The pain of jumping on the dorsum of the left foot may be caused by lactic acid accumulation, dorsalis pedis fasciitis, soft tissue injury and so on. 1. Lactic acid buildup: too much time spent on left foot activities can lead to anaerobic exercise of the muscles to produce a large amount of lactic acid, which accumulates in the dorsum of the foot, resulting in pain, soreness and other symptoms, and aggravate the pain when jumping. 2. Dorsalis pedis fasciitis: prolonged walking or exercise can cause localized muscle strain in the ball of the foot, resulting in aseptic inflammation of the local tendons or fascia, leading to pain in the back of the foot when jumping, and in severe cases, it can lead to activity limitation. 3. Soft tissue injury: the muscles, ligaments and other soft tissues of the back of the foot may be strained due to sudden and strenuous exercise, resulting in pain in the back of the foot. The back of the left foot jumping pain may also have a variety of reasons, it is recommended to go to the hospital in a timely manner to improve the relevant examination, after a clear diagnosis for targeted treatment.