While several factors will influence the effectiveness of your weight training sessions, none makes as big of an impact as lifting an appropriate amount of weight. The load that you place on your muscles and associated connective tissue is what causes the stress that eventually leads to their development. If you use weight that is too light, you won't be putting your muscles under enough stress to elicit strength or size gains. A weight that's too high and your technique will suffer, making the workout less effective.

How to Figure Out What Weight You Should Use

Determining what weight is best for each exercise is essentially a process of guessing and adjusting. The weight that's best is going to vary depending on your personal strength levels, the type of exercise you're doing, and the number of reps you're hoping to complete. The right load will make each set challenging and yet attainable.

Before moving on, keep in mind that completing exercises for 1 to 6 reps is best for building strength, doing 8 to 12 reps is ideal for developing muscle size, and doing sets of 15 reps will help you build muscle endurance. If you're trying to do 15 reps of bench press to build endurance in your chest and shoulders, the weight you should use is going to be lighter than if you're hoping to build strength and setting out to complete 3 reps.

Therefore, monitor how you feel at the end of each set. If you're unable to reach the assigned number of reps, the weight you're using is likely too heavy. If you finish the assigned reps and feel like you could have probably done a few more, then it's likely the weight you're using is too light and it's time to increase your load. Adjust the weight you're using to make each set challenging, yet attainable.

Note for Beginners:

If you're starting to strength train for the first time, begin by using only your body weight. You want to make sure that you've mastered technique and can lift your own weight before adding any more loads. If your technique isn't correct and you increase weight, you could really hurt yourself.

Start by focusing on bodyweight exercises like push-ups, pull-ups, lunges, and squats to build strength. Additionally, incorporate free weight exercises like shoulder press, bench press and rows but without using any bars, dumbbells or added weight. Instead, practice the exercises with a broomstick or PVC pipe in place of a barbell, and use short pieces of PVC pipe or hold your hands in fists in place of dumbbells. Consider practicing at home in front of the mirror or while recording yourself.

Once you feel comfortable with technique, trade out the PVC pipes for the bar or dumbbells. The standard barbell is 45 pounds, and that might be too heavy for you to start out with, but most gyms have an array of lighter and heavier barbells available. For dumbbells, begin with 5 to 10 pound dumbbells. Start small.

When to Lift Heavier Weights

Once you've been lifting consistently, you're going to need to follow a training principle referred to as "progressive overload" in order to see continuous strength gains. Progressive overload means to gradually increase the amount of stress placed on your muscles and connective tissue. You can do this by increasing the number of sets or reps you complete of each exercise, or by bumping up the weight you use. If you stick with the same workout and weight for months, at some point you're no longer going to be putting enough stress on your musculoskeletal system to elicit gains.

With that said, you shouldn't be increasing weight every workout. If your last few reps are slow and strenuous, stick with the same weight. While things will vary depending on your genetics, training history, and muscle make-up, you should be sticking with the same weight for at least three to four weeks before bumping up the load again.

If you find that you're able to get through all your sets and reps without much difficulty, it's time to add some more weight. The weight you add should be relatively small, somewhere around 2.5 percent heavier than what you had been lifting.