Q: Are negative reps really superior
when it comes to building mass?
A: Negative, or eccentric-contraction, exercise
involves the controlled lowering of a weight to the starting
position. Raising the weight is called a concentric contraction.
Most bodybuilding trainers advise that you take about two
seconds to raise a weight during each repetition, followed
by another four seconds to lower it for negative emphasis.
Negative-only repetitions was a style of training advocated
about 10 years ago but never accepted by most bodybuilders.
It required you use weights that were far heavier than you
could use concentrically. It never really caught on because
of the nuisance of needing one to three training partners
to help you raise the heavy weight, then spot you as you lowered
it.
This technique was based on research showing that most of
the strength and size gains accrued from weight training occur
during the negative portion of a rep. So does most of the
muscular soreness you feel after an intense training session
or after you try an exercise you’re not used to.
The explanation given was that when you lower a weight, you
use fewer muscle fibers, but those fibers work harder to control
the weight. As a result, more damage occurs in those fibers.
The body then repairs those fibers, making them thicker as
an accommodation to the higher load imposed by negatives.
This translates into increased muscular strength and size.
The extreme damage to fibers during negative training came
with a cost, however: the need for increased recuperation.
When many bodybuilders became aware of this extra fiber damage
and consequent needed rest time, they reduced the number of
times they trained a muscle group each week.
Thus, instead of working their bodyparts three times a week,
they dropped it to twice or even once a week. While most bodybuilders
didn’t know why they needed the extra rest, they instinctively
sensed how much rest they needed because of rates of muscle
growth and strength gains.
Further studies finally uncovered exactly why eccentric exercise
exacts this muscle damage toll. The extensive damage incurred
during negative reps apparently inhibits glycogen synthesis
in muscle after exercise. Glycogen, a complex carbohydrate
stored in muscle, is not only the primary fuel for weighttraining
but is also needed for muscle repair.
This explained why negative exercise demands extra rest. Unless
the muscle has repaired itself, you can rapidly fall into
an overtrained state if you attempt to train that muscle before
the repair-and-compensation process is complete. The remaining
question was, What causes this diminished glycogen synthesis
after negative training?
Danish scientists had subjects perform negative-accentuated
one-legged exercise, then measured a number of intracellular
mechanisms involved in glycogen synthesis. They found that
negative exercise apparently inhibits an intracellular protein
called GLUT 4, which transports sugar, or glucose, into the
cell. If this activity is inhibited, glycogen synthesis slows
because less glucose is available.
After two days or so the muscle GLUT 4 level returns to normal,
and glycogen resynthesis begins again. In another study the
same researchers discovered a possible antidote to the problem.
Using isolated muscle cells, they found that vanadate, which
is similar to vanadyl sulfate, increased and preserved the
function of GLUT 4 in muscle. This may overcome the deficit
incurred by negative training. It also partially explains
the often-noticed increased carbohydrate utilization after
athletes take supplemental vanadyl sulfate.
In addition, a study reported in a 2003 issue of Medicine
and Science in Sports and Exercise seriously questions the
assumed superiority of negative exercise for producing increased
muscle size and strength. This new study compared concentric
and eccentric contractions at equal power levels, but contrary
to past studies, the researchers found that muscles work harder
during the raising of the weight, the concentric part of the
rep, rather than during the lowering.
Earlier studies verified that negative reps involve a smaller
percentage of muscle fibers compared to concentric, but it
was assumed that since these fewer fibers have to bear an
equal load, more stress is placed on them and they work harder.
Not so, this new study asserts.
The study involved exercising the front-thigh muscles, again
using equal-power negative and positive contractions. The
results showed greater muscular growth and strength after
subjects performed the concentric, or positive, reps, although
the scientists still aren’t sure why this occurred.
Other studies note an increased oxygen intake during concentric
work, and frog muscle studies found that eccentric exercise
uses only one-thirteenth the amount of ATP as concentric work.
All of this doesn’t negate the importance of negative
reps (pardon the pun). It doesn’t mean you no longer
have to control a weight on the way down, but it does point
to the fact that both types of contractions (concentric and
eccentric) are equally important. Significantly, the idea
that you should do only negative exercise as a means of inducing
gains in muscle size and strength now belongs in the pile
of similarly authoritative but misguided pronouncements, such
as “The Earth is flat.”
Related Articles
Forced Reps and Negatives
Using Negatives
in Your Workout
When to Use Partial
Reps?
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