All About Muscle Growth

by Ryan
Andrews, June 28th, 2010.
Hi Everyone,
I hope you have enjoyed some of the post on my blog.Howver to clean up the site and give it better credibility it will be closing and reopening here at our new bog The Core Matrix.
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What is acupuncture?

What is muscle growth?

Muscle growth — sometimes known as hypertrophy — is the development of mass,
density, shape, and function of muscle cells. This adaptation allows the muscle
to meet exercise/function-induced stress.
Muscle cells are sort of like a bunch of sticks bundled up for firewood.
Myofibrils (“myo”, from the Greek mys, refers to muscle) are
cylindrical bundles of filaments composed of sarcomeres. Sarcomeres are the
fundamental unit of muscle contraction and are composed of myosin and actin.
All of these proteins comprise about 20% of muscle. Water, phosphates, and
minerals comprise the other 80% of muscle.

Where does muscle growth come from?

When someone does resistance training consistently, they may notice muscle
growth. The growth is due to an increased water, number of myofibrils, and
connective tissue.
Scientists often break hypertrophy down into two types:
  • Sarcoplasmic hypertrophy increases muscle size by
    increasing the volume of sarcoplasmic fluid in the muscle cell.
  • Myofibrillar hypertrophy (sometimes called “functional
    hypertrophy”) increases muscle size by increasing the contractile proteins.
Some people in the fitness industry will argue that bodybuilders demonstrate
sarcoplasmic hypertrophy, and that their muscles look “puffy”; while
weightlifters demonstrate myofibrillar hypertrophy, and their muscles are
Bodybuilder Weightlifter
bodybuilder_b-IMG_0017 weightlifter myofibrillar

Muscle growth and fibre types

Although growth can occur in all muscle fibre types, different types of
muscle fibres vary in their potential for growth. Fast twitch fibres are more
likely than slow-twitch fibres to grow with intense strength training. This may
be one reason why athletes such as sprinters tend to be bigger and more muscular
than endurance athletes, and why heavier loads tend to stimulate more muscle
growth than light loads.
Marathoner (left) vs sprinter (right)
Marathoner (left) vs sprinter (right)

Muscle growth and hormones

Muscle growth is further influenced by type of exercise, nutritional intake,
and hormonal status. The type of exercise and hormonal status influence nutrient
partitioning — in other words, whether you increase muscle depends on the kind
of activity you do and your hormonal environment, which both tell your body
where to allocate the nutrients you eat.
Eat a lot, train hard, and get lots of recovery, and you’ll put on muscle. Be
malnourished, be sedentary, and be stressed out — and you won’t.
Hormones that modulate muscle growth include:
  • growth hormone
  • testosterone
  • IGF-1
  • cortisol
  • beta-endorphin, and
  • parathyroid hormone.
For more on a few of these hormones, see here:
  • AA Growth
  • AA
  • AA Cortisol

Why is muscle growth so important?

Subjectively, muscle growth improves the appearance of the body. Women who
gain muscle mass while remaining relatively lean appear tighter, firmer, and
more “toned.” Men who gain muscle mass while remaining lean appear stronger,
larger, and more athletic.
Objectively, muscle growth improves function. Larger muscles are often
stronger muscles, leading to improved daily functioning in most individuals.
Muscle is metabolically active, and affects the way the body handles nutrients.
For instance, people who are more muscular (especially combined with lower body
fat) typically have better insulin control.
From a health perspective, advancing age is associated with a loss of muscle
mass, better known as sarcopenia. Preserving muscle mass can preserve strength,
and strength is a predictor of survival as one ages. Loss of muscle function
appears to be due to decreased total fibres, decreased muscle fibre size,
impaired contraction mechanisms, and decreased motor unit recruitment.

What you should know

Muscles respond to demands

Muscles respond to the demands we put on them. Ask your muscles to lift
loads, and they’ll respond by getting stronger. Ask your muscles to help you
make a butt groove in the La-Z-Boy and they’ll shrivel up from disuse, leaving
you weak and skinny-fat.
Intense training (such as heavy weight training) damages muscle, which then
remodels to prevent future injury. Thus, including relatively intense exercise,
particularly resistance training, in your fitness regime is essential — no
matter what your ability or age.

Muscles respond to calories

Restrict calories and you risk muscle loss and metabolic slowdown.

Studies show that people who restrict their calories (i.e., diet) without
also doing resistance training do lose weight, but it’s an even distribution of
muscle and fat — not what you want. Indeed, sometimes calorie restricters who
don’t exercise end up fatter (as a %) than when they started!
How many calories to build muscle?
You need roughly 2,800 calories to build a pound of muscle, largely to
support protein turnover, which can be elevated with training.
The contractile proteins and fluid (sarcoplasm) in muscle fibres are broken
down and rebuilt  every 7 – 15 days. Training alters the turnover by affecting
the type and amount of protein produced. Again, muscles respond to the demands
placed on them.
However, muscles that are overloaded appropriately can actually grow during
starvation (energy from fat stores can be liberated and stored in muscle
tissue), although ample nutrients (e.g., protein, carbohydrate, etc.) can
greatly enhance the extent of the growth response. Although growth can take
place during starvation/restriction, especially for newbies, muscle growth with
inadequate calorie consumption is less likely to take place with advanced
trainees, as their threshold for growth is elevated.
If you’re more experienced and looking to get big and strong, you’ll probably
have to eat more.

Looking to get lean? Make sure you exercise!

The chart below shows the results of an experiment done over 16 weeks with 25
overweight women.
The experiment compared calorie restriction alone (diet), exercise alone, and
calorie restriction + exercise. As you can see, at the end of 16 weeks, the diet
+ exercise group lost the most fat and gained a pound of muscle. The
exercise-only group didn’t lose as much scale weight, but they lost a fair bit
of fat and added 2 lb of muscle. The diet-only group lost scale weight, but not
as much fat, and they were the only ones that lost muscle.
Effects of diet, exercise, and diet + exercise on muscle growth and weight/fat loss
Zuti, W.B. & Golding, L.A. Effect of Diet and Exercise on Weight Loss
and Body Composition of Adult Women. The Physician and Sports Medicine. 4 (1):
49-53, 1976.

Muscles respond to protein

The way our hormones respond to training, and how they affect our muscle
growth, depends a lot on our nutritional status — not just how many calories
we’re taking in.
In a rested state, muscle protein breakdown exceeds protein synthesis. This
net balance can be improved with strength training, but still, normally, we’re
breaking down more than we’re building up.
We want the opposite — to be building up more than we’re breaking down,
especially after resistance training. We need adequate protein to do this.
One bout of resistance training can stimulate protein turnover for at least
48 hours. During this time, if energy intake is adequate and protein represents
at least 12 – 15% of our energy intake, growth can occur.
For those on an energy restricted diet for fat loss, protein needs for muscle
recovery and growth are likely closer to 1.5 – 2.0 grams of protein/kg of
What helps stimulate muscle protein synthesis?
  • Just 6 grams of essential amino acids can stimulate muscle protein synthesis
    after training.
  • We don’t need nonessential amino acids for this stimulation to occur.
  • Elevated levels of insulin can generate muscle growth when amino acid
    consumption is ample, which demonstrates the importance of carbohydrate
    consumption after exercise.
  • Frequent amino acid consumption (from food or supplements) during the waking
    hours may also play a role in muscle growth.
For more on this:
  • All About
  • All About

Summary and recommendations

Muscle growth seems to occur best when training with relatively higher
volumes, close to muscle fatigue, and with shorter rest periods between
  1. When training, 6 – 12 repetitions per set is the optimal range for muscle
  2. Train towards contraction failure.
  3. Take relatively short rest periods — 30 – 90 seconds. Rest-pause techniques
    can also be effective.
  4. Perform 12 – 20 sets per muscle group. Supersets can help add volume and
    improve efficiency.
  5. Be consistent with training.
  6. Consume enough energy (calories), with a minimum of 12 – 15% of calories
    from protein or 1.0 gram of protein per kilogram of bodyweight.
  7. Sleep 7 – 9 hours per night.

For extra credit

The amount of muscle growth that occurs depends on upper genetic limits of
cell size.
An increase in the number of muscle fibres, rather than just the size of
those that already exist, is known as hyperplasia. It has yet to be definitively
measured in humans. If it does occur, it probably accounts for a small portion
of muscle growth (less than 10%).
Changes in cellular oxygen, reactive oxygen species, ATP levels, and
metabolite concentrations during exercise stress may be fundamental stimuli that
lead to muscle growth.

Further reading

protein to 20 grams per meal?
Minutemen: Rest Intervals
Leucine vs. Whey
Comparing Number Of Sets For Muscle Growth

About dkpilates

Pilates Instructor, Yoga Instructor, Personnel trainer and Group Fitness Instructor. Don teaches Contemporary and the Authentic forms of Pilates, in the later 90's, Don began his study of Yoga. His study of Yoga includes the Hatha, Iyengar, Bikram, and Astanga disciplines. His other areas of interest in fitness include Martial Arts, Spin, Boot Camp Training, and Weight Training. Don has extensive training and certifications from AFFA, IDEA, MadDog, B-Fit and Polestar. Don Continues his of Pilates education with Michelle Larson in Santa Fe New Mexico. His personal philosophy related to fitness is to aid students in a personalized balance of strength, stamina and flexibility. He is dedicated to design a program specifically for his students independent of the season of their life to create functional movement and help them reach their fitness goals.
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