It could effect the test. The nuclear tracer, 18FDG, has glucose, which highlights metabolic activity like tumors, which are glucose sensitive. Exercising, talking, even swallowing during test can even highlight the the glucose activity in the muscles. You are not supposed to exercise 48 hours before the test, eat a low carb 24 hrs, not eat 6 hours before test, no heavy lifting day of test, drink 16 ounces water an hour before injection, and relax before test. Call the place of testing, to let them know. Good luck.