When I train athletes my goal is to work toward using a fast eccentric. In fact, that’s why I use slow eccentrics, then heavy eccentrics: to prepare the body for the shock absorption of fast eccentrics by first improving movement control and tendon resiliency then by making you stronger eccentrically.
My progression normally goes like this:
- Slow eccentrics
- Normal eccentriics
- Eccentric overload
- 2/3 eccentric (first 2/3 is controlled, but not snow, last 1/3 is fast)
- Fast eccentrics
- Overspeed eccentrics
The reasons why I want to use fast eccentrics with athletes (warning, it will get a bit complicated… I have a whole article coming up on this topic on my own website):
To maximize the stretch reflex. The faster the muscle/tendons are stretched, the more the reflex is activated and can contribute to an explosive concentric (which is my goal with athletes)
A fast eccentric, coupled with a lightning fast turnaround (from eccentric to concentric) leads to more potential energy stored from the force absorption. We can then use this energy during the concentric to promote faster velocities. Here’s how it happens. To maximize potential energy storage you first need the muscles to be elastic (lower tension). The more elastic they are during the first 50ms (milliseconds) the more energy you can initially store. BUT they tendons/muscle must extremely quickly become stiff to avoid dissipating the energy, that happens during the second 50-75ms of the force absorption phase. Then the muscle fires and uses the potential energy and gets elastic again. That’s how plyometric exercises work: by improving that “elastic-to-stiff” cycle. And fast eccentrics are training the same thing, but with extra resistance.
As Louie Simmons found out during some experiementation with advanced lifters, during dynamic effort work, the fast the eccentric was the faster the following concentric got.
There is a definite advantage to fast eccentrics for power development, provided that the athlete has the structures and movement control in place to do it properly.
But it is NOT superior (or that effective) for hypertrophy purposes.
It’s like with depth jumps (high intensity plyometrics): they found that in advanced athletes with plenty f explosive training experience, they increased power output; but in those with little or no experience, it led to a decrease in performance.
Now, your question was likely more related to hypertrophy.
It is my belief that any new high-force stimulus can provide hypertrophy gains at first, simply because of the novelty and the need to adapt.
And this includes fast eccentrics.
And a fairly recent study has shown that a fast eccentric (shock absorption) on jump squats and ballistic bench press does provide some hypertrophy.
However Chad was wrong when he said that a fast eccentric is superior to stimulate muscle growth.
He was basing himself on studies using an isokinetic device, which is completely different than regular free-weight, machine or pulley lifting.
Isokinetic means “same speed” (well, same movement). Basically, it’s a machine on which you can set a certain speed and apply that speed for the whole movement AND the speed cannot change regardless of how much force you apply on the machine.
For example, let’s say that you are using an isokinetic leg extension set at 120 degrees per second, the machine will move at 120 degrees/s regardless of how hard you push against it. The machine essentially applies the amount of resistance required to get you to move at the programmed speed.
If you apply 20lbs of force during the eccentric, the machine can easily go at 120 degrees/s and thus doesn’t provide much resistance.
If you apply 200lbs of force during the eccentric, the machine needs to apply a lot more resistance to get you to move at 120m/s.
When you set the machine on a fast eccentric speed and the subject is told to resist as hard as possible, the resistance provided by the machine will be much higher than during a slow eccentric because the machine much push hard enough to overcome you end get you moving faster.
BTW, it’s the opposite during the concentric: a faster concentric speed on an isokinetic device provides less resistance to allow you to more easily move rapidly.
In those studies, the fast eccentric did not promote superior hypertrophy results because of the faster eccentric speed but rather because of the much higher resistance applied, leading to more muscle tension.
Now, with any other type of lifting exercise, free-weight, machines, pulleys, what is called “isoinertial” exercises (same resistance) when you do a fast eccentric you must actually reduce muscle tension (as opposed to increasing it during an isokinetic exercise). which makes it less effective for growth. Because the resistance doesn’t change depending on the effort you produce, the more force you produce during the eccentric, the slower the movement gets. And the more force you apply during the concentric, the faster the movement gets.
Basically isokinetic and isoinertial are exact opposites. So you cannot use the results you got with one type and apply it to the other.
I mean, once an athlete that I train has gone through the eccentric progression, most of what we do are fast (even overspeed) eccentrics. And we don’t notice much (if any) muscle growth at that point.
I think it’s also worth mentioning that asking anybody to perform fast eccentrics without first preparing for them is idiotic and dangerous.
I think that Chad suffered a bit from confirmation bias on that one, or the desire for it to be true to come up with something completely new.