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How many reps
should be done to pack on more muscle? There really is
no clear-cut answer when you consider the wide range of
variables involved. It’s easy to suggest a particular
rep range, such as six to eight will influence muscle
hypertrophy; that 3-5 reps will result in strength
increases; or that high-reps are ideal for improving
muscular endurance. But are any of these suggestions
true?
There is
science to back claims made regarding the impact of
training within a specific repetition range, but
individual genetics and method of exercise execution
affect their validity.
For example,
there could be two individuals of seemingly equal size
and physical make-up. One may respond better to a higher
rep range while the other may respond more favorably to
a lower rep range. This could be the result of genetic
differences between the two individuals, or could be due
todifferences in the execution of reps and sets as a
whole. The quality, intensity, or speed of repetitions
in a set can vary from individual to individual. To
determine how many reps should be done to pack on more
muscle, we need to think beyond the simplicity of
attaching specific numbers to specific responses.
First, the
Science
The two major
energy systems relied upon when exercising are anaerobic
(without oxygen) and aerobic (with oxygen). Keep in mind
that during exercise both systems are active, however
the degree to which each is working depends upon the
intensity (effort) and duration of exercise. |
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Exercise of
low intensity and long duration is typically
characterized as being aerobic while exercise of high
intensity and short duration is typically considered
anaerobic. How
aerobic or
how
anaerobic an exercise is depends
mainly on how much physical effort is being exerted
though. A thirty second set of biceps curls with a
light, unchallenging weight would
not
be anaerobic. Running a mile as
fast as possible would not be purely aerobic either.
A
bodybuilder’s priority when exercising is to be sure as
much anaerobic exercise as possible is done to utilize
the chemical resources adenosine triphosphate (ATP),
Creatine Phosphate (CP) and glycogen, fast twitch muscle
fibers, and the release of the hormones testosterone,
growth hormone (GH), and insulin-like growth
factor-1
(IGF-1) responsible for muscular size and strength.1
Unfortunately, many bodybuilders take this objective to
an extreme that may actually hinder their ability to
optimize muscle growth. |
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The anaerobic
system can be further divided into two categories,
anaerobic
alactic and
the anaerobic
lactic.
The anaerobic
alactic
system utilizes CP
for energy, no oxygen, and produces the strongest and
fastest muscle contractions.2 However it also has the
least amount of chemical reactions of all the energy
systems with its peak power output occurring within one
second and lasts for only 20-30 seconds. This is good
for sprinters, power lifters, Olympic lifters, football
linemen or baseball pitchers, but bad for bodybuilders.
Recruitment of fast-twitch muscle fibers is a high
priority for bodybuilders, but recruiting
the greatest
number of
fast-twitch fibers and utilizing the most chemical
energy (ATP, CP and glycogen) is of even higher
priority. Only by stimulating more muscle fibers and
creating an environment where the muscles must “make
room” to store more energy, will optimal muscle
growth occur.
The other category of the anaerobic system,
lactic,
reaches peak power output within
20-30 seconds but may last for upwards of two minutes.3
This means set lengths of 40 seconds minimum and 120
seconds max would be best for achieving muscle
hypertrophy. If sets don’t last
at least
40 seconds, as much is probably not
gotten out of them as could be.
Some people
may have made some great muscular gains without ever
having performed a set that lasted close to
forty-seconds. Less than 40 seconds of
time-under-tension (TUT) may actually be ideal for those
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continued
who are truly gifted and who possess an abundance of
fast twitch muscle fibers throughout their bodies or in
particular muscle groups. Recruitment of fast-twitch
fibers happens very rapidly and quite overwhelmingly for
those types of individuals. For those who are not as
genetically gifted (about 98% of the population) greater
gains can be made by making workouts more effective.
Putting it in the Proper Context
The goal of
any individual—genetically inclined or cursed—looking to
improve muscular development should be to perform
the least
amount of exercise needed to get
the desired response, i.e. increased muscle mass.
Muscles do not grow in
the gym! Workouts are
nothing more than the stimulus for growth. The time
spent recovering from that stimulus is when the growth
actually occurs. Doing the least amount of total work
within a workout leaves more time available for recovery
to reap the benefits of training.
Time is of the Essence
Performing more sets can make up
more time if sets are short, but only if rest periods
between sets are very short (5-30 seconds). When rest
periods are 60 seconds or longer, many of the muscle
fibers worked recover, which essentially would be like
retraining the same group of muscle fibers (slow-twitch
and mixed) over and over again, especially if the first
few sets were not very challenging. In order to train
the larger fast-twitch fibers, sets must be long enough
and demanding enough to call upon this group. This is a
factual statement supported by The Size Principle.
The Size
Principle states:
the recruitment of fiber types usually occurs in a
preferential manner according to the size of the motor
neuron supplying the fibers: the smallest is recruited
first, and the largest, last.4
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This basically
means muscle fibers are recruited on an “as needed”
basis relative to “how hard” work is. At the beginning
of a set, when effort and force output needed to perform
the lift is lowest, the smaller slow-twitch fibers are
recruited to perform the work. As a set continues, each
rep progressively becomes more difficult as muscles
gradually fatigue. Greater force must be generated to
fight resistance to continue completing reps, which
recruits more of the larger muscle fibers
(mixed/intermediate & fast-twitch, in that order) to
generate the force needed to contend with the increasing
demands of the exercise. Motor neurons fire their
fastest, trying to recruit as many fast-twitch fibers as
are available, when approaching muscular failure. When
no more fasttwitch fibers are available or cannot be
recruited (because of neurological ability/limitations),
muscular failure results.
Individual
results will vary
Muscle fiber
recruitment is largely neurological in nature. Certain
individuals are able to call upon fast twitch fibers
more quickly compared to other individuals. In essence
this is what makes a power athlete a power athlete.
He/she is capable of recruiting fast-twitch fibers much
faster and in greater numbers than the average
individual who possesses less fast twitch fibers and
whose motor neurons fire at a slower rate.
Training to
become more efficient and stronger at performing
exercises/skills involving short bursts of powerful
contractions is possible by practicing, but doing so
still does not resolve the issue of recruiting/training
the greatest number of fast-twitch fibers a muscle has
available. That can only be accomplished by performing
an exercise long enough to completely exhaust all the
slow-twitch and mixed fibers
first,
as indicated by The Size Principle. The anaerobic
lactic
system takes 20-30 seconds to reach
peak
power output, so 20-30 seconds of
increasingly difficult work is needed before the larger
fast-twitch fibers begin to be recruited. It can take
even longer for individuals who possess a
greater number
of slow-twitch and/ or mixed fibers. Individuals at the
far end of the continuum may not possess any fast-twitch
fibers at all (usually elite distance runners, those
incapable of building any significant amount of muscle
or strength but have extraordinary muscle endurance). |
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Variance in the percentage of each
muscle fiber type in a muscle determines that muscle’s
TUT, or set length.
So, how many
reps?
The number of
reps that should be used depends upon the rep cadence.
For example, if triceps respond best to 60 seconds of
TUT and triceps extensions are performed with a 3-1- 4
count (3 sec. positive, 1 sec. hold, 4 sec. negative)
then seven to eight repetitions would be needed to reach
a 60 second TUT. If reps were performed using a count of
3-3, then at least 10 reps would be needed to achieve 60
seconds TUT.
The TUT is
what’s important, not a number of reps. Number of reps
is simply a by-product of rep cadence, which should
always be slow and controlled relative to the range of
motion and with constant tension on the target muscle(s).
Determining
the proper TUT can take some meticulous note-taking and
objective observance of response to training within
specific TUT’s. For those looking for simpler methods of
testing a muscle groups Fiber Type make-up and
rate-of-fatigue, I’ve put together in a report titled
Determining Your
Muscle Fiber Type, which
you can get by sending an email to MikeL@PurePhysique.com
with “Fiber Type” in the subject heading.
Using Variety
It’s important
to constantly disrupt what the body is accustomed to in
order to stimulate greater gains. Varying TUT isn’t
necessary though. The body can be disrupted by changing
exercises, exercise order, or even the way exercises are
performed. Don’t stray from what must be done
consistently to get the best results. That means staying
within a proper rep-range, working with a high level of
intensity, and only training with a volume and frequency
needed to get results.
In Closing
The only
concern is making sure as many fast-twitch muscle fibers
are recruited and exhausted as possible
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and to utilize
as much chemical energy as a muscle will offer. Take the
time to uncover
your proper rep-range,
balance it with appropriate intensity, volume and
frequency and then watch your muscle growth take off!
References
1 Kraemer WJ,
Ratamess NA. Hormonal responses and adaptations to
resistance exercise and training. Sports Med 2005;
35(4): 339-61. Review. PMID 15831061
2 Johnston,
Brian D. Exercise Science: Theory and Practice, BODYworx
Publishing 2003, p.22
3 Johnston,
Brian D. Exercise Science: Theory and Practice, BODYworx
Publishing 2003, p.22
4 Kreighbaum,
E., Barthels, K.M.,
Biomechanics: A Qualitative Approach for
Studying Human Movement, 4th Edition.
Allen & Bacon Needham Heights, MA 1996 pg.65
Michael
Lipowski is the author of the book PURE PHYSIQUE: “How
to MAXIMIZE Fat-loss and Muscular Development”, and also
a Certified Fitness Practitioner with the International
Association of Resistance Trainers, a competitive
Natural Bodybuilder and founder
of Pure Physique LLC, a
provider of personal training and fitness consulting
services in Westchester, NY. For more information,
articles, or online coaching go to www.PurePhysique.com
or email MikeL@PurePhysique.com
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