weights for core stability

On Wednesday afternoon I went to the gym for some cycling, body balance, and most importantly, body pump.
On Thursday I had a full session at the gym: on the treadmill I ran 21.3km in 2hrs, speed 10-11km/hr, inclination 1; 27min cycling, resistance 7; 1hr rpm XL class; 40min abs and weight lifting.
My focus is on aerobic/cardio, but I try to do weight lifting and body pump class as frequent as possible. I can definitely tell the difference: strength, posture, core stability, overall fitness have improved!