Complex sentence: Games of one-upmanship between Tom and Butch over the heart of Tom's girlfriend then start as both lift progressively heavier weights; after Butch fails, Tom then barely lifts it, but struggles, falls sideways and is flattened between the weights.
Split into simpler sentences: Games of one-upmanship then start between Tom and Butch over the heart of Tom's girlfriend. Both lift progressively heavier weights; after Butch fails, Tom barely lifts it, but struggles, falls sideways and is flattened between the weights.