A sprinter feels cramps and pain in the thigh muscles after a run. This is due to accumulation of

A sprinter experiences muscle cramps and pain due to the accumulation of lactic acid in the thigh muscles. During high-intensity, short-duration activities like sprinting, the body's demand for energy (ATP) exceeds the oxygen supply available for aerobic respiration [4]. Consequently, muscle cells switch to anaerobic metabolism, where glucose is broken down into pyruvate in the cytoplasm [2]. In the absence of sufficient oxygen, this pyruvate is converted into lactic acid rather than entering the mitochondria for complete oxidation [2]. This rapid buildup of lactic acid in the muscle tissue leads to acidosis, which is traditionally associated with the sensation of burning, fatigue, and painful cramps [1]. While aerobic respiration produces carbon dioxide and water, the anaerobic pathway in humans specifically produces lactic acid, whereas ethanol production is characteristic of fermentation in organisms like yeast [2].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.5 > p. 88
2. [4] https://www.ncbi.nlm.nih.gov/books/NBK546695/
3. [2] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.5 > p. 87