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May 2017
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BASIC PHYSIOLOGY OF MUSCLE CONDITIONING


Muscle conditioning regards the ability to train your muscles to a  degree of contraction that is different to the normal degree, resulting in improved neuromuscular response (tone), improved resistance (endurance) and a better nutritional state (tropism).

Our musculoskeletal systems are made up of around 400 muscles. Each muscle is covered in a connective membrane often  called a ‘fascia’. This fascia is activated by neuromuscular impulses received by general proprioceptors (neuromuscular spindles) which are activated during muscle contraction. These proprioceptors, which connect the motor area of the brain to the muscles, tell us about the state of the muscle tension, the direction of the body with respect to space, and the positions of various parts of the body, with respect to other parts.

The whole muscle activity stimulus and response system works thanks to energy provided by the division of an energy molecule called ATP (adenosine triphosphate) which is at the root of all energy processes.

Before going further into the technical specifics on muscle contraction, one must know which energy systems are used when we move. From this, trainers can then create programmes according to the athletes needs, or the individual who wants to do muscle conditioning.

Aerobic activity, anaerobic alactacid and anaerobic lactacid

The energy provided to contract muscles can be used at the same time and different amounts can be used since there are three energy systems available: aerobic, anaerobic alactacid and anaerobic lactacid  (see benefits of exercise).

The energy a muscle is provided with depends on the extent of the muscular strain and this is defined by the intensity and duration of the work that the muscle undergoes (for example, running for a long time, sprinting 100m or kicking a ball).

We have already discussed aerobic activity in the aerobic exercise section but, to summarise quickly, when working aerobically, energy consumption and replenishment are equal. It is typical of activities that last a long time (marathons, cycling, skiing, etcetera) and it is carried out in the presence of oxygen for the synthesis of carbohydrates and fatty acids.

The anaerobic alactacid system is very intense and can be used for a short period of time (about 8-10 seconds). It is used for extreme strains (like weightlifting) and it is linked to the amount of accumulated energy already present in a muscle cell (phosphocreatine). This energy, which is ready for use, does not need oxygen and does not produce lactic acid therefore, once it has been used up, other energy systems must be used in order to continue with the work, like the anaerobic lactacid system.

The anaerobic lactacid system is for medium-high intensity work and we use it to carry out most of our daily actions as it can be used for 45-60 seconds.
The proof that we use this system is shown by the production of lactic acid produced as a waste product when carbohydrates are broken down (anaerobic glycolysis) in the absence of oxygen. This is where the feeling of fatigue comes from and is causes muscle contraction to slow down which, in some cases, when lactic acid production is very high and is not removed by the liver, nor is it turned into pyruvic acid, can stop muscle contraction altogether, causing cramp.

Types of muscle contractions

When it comes to muscle contractions, one always thinks about the active muscle fibres shortening but, in reality, and depending on the dynamics of motion, the strength triggered by the muscle contraction is closely related to biomechanical issues. With biomechanical issues we mean the dynamic action of the movement that is carried out by the joints to which the muscle that is involved in the movement is inserted (for example, the biceps femoris: pelvis-femur-tibia).
In general, there are three types of contractions:

  1. Concentric contraction (isotonic) The two body parts move towards each other during the contraction, for example, lifting a heavy load.
  2. Eccentric contraction The two body parts move away from each other during the contraction (the muscles try to resist the weight, for example, putting down a heavy load).
  3. Isometric contraction (or static) During this type of contraction, the two body parts remain the same distance apart, for example, holding a suitcase).

A combination of these contractions can give rise to ‘subcategories’:

  • Plyometric contractions These occur when an eccentric contraction is rapidly inversed to a concentric contraction, taking advantage of the elastic energy that accumulates in the eccentric contraction (for example, bouncing and bouncing again after).
  • Auxotonic contractions This is a combination of isometric and isotonic contractions (with the later dominating), for example, starting from the blocks in 100m sprint.

Specificity of muscle action

We have seen that, according to the position of the joints, the muscle can take on different roles. We can define the muscle as:

  • agonist, when it carries out the movement;
  • antagonist, when it carries out the opposite movement to that of the agonist muscle.

It is evident that, from the moment the muscle starts moving in favour of a joint, it becomes the ‘agonist’. During the agonist muscle contraction, the antagonist muscle acts as modulator, or in other words, it relaxes due to neuromuscular impulses (Sherrington’s Law) and, by maintaining some tone and control, it ensures the right coordination of the movement.

We can distinguish three muscle ‘behaviours’ according to the action they carry out:

  • synergistic, when it is not the main muscle involved but aids the movement, thus it acts as an agonist too;
  • fixator, which holds the origin of the agonist stable (for example, the abdomen muscles hold the pelvis when the iliopsoas lifts the legs);
  • neutraliser and guider, when contracting neutralises the action of other muscles (for example, when flexing the leg, the quadriceps femoris is neutralised by the semitendinosus, semimembranosus and biceps femoris, which normally extend the thigh). 

The main points of muscle conditioning

Muscle conditioning training can be categorised into two groups:

  • bodyweight conditioning, when you use your own bodyweight or the weight of a body part;
  • overload, when a foreign object is used (a weight). Here is an example of natural overloading: when lying on the ground on one side, lifting up one leg (abduction) uses the weight of the limb itself, however, you can overload by attaching an exercise band to the ankles.

Before starting any muscle conditioning exercises, some physiological principles must be explained and kept in mind until you notice the neuro-physiological changes you are aiming for. They are:

  • specificity;
  • muscle balance;
  • the principle of overloading.

Specificity
Movement specificity means identifying a group of muscles to work on and then isolating them from other muscles. That means finding movements which have a range that only affects a specific muscle group (for example, to have a specific effect on the deltoid muscle, all you have to do is abduct the arm slowly, along the frontal plane, to 90°). During the exercise, the joint must remain very still and the chosen muscle must be isolated by moving it in a specific way.

Muscle balance
The principle of muscle balance is based on balancing the strain between the agonist and antagonist muscles. The work produced must be proportional and rational so muscle toning of both groups is equal. This type of exercise allows you to lock the joints in place, indirectly reinforcing the posture.
According to the law of alternation, by varying where the weight is applied on the flexor and extensor muscle groups, there will be a momentary active rest which makes the response to the next movement more effective.

The principle of overload
The definition of the principle of overload says that: ‘a greater than normal stress or load on the body is required for training adaptation to take place.’
As previously mentioned, overload can be natural, using your body, or can be helped with weights. In both cases, you work against the muscle that is being provoked. When you overload, you must keep in mind some fundamental principles so you avoid injuries, especially tendon and ligament injuries, which trigger inflammation easily.
Whilst muscle cells adapt quickly to major and minor strain signals coming from the nervous system, in order to adequately and stably withstand weight, tendons and ligaments can only rely on the structure of their tissues and not nervous mechanisms, thus you must wait for the necessary changes to occur to withstand new and heavier weights. Consequently, after reaching a certain weight, you must have break for a few days before increasing it again, even if your muscles could lift it, so the tendons and ligaments have time to adapt.
In summary, the load does not increase linearly rather it is ‘stepped’. Here is an example of how to carry out such exercises: start with a weight you can lift 8 times then, after a few days and using the same weight, do 10 repetitions then, after a few more days of rest, do 12 repetitions. Only at this point should the weight be increased however, you must start again with 8 repetitions, then 10 some days later, and so on. During the days when you use the same weight, the tendons are able to develop normally. Very often and incorrectly however, we tend to speed up the rest time and increase the weight too quickly so we can rapidly increase our strength and muscle mass, however, the consequences on the ligaments can be felt very quickly.

Rhythm and execution time

Varying the way you carry out an exercise means decisively varying the effect it has on the muscles and the circulatory system. When a muscle contracts, the arteries and veins are subject to the mechanical effect of the pressure, caused by the contraction, which blocks the blood flow to the inner muscle. During the relaxation that follows, the blood goes back to flowing fervently, returning to the muscle belly (the central part of the muscle). If the strain lasts a long time (more than 30-40 minutes), large quantities of lactic acid build up which, in the absence of oxygen, inhibit the combustion of sugars and fats.
Beginners and people with circulatory problems should take a break after each set of repetitions or not contract continuously for more than 10-15 minutes at a time.
Vice versa, if you have to work on resisting lactic acid, you must work for 30-40 minutes without taking a break. For example, when carrying out thigh abductions, aimed at getting rid of excess fat in the legs, you have to carry out the exercise in an elastic way, not impeding the movement of the limb when it rebounds or, on the other hand, take a small break between each movement so as to allow oxygen to intervene in the combustion process of the fatty acids.
On the contrary, staying continually tense whilst doing 15 repetitions, for example, will cause high amounts of lactic acid to form. Therefore, a woman with circulatory problems and cellulite would not benefit from the aforementioned exercise (in fact her state would actually get worse) however, if they worked aerobically, her circulatory condition would improve.
Very often, when we choose they type of training we want to do, we only consider the exercise, the number of repetitions and sets and the sequence of them and not the rhythm of the contractions which can actually make our physical state worse. This is also why many aspiring bodybuilders, when carrying out movements in a dynamic way and taking advantage of rebounds and springs or interrupting the continuity of the action, see their efforts to achieve hypertrophy (increase in volume of muscle mass) wasted.

Total Body Conditioning

During training, specific exercises are carried out on the spot, on all fours or on your side, back and front. The first aim is to improve the tone-trophic state of the muscle groups responsible for maintaining correct posture (paravertebral muscles, dorsals, glutei and quadriceps). The second objective is to work on all areas of the body like a ‘buffer’ and tone the parts where fat is deposited the most (stomach, hips, buttocks and thighs). These two goals can be achieved by doing just one type of exercise: muscle definition, that is, determining the best percentage of body fat to muscle mass for you.

Body conditioning is the most common technique used in gyms and it is a fundamental component of all exercise classes. It can be carried out

BASIC PHYSIOLOGY OF MUSCLE CONDITIONING

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