Feeble weekly rhythmicity in hematological, cardiovascular, and thermal parameters in the horse.

The research study investigates the presence of weak, seven-day rhythms in certain biological parameters of athletic and sedentary horses. Despite the potential impact of weekly activity schedules, the evidence found does not support the concept of naturally occurring week-long rhythms in these animals.

Study Overview

In this study, the researchers set out to examine whether there are regular, week-long patterns in certain physiological factors of horses. This concept, known as circaseptan rhythms, refers to an internal biological rhythm with a period of approximately one week. Specifically, they focused on:

• The plasma concentration of lactic acid
• Systolic and diastolic blood pressure
• Rectal temperature

These parameters were compared in two groups of horses: athletic horses that followed a seven-day training schedule and sedentary horses that had a constant schedule without any significant change throughout the week.

Key Findings

The results showed that while exercise, unsurprisingly, had a strong immediate effect on the parameters studied, only one parameter (plasma concentration of lactic acid) exhibited any kind of weekly rhythmicity, and even then, it was only present in a few athletic horses. Furthermore, this weak pattern vanished when more strict statistical criteria were applied.

Interestingly, the study found that all parameters showed 24-hour rhythmicity (circadian rhythms) in all horses, athletic and sedentary alike. This suggests that a regular daily cycle, rather than a weekly one, may be more influential on these physiological parameters in horses.

Conclusion

In conclusion, the researchers determined that the weekly patterns observed in the physiological parameters of the horses were weak and likely resulted from the structured weekly activity schedule. The evidence thus does not support the theory of an innate, seven-day rhythmicity in these animals. Instead, the findings suggest that daily patterns, and the immediate impact of exercise, are more strongly associated with fluctuations in these physiological parameters.