Due to accumulation of which one of the following, joggers experience pain in their leg muscles after running?

Joggers experience muscle pain and cramps due to the accumulation of lactic acid. During intense physical activity like running, the body's demand for oxygen exceeds the supply available to muscle cells. Consequently, the cells switch from aerobic respiration to anaerobic respiration to generate energy [c1, t7]. In this anaerobic pathway, pyruvate is converted into lactic acid, a three-carbon molecule [c1]. The buildup of this acid leads to a burning sensation, muscle fatigue, and acute pain during or immediately after exercise [t4, t6, t9]. While modern research distinguishes between this immediate 'burn' and Delayed Onset Muscle Soreness (DOMS)—which is caused by microscopic muscle tears—the primary substance responsible for the acute pain and cramping during sudden activity is lactic acid [c1, t8, t10]. Other acids like acetic acid (found in vinegar) or citric acid (found in citrus fruits) are not produced by muscle metabolism [c2].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.5 > p. 88
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Table 2.3 Some naturally occurring acids > p. 28
3. [3] https://www.scientificamerican.com/article/why-does-lactic-acid-buil/