Tight and hard calf stomach muscles may be overworked, calf muscle spasm, lumbar disc herniation and other diseases. 1. Excessive exertion: such as standing for a long time, fitness, running for a long time and other activities, can cause the calf area of the muscle strain, which leads to the calf stomach muscle tight and hard. 2. Calf muscle spasm: it is a kind of spontaneous muscle contraction due to lack of calcium, local neurovascular pressure, and also accompanied by strong pain, which can also lead to tight and hard calves. 3. Lumbar disc herniation: a common clinical condition, mainly lumbar pain, if the pressure to the nerve, will lead to lower limb radiating pain, this pain will be from the waist to the back of the buttocks, thighs, calves to the foot, there will be numbness, incontinence and other symptoms, but also lead to the calf tummy muscle tightness and hardness. There are many causes of tight and hard calf tummy muscles, so seek medical attention to identify the cause and treat it according to your doctor’s instructions.