I hope this helps!
Irritable Bowel Syndrome
Menstrual like cramping during exercise may be related to irritable bowel syndrome. Symptoms include severe abdominal cramps, which can occur at any time.
Hypothyroidism occurs when your thyroid is underactive and does not make enough thyroid hormone. The symptoms include excessively painful cramping before and during your menstrual period. Make a note of when the menstrual like cramps during exercise occur – if you find they fall around your period, you may wish to get your thyroid tested.
Hormones
Unexplained cramping during exercise can be a result of hormones. Menstrual cramps are caused by hormones related to your period, and intense exercise may trigger a hormonal response during other times of your cycle. Take an nonsteroidal anti-inflammatory like ibuprofen or naproxen before you exercise to stave off problems.
Exercising with undigested food in the gastrointestinal tract can cause digestive distress. Likewise, exercising on an empty stomach also may lead to feelings of nausea. An April 2001 study published in "Appetite" examined the effects of high and low-intensity exercise on subjects who underwent various eating patterns. Each participant exercised on an empty stomach immediately after eating a beef patty and 60 minutes after eating. For comparison, the digestive system also was studied after eating without exercise. Results found that scores for nausea were highest while exercising on an empty stomach and immediately after eating. Nausea was higher if participating in high-intensity exercise directly after a meal. Researchers concluded that exercise can cause nausea, the severity of which is determined by eating patterns.
Lack of and too much hydration may increase the chances of feeling nauseous during or after exercise. The body produces sweat during exercise to help cool its core temperature. Electrolytes such as sodium and potassium are excreted, along with fluids. Depleted levels of fluids and electrolytes during exercise can lead to nausea. The "European Journal of Applied Physiology" published a study in December 2000 that found dehydration delayed stomach and intestine emptying. Delayed gastric emptying induced symptoms of nausea. Overhydration also can cause stomach sickness. Drinking too much water fills the stomach, leading to a bloated feeling.
If you're experiencing pain because of your menstrual cycle, your cramps may begin a few days before your period and become more severe once your period begins. Increased blood flow to your organs after exercising can increase the pain you experience. If you have severe cramping from a menstrual period, exercise can seem almost impossible. Endometriosis can cause pain in your uterus a few weeks before your period starts. After physical activity and sex, the pain may be most noticeable. If you have an allergic reaction to exercise, cramping of the uterus is one of the many symptoms and can occur during or after exercising, according to the American Academy of Allergy Asthma & Immunology. Pelvic Inflammatory Disease, or PID can also cause lower abdominal pain after exercise that's sometimes accompanied with unusual discharge and possible pain urinating, according to the Center for Disease Control and Prevention.
Your uterus contracts to remove cells and tissues from your body if fertilization has not occurred during the cycle, which results in your period. A hormone-like substance called prostaglandins is often responsible for pain and inflammation you experience with menstrual cramps. Endometriosis is caused by the lining of your uterus growing outside of the uterus, which results in painful scar tissue, according to the UCSF Medical Center. Exercise-induced anaphylaxis is a result of your immune system overreacting to your body's response to exercise and releasing chemicals that cause an allergic reaction, but the cause for the reaction is unknown. PID is usually caused by a sexually transmitted disease, but can also be a result of douching or IUD birth control methods.