Rushing your reps without having good control of your body is a mistake that can result in lower strength and possible injury. We often see this happen in lifts like the squat. A lifter will relax their body and drop into the bottom position of the squat and then try to flex their hip and leg muscles to raise the weight back to the starting position.  They sway from side to side trying to create stability or bounce out of the bottom position. The lack of control can lead to injury for two reasons.

First, the body is not meant to tighten up while moving with a heavy load in this position.  The body protects itself from injury by maintaining stability under load. Maintaining tightness or a flexed position creates stability. We tell clients to pinch their shoulder blades together and maintain an upright chest, brace their abs and squeeze their glutes before they start an exercise. This puts the body in good alignment and creates stability to lift a weight properly.

Second, without control during the descent of the squat, you will end up in different bottom positions each time you squat.  If you are even slightly out of proper alignment, you are putting uneven stress in the body and increasing the risk for injury. For example, your hips may end up slightly to the left or right at the bottom of the movement putting more stress on one side of the body. The additional stress may be enough to cause an injury to the low back, knees or hips.

Take the time to set up properly and maintain control throughout every exercise. The amount of tightness you need will depend on how much weight you are lifting. The object is to control the weight you are lifting, not to let the weight control you. If you are not able to control the weight, you need to lower the weight and work on your form.