It is normal to feel tired after lifting weights. Problems start to arise only when you begin to feel dizzy, nauseated or experience other unusual feelings shortly after an intense workout.
It is common initially for the symptoms of an injury to feel like sickness in the stomach, but it is unlikely that lifting could injure the stomach itself. More likely is that you have injured the abdominals or another internal structure that is causing perceived feelings of sickness in the stomach.
Lifting heavy weights cannot cause stomach illnesses. They can however place stress on the abdominal muscles and even injury.
Lifting Weights Cause Stress
Lifting weights can place a great deal of stress on the body. If you experience stomach illness or pains shortly after lifting weights, it is possible the injury occurred when you were performing a lift that placed significant stress on the abdominal muscles. John Hopkins Medicine says that the stress you place on your body during physical activity can happen quickly or accumulate over time. Various techniques such as continuing to breathe rhythmically while lifting can help you reduce your odds of suffering a stomach injury from lifting, but you may be susceptible even with the right precautions.
Read more: How to Get Started With Weightlifting
Injury to the Abs
It is possible for an injury to the abdominals to cause dizziness or even nausea for the lifter. You may notice the pain fluctuating depending on whether you are inhaling or exhaling. On the surface of your abdominal area you may notice a bulge of varying sizes. Coughing attacks may occur, and these often intensify the pain you are experiencing. Swelling may appear on the surface of the abdominals, and you are likely to find it difficult to lift at your normal workload.
Abdominal Strains or Tears
In some cases, you may have suffered something such as a severe abdominal strain or even a tear of the abdominal muscles. Another common cause is the inguinal hernia, which occurs when part of the small intestine protrudes through a weak hole or tear in the abdominal muscles, according to Mayo Clinic. The American Academy of Orthopaedic Surgeons point out the "sports hernia or athletica pubalgia" which is a strain or tear in the soft tissue of the lower abdomen. Other causes may be possible, but it is less likely they are related directly to lifting weights — it may be that the symptoms arose coincidentally while working out, or that lifting weights triggered the symptoms but is not the cause.
Read more: Muscle Recovery Time After Weight Lifting
If It Gets Worse
If your stomach pains persist or worsen over the course of a few hours, contact a doctor or visit a doctor's office. Your doctor may be able to diagnose your problem over the phone, but if you have a serious stomach injury, such as a severe inguinal hernia, immediate medical attention may be needed. If you experience any stomach pains in the middle of a workout, stop lifting, rest your body and take small sips of cool water.