The big decision someone has to make when he first start his journey to improve his strength is, whether to use free weights (dumbbells, barbell, kettle-bells, bodyweight) or the advanced machinery provided by gyms , this article attempts to prove why free weights are better for strength training.

Machines don't improve strength. They shape the targeted muscle but they won't make it stronger. That's because most of the times the movement you do is linear you move the weight from point A to point B without being able to stray from that line, in everyday life motions are rarely linear, they train the body in movements it will not use. Also they isolate muscles, which is good when you want to shape them (like in bodybuilding) but not when you want to improve your strength. Our body is designed to work as a whole system, when you isolate a certain muscle (or muscle group), you force the body to produce power in a way that is unnatural. One more thing, machines are not tailored to your body, if you are slight taller or shorter than the average it will force you to lift the weight in an awkward way. Machines although have their advantages too. Some of them do a pretty good job if you want to recover from an injury (e.g. leg press).

Free weights are the way to go. They force the body to work as a unit, there is no isolation. When you squat with a barbell on your back, nearly every muscle in the body is activated to lift the weight, in contrast, when using the leg extension machine, you isolate the quadriceps only, so what? When you pick something from the ground squatting deep down, you don't use your quadriceps only; you use your hamstring, glutes and many more muscles. Also compound movements done with free weights train the stabilizing muscles of the body, because you have to actually hold the weight in the right place without falling to any direction. Free weights also use the core muscles, think about it; you can't really do anything without a strong core, nearly every exercise done with free weights uses core muscles, I don't think you train these muscles sitting comfortably on the seat of a machine.

Free weights equal compound movements and the body loves compound movement, it loves to work as a unit. Machines equal isolation, isolation is bad for strength. The body must work as a whole; it's how it was designed to function.