WHY IS HEAVY WEIGHT
Tom McCullough MEd.
Many wonder why so many professional bodybuilders use partial rep
training to grow. These athletes feel they allow heavier
weight to be used and the avoidance of full ROM seem to keep more
tension on the muscle during the set. Science explains this type of
training in studies that show partial ROM equal to full ROM except
the total work done is slightly less. They also point out that
partial ROM training will allow the lifter to add more weight on the
bar thus increasing the intensity.
WHY IS THIS IMPORTANT?
For many years it was thought that increases in muscle size were
largely attributed to two factors: the mechanical load (tension on
muscle) and the growth factor environment that the muscle
experiences (external hormones such as testosterone and GH). So
lifting heavy weight not only increases the amount of tension being
placed on the muscle, it also increases natural anabolic hormones in
our body such as testosterone and GH.
However, new research has come out that tested both animals and
humans and it was discovered that it is very possible to induce
muscular growth without these anabolic hormone concentrations being
Researchers at the Exercise Metabolism Group at McMaster University
found that when human subjects were tested after weight training
there was no change in GH, testosterone or IGF-1 concentrations in
the 90-minute period following exercise. Furthermore there was no
influence of training on the anabolic hormones measured. McMaster
University researchers concluded, unilateral training induced local
muscle hypertrophy only in the exercised limb, which occurred in the
absence of testosterone, GH, or IGF-1 circulating levels. So
apparently all of these by doing short rest periods combined with no
more than 45 minute training do very little to help increase muscle
size as we once thought.
SO WHAT DOES CAUSE GROWTH?
Well let’s go back to our original two factors thought to increase
muscle growth: mechanical load (tension on muscle) and the growth
factor environment that the muscle experiences (external hormones
such as testosterone and GH). Since the later were found to not be
so important, let’s take a look at the mechanical load or the amount
of tension we place on the muscle. Perhaps this is the key?
We do know that exercise does stimulate some GH during the first 30
minutes post-exercise. GH in turn causes the body to release IGF-1.
However, Dr. Goldberg, of the University of London, who has spent
much of his academic career studying how muscles grow, claims that
after IGF-1 is produced in the body it splits in to a variant called
Dr. Goldberg noticed through his experiments on rats that even after
he removed their pituitary so they could not produce GH , IGF-1 or
testosterone, mechanical tension placed on their muscles still cause
muscular growth. He also didn’t feed them and they still grew. What
he did find in the rats exercised muscle was a huge increase in what
he called MGF.
This study showed that mechanical overload increases muscle
hypertrophy independent of testosterone, IGF-1, or GH. MGF seemed to
be a very important substance because as the mechanical stress was
increased so was the amount of MGF present in the exercised muscle.
Not only was this true in rats but later on it was found to be the
same in humans. So Dr. Goldberg concluded that mechanical load
leading to an eccentric stretch, combined with muscle contraction,
leads to a rapid increase in MGF.
Through further studies Dr. Goldberg determined increases in MGF in
an exercised muscle starts the local repair of muscle damage by
activating the muscle stem cells, as well as activating other
anabolic processes. He further stated that maximal tension
development through exercise leads to greater increases in muscle
hypertrophy. In other words the more mechanical load you place on a
muscle when exercising the more MGF which will be released. The more
MGF released through heavy weight training the better recovery as
well and a greater increase in muscle growth.
I WANT TO GET BIGGER: WHAT DO I DO?
Past research has determined muscle hypertrophy to be greatest in
the 8-12 repetition range; this is likely due to the combined
effects of myofibrillar and sarcoplasmic hypertrophy being greatest
at this rep range. This does not mean the athlete should train
exclusively within this rep range. Low rep range training increases
muscle fiber density and higher repetition training (up to 20) has
also recently been shown to up-regulate the genes involved in
Use partial ROM motion training because you are able to add more
weight per rep and keep the tension on the muscle for the entire
set. It is important that you use controlled negatives and very
explosive positive movements when you lift.
Use longer rest periods. We know now that resting 2-5 minutes
between sets enable us to maximize the amount of weight we lift.
This means more mechanical load is used causing more damage to
muscle tissue and greater release of MGF in the exercised muscle.
So don’t be afraid to use heavier weights and rest longer.
Bamman MM, Shipp JR, Jiang J, Gower BA, Hunter GR, Goodman A,
McLafferty CL Jr, Urban RJ.
Mechanical load increases muscle IGF-1 and androgen receptor mRNA
concentrations in humans. Am
J Physiol Endocrinol Metab, 2001 Mar;280(3):E383-90.
Goldspink G: Gene expression in
muscle in response to exercise. Journal Of Muscle Research And Cell Motility 2003,
Goldberg AL, Etlinger JD, Goldspink DF, Jablecki C. Mechanism of work-induced hypertrophy of
skeletal muscle. Med Sci
Sports, 1975 Fall;7(3):185-98.
Kraemer A, Cafarelli et al.: ACSM
Position Stand: Progression Models in Resistance Training for
Healthy Adults. Medicine
& Science in Sports & Exercise 2002, 34(2).
Wilborn CD, Taylor LW, Greenwood M, Kreider RB, Willoughby DS: Effects of different intensities of
resistance exercise on regulators of myogenesis. Journal Of Strength And Conditioning
Research / National Strength & Conditioning Association 2009,
Wilkinson SB, Tarnopolsky MA, Grant EJ, Correia CE, Phillips SM. Hypertrophy with unilateral resistance
exercise occurs without increases in endogenous anabolic hormone
concentration. Eur J Appl