it's the way rather than the weight you lift

Although weight training is about applying resistance to your skeletal muscles in order to stimulate more tone and hypertrophy of the cells, what's often overlooked is the attention to detail in the way an exercise is performed.

Photo by Raymond Cassar in Zebbug, Malta

Several popular exercises, such as bench press involve multiple joints, which means that more than one muscle group is working simultaneously.  Having said that, it's crucial to perform each exercise in a strict manner to ensure you're working the muscle group being targeted. 

So even though certain gym equipment may be labelled as a "back machine" for example, that doesn't mean it will solely work your back muscles no matter how you perform the exercise. Even leaning a little too far back on something as specific as a lat pull-down machine, which is intended primarily for the latissimus dorsi muscle, can shift the tension onto your biceps and rear shoulders. Here's another example, if lets say you incline the bench a little bit too much on a dumbbell chest press exercise you could easily end up working more your front shoulders and triceps, resulting in an underdeveloped upper chest.  You get the gist of it, right?

Therefore to achieve the best possible results in the shortest amount of time, you need to use what we call an isolation technique, whereby you target and work each muscle group individually, or at least ensure most of the resistance is in fact being applied to the correct muscle group. 

Next time you're in the gym try to pay close attention to the way each exercise is performed, and activate that mind to muscle connection to help you feel when it's right. If you're still unsure or somewhat inexperienced about certain exercises, then ask for advice or perhaps hire a personal trainer for a while, because you could be saving a lot of time by doing right in the first place.