Ground Reaction Forces: The Sine Qua Non of Legged Locomotion

Legged locomotion results from the feet pressing against the ground to generate ground reaction forces (GRFs) that are responsible for moving the body. By changing limb coordination patterns and muscle forces, the GRFs are adjusted to allow the horse to move in different gaits, speeds, and directions with appropriate balance and self-carriage. This article describes the typical GRF patterns in each gait, the adaptations that produce turning, and the GRF patterns used to unload the painful limb when the horse is lame. The intent is to provide information that is of practical interest and value to equine scientists rather than being a comprehensive review of the topic. [Abstract copyright: Copyright © 2019 Elsevier Inc. All rights reserved.

Velocity-dependent changes of time, force and spatial parameters in Warmblood horses walking and trotting on a treadmill

Reasons for performing study: Gait analysis parameters are sensitive to alterations in velocity. For comparison of nonspeed-matched data, the velocity dependency needs to be known. Objectives: To describe the changes in gait pattern and determine the relationships between stride duration, vertical impulse, contact time and peak vertical force within a range of walking and trotting speeds. Methods: Thirty-eight nonlame Warmblood horses were subjected to an incremental speed test. The spans of speed were adjusted individually to each horse and ranged from 1.1–2.1 m/s at walk and from 2.5–5.8 m/s at trot. Time, force and spatial parameters of each limb were measured with an instrumented treadmill and analysed with regression analysis using velocity as the independent variable. Results: At a slow walk the shape of the force curve was generally single-peaked in the fore- and trapezoidal in the hindlimbs. With increasing speed, the curves turned into the typical double-peaked shape with a higher second peak in the fore- and a higher first peak in the hindlimbs. With increasing velocity, stride duration, stance durations and limb impulses of the fore- and hindlimbs decreased in both gaits (r2>0.92). Increasing speed caused a weight shift to the forehand (walk: from 56 to 59%; trot: from 55 to 57%). Despite decreasing limb impulses, peak vertical forces increased in both gaits (r2>0.83). The suspension duration of the trot increased with faster velocities and reached a plateau of around 90 ms at the highest speeds. At a slow trot, the forelimbs impacted first and followed the hindlimbs at lift-off; with increasing speed, the horses tended to impact earlier with the hindlimbs. Contralateral symmetry indices of all parameters remained unchanged. Conclusions: Subject velocity affects time, force and spatial parameters. Knowing the mathematical function of these interdependencies enables correction of nonspeed-matched data

Yeasts in mixed deciduous forest areas of Phujong Nayoy National Park and their ability to produce xylanase and carboxymethyl cellulase

A total of 61 yeast strains were obtained from 132 samples collected from various sources such as soil, mushroom,flowers, fruits, tree barks and insect frass in the mixed deciduous forest areas of Phujong Nayoy National Park, Thailand.Based on D1/D2 region at the 5 end of the large subunit ribosomal RNA gene (rRNA gene region D1/D2) analysis, 39 strainswere identified as ascomycetous yeasts and distributed to 7 genera i.e. Blastobotrys, Candida, Debaryomyces, Dipodascus,Kodamaea, Pichia and Torulaspora. Twenty strains were identified as basidiomycetous yeasts which belonged to the generaAsterotremella, Cryptococcus, Sporidiobolus and Trichosporon. Another two strains of yeast-like fungi were belonged togenus Aureobasidium. The predominant genus was Candida with a 31.14% contribution. For testing of xylanase and carboxymethylcellulase production of the 61 strains of yeasts and yeast-like fungi, Candida glabrata and Aureobasidiumpullulans showed xylanase activity of 0.91 and 0.52 UmL-1, respectively, and carboxymethyl cellulase activity of 0.38 and0.44 UmL-1, respectively

Adaptation strategies of horses with lameness

The skill to diagnose lameness in horses is paramount for every equine practitioner. Early recognition of locomotor deficiencies plays a central role in sports medicine management, preventing deterioration of the disease or catastrophic injuries. Horses use characteristic compensatory movements of specific body parts to decrease loading of the affected limb. This article describes the underlying changes in intra- and interlimb coordination and the resulting load redistribution between the limbs. This enables the practitioner to better understand the changes in movement associated with lamenes

The development of locomotor kinetics in the foal and the effect of osteochondrosis

BACKGROUND: Foals stand and walk immediately after birth, but insight into the subsequent longitudinal development of their gait kinetics in the early juvenile phase and the possible influence of osteochondrosis thereon is lacking. OBJECTIVES: To quantify gait kinetics in foals during the first half year of life, taking into account their osteochondrosis status. STUDY DESIGN: Prospective, cohort study performed at a single stud farm. METHODS: Pressure plate measurements at walk and trot from eleven Dutch Warmblood foals during the first 24 weeks of life were used to determine body mass normalised peak vertical force, normalised vertical impulse and stance duration. Coefficients of variation of peak vertical force and stance duration were used as measures for gait maturity. Radiographs of tarsocrural and femoropatellar joints were taken at four to six weeks and after six months to check for osteochondrosis. A linear mixed model was used to determine the effects of age, limb, presence of osteochondrosis and speed on gait parameters. RESULTS: Mean walking and trotting velocity increased over time as did stance duration and normalised vertical impulse, normalised peak vertical force values however remained relatively constant. During the first weeks of their life only the coefficient of variation of stance duration decreased significantly, while the coefficient of variation of peak vertical force did not. None of the foals was visibly lame, but the presence of osteochondrosis resulted in a temporarily but significantly reduced normalised peak vertical force. MAIN LIMITATIONS: This study is a relatively small sample size of one breed from a single stud farm, A stand-alone pressure plate was used and body mass was estimated rather than measured. CONCLUSIONS: Despite being precocious, foals need time to mature their gait. During growth, velocity at walk and trot increases, but normalised peak vertical force remains relatively constant. Although not visibly lame, a temporary reduction in normalised peak vertical force was detected in osteochondrosis positive foals using a pressure plate. This article is protected by copyright. All rights reserved

Compensatory load redistribution of horses with induced weight-bearing forelimb lameness trotting on a treadmill.

The study was performed to obtain a detailed insight into the load and time shifting mechanisms of horses with unilateral weight-bearing forelimb lameness. Reversible lameness was induced in 11 clinically sound horses by applying a solar pressure model. Three degrees of lameness (subtle, mild and moderate) were induced and compared with sound control measurements. Vertical ground reaction force-time histories of all four limbs were recorded simultaneously on an instrumented treadmill. Four compensatory mechanisms could be identified that served to reduce structural stress, i.e. peak vertical force on the affected limb: (1) with increasing lameness, horses reduced the total vertical impulse per stride; (2) the diagonal impulse decreased selectively in the lame diagonal; (3) the impulse was shifted within the lame diagonal to the hindlimb and in the sound diagonal to the forelimb; (4) the rate of loading and the peak forces were reduced by prolonging the stance duration. Except in the diagonal hindlimb, where peak vertical forces increased slightly in the moderate lameness condition, no equivalent compensatory overload situation was observed in the other limbs. Specific force and time information of all four limbs allow the unequivocal identification of the affected limb