ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb04999.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05000.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05001.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThis review provides an overview of the challenges that face man and horses when exercising in the heat. Some of the strategies that are used and are being developed for human atheletes exercising in the heat are reviewed. There are many similarities between human and equine physiological responses to exercise in the heat; and equine exercise science may gain some useful insights from the training, fluid replacement and heat acclimatisation strategies used by human athletes. There are, however, some important differences that impact on the ability of horses to thermoregulate and to regulate fluid and electrolyte balance. The major differences are the low surface area to body mass ratio in horses compared to man; and the high metabolic capacity of equine skeletal muscle. These 2 factors may limit the ability of horses to dissipate heat when exercise is performed under hot conditions. Some of the more important equine differences are highlighted within the context of the ‘human perspective

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05002.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThere is a need to determine objectively the environmental heat load imposed on horses competing to an international standard in 3‐day‐events in environments where there is likely to be a high level of radiation added to high ambient temperatures and relative humidity; the presently used FEI ‘Comfort Index’ is severely limited in its applicability. It is proposed that the Wet Bulb Globe Temperature (WBGT) Index be used. This index was originally established for man exercising strenuously under harsh climatic conditions with high solar radiation levels. It may be defined as:WBGT = 0.7Twb+ 0.3Tgwhere Twbis the wet bulb temperature of the ambient air, measured in the shade and Tgis the black globe temperature. Climatic conditions should be monitored continuously at a site representative of the detailed topography and nature of the terrain of the competition course.The upper limit for the index for competitions involving fit, fully acclimatised horses, running on ground of optimal going, is recommended to be 32.5°C. This limit should be reduced, by an as yet undetermined amount, for unacclimatised and unfit horses or when the going is l

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05003.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe metabolic power required for sustained exercise in the horse is proportional to running speed. Moderately fast speeds require substantial energy expenditure and result in the generation of a massive metabolic heat load. Quantitative estimates of energy expenditure and heat production of horses at various running speeds were developed using empirically derived data from treadmill studies. Total metabolic power represents the sum of aerobic power indicated by the rate of oxygen consumption and net anaerobic power indicated by the rate of plasma lactate accumulation. These data were applied to typical running speeds and distances for each of the 4 phases of the endurance day of an Olympic level (CCI****) 3‐day‐event to provide an estimate of the energy expenditure and heat production during each phase. In a given horse, the rates of energy expenditure and heat production are determined by running speed, while total energy expenditure and heat production are determined by a combination of running speed and duration of exercise at that intensity. The highest calculated rate of energy expenditure and heat production occurred duringPhase B, the steeplechase, followed closely byPhase D, the cross‐country course. Interestingly, the highest total energy expenditure and heat production occurred onPhase C, Roads and Tracks, which is usually considered a period for cool down and recovery between the relatively high speed steeplechase and the demanding cross‐country course. Nevertheless, because the rate of energy expenditure is low during this phase, the horses would be expected to lose heat and lower body temperature during this interval. In hot and humid climates, dissipation of the exercise‐induced heat load may be compromised, leading to a narrower range of safety between the rate of heat production and the ability of the horse to dissipate this heat to the environment The results of this study could be used, should environmental conditions dictate, to provide quantitative guidelines as to how specific alterations of speed or distance of the various phases of the event would affect heat p

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05004.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryPhysiological data were collected during two 3‐day‐event competitions: one (H) held in hot and the other (CL) in cool conditions. During H, ambient temperature and relative humidity were 2.5°C‐35°C and 74‐36% respectively, while during CL, ambient temperature and relative humidity were 7.8°C‐8.3°C and 46%‐41%, respectively. Rectal temperature, heart and respiratory rates were recorded on arrival at the event, at the end ofPhase Cand 6 min later, at the end ofPhase Dand for 30 min at 10 min intervals after each horse finishedPhase D(Recovery Period). Because of the heat, the rest‐pause during the Endurance Test was extended from 10 to 15 min for horses competing in H, and horses at H were aggressively cooled by repetitive bathing with ice water during the rest‐pause and the 30 min Recovery Period. Heart rate was significantly higher (P0.05). Of 10 horses eliminated during the rest‐pause at H, 3 were lame, 1 had exertional rhabdomyolysis, 4 were exhausted and 2 were lame and exhausted. Two horses were eliminated during the rest‐pause at CL: 1 was lame and the other had exertional rhabdomyolysis. There was marked individual variation in horses' responses to heat at H. Heat may have limited the effectiveness of evaporative cooling in horses at H, and resultant thermal stress probably contributed to exhaustion in horses unable to complete the Endurance Test. Aggressive cooling during the rest‐pause and the Recovery Period was important to facilitate heat dissipation in horses at H. These me

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05005.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe present study was undertaken to investigate physiological, metabolic, haematological and biochemical changes in horses competing in the Speed and Endurance test of a Concours Complet International (CCI) **** 3‐day‐event held under FEI rules. A total of 28 horses competing in the Burghley Horse Trials Speed and Endurance test were selected to be monitored: 11 horses in 1993 and 17 horses in 1994. Of the 28 horses selected, 17 completed the Speed and Endurance test and went on to complete the showjumping test. Mean ± s.d. shade temperature and relative humidity, black globe temperature and wind speed were 13 ± 1 and 20 ± 2°C, 54 ± 3 and 55 ± 10%, 17 ± 2 and 29 ± 4°C and 2.7 ± 0.7 and 1.2 ± 0.3 m/s, for 1993 and 1994, respectively. Mean heart rate duringPhases A, BandDwas not significantly different between years, but mean heart rate duringPhases CandXwas significantly higher in 1994. Mean (± s.d.) heart rate onPhases BandDfor all horses in both 1993 and 1994 was 198 ± 8 and 188 ± 11 beats/min, respectively. Mean heart rate duringPhase Dshowed a poor correlation with mean speed (r=0.412). Total mean (± s.d.) weight loss from the start ofPhase Ato the end ofPhase Dwas 15.5 ± 6.1 kg in 1993 and 16.5 ± 5 kg in 1994 and did not differ significantly between years. Following 14–18 h completion ofPhase D, mean bodyweight was not significantly different from that at the start ofPhase Ain either year. Mean rectal temperature at the end ofPhase Dwas 41 ± 0.6°C and 41.1 ± 0.6°C in 1993 and 1994, respectively (P>0.05). Both the lowest (39.7°C) and highest (41.8°C) rectal temperatures were recorded at the end ofPhase Din 1994. Plasma lactate concentrations at the end ofPhase Dwere 8.5–38.5 mmol/1. The highest lactate concentration also coincided with the highest plasma glucose concentration (11.4 mmol/1) as well as the joint fastest time in either year, although overall lactate showed only weak correlations with mean speed onPhase D(r=0.12, 1993; r=0.58, 1994). While the Speed and Endurance test at CCI**** level run in a temperate climate presents a considerable challenge to the fitness and ability of the horses competing, the metabolic and physiological changes are not extreme. The majority of horses that finish the test appear to undergo a rapid and considerable degree of recovery and are able to present sound at the final inspection, take part in the showjumping tes

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05006.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe exercise intensity of horses (n=175) competing in the cross‐country phase of 4 combined training events at 5 levels of competition [novice (N), training (T), preliminary (P), intermediate (I) and advanced (A)] was investigated. Environmental conditions varied from cool and humid (mean ± s.d. temperature and humidity=12.1°C ± 0.6 and 88.4% ± 8.9 RH) to moderately hot and humid (27.8°C ± 2.1 and 62.5% ± 7.8 RH). Heart rates (beats/min) were recorded continuously at 5 s intervals with a heart monitor. Mean ± s.d. heart rates (beats/min) for each level of competition were: 154.4 ± 19.2 beats/min (n=45) (N), 160.4 ± 28.1 beats/min (n=47) (T), 160.6 ± 33 beats/min (n=53) (P), 181 ± 26.6 beats/min (n=29) (I) and 194.6 ± 4.2 beats/min (n=4) (A). Plasma lactate concentration was determined at rest in a random sampling of horses (n=36) from all competitions and within 60 s of completion of the cross‐country phase in all horses. Mean ± s.d. lactate concentration at rest was 0.98 ± 0.3 mmol/1. Mean ± s.d. lactate concentrations (mmol/1) of horses after exercise were: N=8.1 ± 7, T=11.5 ± 4.7, P=17.6 ± 6.1, I=19 ± 6.7 and A=21.3 ± 7.3. Mean plasma lactate increased significantly (P<0.001) as levels of competition increased, although there were few significant differences in heart rate between levels.Rectal temperatures were taken immediately after completion of the cross‐country phase and 10 min later. Mean ± s.d. rectal temperatures were significantly higher 10 min after completion of the cross‐country than those taken immediately after cross‐country (P<0.001). Rectal temperatures 10 min after completion of exercise were significantly higher as the level of competition increased for N through I (P<0.001). Rectal temperatures 10 min after completion of exercise were correlated with ambient temperatures (r=0.22, P=0.01). There was no significant correlation between either pulse or respiratory rate taken immediately after completion of exercise wi

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05007.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryThe exercise intensity of horses competing in 3‐day combined training events at 3 different levels of competition (CCI***, n=7; CCI**, n=11; CCI*, n=23) was investigated. Environmental conditions during all events were cool with 100% cloud cover. Heart rates were continuously recorded at 5 s intervals by a heart rate monitor. Mean ± s.d. heart rate for all horses during each phase were:Phase A=118 ± 11 beats/min,Phase B=179 ± 22.7 beats/min,Phase C=129 ± 13.9 beats/min andPhase D=174 ± 19.6 beats/min. Mean ± s.d. heart rates onPhases AandCwere significantly different from mean heart rates onPhases BandD.Plasma lactate concentrations were determined at rest, within 60 s and 10 min after the end ofPhase Dor the cross country test. Mean ± s.d. lactate concentrations were highest immediately post exercise (mean=18.4 ± 5 mmol/1 for all horses) and had declined significantly in 10 min (mean=15 ± 6.8 mmol/1 for all horses). Mean ± s.d. heart rates and lactate concentrations were not significantly different among levels of competition at each time period. The intensity of work of fit horses successfully competing in 3‐day combined training events consists of both low intensity aerobic exercise and more intense submaximal work with significant anaerobiosis. The work intensity is remarkably constant throughout different levels of competition, despite the increasing distance, number and difficulty of jumping efforts and faster o

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1995.tb05008.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY