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PRINCIPLES AND EFFECTS OF TRAINING
It should be emphasized that there is no one program or set of programs that is best for everyone or even for the same person over time as interests, needs, goals, and capabilities change. People also respond differently to exercise and adapt differently to training.
The training -program must stress the system above the level to which it is accustomed. The training effect is quickly lost (reversibility), studies have demonstrated that within two weeks after the cessation of training, significant reduction in VO2max can occur.
A classic study after twenty days of bed rest, a group of subjects showed a 25% reduction in VO2max and maximal cardiac output. These rather dramatic decrements in working capacity as a result of inactivity clearly demonstrate the rapid reversibility of training.
The two major principles of training that apply to all individuals are overload and specificity. Related to overload are the principles of reversibility and maintenance.
Overload:
If the body is not required to adapt, it will not. For adaptation to occur, the body and its various parts and systems must be stimulated at levels greater than those they habitually encounter. A safe and effective training program is one that progressively overloads the body and allows adequate time for adaptation to each level of stimulation.
Specificity:
The effects of training are specific to those parts and systems of the body that are overloaded. As an example, weight lifting produces muscle hypertrophy and strength, whereas distance running produces cardiorespiratory endurance but no hypertrophy.
In other words, the effects of training depend have greatly on the activities that are selected. The principle of specificity is probably most important for those persons with specific goals.
Reversibility:
Because the body adapts to its habitual level of stimulation, the changes brought about by training reverse if the individual becomes more sedentary.
In other words, the effects of training are transient and reversible. The opposite of overload, this principle states that the body can also adapt to inactivity.
Maintenance:
Maintenance takes less time and effort to maintain an improved level of fitness than it does to attain it. Once people adapt to a level of stimulation and there is no overload, further adaptation is not required.
If they are satisfied with their current level of fitness, they may be able to maintain it by continuing to do the same amount of training per week and even by slightly reducing their ram is training for brief periods.
It is a common observation that individuals differ greatly in the degree of improvement resulting from training programs. Many factors contribute to the observed individual variations in the training response.
Each of these factors can modify the selection and performance of activities, physiologic (functional) age is more important than chronologic age in the type of activity chosen, but age is a risk factor in itself and must be considered physiologically, there is little difference in the mechanisms used by men and women to respond to exercise or to adapt to training.
Any differences are more likely to be quantitative (Partly related to body size). There will also be differences in the types of activities selected. Because environment (heat, cold, and altitude) can affect the capacity to perform exercise, it can also modify an exercise prescription.
At one time, it was believed that conditioning programs for women had special requirements that differed from those used to train men. Today, however, ample evidence exists to demonstrate that men and women respond to training programs in a similar fashion. Therefore, the same general approach to physiological conditioning can be used in planning programs for men and women.
The physical training of elderly subjects requires consideration of many variables. These variables include exercise intensity, duration, frequency and mode, age, sex, general musculoskeletal status of the subject, time since heart disease involving or surgery, size of the lesion, subsequent complications such as development of angina pectoris or other signs of myocardial ischemia, and medications, as well as, the patient’s ours goals.
Additionally, it seems likely that genetics plays an important role in how an individual responds to a training program. For instance, an individual with a high genetic endowment for endurance sports is likely to respond differently to endurance training when compared to an individual with or markedly different genetic profile. If you want to become a world class athlete you must choose your parents wisely.
The energy to perform long-term exercise (i.e. > ten minutes) comes primarily from aerobic metabolism. A steady state oxygen uptake can generally will also be maintained during submaximal exercise of moderate duration.
However, two exceptions to this rule exist. First, prolonged exercise in a hot/humid it can also environment results in a “drift” upward of oxygen uptake; therefore, a steady state is not maintained in this type of exercise. Second, continuos exercise at a high relative work rate (i.e., > 70% VO2max) results in a slow rise in oxygen uptake across time.
In each of these two types of exercise, the drift upward VO2max is due principally to the effects of increasing body temperature and to a lesser degree to rising blood levels of the hormones epinephrine and norepinephrine. Both of these variables tend to increase the metabolic rate resulting in increased oxygen uptake across time.
The physiological factors that influence VO2max are:
1- The maximum ability of the cardiorespiratory system to deliver to the contractile muscle; and
2- The muscle’s ability to take up the oxygen and aerobically produce ATP.
The fuel utilization during exercise including proteins, play only a minor role as a substrate during exercise, with fat and carbohydrate, serving as the major sources of energy during activity in the healthy individual consuming a balanced diet. Carbohydrates are used as the primary fuel during short duration incremental (i.e., 6-12 minutes) or high intensity exercise.
Further, carbohydrates serve as the major substrate at the onset of low-to-moderate intensity exercise. However, during prolonged work (i.e. > 30 minutes) there is gradual shift from carbohydrate metabolism toward an increasing reliance on fat as a substrate.
Components of a training session:
Every training session should consists of three components:
(1) Warm-up,
(2) workout, and
(3) cool down.
The warm-up prior to a training workout has several important objectives. First, warm-up exercises increases cardiac output and blood flow to the skeletal muscles to be used during the training session.
Secondly, the warm-up activity results in an increase in muscle temperature, which elevates muscle enzyme activity.
Finally, preliminary activity affords the subject an opportunity to perform stretching exercises. it is commonly believed that a proper warm-up may reduce the possibility of muscle injury due to pulls or strains. The duration of the warm-up may be from 5 to 20 minutes, depending on environmental conditions and the nature of the training activity.
Immediately following the training session, a period of low intensity, “cool down” exercises should be performed. The principal objective of a cool down
Is to return “pooled” blood from the exercised skeletal muscles back to the central circulation. Similar to the warm-up, the length of the cool down may vary from five to thirty minutes, depending on environmental conditions, the age and fitness level of the individual, and the nature of the training session.
Considerations in prescribing exercises:
Medical-physiologic factors
o Reduced cardiorespiratory capacity.
o Less ability to perform moderate and high intensity exercise.
o Decreased ability to adapt to and to recover from erogenous physiologic stimuli (e.g., exercise, heat, and cold).
o Reduced adaptability to physical training (degree and/or rate of improvement).
o Muscle weakness and increased fatigability.
o Degenerative bone, joint, and tendon problems.
o Increased susceptibility to soreness and injury.
o Impaired balance and neuromuscular coordination.
o Impaired vision and hearing.
o Senile gait disorders and foot problems.
Physiologic factors
o Lack of encouragement to be active.
o In accurate perception by young and old of how active the elderly are, can be, or should be.
o Increased inhibitions and depression.
o Negative attitudes toward physical activity.
o Distorted self image.
The normal cardiopulmonary response to exercise:
During exercise there is an increase in oxygen demand to meet the metabolic requirements of the exercising muscles. The increased oxygen demand is accomplished by the integrated response of the cardiopulmonary system, blood redistribution, and oxygen utilization by the exercising muscles.
At maximal exercise, oxygen consumption can increase up to 18-fold, heart rate two to three fold, stroke volume by twofold, cardiac output fivefold, VE 20 to 25 times, and oxygen utilization by the muscles two to three times.
The lactate threshold:
The lactate threshold, also called the anaerobic threshold. is an estimator of the onset of the metabolic acidosis associated with the increase in lactic acid in the blood. Although its meaning is controversial, it appears to be related to hypoxia of the exercising muscles, which occurs at approximately 50% of the VO2max in normal individuals.
The increase in lactic acid triggers physiologic responses. including increases in VO2max and VE that are disproportionate to oxygen consumption. These changes allow the lactate threshold to be determined noninvasively by ventilatory variables; lactate can also be measured directly in the blood. The lactate threshold is used as an indicator of level of fitness, a monitor of the effect of physical training, and a supplementary variable in the diagnosis of exercise limitation.
The best index of exercise capacity:
Measurement of the VO2max, the amount of oxygen consumed per minute at the highest level of work that the test subject is capable of performing, remains the best available index for the assessment of exercise capacity.
Approaching or achieving maximal V02 predicted from normal reference values is an important criterion used for the determination of maximal aerobic capacity. Traditionally VO2max values have been regarded as most reliable when a V02 plateau (no further increase in VO, as work rate increases) is achieved at the end of the exercise. Because such a plateau is often not seen in patients, the highest level Of V02 achieved, or VO, peak, is reported. Clinically, VO, peak and VO2max are used interchangeably.
A reduced VO2max response reflects oxygen delivery (heart, lung, systemic, and pulmonary circulation) or peripheral utilization (i.e., peripheral circulation and/or muscle) abnormalities. A reformatting of the Fick equation demonstrates how dysfunction of different organ systems may affect aerobic capacity.
Mechanisms are involved in exercise limitation:
Exercise in normal subjects is usually thought to be limited by cardiovascular factors. There are three major categories of exercise limitation in patients with reduced VO2 max:
* Cardiovascular limitation, which includes the heart, pulmonary, and systemic circulation and blood (anemia, carboxyhemoglobin).
* Respiratory limitation, which includes ventilatory (mechanical) and gas exchange factors
* Peripheral factors, which include a broad spectrum of neuromuscular-related abnormalities that could affect oxygen utilization and mechanisms of contraction.
A peripheral limitation to exercise may occur in the presence of suspected neuromuscular problems, myopathies or other muscle enzymatic deficiencies, or in severe deconditioning (e.g., heart or heart-lung transplantation). Patients with peripheral limitation have low VO2max and both HRR and VR.
N.B.
Heart rate reserve (HIRR) =
predicted maximal HR - measured maximal HR
Ventilatory reserve (VR) =
Maximal Voluntary Ventilation (MVV) -VEmax or VEmax/MVV |
Training Principles and Effects
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