1. Forced Reps
This is the most popular and probably the most abused intensity technique. A spotter is used to provide enough assistance for the person lifting to be able to complete the rep.
-The problem comes when the person lifting relies on the spotter for assistance during most of the set. The most obvious example is the bench press!
-Forced reps should not be done every set like some people do. When done properly, forced reps are very demanding and will severely tax your recovery systems.
-Spotters should also provide just enough help to keep the weight moving. They should not take the weight away from the trainer. We prefer a "tapping" technique!
This is simply moving the weight through a partial range of motion... usually, but not always, the strongest range of motion of the exercise, like maybe using the top 6 inches of the bench press. This allows much more weight to be used.
Partials can also be done at the end of a set to extend it. Continue with the same weight but do partial reps, shortening the range of motion more as you tire until you are just doing lockouts.
For strength gains
-Pure partials are often done in the power rack with the pins set at appropriate levels. Partial squats are done with the pins in the rack set near the top of the range of motion. Moving the bar only a few inches with a huge amount of weight on your back, is a great way to build power, density, and confidence.
-Partials can be done anywhere in an exercise's range of motion. They can help you get through sticking points if you do partials at and through the sticking point. The heavy weight is very useful for building tendon and ligament strength. Sometimes when you hit a plateau, it is not due to muscle strength but connective tissue strength. Partials can help overcome this.
-Partials can be done in a continuous without taking tension off the muscles, or in brief reps, allowing the weight to be supported on the racks for a few moments before doing the next rep. The continuous style provides more muscle tension but reduces the amount of weight that can be used. Don't bounce the bar off the pins. Develop tension in the muscles gradually so you don't jerk anything out of the sockets.
If you use a lot of partial movements, it is very important to stretch after each set. It is also a good idea to finish with a set that takes the muscle through a full range of motion. A static hold and a negative is a good way to do this as it keep a lot of tension on the muscle all the way through the entire range of motion. Hold in the stretch position for as long as possible at the bottom of the movement.
3. Pre-Exhaust Training
Do a set of an isolation exercise for a muscle group, then, with no rest, do a compound movement for it, e.g. leg extensions then barbell back squat. This fatigues the target muscle then allows the fresher secondary movers push the target muscle harder.
A variation of this is the pre-exhaust giant set. A good example is triceps, shoulders and chest. This variation will push the triceps to the limit, and work the shoulders hard.
-Start with a triceps isolation exercise such as pushdowns.
-Go to shoulder press, which works triceps and shoulders.
-Next, do bench press, which works the triceps, shoulders and chest.
Each progressive set will allow another muscle group to continue assisting.
For lower body, try it with hamstrings.
-Start with leg curls which isolate the hams
-then move to stiff-legged deadlifts, which work the hams and glutes
-then move to lunges which work the hams, glutes and quads.
The pre-exhaust concept can be extended to an entire workout. If you wish to push your triceps harder, try doing them first, followed by chest. You may limit your chest workout but your triceps will be pushed a lot harder by doing them first. This can be applied to biceps and back, shoulders and chest, or calves and thighs.
At the end of a set, when you can't do any more reps with good form, use a bit of body swing or momentum to help get the weight past the sticking point, e.g. swinging the weight up a little at the start of a barbell curl.
-Do not cheat excessively or you may cause injury.
-Cheat only to work the muscle harder, not to make the exercise easier.
-Do not cheat through your whole set
5. Drop Sets
This entails doing a set to failure with a weight then immediately doing another set to failure with a lighter weight. This can be done as double-drop (reduce the weight once), triple-drop (reduce the weight twice), or down-the-rack (use every set of dumbbells down a rack or keep moving pin down rack).
Usually we want to reduce the weight around 10% with each drop. Another useful way to do drop sets is to pull plates off if you're doing an exercise where several are being used (e.g. squats, bench). It is sometimes easier to load the bar with smaller plates to reduce the amount of weight dropped. This is one of the most time/energy efficient ways to train, especially if doing an abbreviated or maintenance program.
You may find that certain methods work best for certain exercises, play around and figure out what works best for you :)
Now go forth and get those gains!!