Plasma K+ dynamics and implications during and following intense rowing exercise.

Area of Science:

• Exercise Physiology
• Human Physiology
• Sports Science

Background:

• Potassium (K(+)) disturbances are common during intense exercise.
• Large muscle mass activation may exacerbate these disturbances.
• Understanding potassium shifts is crucial for exercise performance and safety.

Purpose of the Study:

• To investigate the effects of maximal 2,000-meter rowing on radial arterial plasma potassium concentration ([K(+)]a).
• To examine the relationship between exercise intensity, fatigue, and plasma [K(+)]a during and after rowing.
• To compare rowing-induced potassium changes with those observed in other intense exercise modalities.

Main Methods:

• 11 healthy adults performed maximal 2,000-m rowing.
• Radial arterial blood samples were collected at rest, during exercise (every 30s), and for 30 min post-exercise.
• Measurements included plasma [K(+)]a, blood lactate, plasma volume, and arterial pH.
• Electromyography (EMG) and power output were monitored to assess fatigue.

Main Results:

• Plasma [K(+)]a increased significantly from rest (3.89 mM) to 6.13 mM by 90 seconds of rowing, remaining elevated throughout exercise.
• Power output decreased by 19.9% and EMG median frequency by 5.5% by the end of the exercise.
• Post-exercise, plasma [K(+)]a dropped below resting levels, reaching 3.33 mM at 5 minutes and remaining low for 30 minutes.
• Blood lactate increased to 10.87 mM, plasma volume decreased by 9.7%, and pHa dropped to 7.10.

Conclusions:

• Maximal rowing induces sustained arterial hyperkalemia, reflecting a balance of potassium release and uptake in active and inactive muscles.
• The observed hyperkalemia was lower than anticipated compared to maximal cycling or sprinting.
• Fatigue during rowing was associated with reduced power output and EMG activity.
• Prolonged post-exercise hypokalemia suggests continued muscle Na(+),K(+)-ATPase activity.