Skeletal muscle Na(+)-K(+)-ATPase and K+ homeostasis during exercise: effects of short-term training.

The study investigates the impact of 10 days of moderate intensity training on muscle homeostasis and plasma potassium regulation in horses. The findings indicate that such training results in an increase in muscle Na(+)-K(+)-ATPase and a reduction in plasma K+ during high-intensity exercise.

Research Purpose and Methodology

• The goal of this study was to explore the effects of a short term, 10 consecutive days of moderate exercise training on the concentration of the Na(+)-K(+)-ATPase enzyme in the middle gluteal muscle in horses. The study also examined plasma potassium regulation in horses before, during, and after high-intensity exercise.
• Three separate groups of horses were used in the study. The first group had six mature, unfit Thoroughbred horses that underwent both incremental and high-intensity exercises before and after training. The second group involved three more horses which didn’t undertake any training or exercise tests, serving as controls for determining levels of Na(+)-K(+)-ATPase in the middle gluteal muscle. The training consisted of running at 55% of maximum oxygen consumption (VO2max) for an hour every day, covering a distance of 13-14 km.

Results of the Study

• The training led to a 13.8% increase in resting plasma volume and an 8.9% rise in VO2max during high-intensity exercises. Moreover, plasma potassium concentration and content experienced a decrease by 13% and 7% respectively after the training. However, there was no impact of the training on the rise in packed cell volume, plasma total solids and erythrocyte K+ concentration, and content during the exercise.
• Post-training, a significant increase of 23% was observed in the Na(+)-K(+)-ATPase concentration in the middle gluteal muscle biopsies, which was measured by vanadate-facilitated 3H[ouabain binding.

Conclusion and Implications

• The researchers concluded that moderate intensity exercise for 10 days resulted in an increase in skeletal muscle Na(+)-K(+)-ATPase and a decrease in plasma K+ during high-intensity workouts at the same absolute workload.
• The increased concentration of Na(+)-K(+)-ATPase enzyme in the middle gluteal muscle after the training period may suggest a reduced leakage of K+ from muscles during exercise. Thus, it means that moderate-intensity training can help maintain healthier K+ levels during high-intensity workouts.