Abstracts � Vol 29, No 5 (2009) 307

8. Firth EC, Rogers CW, Perkins NR, Anderson BH, Grace ND. Muscu-

loskeletal responses of 2-year-old Thoroughbred horses to early train-

ing. 1. Study design, and clinical, nutritional, radiological and

histological observations. New Zealand Vet J 2004;52(5):261-271.9. Murray RC, Zhu CF, Goodship AE, Lakhani KH, Grawal CMA, Atha-

nasiou KA. Exercise affects the mechanical properties and histological

appearance of equine articular cartilage. J Orthopaedic Res 1999;17:725-731.

31552 Reproducibility andRepeatability of Equine MuscleThickness Measured with Ultrasound

A. Lindner,*1 R. Signorini,2 J. Vassallo,2 F. Tomatis,2

F.M. Flores,2 M.E. Gagliano,2 J. Curiotti,2 E. Terragona,2

P.B. Suarez,2 and F. Nuovo2, 1Arbeitsgruppe PFERD,Julich, Germany, 2Facultad de Veterinaria, Universidaddel Litoral, Esperanza, Argentine

INTRODUCTIONUltrasound imaging is used for measuring thickness ofmuscles in man and horse to evaluate the effect of trainingand rehabilitation measures as well as the development ofmedical conditions1-3. Except for the extensor digitorumcommunis the repeatability of muscle thickness measure-ments has not been described for horses 4. The purposeof this study was to determine reproducibility and repeat-ability of thickness measurements of several equine musclesdone with ultrasound.

MATERIAL AND METHODSFive Thoroughbreds horses were used (4 to 6 yrs old, 3stallions, 2 geldings; BCS score 3-5.5). All of them hadbeen racing, but four of them were recovering from in-jury.A Mindray 6600 ultrasound machine was used toscan the thickness of the muscles after applying ultrasoundgel on the skin shaved on the measurement site. Three ex-aminers measured on 3 consecutive days the thickness ofthe muscles. Using defined anatomical landmarks the fol-lowing muscles were measured on the left and right sideof the horses:

� Extensor carpi radialis: (flexed and extended): 30 cmabove the medial aspect of the Tuberositas radii, holdingthe probe as much as possible perpendicular to the radius

� Extensor digitorum longus (flexed and extended): Onthe site where the muscle seemed to be most thick(around 30 cm from the Tuberositas tibiae), applyingthe probe as much as possible perpendicular to the tibiae.

� Gluteus medius: In the middle of the distance betweenthe first coccigeal vertebrae and the Tuber coxae

� Longissimus lumborum: 20 cm cranial to the Tubersacrale of the Ilium, 3 cm off the midline of the back

� Semitendinosus: 20 cm below the Tuber ischiadicum� Supraspinatus: In front of the Tuber spinae scapulae

Analysis of variance for repeated measurements was ap-plied to determine the effect of the day of measurementand of the examiner. Fishers test was applied as post-hoctest when significant effects were found. The coefficientof variation for the three measurements realized by each ex-aminer for every muscle was calculated. One way analysis ofvariance was used to determine whether there was an effectof the examiner on the coefficients of variance (C.V.).Fishers test was applied as post-hoc test when significant ef-fects were found. A probability at or below 0.05 was de-fined as the level to denote a significant difference.

RESULTSThe day of measurement did not have an effect onthe mean value of the thickness of the muscles examined(p > 0.05). This holds for all examiners. The left longissi-mus lumborum muscle was the only muscle for which thesecond measurement differed from the first and the third:values were higher on the 2nd day (p< 0.05 for both com-parisons).The examiner had an effect on the mean C.V. ofthe thickness of the left extensor carpi radialis and the leftextensor digitorum longus, both in flexed condition. Theday by day measurements differed more in one of the exam-iners compared with the others. Overall mean C.V. aboveor close to 10% were found for both sides of the extensordigitorum longus scanned in flexed posture and of thesupraspinatus muscles. The lowest mean C.V. were calcu-lated for the longissimus lumborum and the semitendino-sus when kept extended for the examination (<5%). Thelargest disagreements between the examiners was observedfor the extensor digitorum longus kept in a flexed positionand the supraspinatus on both sides of the horses (>10-<20%). The best agreement was measured for the extensorcarpi radialis kept in an extended posture and the longissi-mus lumborum (>3-<7%).

DISCUSSIONThe advantages of ultrasound are the lack of ionizing radi-ation, its inexpensiveness once the machine is available andease of handling. Also it enables records in ’real time’ andcan be repeated with no harm for the horses. The C.V.for the thickness measurements of the extensor digitorumcommunis previously determined4 was 1%. In this studythe C.V. was higher for all selected muscles. This couldbe because for the muscles selected it was more difficultto find exactly the same location for the measurement.Also differences between the examiners in the pressure ap-plied to hold the probe at the surface of the measurementsite can influence the C.V. The results show that much cau-tion should be paid to these aspects. The measurements of

308 Abstracts � Vol 29, No 5 (2009)

the thickness of the longissimus lumborum, semitendino-sus and the extensor carpi radialis muscles seem to be thebetter reproducible and repeatable ones.

Keywords: Horse; Muscle; Reproducibility;Ultrasound; Thickness

REFERENCES

1. Reeves ND, Maganaris CN, Narici MV. Ultrasonographic assess-

ment of human skeletal muscle size. Eur J Appl Physiol.

2004;91:116–118.2. Severinsen K, Andersen H. Evaluation of atrophy of foot muscles in di-

abetic neuropathy – a comparative study of nerve conduction studies

and ultrasonography. J Clin Neurophysiol. 2007;118:2172–2175.

3. Abe T, Kearns CF, Manso Filho HC, Sato Y, McKeever KH. Muscle,tendon, and somatotropin responses to the restriction of muscle blood

flow induced by KAATSU-walk training. Equine Vet J 2006;Suppl.

36:345-348.4. Abe T, Kearns CF, Manso Filho HC, Sato Y, Sleeper M, McKeever

KH. Acute vascular occlusion in horses: effects on skeletal muscle

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239-243.

EXERCISE PHYSIOLOGY - POSTERS

31811 Temporal Variables of thePleasure and Road Trots of the MorganEnglish Pleasure HorseM. Nicodemus,* Mississippi State University,Mississippi State, MS, USA

INTRODUCTIONThe Morgan English Pleasure horse is required to performtwo types of trot in the show arena, the pleasure (PT) androad trots (RT), but gait definitions according to breedstandards are vague and unclear. While research has assistedin defining other saddleseat performance types, gait analy-sis is unavailable for the English Pleasure horse.1,2 Studyobjectives were to define the PT and RT of the Morgan En-glish Pleasure horse and to distinguish between the twogaits.

MATERIALS AND METHODSSeven registered Morgan horses showing in a champion-ship English Pleasure class at Morgan Horse Grand Na-tionals were filmed at 60 Hz throughout the duration ofthe class. The camera was set to film along the long sideof the show arena with the camera set perpendicular tothe plane of motion at a distance of 8.5 m from the longside of the arena. Strides of both the PT and RT thatwere judged as desirable by carded judges according to

breed standards were evaluated using frame-by-frame anal-ysis. Means (SD) were determined for 5 strides for eachhorse for each gait with swing duration, advanced place-ments, and limb support given as % of stride. Effect oftrot-type for each variable was tested using a one-way anal-ysis of variance based on a general linear model procedure(SAS) (p< 0.05).

RESULTSWhile velocity (PT: 4.8� 0.6 m/s, RT: 5.3� 0.6 m/s)and stride length (PT: 3.2� 0.4 m, RT: 3.3� 0.5 m) andrate (PT: 1.5� 0.1 strides/s, RT: 1.6� 0.1 strides/s)were not significantly influenced by trot-type (p> 0.05),stride duration did shorten from the PT (642� 15 ms) tothe RT (621� 28 ms) (p< 0.05). Majority of stride forboth the PT (Forelimbs: Right¼ 62� 3%, Left¼ 62� 2%;Hind Limbs: Right¼ 58� 4%, Left¼ 58� 3%) and RT(Forelimbs: Right¼ 65� 2%, Left¼ 66� 4%; HindLimbs: Right¼ 57� 2%, Left¼ 57� 2%) was spent inswing with forelimb swing increasing at the RT(p< 0.05). While both gaits performed a 4-beat rhythm,the duration between the impact of the hind limb and thediagonal forelimb increased from the PT (Advanced Place-ments: Right Hind-Left Fore¼ 3� 2%, Left Hind-RightFore¼ 3� 2%) to the RT (Advanced Placements: RightHind-Left Fore¼ 6� 1%, Left Hind-Right Fore¼6� 2%). Both gaits demonstrated periods of diagonal bi-pedal support (PT: 72� 4%, RT: 70� 5%) and unipedalhind limb support (PT: 10� 5%, RT: 15� 5%) with trot-type influencing the duration of suspension (PT: 18� 6%,RT: 14� 2%) (p< 0.05).

DISCUSSIONWhile Clayton3 reported an increase in velocity as the dres-sage horse went from the collected to the extended trot,changes in temporal variables between trot-types of theEnglish Pleasure horse were not associated with changesin velocity. Absence of velocity increase from the PT tothe RT follows breed standards as excessive speed is penal-ized at the RT. Changes in forelimb swing, stride duration,diagonal advanced placements, and suspension were asso-ciated with trot-type and can assist in distinguishing be-tween the two gaits. Research on the Country EnglishPleasure trot did not report a 4-beat rhythm or periodsof unipedal support in which these differences may be asso-ciated with performance type1, and while these variableswere found in the park trot, the duration of the variablesreported in this study were unique from those found inthe previous study of the Morgan Park horse2. Differencesfound between trot variables can be applied when judgingperformance in the show arena.