Complex sentence: Kroczaleski weighed 118 pounds as a high school freshman, and, after graduating high school at Standish-Sterling Central, joined the Marines in 1991 and entered powerlifting contests.
Split into simpler sentences: Kroczaleski weighed 118 pounds as a high school freshman. After graduating high school at Standish-Sterling Central, she joined the Marines in 1991 and entered powerlifting contests.