Which by-product of the energy systems can cause muscle fatigue?

Hydrogen ions are indeed a by-product of the anaerobic energy systems, particularly during high-intensity exercise like sprinting or weightlifting. When carbohydrates are metabolized without sufficient oxygen, lactic acid is produced, which dissociates into lactate and hydrogen ions. The accumulation of hydrogen ions in the muscle tissue lowers the pH, creating an acidic environment. This shift in pH can interfere with muscle contraction and the energy-producing processes, contributing to the sensation of muscle fatigue. As a result, athletes may experience a decrease in performance, slowing down their ability to maintain intensity during exercise.

Other substances like water, creatine phosphate, and oxygen do not directly cause the same level of fatigue. Water is essential for various physiological functions and can help with recovery. Creatine phosphate serves as a quick energy reserve during short bursts of activity but does not accumulate to the same extent as hydrogen ions. Oxygen is crucial for aerobic metabolism and higher energy production and is not a by-product that contributes to fatigue in the same manner as hydrogen ions do.