Complex sentence: However, in the non-olympic sport of powerlifting, many world records in several weight divisions have been accomplished by athletes well into their forties, purportedly, "verified" by the International Powerlifting Federationto have been accomplished drug-free.
Split into simpler sentences: However, in the sport of powerlifting, many world records in several weight divisions have been accomplished by athletes well into their forties. These world records are verified by the International Powerlifting Federation, and are certified by that organization to have been accomplished drug-free.