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Lameness and heart rate elevation in the exercising horse
,~. . ~ :
~
~i~.~,~.... .~;%~:~:~
::~:.;
Refereed
LAMENESSAND HEARTRATEELEVATION IN THE EXERCISINGHORSE Jonathan H. Foreman, DVM, MS; 1 Laurie M. Lawrence, PhI~
SUMMARY Seven, healthy, conditioned, Quarter Horse mares with previous treadmill experience were each fitted with an adjustable heart bar shoe on the left front foot and a counterbalanced bar shoe on the right front foot. Three treatments were studied: sound, slightly lame, and obviously lame at a trot. Each subject performed one standardized exercise test (SET) daily on three consecutive days. Each subject underwent one treatment during a SET. Treatment order was randomly assigned. The SET consisted of a 5-rain exercise period at 3.2 m/ sec on a treadmill at an 11% grade. Heart rate (HR) was determined at rest, 20 rain after the induction of lameness before the SET, during the last 30 sec of the SET, and at 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, and 60 min postexercise. The Student's paired t test was used to compare HR means for the three treatments at each monitoring interval. Heart rate was higher in slightly lame trials compared Authors' address: Department of Veterinary Clinical Medicine, College of
Veterinary Medicine, 1 and Department of Animal Sciences, College of Agriculture, 2 University of Illinois at Urbana-Champaign, 1008 West Hazelwood Drive, Urbana, Illinois 61801. Reprint requests should be addressed to Dr. Foreman. Presented in part at the-lOth Equine Nutrition and Physiology, Fort Collins, Colorado, June 12, 1987. Supported by a Biomedical Research Support Grant. Acknowledgment: The authors thank Mark Fisher and Terri Gibbs for technical assistance.
to sound trials as rest and at 0.5 through 10 and 30 through 60 min postexercise (P<0.05 to P<0.001). Lame trials evidenced higher HRs than slightly lame trials at rest and at 0.5, 2, 4, and 5 rain of recovery (P<0.05). When lame HRs were compared to sound HRs, differences were noted at rest and at 0.5 through 60 min postexercise (P<0.01 to P<0.001). The heart bar shoe as designed for the treatment of laminitis was effective as a noninvasive, nonpermanent model of lameness pain in normal horses. Increases in HR at rest and during recovery from exercise were observed with experimentally induced lameness. The degree of HR increase seen with lameness was a function of the degree of lameness induced.
INTRODUCTION While the methods for diagnosis and treatment of equine lameness have improved dramatically in recent years, little attention has been given to the concept of prevention of lameness by improved training techniques and by improved monitoring during training. The development of such preventive techniques has become one of the stated goals of the American Association of Equine Practitioners. 13 Trainers currently engaged in more scientifically based conditioning of performance horses have utilized on-board heart rate (HR) meters carried by the rider or driver to monitor their horses' workouts.8 Abnormal or unexpected changes in HR have been reported by trainers to be the first
..:i~.:~ "
N
indication that a horse has become unduly stressed, a Such HR changes may be the earliest indicators of impending cardiopulmonary or musculoskeletal infirmities.1,2,s,6,11,14 The correlation between elevated HR, injury, and/or fatigue is well documented in human runners 14and swimmers.1Persson has anecdotally suggested such a correlation in the exercising StandardbredY A retrospective analysis of data collected during the monitoring of Thoroughbred racehorses in training showed that there was a significant correlation between the existence of lameness after a workout and an elevation of HR during and after that workout.5 Erickson et al. have also retrospectively identified a decrease in V 14o(the velocityrequired to maintain a HR of 140 bpm) when lameness became evident in Quarter Horses in training. 2 There are, however, no published prospective controlled studies in horses correlating the existence of lameness with a higher-than-expected elevation of HR during and after exercise.
MATERIALS AND METHODS Horses Seven Quarter Horse mares (mean age = 7.3 + 1.8 years, range = 5 to 9 years) with extensive treadmill exercise experience were studied. At the time of this study, they had just completed a separate treadmill project and thus were well conditioned. This conditioning eliminated unfimess as a variable in the exercise and recovery HRs. s Complete physical and lameness examinations were made of each subject and were normal.
Lameness Model The adjustable heart bar shoe was developed for the treatment of laminitis.6,7 It has a lever arm which hinges on a solid rod welded across the heel of the shoe. The apex of the heart bar fits over the frog of the foot. Pressure of the heart bar against the frog can be adjusted by the tightening or loosening of one Allen screw in the bottom of the shoe. In clinical laminitis cases, the heart bar is believed to provide mechanical support under the third phalanx.6,7In numerous clinical instances, it has been evident that the tighmess of the Allen screw can make an individual horse's gait vary from sound to extremely lame.6,7 Our hypothesis was that a sound horse shod with an adjustable heart bar shoe could be made lame when the Allen screw was tightened against the bottom of the foot and that the lameness would be reflected in the horse's FIR. A similar model
of equine foot lameness utilizing screws placed laterally near the heels of the shoe has also recently been described.9,1° An adjustable heartbar shoe was applied to the left front foot of each subject. A shoe with a mid-foot bar fitted flush with the shoe (to make the weight similar to the heart bar shoe) was applied to the right front foot for balance. Three days of stall rest were allowed before the standardized exercise tests (SETs) were begun to allow for the detection of any adverse effects in either limb from shoeing. Before the SETs, lameness examinations were repeated to ensure the soundness of each subject.
Standardized Exercise Test Each subject performed a SET once daily for three consecutive days. Each individual performed one sound, one slightly lame, and one lame SET in arandomized order. A previously used method of lameness grading (0 through 5, where 0=sound and 5=nonweight bearing) was utilized to standardize the degree of lameness. 5 During the lame SETs, the Allen screw was adjusted to create a lameness that at a got was either slight and intermittent (grade 2/5) or obvious (grade 3/5). The number of turns of the Allen screw was recorded for each horse and was standardized throughout the study. The SET consisted of a 5-min exercise period at 3.2 m/ sec on a treadmilla at an 11% grade. This speed constituted a moderate trotting pace with an expected heart rate of approximately 140-150 bpm. HR was determined during the last 30 sec of the SET by a commonly used HR meter~ which has previously been shown to be accurate when compared to ECG-determined HRs (r=0.884, P<0.001 to r=-0.987, P<0.001). 3,4,12 Heart rates were monitored with the HR meter at 0.5,1, 2, 3, 4, 5, and 10 min postexercise and by stethoscope auscultation at rest, 20 min after the induction of lameness, and at 20, 30, 40, and 60 min postexercise. These monitoring intervals and techniques have been used previously on Thoroughbred subjects undergoing conventionalconditioning exercises on a racetrack and have been shown retrospectively to be capable of documenting problems of fatigue or injury after exercise,s
Statistical Analysis The mean and standard deviation for HR at each point in time were determined for each treatment. Significant aAnamill® Treadmill, Gullwing, Inc., Sandusky, OH. bEquistat® HR/7A Heart Rate Microcomputer, Equine Biomechanics and Exercise Physiology, Inc., Unionville, PA.
differences between treatments were determined by the Student's paired t test at each monitoring interval. The level of significance was considered to be P<0.05.
T a b l e 1. Heart rate responses to s t a n d a r d i z e d e x e r c i s e test for sound, slightly lame, and lame treatments. All values = m e a n s + sd in bpm (n=7).
Sound Slightly lame RESULTS
Mean HRs are summarized in Table 1. There were significant differences between sound and slightly lame subjects at rest and at 0.5 through 10 and 30 through 60 min postexercise (P<0.05 to P<0.001). Lame trials evidenced higher HRs than slightly lame trials at rest and at 0.5, 2, 4, and 5 min of recovery (P<0.05). When lame HRs were compared to sound HRs, differences were noted at rest and at 0.5 through 60 rain postexercise (P<0.001 to P<0.001).
DISCUSSION
There are few reports of noninvasive, nonpermanent models of musculoskeletal pain in the horse.9,1° Recent work utilizing a similar concept, that of the shoe being tightened and thus pinching the foot, has been reported with regard to force plate analysis of the lameness. 9,1° In that model, screws were placed through set holes on the axial edge of the shoe in the heel region. As in our model, increased tighmes s of the screw resulted in a directly proportionate increase in the degree of lameness. Both of these models of pain should prove to be of great value in the future study of the biomechanics and medical therapy of equine skeletal pain. These data demonstrate in a prospective manner that it is possible to detect lameness by monitoring recovery HRs after exercise in the horse. This relationship between elevated HR and lameness has previously been shown only in a retrospective manner. 2.5 Furthermore, these data show that the degree of HR elevation due to lameness is a function of the severity of that lameness. As with the previous retrospective Thoroughbred training data,5 elevations of HR with lameness were seen during recovery but not consistently during exercise. Erickson et ai.s' Quarter Horse data also showed some inconsistency in the documentation of elevated HRs during exercise with lameness.2We believe that these studies indicate that recovery HRs provide a more reliable indicator of lameness than exercise HRs. It is our contention that the physiological demands of the actual exercise event may override the psychological factors of lameness pain in determining the
Rest Rest, 20 min post lameness induction Trot, 5 min Recovery, min 0.5 1 2 3 4 5 10 20 30 40 60
32.0+2.3 32.0 _+2.3 142.1+3.8 80.0+7.8 68.0+11.5 61.1 +8.0 58.1 _+6.7 55.7 + 7.0 52.9 + 6.3 44.6+4.4 38.9 + 3.8 34.9 +4.5 34.3 + 4.5 32.6 _+2.8
33.1 +3.0
Lame 33.1 +2.0
39.4 + 1.5"- 46.9 + 6.0 "~-+ 141.0+2.9 143.4 + 6.0 87.1 +7.4"" 75.3+8.8" 67.9 + 9.9" 63.1 +9.5" 60.9 -+ 7.857.4 + 6.9"" 53.1 +4.8"'" 44.6 + 6.7 41.1 _+6.0" 40.6 _+5.4 °" 39.4 -+ 5.4"
96.1 +8.1 "/*+* 87.3_+11.1 ++ 80.6+ 11.8 "j++ 74.7+ 12.1 *÷ 71.4 + 10.9 "/+* 67.9 _+ 11.3 v++ 62.7+ 12.8 +÷ 52.6 + 9.4 ++ 49.1 + 10.0 *÷ 48.0 + 9.8 ÷* 44.6 + 9.4**
Significant differences from less lame test: "P<0.05; "'P<0.01; ""P<0.001. Significant difference lame versus sound: ÷P<0.05; ** P<0.01; +++P<0.001.
degree of HR elevation with exercise. Heart rate is subject to fluctuationsdue to other psychological pressures such as the individual's calm or excitable nature, the individual's resistance to pain, and the presence of other stimuli such as other horses (or lack thereof), people, vehicles, track surface changes, and weather changes in the testing environment.2'5'8'11 In fact, the HR monitor was used only during and immediately after exercise because these horses tended to manifest mild elevations in HR at rest (5 to 10 bpm) simply by equipping them with the HR monitor, saddle, and girth. Caution must, therefore, be used in the interpretation of recovery HRs. Variation among our subjects underscores the concept that each subject is best studied using itself as its own conlIol. The detection of lameness by HR monitoring during and after exercise may prove to be helpful in the prevention of the exacerbation of subclinical lamenesses. These data support the concept that any horse manifesting exercise intolerance or a sudden decrease in performance should, if other problems are not evident, undergo a SET to evaluate the HR response to a standardized workload. Earlier testing when athletically sound would supply a baseline to which to compare the SET performed after a decline in performance. Such testing may demonstrate an elevated HR during work and/or recovery. Such a response would provide additional evidence that the horse truly has a physical problem which is precluding maximal performance.
~•~iiiii~ii:i .............®!~i~i~i
REFERENCES 1. Counsilman JE: The Science of Swimming. Prentice Hall, Inc., Englewood Cliffs, NJ, 1968. 2 .Erickson BK, Erickson HH, Sexton WL, Coffman JR: Performance evaluation and detection of injury during exercise training in the Quarter Horse using a heart rate computer. In Equine Exercise Physiology 2, Gillespie JR, Robinson NE (eds). ICCEP Publications:Davis, CA, pp.92-101,1987. 3. Evans DL, Rose RJ: Method of investigation of the accuracy of four digitally displaying heart rate meters suitable for use in the exercising horse. Equine VetJ 18:129-132,1986. 4. Foreman JR, Rabin D: Determination of accuracy of digitally displaying equine heart rate meter. J Equine Vet Sci 3:161-163,1984. 5. Foreman JH, Bayly WM, Grant BD, Gollnick PD: Standardized exercise test and daily heart rate responses of Thoroughbred horses undergoing conventional race training and detraining. Am J Vet Res 50:914-920,1990. 6. Goetz TE, Comstock C: The use of adjustable heart bar shoes in the treatment of laminitis in horses. Proceedings Amer Assoc Equine Practnr, 31:605-616,1985. 7. Goetz TE:Anatomic, hoof, and shoeing considerations for the treatment of laminitis in horses. J Am Vet Med Assoc 190:1323-1332,1987.
8. Ivers T: The practical applications of various equine conditioning techniques and common errors of application. Proceedings Amer Assoc Equine Practnr, 28:21-29,1982. 9. Merkens HW, Schamhardt HC: Evaluation of equine locomotion during different degrees of experimentally induced lameness. I: Lameness model and quantification of ground reaction force patterns of the limbs. Equine Vet J Suppl. 6:99106,1988. 10. Merkens HW, Schamhardt HC: Evaluation of equine locomotion during different degrees of experimentally induced lameness. I1. Distribution of ground reaction force patterns of the concurrently loaded limbs. Equine Vet J Suppl. 6:107-112,1988. 11. Persson SGB: Evaluation of exercise tolerance and fitness in the performance horse. In Equine Exercise Physiology, Snow DH, Persson SGB, Rose RJ (eds). Granta Editions:Cambridge, England, pp.441-457,1983. 12. Physick-Sheard PW, Harman JC, Snow DH, Woakes A J: Evaluation of factors influencing the performance of four equine heart rate meter~. In Equine Exercise Physiology 2, Gillespie JR, Robinson NE (eds). ICEEP Publications:Davis, CA, pp.102-110,1987. 13. Toby MC:Aimed at preventing instead of curing problems. The Blood Horse, December 19, 1981. 14. Wallingford R: Long distance running. In The Scientific Aspects of Sports Training, Taylor AW (ed). Charles C. Thomas, publisher, Springfield, IL, 1975.
YOU S H O U L D BE GETTING
THE LARGE ANIMAL VETERINARY REPORT Every general veterinary practitionershould have a personal subscriptionto The Large Animal Veterinary Report. Practice is becoming more complicated every day. Not so much from the animal health pointof view, but fromthe changing situationbetween veterinarypractice and our society. Rules and regulationschangedaily.As a practitioner,you need to keep up withwhat is happening. The Large Animal Veterinary Report will keep you abreast of these changes.
$48 for a
1 year subscription;
$60 overseas
and libraries; $ 5 0 Canada and Mexico
Available from Veterinary Data, PO Box 1209, Wildomar, CA 92395 For credit card orders call 714-678-1889
~
~i~.~,~.... .~;%~:~:~
::~:.;
Refereed
LAMENESSAND HEARTRATEELEVATION IN THE EXERCISINGHORSE Jonathan H. Foreman, DVM, MS; 1 Laurie M. Lawrence, PhI~
SUMMARY Seven, healthy, conditioned, Quarter Horse mares with previous treadmill experience were each fitted with an adjustable heart bar shoe on the left front foot and a counterbalanced bar shoe on the right front foot. Three treatments were studied: sound, slightly lame, and obviously lame at a trot. Each subject performed one standardized exercise test (SET) daily on three consecutive days. Each subject underwent one treatment during a SET. Treatment order was randomly assigned. The SET consisted of a 5-rain exercise period at 3.2 m/ sec on a treadmill at an 11% grade. Heart rate (HR) was determined at rest, 20 rain after the induction of lameness before the SET, during the last 30 sec of the SET, and at 0.5, 1, 2, 3, 4, 5, 10, 20, 30, 40, and 60 min postexercise. The Student's paired t test was used to compare HR means for the three treatments at each monitoring interval. Heart rate was higher in slightly lame trials compared Authors' address: Department of Veterinary Clinical Medicine, College of
Veterinary Medicine, 1 and Department of Animal Sciences, College of Agriculture, 2 University of Illinois at Urbana-Champaign, 1008 West Hazelwood Drive, Urbana, Illinois 61801. Reprint requests should be addressed to Dr. Foreman. Presented in part at the-lOth Equine Nutrition and Physiology, Fort Collins, Colorado, June 12, 1987. Supported by a Biomedical Research Support Grant. Acknowledgment: The authors thank Mark Fisher and Terri Gibbs for technical assistance.
to sound trials as rest and at 0.5 through 10 and 30 through 60 min postexercise (P<0.05 to P<0.001). Lame trials evidenced higher HRs than slightly lame trials at rest and at 0.5, 2, 4, and 5 rain of recovery (P<0.05). When lame HRs were compared to sound HRs, differences were noted at rest and at 0.5 through 60 min postexercise (P<0.01 to P<0.001). The heart bar shoe as designed for the treatment of laminitis was effective as a noninvasive, nonpermanent model of lameness pain in normal horses. Increases in HR at rest and during recovery from exercise were observed with experimentally induced lameness. The degree of HR increase seen with lameness was a function of the degree of lameness induced.
INTRODUCTION While the methods for diagnosis and treatment of equine lameness have improved dramatically in recent years, little attention has been given to the concept of prevention of lameness by improved training techniques and by improved monitoring during training. The development of such preventive techniques has become one of the stated goals of the American Association of Equine Practitioners. 13 Trainers currently engaged in more scientifically based conditioning of performance horses have utilized on-board heart rate (HR) meters carried by the rider or driver to monitor their horses' workouts.8 Abnormal or unexpected changes in HR have been reported by trainers to be the first
..:i~.:~ "
N
indication that a horse has become unduly stressed, a Such HR changes may be the earliest indicators of impending cardiopulmonary or musculoskeletal infirmities.1,2,s,6,11,14 The correlation between elevated HR, injury, and/or fatigue is well documented in human runners 14and swimmers.1Persson has anecdotally suggested such a correlation in the exercising StandardbredY A retrospective analysis of data collected during the monitoring of Thoroughbred racehorses in training showed that there was a significant correlation between the existence of lameness after a workout and an elevation of HR during and after that workout.5 Erickson et al. have also retrospectively identified a decrease in V 14o(the velocityrequired to maintain a HR of 140 bpm) when lameness became evident in Quarter Horses in training. 2 There are, however, no published prospective controlled studies in horses correlating the existence of lameness with a higher-than-expected elevation of HR during and after exercise.
MATERIALS AND METHODS Horses Seven Quarter Horse mares (mean age = 7.3 + 1.8 years, range = 5 to 9 years) with extensive treadmill exercise experience were studied. At the time of this study, they had just completed a separate treadmill project and thus were well conditioned. This conditioning eliminated unfimess as a variable in the exercise and recovery HRs. s Complete physical and lameness examinations were made of each subject and were normal.
Lameness Model The adjustable heart bar shoe was developed for the treatment of laminitis.6,7 It has a lever arm which hinges on a solid rod welded across the heel of the shoe. The apex of the heart bar fits over the frog of the foot. Pressure of the heart bar against the frog can be adjusted by the tightening or loosening of one Allen screw in the bottom of the shoe. In clinical laminitis cases, the heart bar is believed to provide mechanical support under the third phalanx.6,7In numerous clinical instances, it has been evident that the tighmess of the Allen screw can make an individual horse's gait vary from sound to extremely lame.6,7 Our hypothesis was that a sound horse shod with an adjustable heart bar shoe could be made lame when the Allen screw was tightened against the bottom of the foot and that the lameness would be reflected in the horse's FIR. A similar model
of equine foot lameness utilizing screws placed laterally near the heels of the shoe has also recently been described.9,1° An adjustable heartbar shoe was applied to the left front foot of each subject. A shoe with a mid-foot bar fitted flush with the shoe (to make the weight similar to the heart bar shoe) was applied to the right front foot for balance. Three days of stall rest were allowed before the standardized exercise tests (SETs) were begun to allow for the detection of any adverse effects in either limb from shoeing. Before the SETs, lameness examinations were repeated to ensure the soundness of each subject.
Standardized Exercise Test Each subject performed a SET once daily for three consecutive days. Each individual performed one sound, one slightly lame, and one lame SET in arandomized order. A previously used method of lameness grading (0 through 5, where 0=sound and 5=nonweight bearing) was utilized to standardize the degree of lameness. 5 During the lame SETs, the Allen screw was adjusted to create a lameness that at a got was either slight and intermittent (grade 2/5) or obvious (grade 3/5). The number of turns of the Allen screw was recorded for each horse and was standardized throughout the study. The SET consisted of a 5-min exercise period at 3.2 m/ sec on a treadmilla at an 11% grade. This speed constituted a moderate trotting pace with an expected heart rate of approximately 140-150 bpm. HR was determined during the last 30 sec of the SET by a commonly used HR meter~ which has previously been shown to be accurate when compared to ECG-determined HRs (r=0.884, P<0.001 to r=-0.987, P<0.001). 3,4,12 Heart rates were monitored with the HR meter at 0.5,1, 2, 3, 4, 5, and 10 min postexercise and by stethoscope auscultation at rest, 20 min after the induction of lameness, and at 20, 30, 40, and 60 min postexercise. These monitoring intervals and techniques have been used previously on Thoroughbred subjects undergoing conventionalconditioning exercises on a racetrack and have been shown retrospectively to be capable of documenting problems of fatigue or injury after exercise,s
Statistical Analysis The mean and standard deviation for HR at each point in time were determined for each treatment. Significant aAnamill® Treadmill, Gullwing, Inc., Sandusky, OH. bEquistat® HR/7A Heart Rate Microcomputer, Equine Biomechanics and Exercise Physiology, Inc., Unionville, PA.
differences between treatments were determined by the Student's paired t test at each monitoring interval. The level of significance was considered to be P<0.05.
T a b l e 1. Heart rate responses to s t a n d a r d i z e d e x e r c i s e test for sound, slightly lame, and lame treatments. All values = m e a n s + sd in bpm (n=7).
Sound Slightly lame RESULTS
Mean HRs are summarized in Table 1. There were significant differences between sound and slightly lame subjects at rest and at 0.5 through 10 and 30 through 60 min postexercise (P<0.05 to P<0.001). Lame trials evidenced higher HRs than slightly lame trials at rest and at 0.5, 2, 4, and 5 min of recovery (P<0.05). When lame HRs were compared to sound HRs, differences were noted at rest and at 0.5 through 60 rain postexercise (P<0.001 to P<0.001).
DISCUSSION
There are few reports of noninvasive, nonpermanent models of musculoskeletal pain in the horse.9,1° Recent work utilizing a similar concept, that of the shoe being tightened and thus pinching the foot, has been reported with regard to force plate analysis of the lameness. 9,1° In that model, screws were placed through set holes on the axial edge of the shoe in the heel region. As in our model, increased tighmes s of the screw resulted in a directly proportionate increase in the degree of lameness. Both of these models of pain should prove to be of great value in the future study of the biomechanics and medical therapy of equine skeletal pain. These data demonstrate in a prospective manner that it is possible to detect lameness by monitoring recovery HRs after exercise in the horse. This relationship between elevated HR and lameness has previously been shown only in a retrospective manner. 2.5 Furthermore, these data show that the degree of HR elevation due to lameness is a function of the severity of that lameness. As with the previous retrospective Thoroughbred training data,5 elevations of HR with lameness were seen during recovery but not consistently during exercise. Erickson et ai.s' Quarter Horse data also showed some inconsistency in the documentation of elevated HRs during exercise with lameness.2We believe that these studies indicate that recovery HRs provide a more reliable indicator of lameness than exercise HRs. It is our contention that the physiological demands of the actual exercise event may override the psychological factors of lameness pain in determining the
Rest Rest, 20 min post lameness induction Trot, 5 min Recovery, min 0.5 1 2 3 4 5 10 20 30 40 60
32.0+2.3 32.0 _+2.3 142.1+3.8 80.0+7.8 68.0+11.5 61.1 +8.0 58.1 _+6.7 55.7 + 7.0 52.9 + 6.3 44.6+4.4 38.9 + 3.8 34.9 +4.5 34.3 + 4.5 32.6 _+2.8
33.1 +3.0
Lame 33.1 +2.0
39.4 + 1.5"- 46.9 + 6.0 "~-+ 141.0+2.9 143.4 + 6.0 87.1 +7.4"" 75.3+8.8" 67.9 + 9.9" 63.1 +9.5" 60.9 -+ 7.857.4 + 6.9"" 53.1 +4.8"'" 44.6 + 6.7 41.1 _+6.0" 40.6 _+5.4 °" 39.4 -+ 5.4"
96.1 +8.1 "/*+* 87.3_+11.1 ++ 80.6+ 11.8 "j++ 74.7+ 12.1 *÷ 71.4 + 10.9 "/+* 67.9 _+ 11.3 v++ 62.7+ 12.8 +÷ 52.6 + 9.4 ++ 49.1 + 10.0 *÷ 48.0 + 9.8 ÷* 44.6 + 9.4**
Significant differences from less lame test: "P<0.05; "'P<0.01; ""P<0.001. Significant difference lame versus sound: ÷P<0.05; ** P<0.01; +++P<0.001.
degree of HR elevation with exercise. Heart rate is subject to fluctuationsdue to other psychological pressures such as the individual's calm or excitable nature, the individual's resistance to pain, and the presence of other stimuli such as other horses (or lack thereof), people, vehicles, track surface changes, and weather changes in the testing environment.2'5'8'11 In fact, the HR monitor was used only during and immediately after exercise because these horses tended to manifest mild elevations in HR at rest (5 to 10 bpm) simply by equipping them with the HR monitor, saddle, and girth. Caution must, therefore, be used in the interpretation of recovery HRs. Variation among our subjects underscores the concept that each subject is best studied using itself as its own conlIol. The detection of lameness by HR monitoring during and after exercise may prove to be helpful in the prevention of the exacerbation of subclinical lamenesses. These data support the concept that any horse manifesting exercise intolerance or a sudden decrease in performance should, if other problems are not evident, undergo a SET to evaluate the HR response to a standardized workload. Earlier testing when athletically sound would supply a baseline to which to compare the SET performed after a decline in performance. Such testing may demonstrate an elevated HR during work and/or recovery. Such a response would provide additional evidence that the horse truly has a physical problem which is precluding maximal performance.
~•~iiiii~ii:i .............®!~i~i~i
REFERENCES 1. Counsilman JE: The Science of Swimming. Prentice Hall, Inc., Englewood Cliffs, NJ, 1968. 2 .Erickson BK, Erickson HH, Sexton WL, Coffman JR: Performance evaluation and detection of injury during exercise training in the Quarter Horse using a heart rate computer. In Equine Exercise Physiology 2, Gillespie JR, Robinson NE (eds). ICCEP Publications:Davis, CA, pp.92-101,1987. 3. Evans DL, Rose RJ: Method of investigation of the accuracy of four digitally displaying heart rate meters suitable for use in the exercising horse. Equine VetJ 18:129-132,1986. 4. Foreman JR, Rabin D: Determination of accuracy of digitally displaying equine heart rate meter. J Equine Vet Sci 3:161-163,1984. 5. Foreman JH, Bayly WM, Grant BD, Gollnick PD: Standardized exercise test and daily heart rate responses of Thoroughbred horses undergoing conventional race training and detraining. Am J Vet Res 50:914-920,1990. 6. Goetz TE, Comstock C: The use of adjustable heart bar shoes in the treatment of laminitis in horses. Proceedings Amer Assoc Equine Practnr, 31:605-616,1985. 7. Goetz TE:Anatomic, hoof, and shoeing considerations for the treatment of laminitis in horses. J Am Vet Med Assoc 190:1323-1332,1987.
8. Ivers T: The practical applications of various equine conditioning techniques and common errors of application. Proceedings Amer Assoc Equine Practnr, 28:21-29,1982. 9. Merkens HW, Schamhardt HC: Evaluation of equine locomotion during different degrees of experimentally induced lameness. I: Lameness model and quantification of ground reaction force patterns of the limbs. Equine Vet J Suppl. 6:99106,1988. 10. Merkens HW, Schamhardt HC: Evaluation of equine locomotion during different degrees of experimentally induced lameness. I1. Distribution of ground reaction force patterns of the concurrently loaded limbs. Equine Vet J Suppl. 6:107-112,1988. 11. Persson SGB: Evaluation of exercise tolerance and fitness in the performance horse. In Equine Exercise Physiology, Snow DH, Persson SGB, Rose RJ (eds). Granta Editions:Cambridge, England, pp.441-457,1983. 12. Physick-Sheard PW, Harman JC, Snow DH, Woakes A J: Evaluation of factors influencing the performance of four equine heart rate meter~. In Equine Exercise Physiology 2, Gillespie JR, Robinson NE (eds). ICEEP Publications:Davis, CA, pp.102-110,1987. 13. Toby MC:Aimed at preventing instead of curing problems. The Blood Horse, December 19, 1981. 14. Wallingford R: Long distance running. In The Scientific Aspects of Sports Training, Taylor AW (ed). Charles C. Thomas, publisher, Springfield, IL, 1975.
YOU S H O U L D BE GETTING
THE LARGE ANIMAL VETERINARY REPORT Every general veterinary practitionershould have a personal subscriptionto The Large Animal Veterinary Report. Practice is becoming more complicated every day. Not so much from the animal health pointof view, but fromthe changing situationbetween veterinarypractice and our society. Rules and regulationschangedaily.As a practitioner,you need to keep up withwhat is happening. The Large Animal Veterinary Report will keep you abreast of these changes.
$48 for a
1 year subscription;
$60 overseas
and libraries; $ 5 0 Canada and Mexico
Available from Veterinary Data, PO Box 1209, Wildomar, CA 92395 For credit card orders call 714-678-1889