Hello, You should not have increased your exercise regime, strenuous and vigorous activity may cause increased blood flow causing the veins beneath the skin become enlarged and visible. Sometimes, ageing (you have not mentioned your age), genetics or or loosing weight may make skin weaker and blue veins may become visible. However, serious medical conditions may also cause similar symptoms like liver disorder(cirrhosis), superior vena cava syndrome or cancer. You are suggested to get physically examined by a GP, you need immediate diagnostic evaluation and therapy for your symptoms(of superior vena cava syndrome - SVCS) may be indicative of medical emergency. Get blood tests and investigations done to be at the safer side. Get treated at the earliest. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician