Negative reps (aka “eccentric exercise”) produce greater force than other types of resistance training, the Journal of Applied Physiology reports. “After a judicious adaptation period of a few weeks,” says author Paul LaStayo, Ph.D., “perform the eccentric lowering phase with a greater external load than in the concentric phase.” That is, if you can bench press 200 pounds for five normal reps, try 225 for five reps, but start at the top with elbows locked and lower the bar slowly to your chest. (Have a partner help lift the weight to the up position each time.) This creates more muscle damage, leading to more growth and greater strength. But: It’s very stressful on muscles, joints, and tissues, so always have a spotter, and don’t do negs for more than three to four weeks straight.