Interstitial pH in human skeletal muscle during and after dynamic graded exercise

Area of Science:

• Exercise Physiology
• Human Physiology
• Biochemistry

Background:

• Muscle interstitial pH plays a crucial role in cellular function during exercise.
• Previous methods for measuring interstitial pH during exercise have limitations.
• Understanding exercise-induced pH changes is vital for interpreting physiological responses.

Purpose of the Study:

• To introduce and validate a novel method for continuous interstitial pH measurement in human muscle during graded exercise.
• To quantify the changes in muscle interstitial pH at varying exercise intensities.
• To characterize the recovery kinetics of interstitial pH following exercise cessation.

Main Methods:

• Utilized microdialysis with the pH-sensitive fluorescent dye 2',7'-bis-(2-carboxyethyl)-5-(and -6)-carboxyfluorescein (BCECF) for continuous interstitial pH monitoring.
• Subjects performed 5-minute bouts of one-legged knee-extensor exercise at 30, 50, and 70 W.
• Measured interstitial pH continuously from rest through exercise and into the recovery period.

Main Results:

• Resting interstitial pH was 7.38 ± 0.02, decreasing linearly with exercise intensity.
• Lowest interstitial pH values ranged from 7.27 at 30 W to 7.04 at 70 W.
• Post-exercise pH nadir occurred 1 minute after exercise, with recovery half-times averaging 5.2 minutes.
• Interstitial pH changes were more pronounced than concurrent venous blood pH changes.

Conclusions:

• Muscle interstitial pH decreases progressively with increasing exercise intensity.
• These exercise-induced pH shifts may influence local blood flow regulation.
• Modulations in interstitial pH could impact cellular membrane transport systems during physical exertion.