For the last few weeks I have either vomited or felt incredibly sick immediately following exercises targeting the core such as Russian twists and kettlebell windmills. I do not have this feeling following any form of exercise during the workout. For instance I completed some deadlifts and lateral pull downs today with no ill effects but as soon as I tried Russian twists I felt very sick. I am at a loss as to why this is happening. I thought maybe it could have been a one off but this has continued for 4 weeks now. I never had this problem before 4 weeks ago.