If you've been doing the same training program for a few months now, simple straight sets using the same weight, it is definitely time to change your workout structure. You need to push your body past it's limits and keep it guessing as to what you are going to demand of it next. The perfect solution to this problem is that of pyramid sets.
Basically, what you will do during a pyramid set is start with one set that uses a lighter weight but encompasses many reps. For example, performing a set of dumbbell curls for 15 reps using 20 pound dumbbells.
After that set and rest period is completed, you then move onto the next set where you use a slightly higher weight and perform fewer repetitions. The next set, you will progress to an even heavier weight, with fewer repetitions still. So you are essentially building a pyramid when referring to how many reps you are doing.
As you move to the top of the pyramid, you will use heavier and heavier weights, however you will be lifting them for a shorter period of time.
A WIDE VARIETY
One of the biggest advantages to this type of training is that it trains your body to get used to a wide variety of weights. If you are always training with heavy weights and low reps, your body will adapt to this and you will find yourself not as strong if you have to perform any type of activities that require muscular endurance.
On the other hand, if you specifically train for muscular endurance with large numbers of reps, you are most likely not maximizing your strength potential.
OUTSIDE THE COMFORT ZONE
The second advantage to this type of training is that it really pushes you past your comfort zone. Most people really don't realize just how strong they are. They never attempt to do a 1 rep max to see how much weight they could be lifting. They simply just lift what feels comfortable and allows them to get to the 8-12 rep range.
By pushing yourself to move lower into the 6 rep range or so, you will see that you can actually handle more weight, which will serve to allow your body to grow stronger more quickly, and thus allow you to progress at a higher rate.
A WORD OF CAUTION
One word of caution however that you must be aware of when you are performing pyramiding sets and are using higher weights is that proper form remains very critical. It won't do you much good if you are lifting massive amounts of weight but your form is way off.
In fact, this will only serve to do you more harm than good. It is a good idea to perform this type of workout with a partner so they can spot you as your reach your heavier sets. They may help guide you along slightly so that you are able to complete your set without sacrificing your form.
CHOOSING A PYRAMID SCHEME
If you would consider yourself more of a beginner, it would probably be advisable to perform 3 sets of one exercise with three different weight levels, jumping in increments of about 2-5 pounds (usually the more complex lifts, for examples squats), will call for a larger increment to produce a noticeable difference versus say a dumbbell curl where a jump of 2 pounds might very well be enough to make you need to reduce your total number of reps.
Those who are more advanced may wish to perform 4-5 sets, using their first set as more of a warm-up and progressing through sets with reps of 12, 10, 8, 6 and maybe even 4 reps. Another option here would be to do a reverse pyramid as well where you would work your way up (using heavier weights and less reps) and then back down once again.
This would produce quite a high volume however, so you would need to reduce the number of other exercises you do in the same session to reduce the chances of overtraining yourself.
Larger, more compound exercises are generally better with regards to using the compound principle simply because you can handle more weight with them. Smaller muscles tend to be a little weaker and you may find that after one or two jumps in weight you simply cannot perform even one rep with proper form.
Also, these muscles will fatigue faster therefore you may not be able to execute the required number of sets to achieve your goal weight (for instance if you are hoping to use 5 incremental weights).
To take this factor into consideration, use the pyramid principle for the compound exercises (such as squats, bench press, deadlifts) and then perform normal straight sets for the smaller, 'helper' muscles such as biceps and triceps.
Since these smaller muscles will indirectly be working in your larger lifts, such as bench press for example, they will already be pre fatigued and will get a better than normal workout anyway, than if you would have simply just started working them in the beginning.
The final factor to consider is the intensity of pyramid sets. They are a more physically demanding type of workout since not only does your body have the stress of the weight but it also has to deal with the stress of adjusting to various weights and reps. You also will likely be performing more sets as well, as mentioned above, which means more volume and thus more rest will be needed.
So if you are going to incorporate pyramid sets into your workout, it may be a good idea to ensure 2 full days of recovery between workouts just to give your body a little extra time to rebuild and prepare itself once again.
So, if it's time to advance your workout and challenge your body to a new level, give pyramid sets a try. You don't necessarily have to use pyramid sets for every workout either. For example, you may only choose to use this format for your chest and keep the rest of your workouts as they were before.
This is fine too, and will create less of a stress on your whole body while allowing you to kick up the progress in one particular area (possibly your 'trouble' area). Just be sure to keep in mind that you still must maintain proper from and that it's always better to use a spotter if you are unsure.