The Princeton Longevity Center Medical News
The Anatomy of Resistance Training
By: Christopher Volgraf, ACSM HFI©, NSCA
Muscles are made up of thousands of cylindrical muscle
fibers that lie parallel to each other. There are two contractile proteins
that slide past each other to produce a contraction of the muscle. A muscle
shortening contraction is called a concentric contraction, a muscle
lengthening contraction is called an eccentric contraction, and a muscle
contraction in which the muscle does not change in length (remains stationary)
is called an isometric contraction.
Genetics plays a big role in personal muscle
make-up. Have you ever noticed that some people can run faster, jump high and
perform explosive movements with relative ease? This is due to their genetic
make-up of predominantly fast twitch muscle fibers as apposed to slow twitch
Fast twitch muscle fibers respond rapidly, but fatigue easily. These properties make them suitable for
performing activities that require intense responses over a short period of
Slow twitch muscle fibers are
more aerobically suited to perform activities of longer duration thanks in
part to their rich supply of blood (to aid in O2 & CO2 transport).
Usually, humans are born with a relatively
equal distribution of both slow and fast twitch muscle fibers. But there are
always exceptions to the rule…professional athletes all around the world
continue to show what “good genes” can do for ones performance. A
resistance-training program can improve the ratio of slow to fast twitch
fibers and overall hypertrophy (increase in cross-sectional size), but nowhere
near a genetically blessed individual!
Responses to Resistance Training
The initial adaptations to resistance
training occur in the first weeks of training. The neuromuscular system is
the major player in these adaptations through increases in the number of
neuromuscular junctions or motor units. A motor unit is a number of muscles
innervated by the same motor neuron or nerve. Consistent resistance training
causes an increase in the total number of motor units by recruiting muscles
that may have been “dormant” and connecting them with a motor neuron.
Strength increases are a direct result of the increased number of muscle
fibers performing the work.
Hypertrophy or an increase in cross-sectional
diameter of the muscle fibers occurs 4-8 weeks from the initiation of the
training program due to an accumulation of proteins. The “visual results” as
some call them are due to an increase in muscle mass, not an addition of
muscle. Be careful though…after results begin to show, atrophy, or the
decrease in muscle size and mass, occurs 3 times faster than hypertrophy. In
other words, don’t take too much time off!
Different types of training for different results
There are different types of training that will elicit
better results for individuals who wish to focus on
muscular power, or
Each category uses a different number of sets and
repetitions, differing rest periods, and the velocity of the exercise.
Muscular strength results from the proper activation of specific
muscle fibers, which are recruited in response to the demands of the
resistance-training program. This category results in muscle tone,
hypertrophy, and overall strength. The ACSM now recommends that
new and intermediate lifters use 60-70 percent of their repetition maximum capacity for one lift, and that they progress
at a rate of two to ten percent increase, depending on the muscle group involved.
which is the product of load and number of repetitions, should be low for
beginners and increase systematically (but not dramatically) to best increase
muscle strength. Choice of exercise should include single joint (bicep curls)
and multiple joint (squat-hamstrings, hip flexors and quadriceps using the
hip, knee and ankle joints), with emphasis o the multiple joint movements.
The ACSM recommends that a combination of free weights and
machines be used in a beginning weight-training program. Emphasis on free
weights is advised for advanced strength training. The recommended training
sequence of muscles is large before small, multiple joint before single joint,
and higher before lower intensity exercises.
Muscular power is important to
both sports and everyday functional ability. Power increases when the muscle
produces the same amount of work in a shorter time or more work in the same
time. To increase power, the ACSM recommends predominantly
multiple joint exercises in the same sequence as for strength training.
Muscular endurance, or the
ability of a muscle to produce a maximum number of repetitions with a specific
training load, is enhanced by long duration sets and shorter recovery time
between sets. The ACSM recommends that both single and multiple
sets be included, targeting specific muscle groups. Keep the weights light,
the repetitions high and the rest periods between sets short.
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