1 – Lifting weights too quickly

An important concept behind resistance training is that the body will increase strength of a muscle when the muscle is stressed.  In this case, “stressed” refers to putting a larger than usual load on the muscle while maintaining tension in the muscle.  Maintaining tension is key – when a person raises (or lowers) weights too quickly, they will see significantly fewer strength gains than if a cadence of 2-3 seconds up and 2-3 seconds down was followed.  If you cannot lift a weight with that level of control, the weight is not optimal.  You will actually see more progress in an exercise using 5 lb weights and maintaining control than using 10 lb weights and flinging them through the air.  The most useful technique is not always the most visually impressive to the untrained eye.

2 – Using an incorrect amount of weight

You may already have heard that performing 8 to 12 repetitions in a set is an effective way to increase strength, but where many people go wrong is that they use an incorrect weight within those parameters.  Performing 8 repetitions means (unless you are a beginner) using an amount of weight that will challenge you by the end of your set, causing you to notice shaking in the muscle and reduced speed of the motion.  If you finish a set of 12 and feel you could have performed 30 additional repetitions, you have left a large portion of that muscle untouched and will not gain strength.

This also means that as you become stronger, you must increase the resistance.

3 – Not working through a full range of motion

Resistance training (not bodybuilding) is training your body to be strong and safe in real-life situations working against a weight.  Think of real-life situations when you’re deciding how to do an exercise!  It is possible for many individuals to load up 135 lbs on the bar, bend the knees ever so slightly and say that they can squat 135 lbs.  Now imagine what would happen if this person was standing in front of a 135 object on the ground in real life and had to pick it up – nothing!  Their muscles would have been trained only through the range of motion they used in the gym, and they will have gained no strength in a real application.  Reiterating the first point, performing an exercise going through half of movement with 50 lbs will be far easier, far less useful, and far less impressive than performing the exercise with 25 lbs, and a full range of motion.