Characteristics of Respiratory Function during Swimming Exercise in Thoroughbreds.

Abstract

ABSTRACT. Equine respiratory patterns during swimming were examined in five normal horses. The experiment included a preliminary warming-up stage and 6 circuits of swimming around an annular pool of a 50-meter-circumference. The horses were examined for respiratory rates, intratracheal pressures, inspiratory time (T I ), expiratory time (T E ), respiratory cycle (T; T I +T E ), heart rates, blood lactate concentrations, hematocrit and blood gases. The respiratory rates were maintained around 25/min. Blood gas values changed significantly during swimming. The intratracheal pressures during expiration and inspiration increased significantly with exercise duration compared to the immediately after the warming-up stage. The duty ratio (T I /T) averaged 0.33, which implied that the expiratory time was roughly doubled the inspiratory time. We considered that a longer expiratory time may limit sudden collapse of airways by water pressure during swimming and prevent a radical decrease of air space volume, thus maintains buoyancy. -KEY WORDS: blood characteristic, duty ratio, equine, respiratory function, swimming.J. Vet. Med. Sci. 60(6): 687-689, 1998 Measured items and measuring method: Intratracheal pressures, heart rates and pulmonary arterial temperature were measured. Venous and arterial blood samples were collected in parallel. The blood was taken during the resting period, immediately after the warming-up (just before entry into the annular pool), after the second, fourth and sixth round of swimming and at 3, 6 and 10 min after starting the cooling down.The intratracheal pressures were measured based on the method used by Williams et al. [9]. The signals were detected as varied intratracheal pressure through a thermodilution catheter (Criti Cath, Ohmeda, Tokyo) and recorded (Bioview E, Nihondenki Sanei, Tokyo) to output its respiratory waves through a recorder (Bioview printer, Nihondenki Sanei, Tokyo). Obtained respiratory waves were analyzed for a 20-sec run prior to each blood collection to calculate the respiratory rates, inspiratory pressure, expiratory pressure and duty ratio (T I /T; T I =inspiratory time, T=inspiratory time + expiratory time).The heart rates were calculated based on cardiogram (A-B lead) using the same setting of equipment. The data for the heart rates were analyzed for a 20-sec run prior to each blood collection.Venous blood samples, drawn from the thermodilution catheter inside the pulmonary artery, were used to measure blood lactate concentrations and hematocrit. The blood lactate concentrations were measured with a lactate analyzer (YSI-1500 sports, Yellow Spring Instruments, Ohio, U.S.A.) after sodium fluoride was added to the blood, while the hematocrit was determined using the conventional method after heparin sodium was added to the blood. Pulmonary arterial blood temperature was measured by a thermistor fixed to the end of the thermodilution catheter and monitored by a cardiac output computer (MTC-6210, Nihon Koden, Tokyo) .The arterial blood was obtained anaerobically through...

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“…The heart rate values of 130 -202 bpm obtained during the swimming tests were closely comparable with the 130 -210 bpm previously reported (Hobo et al 1998, Misumi et al1994aand b, Thomas et al 1980. Maximum heart rate during the swimming test in the present study (202 bpm) was lower than the average maximum heart rate of 223 bpm in Thoroughbred horses during a race (Krzywanek et al 1970).…”

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“…Previous studies have investigated the effectiveness of a swimming exercise test for evaluating changes in performance measures, skeletal muscle composition (Misumi et al, 1994, 1995), and respiratory function (Hobo et al, 1998). However, previous studies, have not established the physiological benefits of swim training for horses; therefore, the aim of this study was to examine the effect of swim training duration on physiological characteristics in Jeju crossbred riding horses.…”