THE MUSCLE: REMINDERS.
Muscle is made up of a bundle of fibers surrounded by connective tissue. The myofibrils that fill the inside of a fiber are the same length as it. They react to nerve impulses by causing the muscle to contract.
A myofibril is made up of subunits : the sarcomeres linked end to end, themselves made up of 2 proteins, actin and myosin, the bringing together of which causes muscle contraction . The muscle will produce different forms of muscle contractions to build up strength.
The driving unit is the motor neuron . This muscle contraction unit is made up of 1 nerve fiber and the muscle fibers it innervates (from 10 to 1000 depending on the type of muscle). A nerve fiber innervates a thousand muscle fibers in the leg while it controls only a few fibers in the eye or fingers, giving it increased precision.
Muscle also contains elastic fibers of 2 types which allow it to produce strength by restoring the elastic energy stored in its fibers:
rubber bands in parallel: contained in the acto-myosin bridges
rubber bands in series: contained in the tendons.
The different types of muscle fibers are determined by myosin, which exists in 3 forms (isoforms) and gives fibers with different characteristics:
slow fibers, aerobic, type I
intermediate fibers, type II A
fast fibers, anaerobic, type II B
Fiber transformation . The muscle fibers of a subject can be transformed in the fast fiber direction (IIB) to slow fiber e (I): IIB IIA I .
C is the electrical stimulation transmitted from the motor nerve which determines the type of fiber. A fast fiber stimulated like a slow one will eventually become a slow fiber because it goes under revving. The reverse will not be able to happen : the slow fiber will not be able to go beyond its possibilities.
Muscle contraction diets
anisometric
concentric contraction: when the Force is greater than the Resistance, during the contraction : the insertions come closer
eccentric contraction: when the Resistance is greater than the Force, during the contraction, the insertions move away
plyometric: when the insertions move away and come closer in a very short time.
isometric : the muscle produces force without moving the insertion points.
Development of muscle fibers
The lengthening of the muscle in children is linked to the conjuncture of 4 factors: permanent stretching due to the lengthening of the bones (formation of sarcomeres ), nutrition , hormonal factors (production of testosterone ) and physical exercise.
The multiplication of the number of fibers ends around the age of 10 years . In adolescence, growth is essentially carried out by an increase in the size of each fiber. As with muscle hypertrophy, muscle gain depends on both the mechanical load and the hormonal climate.
From 40 to 50 years of age, there is a slow degeneration : the size and the number of fibers gradually decrease (sarcopenia). But the elderly are very sensitive to training : in those who exercise regularly, a number of fibers close to those of a young subject.
DEFINITIONS
Bodybuilding : set of training methods and means for improving muscle strength.
Muscle strength : neuromuscular ability to overcome or oppose resistance.
Strength is a global concept that brings together several complementary notions, and in particular : maximum strength, strength, speed and strength endurance, specific strength and relative strength.
Maximum force : this is the maximum force that the neuromuscular system can deploy for maximum voluntary contraction. It depends on:
- the transverse section of the muscle (hypertrophy )
- intramuscular coordination (nervous recruitment )
- intermuscular coordination (agonist - antagonist synergy )
Force speed ( explosiveness ): it is the capacity of the neuromuscular system to overcome resistance with the greatest possible speed. Strength training will aim to develop the best Strength - Speed ratio
Endurance strength : this is the capacity of the neuromuscular system to resist fatigue during long-term effort. Strength training will aim to maintain a high percentage of Maximum Strength for as long as possible.
Specific strength : it is the force that is developed by the muscle in the conditions closest to sports practice.
Relative strength : this is the ratio between muscle mass and body weight.
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