Influence of time of day on body temperature, heart rate, arterial pressure, and other biological variables in horses during incremental exercise.

The research article discusses how the time of the day, either morning or afternoon, influences various physiological variables such as body temperature, heart rate, blood pressure, etc in horses during their exercise routine.

Research Focus and Methodology

• The researchers were interested in studying how different physiological variables in horses responded to exercise during different times of the day.
• For a period of eight days, they observed horses performing the same exercise routine either in the morning (a.m.) or in the afternoon (p.m.).
• The variables they monitored included heart rate (HR), systolic and diastolic blood pressure (BP), body temperature (BT), blood glucose, blood lactate, and skin temperature.

Research Findings

• The researchers found that heart rate, blood pressure, and body temperature were consistently higher in the afternoon compared to the morning sessions.
• For blood pressure and body temperature, the increase from morning values was the same both at rest and during exercise.
• The absolute increase in heart rate was greater during exercise. However, the percentage increase was the same as during rest.
• Exercise led to a decrease in blood glucose, but an increase in blood lactate and skin temperature was seen. These changes were consistent regardless of whether the exercise was performed in the morning or the afternoon.

Interpretation and Conclusion

• The findings led the researchers to conclude that there were no significant differences in how heart rate, blood pressure, and body temperature responded to exercise in the morning versus the afternoon.
• However, the fact that the absolute values of these variables did change throughout the day highlighted that circadian oscillations could potentially influence these parameters.
• This suggested that horses might have decreased safety margins against conditions like hyperthermia (overheating) and hypertension (high blood pressure) during afternoon exercise.