Complex sentence: Throughout the 1990s, he was a prolific steeplechaser, specializing in the 3000 metres steeplechase in which he finished in first place at the 1991 Asian Athletics Championships.
Split into simpler sentences: Throughout the 1990s, he was a prolific steeplechaser, specializing in the 3000 metres steeplechase. He finished in first place in the 3000-metre steeplechase at the 1991 Asian Athletics Championships.