The straight - leg sit up and swiss ball jack knife displayed greater external oblique muscle activity than the back squat and overhead squat. (strengthandconditioningresearch.com)
However, only the Swiss ball prone jack knife can outperform curl ups for rectus abdominis and external oblique muscle activity. (strengthandconditioningresearch.com)
Queen bed in front, jack knife sofa, bunk beds, large u shaped dinette makes into bed that sleeps 2 easily. (shoppok.com)