Complex sentence: During the Razorback Invitational, Fernandez broke a World Junior Record by running 3:56.5 indoors, then at the Big 12 Championships, ran 3:55.02 to further his record and beat the converted collegiate record in the mile.
Split into simpler sentences: During the Razorback Invitational, Fernandez broke a World Junior Record by running 3:56.5 indoors. At the Big 12 Championships, he ran 3:55.02 to further his record and beat the converted collegiate record in the mile.