The correct answer is option 1: Lactic acid.

When joggers engage in high-intensity exercise, their muscles require a lot of energy. To produce this energy, the body breaks down glucose through a process called aerobic respiration. However, during intense exercise, there may not be enough oxygen available for aerobic respiration to occur efficiently. In this case, the body switches to anaerobic respiration, which breaks down glucose without oxygen.

During anaerobic respiration, one of the by-products is lactic acid. As the intensity of exercise continues, lactic acid begins to accumulate in the muscles. This accumulation of lactic acid can lead to soreness and pain in the leg muscles after running.

It is important to note that lactic acid is not the cause of muscle fatigue during exercise itself. Instead, lactic acid buildup occurs after exercise as a result of the body`s attempt to restore its energy balance. The lactic acid will eventually be reconverted back into glucose by the liver or metabolized by other tissues.

Therefore, option 1, lactic acid, is the correct answer to the question.