The more I read about eccentric exercise (also called negative work), the more I'm convinced it's a waste of time for a power and speed oriented athlete.
What is negative resistance? Think of resisting the downward path of a weight. When you lift a weight up, that's a positive (concentric) contraction (muscle
shortening). When you lower weight, resisting as you do, that's a negative (eccentric) muscle contraction.
Although physicians and physical therapists have utilized negative resistance as a rehabilitation tool for some time, and Joe Weider based his retrogravity
training on it years ago, the idea of actually devoting entire workouts to negative exercise or negative-assisted exercise started in about the mid-'70s when
it was plugged by Nautilus gurus.
Physiologists know it requires less motor-unit and muscle-fiber involvement to do negative work than positive work. The fact that it is
easier to do negative work is also correlated by the observation that one gets sorer from negative work (this observation must be kept in context and is
not always true). This is what makes negative exercise useful in stroke therapy.
Frequently, a stroke victim will suffer an initial flaccidity or complete loss of muscle tone on one side of the body. Gradually, muscle tone will return,
although often slowly. At the onset of therapy, however, when muscle tone is nil or minimal, the patient may not have enough strength to lift a limb (even
without having to move external resistance).
While doing a one-arm biceps curl, for instance, gravity imposes a weight demand on the power of the biceps (the resistance of the lower arm) in the normal
antigravity movement. Many times the stroke patient can't overcome this. If the patient turns on his side, though, with the upper arm supported, sometimes
he can curl his arm in toward his body because he is now working with gravity or in a line parallel to the downward pull of gravity and not 100% directly
against gravity. He may have enough strength to muster up this type of biceps curl.
Additionally, the same subject may be able to start in the fully curled position and hold his fist to his chest/shoulder using isometric contraction of his
upper-arm flexors (with some help from his pectoral muscle and anterior deltoid heads, of course). Or the patient may be able to lower his upper arm through
eccentric contraction and actually slow his lower arm's descent by producing some muscle power from his biceps. Indeed, it is far easier to slow the forearm
against gravity than it is to lift it up and overcome gravity. By repetitively exercising the arm in this negative fashion, a patient can bring muscle tone
to his arm until he can gradually generate enough power to lift the forearm in a positive contraction.
INTERNAL FRICTION IN MUSCLE
The fact that you are stronger doing negative work (remember the stroke patient) does not imply that you are using more muscle.
Most physiologists feel that reversing the actin-myosin protein cross-bridges within the muscle during negative work creates a great deal of internal friction,
which assists the muscle when lowering a weight against gravity. This "raking" of the cross-bridges may also be the cause of the muscle soreness that accompanies
pure negative work.
Much has been made of the observation that negative exercise causes more muscle soreness and that if the negative phase was eliminated, one would not get
sore from heavy exercise. While negative work may cause soreness, the belief that it is responsible for all soreness is baloney. So is the idea that negative
work is more beneficial because it produces this soreness.
You can tell the theories are baloney by doing the "stairs test." Climb up 30 flights of stairs and then descend. Going up the stairs produces
muscle fatigue and heavy breathing (oxygen debt), while going down the stairs may do nothing except hurt your knees. There is no oxygen debt developed and
little muscle work done.
Researchers have reputedly shown that intense eccentric exercise produces "ultra" structural damage associated with the onset of delayed muscle soreness
(24-48 hours after exercise). Ultra structural damage occurs in the muscle membrane and the contractile elements themselves. Membrane disruption causes muscle
cells to "leak." By using the blood enzyme marker CPK (creatine phosphokinase), re- searchers are able to measure muscle damage (or so they say). The normal
level of CPK is considered to be 15-150 U/L. Levels can rise to 2,000 U/L after intense training. This indicates severe muscle damage. I used to routinely have
levels of 2,400-2,700 U/L CPK when I was doing competitive Olympic-lifting workouts.
In fact, seven days following a session, my CPK would still be at about 1,400-1,700 U/L! This was during a time when I did hardly any negative exercise. In
Olympic lifting, I worked with a platform and rubber bumper plates, so I would lift the weight in the snatch or jerk and then simply drop it, doing no negative
work whatsoever! I still got sore and I still had elevated CPK levels.
In fact, muscle soreness results from both positive and negative work, and I'm sure that delayed muscle soreness is an inflammation type of
response in the muscle. Enzymes leak, macrophage and mast cells appear and general edema takes place. All of this occurs to repair muscle cells damaged through
exercise. One of the responses can be hypertrophy (muscle-cell growth) of differing muscle elements, depending upon the nature of the stimulus causing the
soreness in the first place, and provided that the individual doing the exercise is getting proper nutrition.
In the early '70s, people took the negative-soreness theories and the fact that they were so strong in negative work out of context and tried to apply them to
improve athletic performance or muscle mass or both. Hundreds of beginning bodybuilders were doing negative squats, negative bench presses, negative this and
negative that. Today, almost nobody does them because they don't work.
I was also a willing victim of the hype when, for almost a year, I introduced an emphasis on negatives into my training. Since I was a shot-putter interested
in power and strength, I did normal positive work for two days of my weekly training cycle (Monday and Saturday). Wednesday was my negative-only day. I worked
especially hard on negative triceps pushdowns and bench presses, since these two movements were very amenable with help from my two spotters. I found that it
was a year wasted. I got neither bigger nor stronger from the effort.
MACHINES & NEGATIVES
Most machine manufacturers who place inordinate emphasis on the negative aspect of each full-range repetition are out of touch with actual
data on negative versus positive exercise, want to emphasize safety or are trying to hide a potential flaw in their machines. On the other hand, some machines
now incorporate negative resistance that can be equal to or greater than positive resistance. Having experimented with these machines, I know that many of them
produce a very effective pump. This may mean future growth or strength increases and, then again, it may not. Only time will tell. However, some of these
machines have been around for a while and their popularity doesn't seem to be increasing. Bodybuilders and other athletes still seem to prefer to use a normal
repetition on normal machines and free weights.
As far as free weights, athletes have little to gain from negative barbell exercises, since the motor-unit recruitment and actual muscle-fiber use are both
less than with positives.
I suppose (like in the movies) you could find yourself lying on your back in a hand-to-hand battle with someone holding a knife, with your opponent bearing
down positively while you resist negatively. You're lucky if you're stronger negatively (internal muscle friction), but what happens if the action is reversed?
This same sort of thing happens in arm wrestling. You can often hold or resist your opponent (negative) but cannot overcome his force (positive) to put him
down. Once again, negative is stronger than positive. It can make for a very long match.
And what about bodybuilding? I do feel that bodybuilders can get some benefits from occasionally doing a few negatives at the end of a positive set, only
because the additional muscle contraction keeps blood out of the muscle for a slightly longer time and creates a greater reactive perfusion, meaning more blood
will come in when the muscle relaxes - and that can mean enhanced growth. Still, if you've done a positive set properly, you will be able to do only one or two
negative reps anyway because your level of fatigue will be too high.
Negatives, along with forced reps, push the body beyond its normal capacity and can be dangerous. They can also lead to severe overtraining, just as working the
same muscle group heavy every session every day can. My advice is do not train in a negative-only fashion and use negative reps sparingly. If you use the Weider
Retrogravity Principle, also stressing the downward negative aspect of the repetition, understand that it is a way to make your muscle more congested. Thus, you
must be careful not to do sets or too many exercises for that particular bodypart. This is the way Joe Weider originally intended this principle to be used.