Rep tempo...going in circles with this

I really don't know what to decide with this issue...I have read about this considerably but I still can't decide...

Is it better to just pick a heavier weight/harder exercise that will force you to move slowly, or is it better to intentionally make the tempo slower?

Take rows for example, I can do at least 5 with my feet at the same height as the rings, doing the eccentric slower and the concentric faster, but if i do the concentric slow as well, like 3 seconds...I barely squeeze out 3 with my feet on the ground and my shoulders/head way behind the anchor point...

Most of what i read said to do the lowering slow or controlled and the lifting/pushing as fast as possible.

Then there's Pavel who says in PTTP to do it slow all the time, at least 3 up 3 down.

I know it's a lot harder to do it slowly, but somehow lifting/pushing slowly feels kinda unnatural to me, in a way.

There does come a point in time where moving onto the next hardest variation is better than sticking with a previous one with just more time under tension. However it is better to reach a given level of proficiency before moving onto the next hardest variation.

The point Pavel seeks to get across in his book is tension creates greater strength and ultimately greater neuromuscular control without the need of additional mass. The longer you force your body to remain under constant tension, the body uses more muscle fibers to maintain control of something and complete a given task.

Going slowly is unnatural to almost everyone, because almost everyone just wants to get things done so that they can get back to being lazy again. (IE: 30 minute workouts, 30 minute meals, broadband internet connection vs dial up, etc.) However if gaining additional strength is your goal or part of your goals going slower will get you there.

They say it goes the other way around: that a fast (but controlled) concentric and a controlled eccentric with a heavy weight/hard exercise creates more tension than moving a lighter weight slower on purpose.

A poster on bodybuilding.com said this:

Powerlifters move the bar REALLY fast. World record deadlifts go up in like 2 seconds. That doesn't mean they can do more, it means if the weight slows down AT ALL, it's not coming up. Basically just seconding what bmontgomery said.

I look at TUT manipulation like higher volume. You'll be able to make the most out of it once you're strong. And you'll get stronger faster with lower reps done as fast as you can while still maintaining control.

No one's advocating going so quickly you're out of control, or dropping the weight on the eccentric or anything like that. Just moving the bar as quickly as possible under control and with good form.

Then another poster said the following:

It seems that a lot of people like the idea of time under tension (TUT) and believe it to be an important aspect of training for hypertrophy. The truth is that, although TUT is associated with factors that do cause hypertrophy, it is not a cause in itself.

Let me explain. We know that a sufficient amount of volume at a high enough intensity (>70% of your 1RM) is required for hypertrophy. This means that the stimulus for a given training session = sets X reps X weight = workload.

It is fair to say that with an increase in workload, there is also an increase in microtrauma to the muscle. This relationship is also pretty linear for the most part (although microtrauma would become disproportional at extreme levels of workload, but for all practical purposes this statement is appropriate). TUT correlates with workload because it understandably takes more time to do more work.

However, if we took TUT to be the cause of stimulus and separated it from workload, the whole idea of TUT would collapse. TUT suggests that stimulus for a given training session = duration X sets X reps X weight = work done.

This would mean that a given amount of workload (sets X reps X weight) performed for a given duration would create an equal stimulus to half that amount of workload performed for twice that duration. In reality, all you are doing is performing less work, more slowly.

If TUT was the cause of hypertrophy, then it would be beneficial to perform repetitions as slow as possible, and less reps but in a longer period of time. Unfortunately, this just isn't the case.

A lot of people will argue about this, particularly those who prefer low volume training. Since your ability to vary the intensity (weight) of your workload is fairly limited (due to intensity needing to be >70% of your 1RM for hypertrophy), volume (sets X reps) plays a very important role in achieving a workload capable of sufficient stimulus for hypertrophy. This is the exact opposite of what most low volume guys want to be told, which is why they love the idea of TUT.

Understand that workload is the key to creating adequate stimulus for hypertrophy. TUT is a great example of ex post facto reasoning. TUT just happens to correlate with workload, but as a stand alone concept, holds no value.

But What about Motor Unit Recruitment?

A motor unit consists of a single motor neuron, and all of the muscle fibers it contracts. The more motor units activated, the more muscle fibers are contracted. Therefore, motor unit recruitment determines how much contractile strength a muscle produces.

A 1RM lift will recruit 100% of your motor units, since every contractile fibre is needed to perform the repetition. Speed is not an apparent factor in a 1RM lift since you are already lifting the bar with everything you have (therefore with maximum speed). However, when considering loads below your 1RM, speed of the bar becomes a more obvious factor since it is susceptible to change by the lifter.

If you lift a lighter load (say around 70% of your 1RM), you have more choice over the speed of the bar. You can choose to either lift as fast as possible, or perform some type of slow controlled movement. The reason the bar is moving at different speeds is due to the number of motor units you are recruiting.

A slower bar speed requires less motor units; therefore leaving a certain percentage of your motor units unrecruited. Thus, a faster bar speed requires a higher percentage of recruited motor units, and the fastest bar speed requires the highest percentage of recruited motor units (100%). From this, it is understandable that accelerating the bar as fast as possible will use the most muscle fibers.

But wait, there’s more. Not only does bar speed relate to the number of motor units recruited, but also to the type of units recruited. The ‘size principle’ of motor neurons states that the smallest motor units are recruited first and the largest are recruited last.

What this does not mean is that you have to spend a few seconds under the bar before the larger motor units activate.

What this does mean is that if you are only recruiting say, 80% of your motor units (due to a deliberately slow bar speed), then the 20% that are not recruited are in fact your largest motor units. Incidentally, these large motor units are the ones that have the most potential for strength and size gains.

From both of these observations, it is clear that maximum muscle fiber stimulus comes from lifting the load as quickly as possible.

Notice that I didn't say “lifting the load quickly”, but rather “lifting the load as quickly as possible”. That last part is very important. Understandably, heavy loads (close to your 1RM) will not move quickly no matter how hard you try. However, it is the trying to move quickly that is the important factor here. If you have read this and now believe I am putting forward the idea that a fast bar speed means bigger and stronger muscles, then you have the wrong idea.

What I am saying is that, deliberately using a slower bar speed than you are able to do so is not an effective way of training. If you can move the bar more quickly, then you should be.

http://forum.bodybuilding.com/showthread.php?t=152136343

Note the bolded and underlined parts.

(Youtube video) Elliot Hulse: Strength Camp- Light weights are better for getting stronger.

In a competitive setting a given powerlifter will lower and lift the loaded free weight faster than in a training setting. Don't confuse training with competition.

The human body will only recruit just enough muscle fibers to control and complete a given task.  Go to a nearby chin up bar and hang with your chin over the bar for at least 60 seconds, without switching grips. rest 45 seconds and repeat four more times. If that is too easy for you, do the same while hanging off of the moulding around a door frame.

I didn't say the thing about competition vs training speeds, that was the poster from BB.com

What is your point with the chin up hang?

If you are using lighter weights or less strenous bodyweight exercises(30% of 1RM in one study), more TUT will increase the rate of muscle protein synthesis. I guess this also applies to heavier weights up to 50% or more. A good approach if you want to increase muscle mass doing one exericise under a fixed load. 

More TUT also means more fatigue, which will limit the amount of mechanical work you can do. For training programs based on increasing the resistance with load or progressing to harder exercises(strength training), it makes no sense, to me at least, to increase TUT. Simply perform the concentric as fast as possible and eccentric with control, but not too slow(but there is always an exception, like negatives).

Mike Mentzer once said "it's called weight lifting, not weight throwing" in regards to lifting with control.  If you let momentum do most of the "heavy" lifting for you, you're not really lifting the weight.  You should be able to hold the weight at the top of the lift, otherwise you "jerked" it up. Not only are not using real strength, you're also putting yourself at risk for injury.  It's the same idea behind why so many of us frown upon kipping pullups.  

He advocated a 424 tempo (4 up, 2 second hold, 4 down), which can feel pretty slow for most.  

Deft-Mastery said:

What is your point with the chin up hang?

The point is that your body will only recruit just enough muscle fibers to do a specific task with control. If, at the moment, you are unable to complete the task given to you, your body is still in the process of becoming stronger through the recruitment of more muscle fibers.