enhance the rate of wound healing in rats and resulted in thicker epidermis than untreated controls. Crosslinked films were used to treat wounds on forelimbs of dogs and horses. Although wounds healed slower compared to rats, the films again enhanced wound healing compared to untreated controls, both in terms of wound closure and quality of tissue. This study indicates that these crosslinked HA-based biomaterials enhance wound healing across multiple species and therefore may prove particularly useful in veterinary medicine. Reduced wound closure times and better quality of healed tissue would decrease risk of infection and pain associated with open wounds.

Function of the extrinsic hindlimb muscles in trotting dogs

The extrinsic appendicular muscles of mammals have been suggested to impose parasagittal torques on the trunk that require recruitment of the oblique hypaxial muscles for stabilization. To determine if the recruitment of the protractors and retractors of the hindlimb are compatible with this hypothesis, we monitored changes in the recruitment of eleven muscles that span the hip joint to controlled manipulations of locomotor forces in trotting dogs. The results indicate that the primary retractor muscles of the hindlimb produce a small retraction moment at the hip joint early in the support phase during trotting at constant speed on a level surface. Thus, although the forelimb of dogs appears to function as a compliant strut, the hindlimb functions as a lever early in stance phase. Nevertheless, our results indicate that when dogs run at constant speed on a level surface a primary function of both the retractor and protractor muscles of the hindlimb is to produce swing phase of the limb. When the trotting dogs did net work in the fore-aft direction, by running uphill or downhill or by resisting a horizontally directed force, recruitment of the protractor and retractor muscles of the hip joint increased or decreased in the anticipated fashion. These observations are consistent with the hypothesis that recruitment of the oblique hypaxial muscles in trotting dogs function to stabilize the trunk against torques produced by protractor and retractor muscles of the hindlimb.

Morphometric and anatomic study of the forelimb of the dog

The object of this study was to obtain the anatomic and morphometric data required for biomechanical analyses of the forelimb in dogs. Following the euthanasia of four healthy, adult, crossbred dogs, 44 muscles of the right forelimb were identified and meticulously removed. Morphometric data for all muscles were collected and physiologic cross-sectional areas (PCSA) and architectural indices (AI) were calculated. The coordinates of the origin and insertion of each muscle were determined using orthogonal, right-handed coordinate systems embedded in the scapula, humerus, and radius-ulna. The PCSA and AI were calculated for all the muscles and coordinates for the origins and insertions of these muscles were determined. Results provide the morphometric and anatomic data necessary for three-dimensional biomechanical studies of the forelimb in dogs.

Getting the Dog Moving After Surgery

Getting the Dog Moving After Surgery

Two-dimensional link-segment model of the forelimb of dogs at a walk.

To calculate normative joint angle, intersegmental forces, moment of force, and mechanical power at elbow, antebrachiocarpal, and metacarpophalangeal joints of dogs at a walk. 6 clinically normal mixed-breed dogs. Kinetic data were collected via a force platform, and kinematic data were collected from forelimbs by use of 3-dimensional videography. Length, location of the center of mass, total mass, and mass moment of inertia about the center of mass were determined for each of 4 segments of the forelimb. Kinematic data and inertial properties were combined with vertical and craniocaudal ground reaction forces to calculate sagittal plane forces and moments across joints of interest throughout stance phase. Mechanical power was calculated as the product of net joint moment and the angular velocity. Joint angles were calculated directly from kinematic data. All joint intersegmental forces were similar to ground reaction forces, with a decrease in magnitude the more proximal the location of each joint. Flexor moments were observed at metacarpophalangeal and antebrachiocarpal joints, and extensor moments were observed at elbow and shoulder joints, which provided a net extensor support moment for the forelimb. Typical profiles of work existed for each joint. For clinically normal dogs of a similar size at a walk, inverse dynamic calculation of intersegmental forces, moments of force, and mechanical power for forelimb joints yielded values of consistent patterns and magnitudes. These values may be used for comparison in evaluations of gait in other studies and in treatment of dogs with forelimb musculoskeletal disease.

Computed tomography of the elbow joint in clinically normal dogs.

To use computed tomography (CT) to provide a detailed description of elbow joint structures in clinically normal dogs. 6 clinically normal adult mixed-breed dogs weighing 24 to 37 kg and one 12-month-old Labrador Retriever weighing 27 kg. To perform CT of both elbow regions, dogs were anesthetized and placed in lateral recumbency. One- and 2-mm contiguous slices were obtained by use of a third generation computed tomographic scanner. Good resolution and anatomic detail were acquired from the computed tomographic images by use of a bone (window width, 3,500 Hounsfield units; window level, 500 Hounsfield units) and soft-tissue setting (window width, 400 Hounsfield units; window level, 66 Hounsfield units). After euthanasia, the forelimbs from the Labrador Retriever were removed and frozen in water at -18 degrees C. Elbow joints were sectioned into approximately 1-mm-thick slab sections by use of an electric planer. Anatomic sections were photographed and compared with the corresponding computed tomographic images. Computed tomographic reconstructions of the elbow joint were created in sagittal and dorsal planes. Structures on the computed tomographic images were matched with structures in the corresponding anatomic sections. The entire humeroradioulnar joint surface could be evaluated on the reconstructed images in the sagittal and dorsal plane. Computed tomographic images provide full anatomic detail of the bony structures of the elbow joint in dogs. Muscles, large blood vessels, and nerves can also be evaluated. These results could be used as a basis for evaluation of computed tomographic images of the forelimbs of dogs with elbow joint injuries.

External work and potential for elastic storage at the limb joints of running dogs.

The storage and recovery of elastic strain energy in muscles and tendons increases the economy of locomotion in running vertebrates. In this investigation, we compared the negative and positive external work produced at individual limb joints of running dogs to evaluate which muscle-tendon systems contribute to elastic storage and to determine the extent to which the external work of locomotion is produced by muscles that shorten actively rather than by muscles that function as springs. We found that the negative and positive external work of the extensor muscles is not allocated equally among the different joints and limbs. During both trotting and galloping, the vast majority of the negative work was produced by the two distal joints, the wrist and ankle. The forelimb produced most of the negative work in both the trot and the gallop. The hindlimb produced most of the positive work during galloping, but not during trotting. With regards to elastic storage, our results indicate that the forelimb of dogs displays a greater potential for storage and recovery of elastic energy than does the hindlimb. Elastic storage appears to be more important during trotting than during galloping, and elastic storage appears to be more pronounced in the extensor muscles of the distal joints than in the extensor muscles of the proximal joints. Furthermore, our analysis indicates that a significant portion of the external work of locomotion, 26 % during trotting and 56 % during galloping, is produced by actively shortening muscles. We conclude that, although elastic storage of energy is extremely important to the economy of running gaits, actively shortening muscles do make an important contribution to the work of locomotion.