摘要:

SummaryThe aim of the present study was to determine the effect of different environmental conditions on physiological response to exercise. Four winter acclimatised, nonheat acclimated horses of different breeds were exercised at 20°C/40%RH (CD), 30°C/40%RH (HD) and 30°C/80%RH (HH). The exercise test was designed to represent the structure and intensity of a One star Speed and Endurance test (competition exercise test [CET]). All 4 horses were able to complete the full CET (60 min + 30 min active recovery) in CD and HD, but only one horse completed the CET in HH. Two horses were stopped because of pronounced general fatigue and one because of a right atrial temperature (TRA) of 43°C. Oxygen uptake on each phase was not different between CD and HD, but was higher duringPhases B, CandDin HH. Mean peak TRAat the end ofPhase Dwas 40.3 ± 0.2, 41.6 ± 0.4 and 42 ± 0.3°C for CD, HD and HH, respectively. Corresponding, mean peak rectal temperatures (TREC) followingPhase Dwere 39.5 ± 0.1, 40.6 ± 0.1 and 41.5 ± 0.1°C for CD, HD and HH, respectively. Mean time to peak TRECwas 9.3 ± 1.1 (CD), 7.3 ± 1.8 (HD) and 10.8 ± 2.3 (HH) min and was not significantly different between conditions (P>0.05). Heat dissipation amounted to 83 ± 1, 73 ± 2 and 70 ± 1% of heat production in CD, HD and HH, respectively. Weight loss was significantly correlated with both body surface area (CD r = 0.85; HD r = 0.87; HH r = 0.81) and bodyweight (CD r = 0.97; HD r = 0.93; HH r = 0.94). The greatest weight loss recorded was 4.6% bodyweight in one horse in HD. The mean increase in exercise intensity over the whole CET (in terms of V̇O2) of HD and HH compared with CD was 5 ± 3 and 14 ± 3% higher, respectively. The exercise induced hyperthermia and the reduced capacity for heat dissipation produced partial compensatory responses in minute ventilation (V̇E), particularly duringPhase C, when the horses were trotting. In HD, the increase in V̇Ewas achieved mainly through an increase in frequency, whilst in HH it was achieved through an increase in tidal volume (VT). The horses demonstrated a high degree of tolerance to environmental heat load, suggesting a high thermoregulatory capacity. However, for unacclimatised animals exercising in severely hot and humid conditions, perf

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1996.tb05034.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryThis study was designed to characterise the acid‐base and electrolyte effects of shortening the distance required during steeplechase (Phase B) in the face of hot and humid weather conditions during a treadmill‐simulated Speed and Endurance test.Eight conditioned Thoroughbred horses underwent 3 randomised permutations of a standardised exercise test on a high speed treadmill. Each test consisted of trotting at 3.7 m/s for 10 min (Phase A); galloping at 11 m/s (Phase B) for 4 (cool laboratory conditions), 3 (hot and humid), or 2 (hot and humid) min; trotting at 3.7 m/s for 30 min (Phase C); and walking at 1.8 m/s for 10 min (Phase X). The treadmill slope was 4% for trotting and galloping and 0% for walking. Cool versus hot and humid conditions were 20°C and 50–60% relative humidity vs. 26–28°C and 80–85% relative humidity, respectively.Pulmonary artery blood samples were obtained at rest prior to exercise (Rest); at the end ofPhases A(A10) andB(B2‐4); at 10 (C10), 20 (C20) and 30 (C30) min throughPhase C; and at 5 min intoPhase X(X5). Additional samples for lactate (LA) and glucose (GLC) analysis were obtained 5 min intoPhase C(C5) and at the end ofPhase X(X10). Samples were analysed for packed cell volume (PCV), haemoglobin (HB), total plasma protein (TP), sodium (Na), potassium (K), chloride (Cl), anion gap (AG), plasma glucose (GLC) and lactate (LA), pH, PCO2, bicarbonate (HCO3) and base excess (BE).Shortening steeplechase distance by 50% under hot and humid conditions (2 min B) resulted in a consistent return to control measurements (4 min B) only for plasma LA. Changes in PCV, HB, TP, K and Cl were related more to the longer galloping distance in the 4 min B trials than to hot vs. cold laboratory conditions. Alternatively, changes in LA, GLC, pH, PCO2and AG were more related to hot and humid laboratory conditions than they were to galloping distance. These latter variables, when combined with physical measures such as core temperature, bodyweight loss, point of fatigue onPhase Cand recovery heart rates may serve as the best monitors of positive responses in future studies of proposed modifications toPhase C, rather than those variables which were more distance than we

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1996.tb05035.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryBlood samples were collected 12–16 h before the Speed and Endurance test, immediately after steeplechase, midway throughPhase C(4 km marker), at the end ofPhase Cand immediately after cross‐country from 36 horses that completed a 3‐day‐event at the CCI* (n = 19) or CCI**(n = 17) level. Packed cell volume (PCV), plasma concentrations of sodium, potassium, chloride, ionized calcium, pH and lactate; and serum concentrations of total protein (TP), albumin, total calcium, alkaline phosphatase (AP), gamma glutamyl transferase (GGT), creatine kinase (CK), aspartate aminotransferase (AST), glucose and creatinine were measured. No differences were noted in any biochemical measurements between the CCI* and CCI** horses at any sampling time, despite differences in speed and length of various phases of the Speed and Endurance test. For all horses (n = 36), biochemical parameters changed significantly over time (P<0.01). The PCV, calcium, potassium, lactate, total protein and albumin concentrations were significantly increased over pre‐exercise concentrations immediately afterPhase B.DuringPhase C, these parameters decreased towards pre‐exercise concentrations, thereby supporting the concept thatPhase Cis a recovery phase. In contrast, chloride concentration decreased, and the creatinine concentration and CK increased compared to pre‐exercise concentrations from the end ofPhase Bto the end ofPhase C.These changes probably resulted from fluid and electrolyte losses in sweat, reduced renal blood flow and continued muscular activity. Many parameters did not change significantly between the 4 km marker (midway point onPhase C) and the end ofPhase C.However, there were a few notable exceptions: potassium, chloride, lactate and glucose concentrations decreased, whereas pH and creatinine concentrations increased significantly from the 4 km marker to the end ofPhase C.The most significant benefit of the extra distance from the 4 km marker to the end ofPhase Cwas that it facilitated further dissipation of lactate concentrations prior to the st

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1996.tb05036.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryTo avoid dehydration and a decrease in performance capacity in horses, fluid and electrolyte losses need to be compensated for during long distance rides as well as on other occasions when sweat losses are high during exercise. Thirteen endurance‐trained horses, age 5–14 years, were used to compare 3 strategies of voluntary rehydration during prolonged exercise, offering 1)water, 2) water after administeringsalt paste(3 times 30 g of NaCl)per osand 3) 0.9% saline. The ride covered 62 km and consisted of 3 rounds, of 20, 22 and 20 km, respectively. During the first 20 km, no fluid was offered to any of the horses. Thereafter, fluid was repeatedly offered from buckets at the ‘vet gates' and at fluid stations situated in the middle of the rounds. Fluid intake and bodyweight were measured during the ride and up until 3 h after the ride. The low heart rates and unchanged plasma glucose concentration indicated that the work load was moderate. Total fluid intake was significantly higher in thesalinegroup than in thewatergroup or thesalt pastegroup. The total plasma protein concentration (TPP) fell below resting values in thesalinegroup post exercise, indicating an increase in plasma volume. No changes in TPP were seen in the other groups. Plasma sodium concentration during the ride increased in thesalt pastegroup but not in thesalinedrinking horses despite their higher NaCl intake. Thewatergroup had an increased plasma aldosterone concentration post exercise, indicating that sodium‐conserving mechanisms had been activated. Plasma potassium concentration decreased in all treatments from pre‐ to post ride. It was concluded, that drinking saline solution during and after exercise is a good strategy for rehydration since this group showed the fastest recovery of their bodyweight losses. The persistently elevated plasma sodium concentration in thesalt pastegroup during the ride, is indicative of a disturbance in the fluid distribution between the body fluid compartments, which can be exacerbated by the low water intake. To give salt paste immediately before or during exercise is, therefore, not re

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1996.tb05037.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

SummaryNine adult riding horses performed on a treadmill a competition exercise test (CET) and 24 h later a standardised exercise test (SET) at mean temperature 28°C and relative humidity 58%. Each horse performed the tests 5 times at 2 week intervals. The horses were given isotonic glucose‐electrolyte solution via a nasogastric tube 30 min after the CET, except after the last trial when water was given. Blood lactate, plasma concentration of aldosterone, arginine vasopressin, protein, sodium, potassium, chloride, magnesium and calcium were measured. Heart rate at blood lactate concentration 4 mmol/l (PLa4) in the SET, plasma volume (PV) and red cell volume (CV) were determined. Mean weight loss after CET was 3.1% and did not change significantly during the study. Bodyweight loss (BWL2) before SET (−1.8% after the first trial) decreased linearly with time (P<0.05) and was −0.8% after the fourth trial. After the fifth trial, when only water was given, the weight loss was −2.5%. PLa4correlated significantly (P<0.001) with BWL2when BWL2was greater than −1.2%. The horses acclimated to exercise in hot and humid conditions as indicated by better recovery of bodyweight, increased PV, lower peak lactate concentrations and heart rate and attenuated decrease in the concentrations of sodium and chloride.It is concluded that changes in bodyweight provide a good indication of recovery of horses after exercise in hot and humid conditions; and administration of an isotonic glucose‐electrolyte rehydration solution after exercise helps to overcome dehydration better than

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1996.tb05038.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY