The concept of compensatory acceleration training (CAT) was popularized by powerlifting legend Fred Hatfield. The basic premise is simple:

Force is equal to mass times acceleration (F = ma).

In other words, you can increase the amount of force the muscles have to produce by increasing the mass (weight on the bar) and/or the acceleration you impart on the barbell when you lift it.

So the principle behind CAT is that when you're lifting a submaximal weight, you can compensate for that lack of resistance by accelerating more quickly.

What does such a rep look like? Let's say you're doing a bench press. It means trying to blast the barbell off your chest and trying to accelerate it as much as possible for as long as possible.

Another aspect of CAT is the transition between the eccentric (lowering) and concentric (lifting) portions. The transition itself should be rapid. This requires very strong antagonist muscles to stabilize the joints at the point of reversal. For example, you need strong rhomboids, rear delts, and lats to do a fast turnaround on the bench. Even the biceps can help.

The majority of the eccentric phase should be done under control (not slowly, but you must control the barbell), but the transition point is rapid and then you attempt to produce as much acceleration as possible on the way up.

If the weight is heavy, the bar might not actually move fast. The acceleration is meant to compensate for the lower weight, and a heavy weight means you won't be able to compensate much and the acceleration won't be high. Regardless, you still attempt to produce as much acceleration/speed as possible.

Pros of CAT

• This rep style maximizes peak force production at any given load, so it makes the muscles stronger.
• By working on acceleration you'll also develop more power/explosiveness than if you used a more "regular" lifting style, which is good if you're an athlete trying to be explosive.
• By attempting to move as fast as possible you maximize fast-twitch motor unit recruitment. Over time you'll become more efficient at recruiting those fibers, which will obviously help you gain more strength, size, and power in the future.
• By using the stretch reflex at the turnaround point, you become more efficient at using it in muscle actions, which can help you in athletic activities that require the use of the stretch reflex.

Cons of CAT

It will sound weird because I mentioned that CAT maximizes peak force output during a rep at a given weight, but CAT actually isn't optimal for building "1RM slow-speed strength."

You'll become very strong on fast reps, but as soon as the weight is too heavy for you to accelerate, you won't be able to push it farther. Someone who trained otherwise, however, will normally be able to grind out a weight much heavier than the one he can lift with acceleration.

I also mentioned that CAT leads to a higher peak force production for a given weight. That's true. But it doesn't mean that the average force production of the whole range of motion is higher. In fact it isn't.

What happens is that you produce a very high peak of force initially, but the later portions of the range of motion have a fairly low force production level because you're relying on the momentum built from the initial thrust.

In reality, the momentum actually "lowers the mass to overcome" in later parts of the movement, which diminishes the amount of force to produce.

What happens is that you become very good at producing a burst of force over a very short time frame/range of motion, but you lose the capacity to keep that force production "turned on" for the duration of the rep.

That means you won't be able to grind weights up. When momentum from the initial thrust dies, the lift dies, too!

That's why we sometimes use chains and bands. These tools adjust the resistance upward in the range of motion. They can counteract the effect of the created momentum and allow you to sustain a higher force production during the whole range of motion.

Unfortunately, bands can't be used for too long. They drastically increase eccentric stress during a lift, which significantly prolongs the recovery period. You should not use bands for more than three weeks in a row. Chains are more forgiving and can be used more often.

When to Use CAT

CAT should only be used on big compound movements, specifically with exercises of a pressing/pushing nature like bench press, military press, push press, squat, or front squat.

The deadlift doesn't work that well with CAT because you lose your position during the first pull (from floor to knees), which is both inefficient and dangerous. The deadlift is better performed with a more gradual acceleration.

Pulls like chin-ups, pull-ups, and rows also aren't ideal for CAT, as much of the workload gets shifted to the biceps and forearms and less on the back.

CAT should only be used when you have a sound and solid lifting technique on the movements you want to use it with. Using CAT on movements where your technique is not stable will often lead to bad form or at the very least, a form that isn't the same as for your heavy lifts.

Ironically, CAT is a method that builds a lot of power and explosiveness, but people who already are very explosive shouldn't use this technique too often. The more explosive you are, the lower the average force produced over the whole range of motion because someone who's super explosive can create a ton of momentum with the initial burst.

So, it is best to use CAT on big, compound pressing movements by people who aren't naturally explosive and who have good lifting technique.

The basic premise of dynamic correspondence is that any lift should look exactly like a maximum effort lift. That is, if you want to become good at showcasing strength during a maximal effort lift, you should get as much practice under the same conditions.

A lot of people have superb lifting technique with weights up to 90-92% – tempo is great, lift looks solid, no technique breakdown. But when the lifter gets into the 95-100% zone, it all goes to hell.

Technique is thrown out the window and ultimately the lifter's maximum lift isn't much higher (if at all) compared to his 3RM (maximum for 3 reps).

I addressed this topic somewhat when I talked about the cons of compensatory acceleration training: You become good at demonstrating strength under a certain type of contraction or condition, but when the weight forces you to use a different force production strategy, you lose all efficiency.

So the principle behind dynamic correspondence is that you should strive to make any rep on a big lift look exactly like a max effort would look. This means lowering and lifting the weight the same way you handle your max lifts – same speed, same acceleration, and same tension.

When performing CAT you compensate for the lack of weight by an increase in acceleration, but with dynamic correspondence approach you compensate for the lack of weight by increasing how hard you contract the muscles involved in the movement – kind of like if you were trying to flex the muscles as hard as possible when lifting.

This action could also be called compensatory tension since you're compensating for the lower weights by an increase in voluntary muscle tension.

Pros of Dynamic Correspondence

• Dynamic correspondence makes you efficient at overcoming a resistance under maximum-like conditions. This means that your form is likely to be a lot more stable with maximal weights and should allow you to reach higher maxes and do them safely.
• It also teaches you to recruit your muscles more and make the joints involved in the movements more stable.
• This capacity to recruit the muscles more efficiently will eventually become automatic and you will 1) be naturally better braced when doing big lifts, and 2) stimulate the muscles more because you're more efficient at recruiting them.
• You're also more aware of your body position during those types of reps, which will make it easier to learn and perfect technique.

Cons of Dynamic Correspondence

The main drawback is that if it's done exclusively you will lose the capacity to produce force during high speed/explosive actions. This isn't exactly desirable for any type of athlete.

When you do these reps right (producing maximum tension by tensing the muscles as hard as you can), you actually make each rep a lot more demanding and it will severely cut into the number of reps you can perform. Fatigue will set in much faster than with normal reps. For that reason, dynamic correspondence is better used for sets of low reps, say 1 to 3.

It can be done for up to 5 reps, but the last two might not have the same level of tension. That's fine because the fatigue "makes the load heavier" (relatively speaking), so by the time you reach reps 4 and 5 it will actually feel like a max even though you're not using as much tension.

Some people simply do "slower reps," mimicking the speed on a maximal lift, without contracting their muscles as hard as they can. If you do this you're actually likely to lose strength because your force output will be low. If you do dynamic correspondence reps, a lift should feel and look like a max rep. You actually make a lighter weight as draining as a max.

When to Use Dynamic Correspondence

It's best to use dynamic correspondence when focused on maximal strength, while using a progressive load cycle (like my 915 plan) where you start a training cycle with a moderate weight and low reps and gradually increase the weight until going for a max 8-12 weeks later.

In that case, the main lifts – the ones on which you'll test yourself at the end of the cycle – are done using dynamic correspondence while the assistance work can use CAT or normal reps.

It's also a good way to do your reps if you're fond of high frequency training. For example, if you decide to train the bench press and deadlift five times per week, it's best to use a lighter load and keep the reps low.

Such an approach typically has you staying in the 75-80% range most of time (with an occasional day at 90-95% to see where you are at) and doing 3-5 reps or even lower.

The dynamic correspondence method is well adapted to this type of training because it aims at developing strength-skill: The ability to display strength under a max effort condition.

Constant tension reps are based on the principle of occlusion, which is when blood entry in the muscle is limited, depriving it of oxygen.

This lack of oxygen, as well as the incapacity to remove the waste products accumulated during muscle contractions, increases the release of local growth factors, which can trigger hypertrophy or muscle growth.

Occlusion can be achieved by using a strap around your limbs, but constant tension can also do the trick.

When a muscle contracts, blood entry into the muscle is stopped or greatly reduced. It's when the muscle relaxes that blood can come in. The harder a muscle contracts, the less blood can come in.

So if the target muscle remains contracted throughout the set, never relaxing, you'll create an occlusion effect. To do this it's imperative that you flex the target muscle as hard as possible during every inch of every rep. You can only let go of the contraction when the set is over.

Imagine that you aren't lifting a weight, but rather that you're flexing your muscle. Each phase of the rep is done slowly to maximize both time under tension and the amount of tension. If you go too fast you'll have brief periods of partial relaxation due to the momentum, which destroys the effect.

Pros of Constant Tension

• This rep style works very well to isolate a muscle group and stimulate local hypertrophy. It does so via the release of local growth factors, not muscle damage or heavy mechanical work. You don't have to use a heavy weight since studies have reported gains with only 30% of your maximum done with this style of contraction.
• It can be done very frequently and won't negatively affect subsequent workouts.
• It will improve mind-muscle connection with the target muscle, which means that in the future you'll be better at recruiting muscle fibers.
• It's also very safe because of the slow movement being done with a high level of tension.

Cons of Constant Tension

It won't build strength. And if you only train this way you might end up with larger muscles, but you'll be weak. It's a great method to learn to use a specific muscle but it can actually screw up the mechanics of a big compound lift.

It also requires a lot of mental focus and significant pain tolerance because for this type of rep to work, you have to go deep into the "intra-set burn." The burn indicates a large accumulation of metabolites which can stimulate growth factors.

You will rarely be limited by your strength with this method. Instead, the limit will be based on how much burning you can handle. Over time this can get mentally draining.

Constant tension doesn't work well with compound movements. It's best suited for isolation work and it should never be the cornerstone of your training. So while this method is effective, it has limited application for someone who prefers to focus on the big basics.

When to Use Constant Tension

Constant tension is best used with isolation exercises. I prefer to do almost all of my isolation work this way. I do a lot of heavy lifting on the big compound movements that help me build strength and explosivity, so doing constant tension on isolation exercises gives me what I don't get from my main movements.

Also, I like constant tension for isolation work because it "teaches me" to use those muscles. Therefore, I use them for my weakest links to not only build them up, but to make me better at recruiting those muscles, which will in turn make me use them better in my big lifts.

The only time I might use constant tension on a multi-joint movement with clients is with body weight exercises like bodyweight squats, push-ups, dips, etc. In these movements the external load is fairly light I only use it if the client can do at least 15 reps on the movement.

By normal reps I mean reps done without...

• a specific effort to explode as much as possible
• a specific effort to create as much tension as possible
• trying to contract the target muscle every inch of every rep
• making every rep with minimal effort/accumulated fatigue

It doesn't mean sloppy reps or reps done without focus. It means lowering the weight under control and lifting it solidly, dominating the weight but not accelerating excessively.

The weight is lowered under control, not slowly, but mastering the weight in such a way that you could pause it at any point of the range of motion without problem.

They're also characterized by a rapid but smooth transition into the concentric. Contrary to the "perfect rep/CAT," you don't try to do the transition as fast as possible and explode into the concentric using the stretch reflex. Instead, you reverse direction under control, and when you move into the concentric it's a smooth press/pull.

You do the concentric part of the movement by producing enough force to overcome the weight solidly, but not accelerating it as much as possible. The goal is to do each rep with force and perfect technique, but not burn yourself out.

At the top you take the time to hold the weight a second before going into the next rep.

Pros of Normal Reps

• Normal reps are the happy medium between CAT/Dynamic correspondence (where you make the reps more demanding by producing more force than required) and reps where you perform each repetition with the least amount of fatigue possible, as in doing kettlebell swings for volume or Crossfit WODs.
• They allow you to have energy to do more reps at a given weight while still using enough force to stimulate growth and strength gains.

Cons of Normal Reps

While normal reps are good for hypertrophy because they allow you to do more reps at a given weight, they aren't optimal for building strength unless you use a heavy weight.

You can build strength with CAT and dynamic correspondence when using 70% of 1RM because you "artificially" increase how much force you produce. That won't work with normal reps.

When to Use Normal Reps

It's best to use normal reps when using a moderate weight for moderate to high reps – sets of at least 6 reps and up to 15-20, at least on compound lifts.

It's also the way to do isolation work for low reps/strength. We don't often do isolation work for strength, but it is possible if the goal is to strengthen an individual muscle rather than make it larger.

In that case, normal reps are the best option. Constant tension won't allow you to use enough weight and CAT reps will make most of the movement worthless because the momentum will do most of the work for you.

Tons! Other styles exist for more specific applications, but 90% of the time the ones discussed here are the way to go. Master them and you'll never complain about your gains again.