It is widely accepted that warm-up exercise should be performed before the main bout of activity during athletic competition. The benefit of such practice is that the warm-up exercise may improve performance, although there is limited evidence as to the mechanisms causing these effects.1,2 How warm-up exercise should be structured in terms of its intensity, duration, and mode and the recovery time between the warm-up and performance has not been systematically and objectively evaluated, particularly for horses. Several studies in humans3,4 and horses5,6 have revealed that warm-up accelerates kinetics of O2 during subsequent intense exercise. However, the mechanisms causing this acceleration have not been clearly delineated. It has been proposed that increases in muscle blood flow and temperature following a prior exercise bout enhance oxygen delivery and use in working muscle.3,7
Although the aerobic contribution to total metabolic power during supramaximal exercise in human athletes has been estimated to be < 50%,8 Eaton et al9 reported that the aerobic contribution to total energy expenditure in Thoroughbreds was > 80% for 120-second sprint exercise. This estimate suggests that horses quickly produce high aerobic power and have rapid kinetics of respiratory gas exchange during exercise, compared with other larger mammalian species that have been studied, despite the allometric tendency for physiologic events to take longer to occur in larger animals.10 Thus, increasing O2 kinetics with warm-up exercise would be a substantial advantage during supramaximal exercise in horses, and horses might be good experimental models in which to determine the mechanisms by which these effects take place.
Previous studies5,6,11,12 that have examined the effects of warm-up exercise in horses used warm-up durations of ≥ 5 minutes. However, warm-up routines usually performed in conjunction with Thoroughbred races are different, and the duration of warm-up prior to racing in Japan is usually much shorter (≤ 1 minute). The duration of warm-up exercise is an important component when considering its effects on metabolism and, potentially, on performance in subsequent highintensity sprint exercise.
We hypothesized that altering the intensity, duration, or presprint interval of warm-up exercise would alter the kinetics of aerobic power, the contribution of aerobic power to total metabolic power, and the peak aerobic power attained in subsequent supramaximal exercise. Thus, the aim of this study was to compare the effects of different warm-up exercise protocols on aerobic metabolism in Thoroughbreds. The duration of prior exercise used in this study was shorter than that of previous studies and was consistent with actual warmup protocols used in Thoroughbred races in Japan.
Oxygen consumption rate
Maximal oxygen consumption rate
Carbon dioxide production rate
Blood lactate concentration
Blood lactate accumulation rate
Moderate-intensity warm-up (1 minute at 70% maximal oxygen consumption rate) .
High-intensity warm-up (1 minute at 115% maximal oxygen consumption rate)
Arterial oxygen saturation
Pulmonary arterial temperature
Arterial oxygen concentration
Mixed-venous oxygen partial pressure
Mixed-venous oxygen saturation
Arterial mixed-venous oxygen concentration difference
Mustang, Kagra AG, Fahrwangen, Switzerland.
SM-29, Fukuda Denshi, Tokyo, Japan.
DATAQ, Akron, Ohio.
G. N. Sensor, LF-150B and TF-105, VISE Medical, Chiba, Japan.
METS-900, VISE Medical, Chiba, Japan.
Surflow, Telmo, Tokyo, Japan.
MO95H-8.5, COM-2 cardiac output computer, Baxter, Tokyo, Japan.
Viggo-Spectramed, Tokyo, Japan.
Statham P23d, Ohmeda, Madison, Wis.
ABL-505 and OSM3, Radiometer, Copenhagen, Denmark.
Lex-O2-Con K, Lexington Instruments, Waltham, Mass.
YSI 2300 STAT Plus, Yellow Springs Instruments, Yellow Springs, Ohio.
JMP, version 5.0.1a, SAS Institute Inc, Cary, NC.
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