Your lumps are fat. The way to lose fat anywhere is always the same: burn more calories than you take in. The wrong way is to simply eat less than you burn. That way, you lose some fat and some muscle. Muscle loss lowers your metabolism, making it easier to gain weight even when eating fewer calories. The right way is to raise the metabolism through strength training and to also burn off excess calories through cardiovascular exercise. The strength training and cardio must be supported with proper nutrition or it's a waste of time. Another waste of time is the torso twists recommended above. If done while sitting and/or with weights, they are a great way to grind your lumbar vertebrae to dust while doing nothing for the lumps. Back extensions will strengthen the lower back, which is a good thing, but will burn very few calories. Strength training that involves all the major muscle groups, and cardio supported by adequate nutrition is the answer to the problem. You wind up toned, slim, and healthy.
Sorry, Sabrins. Wrong answer.