Water and ion losses during the cross-country phase of eventing.

This study examines the impact of prolonged exercise on horses’ bodies, focusing on how much water and ions they lose during different stages of cross-country eventing. It was found that these losses generally increase as the difficulty of the event increases, and that these deficits in water and ions can still be present many hours after exercise.

Study Parameters and Process

• The researchers studied total body water (TBW) and extracellular (ECF) ion losses among 49 horses participating in Preliminary, Intermediate, and Advanced Horse Trials and CCI level 3-day-events.
• They collected data on each horse’s body mass and jugular venous blood samples when they were at rest, before and after the cross-country phase of the event, and after 30 minutes of recovery.
• The plasma separated from the blood was analyzed for levels of different ions, including sodium (Na+), potassium (K+), chloride (Cl-), and ionized calcium (Ca+2), as well as glucose, lactate, packed cell volume (PCV), and plasma protein levels.

Observations

• Distances for the cross-country phase varied from 3,000 to 6,000 meters, with speeds of 500 to 570 meters per minute.
• Losses of TBW were observed post-cross-country phase, ranging from 2-6.1% of resting values or 8.9-12.6 liters at the Preliminary level to an average of 20.4 liters for CCI.
• Losses of ECF ions ranged from 0.5-6.4% for Na+, 1.2-7.7% for Cl-, while K+ and Ca+2 levels varied, with some instances of gains and some losses.
• Significant increases in plasma protein and PCV were noted after cross-country phase, and PCV levels remained elevated even after 30 minutes of recovery.

Conclusions

• The study found that performing prolonged exercise, specifically the cross-country phase of eventing, resulted in significant losses of water and ions in horses.
• The amount of water and ions lost typically increased with the level of difficulty of the event.
• Even after 30 minutes of recovery, these deficits persisted, and in some cases, were still present overnight.
• This research suggests that hydration and electrolyte balances are critical factors to monitor and manage in horses participating in prolonged physical activities like cross-country eventing.