or legs to a vertical upright position. This is a compound exercise that also involves the hip flexors. Equipment: body weight or dumbbell. Major variants: hanging ~ (hanging from a high bar), side ~ (lying on side), knee raise (lying on back, drawing knees to chest). The Russian twist is a type of exercise that is used to work the abdomen muscles by performing a twisting motion on the abdomen. This exercise is performed sitting on the floor with knees bent like in a "sit-up" position with the back typically kept off the floor at an angle of 45°. In this position, the extended arms are swung from one side to another in a twisting motion with or without weight. Equipment: body weight, kettlebell, medicine ball, or dumbbell. Major variants: back kept off the floor at 45° angle, back rested on exercise ball, feet resting on the floor, anchored or kept off the floor. Lower back Back extension The back extension is performed while lying face down partway along a flat or angled bench, so that the hips are supported and the heels secured, by bending down at the waist and then straightening up again. This is a compound exercise that also involves the glutes. Equipment Body weight, dumbbell or back extension machine. Major variants Without bench (lying face down on the floor). Deadlift The deadlift is a very effective compound exercise for strengthening the lower back, but also exercises many other major muscle groups, including quads, hamstrings and abdominals. It is a challenging exercise, as poor form or execution can cause serious injury. A deadlift is performed by grasping a dead weight on the floor and, while keeping the back very straight, standing up by contracting the erector spinae (primary lower back muscle). When performed correctly, the role of the arms in the deadlift is only that of cables attaching the weight to the body; the musculature of the arms should not be used to lift the weight. There is no movement more basic to everyday life than picking a dead weight up off of the floor, and for this reason focusing on improving one's deadlift will help prevent back injuries. Wrong technique and forward lean posture with a flexed spine can lead to discal injuries of the lower back. Correct technical performance with a slightly hollow or extended back and a hip hinge to keep the normal curvature