Adaptations to Training
Flexibility
Strength Training in Young Athletes
Training to Reduce Injuries
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Adaptations to Training
Introduction
Athletes train the various physiological systems to adapt to the stresses of sports; they also train to alter certain geometric structures (hypertrophy) of the body. Their training is specific to their sport and the outcome of the adaptations is specific to the training program. Sports pose many stresses on the body. Stresses come in all shapes and sizes such as heat, cold, dehydration, external and internal forces acting on the body, and many more. The battle of competition poses the greatest stresses on the body. Training is employed to adapt the body to those stresses and allow the athlete to efficiently, effectively, and safely compete in athletic competition. They also train to increase performance.
Training can consist of resistance training or endurance training. It can also consist of strength, speed, power, agility, hypertrophy, and more types of training. The adaptations are specific to the training involved. Therefore, this section will explain general adaptations that occur with most training programs. There are many changes that can occur both structurally and biochemically. These changes can become very complex and hard to understand without years of study in exercise physiology. Therefore, they will be left out. Just remember that there are hundreds of other small structural and biochemical changes that may occur when the body adapts to the stresses of exercise.
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Bone Adaptations
The stresses of exercise cause bones in the body to deform. The forces may cause the bone to bend, compress, twist, pull apart, or a combination of these forces may be applied to the bone. Muscle contractions apply various forces to the bone, as does impact forces. Three variables can happen when stress is applied to the bone. The stress will have no effect on the bone because it is to low, the stress will induce physiological and structural changes to make the bone stronger, or the stress will be too great and the bone will fracture. If the force is sufficient enough to induce a physiological and structural change and it is repeated enough, it will cause osteoblast to strengthen the bone in the areas of stress. Osteoblasts are cells that manufacture and deposit molecules in the areas of stress within the bone to make the bone stronger. When this is done the bone increases in size. The increased size causes the forces exerted on the bone to be distributed over a larger surface area, which decreases the amount of force per unit area. After the bone growth occurs the bone will be able to withstand greater forces. In addition, the micro architecture of the bone alters to make the bone even stronger. This process is like an architect placing braces within a building to make the building stronger.
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Tendon Adaptations
Exercise causes an increase in systemic anabolic hormones which stimulates growth of tendons. As muscles become stronger, they apply greater forces on the tendons and bones. This causes changes in the internal architecture of the tendon and the tendons attachment site on the bone. The changes in internal architecture cause the structures to become stronger. If they did not become stronger, then the tendon would detach from the bone, or the tendon would pull a piece of bone off with it due to the high levels of force exerted on the bone by the tendon and muscle. Therefore, the tendon and bone have to strengthen to cope with the increasing strength of the muscle (increases the force applied to the tendon and bone). If they do not adequately strengthen, then injury will result.
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Neurological Adaptations
Nerves connect to muscles and provide an electrical charge which activates certain biochemical processes to initiate a muscle contraction. During training the patterns in which these nerves fire electrical signals becomes altered. Different training causes different patterns of electrical signals. In addition, the nerves enlarge and multiply which causes the efficiency and effectiveness of the electrical signals to increase. Thus movements become more efficient and fluid. Through training, reflex pathways become faster and more efficient. This leads to faster reaction times. There are many more adaptations that can occur but these adaptations become very complex, and anatomy and physiology specific. Therefore, they will not be mentioned in this section.
Neural adaptations have a direct affect on performance. For instance, the initial gains in strength seen in a strength training program during the first four weeks of training, is usually due to a neural adaptation. Another example of the affects of neural training is that if one limb is trained at time (e.g. single arm bicep curl) instead of both limbs being trained (straight bar curl), then the limb will become stronger than if it was trained simultaneously with the other limb. The loss of strength is termed bilateral deficit. If athletes have unilateral limb movements in their sport, it is important for the athletes to incorporate unilateral limb movements into their training program. In fact if training is not done properly (wrong mode, intensity, duration, and frequency of exercise) it can alter neural firing patterns and decrease an athletes performance. If training is done properly it can greatly enhance performance. Remember some training programs may be excellent for some sports, but those same programs may be bad for other sports, because it may provide the athlete with the wrong neural adaptations. Different sports require different neural adaptations and those adaptations will greatly affect performance.
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Muscular Adaptations
Athletes undergo rigorous training in order to induce changes within muscles. They seek these changes to increase performance and safety. Various training parameters will cause different adaptation to the muscle. When seeking optimal performance, some muscular adaptations are good for some sports and not good for others. For instance, a soccer player will not want big bulky muscles as this will just be added weight to carry around on the field, it will slow the athlete down, and probably cause the athlete to fatigue sooner. Therefore, specific training must be geared towards the desired outcome of performance.
There are usually three forms of exercise that pertain to muscle adaptations. They are strength, hypertrophy (muscle growth), and aerobic endurance. Strength training usually involves lifting weights at near maximal efforts. Strength training produces changes (increase) in the cross sectional area of the muscle. Type IIa and IIb muscle fibers (see exercise physiology section-Fiber Types) increase more readily than type I muscle fibers. This is because type II fibers are larger and produce a greater force output than type I fibers. Thus the training of these fibers produces a greater increase in strength, a greater contraction velocity, and an increase in lean muscle mass.
Hypertrophy training will enable an athlete to increase the cross sectional area of a muscle. This type of training uses more repetitions and lighter loads than strength training. The loads are heavy enough to produce failure or an inability to eccentrically and concentrically contract the muscle. This is accomplished by completing 6 to 12 repetitions, sustaining short rest periods, and exercising muscle groups for up to 12 to 20 successive sets. The sets are usually divided up into three or more different exercises such as bench press, flies, and jammer press.
Note: 12-20 sets can be very stressful to the tissues. Athletes should work their way up to completing that many sets over a period of time and use caution with implementing that many sets. Consult your doctor, athletic trainer, or a strength coach before completing that many sets.
Endurance exercise training programs involve sub maximal contractions for extended exercise periods. This means that there will be a large number of repetitions and a very short rest period or no rest period will be involved. The intensity is very low and the volume is very high. Since type I fibers are considered to be a more aerobic type fiber this type of training enhances the type I fibers aerobic abilities. This type of training does have minute affects on the type II fibers but the largest impact of this training is on the type I fibers. Endurance training can reduce the overall muscle mass and glycolytic (glycogen break down) enzymes of the type II fibers. It can also change the characteristics of type two fibers to type I fibers. Though most evidence states that it will not fully change a type II fiber to a type I, it can change the make up of the fiber to take on more type I characteristics. The result of this change is to make the body better able to handle the stresses of endurance activity. In addition, there will be more mitochondria (part of the cell responsible for aerobic production of ATP) and more myoglobin (transports oxygen within the cell) within the cell. The combination of these two enhances the aerobic capacity of the muscle tissue.
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Cardiovascular Adaptations
There are many cardiovascular adaptations that can result from training. The type of training will greatly influence the adaptation by the cardiovascular system. Athletes usually experience a reduction in resting heart rate with training. Another change the cardiovascular system will have is an increase in maximal cardiac output. This may be due to an increased stroke volume (volume of blood pumped out by the heart). The heart may increase in size with prolonged training. This is referred to as cardiac hypertrophy and is usually associated with an increase in size of the left ventricle of the heart (left ventricular hypertrophy). The myocardium (muscle of the heart) improves its ability to achieve a larger stroke volume. This may reduce the heart rate during sub maximal exercise (heart becomes more efficient).
Capillary circulation is responsible for delivering oxygen to cells, delivering nutrients to cells, and the delivery of hormones to cells. Capillary circulation also helps remove metabolic waste products and heat. With certain types of training, there will be an increase in the amount of capillaries per area of muscle (capillary density). These adaptations facilitate delivery of blood to the muscles and facilitates extraction of heat and metabolic by products.
There are certain adaptations that occur to the blood with prolonged training. Most of them are complex biochemical adaptations and will not be mentioned. However, two major adaptations will be the total plasma volume will increase, as will the total hemoglobin (oxygen transporter). These increases help facilitate oxygen delivery and enhance circulatory and thermoregulatory (heat regulation) dynamics.
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Pulmonary Adaptations
The respiratory system is responsible for delivering oxygen to the blood and removal of metabolic by products such as carbon dioxide from the blood. As athletic activity increases, so does the demand for oxygen delivery and carbon dioxide removal. The pulmonary system adapts by increasing the tidal volume (amount of air inspired and expired during normal breathing). This reduces the number of respirations per minute as the lungs become more efficient. In addition, the ability of the cardiovascular system and pulmonary system to deliver and extract oxygen is enhanced. For instance, in most cases athletes breathe in 20.93% oxygen and expire approximately 14.5% oxygen, whereas a sedentary person may breathe in 20.93% and breath out 18% at the same work level.
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