REVIEW ARTICLE

Health Promotion and Exercise Training Atko Viru and Tamara Smirnova Institute of Exercise Biology, University of Tartu, Tartu, Estonia

Contents Summary ... .... .. . ... . . . 1. Genotype and Phenotype . . . . . . 2. Effects of Physical Training on Health

2.1 Improvement and Regulation of the Central Nervous System 2.2 Increased Capacity of Endocrine Systems ..... . 2.3 Increased Energy Potential . . . . . . . . . . . . . . . 2.4 Improved Capacity of the Oxygen Transport System 2.5 Training and Oxidation Processes. . . . . . . . . 2.6 Increased Metabolic and Functional Economy 2.7 Increased Functional Stability . . . . . 2.8 Increased Number of Na+,K+-Pumps . 2.9 Immunoactivity . .... .

3. Training and Adaptivity . . . . . . . 4. Antisclerotic Effect of Training . .. 5. Effects of Different Types of Training 6. Conclusions . . . . . . . . . . . . . .

SportsMed. 19(2): 123·136. 1995 0112·1642/95/0002-{)123/S07.00/0

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123 125 125 126 126 126 127 127 128 128 129 129 130 131 131 132

Summary Health is determined not only by the absence of disease, but also by an indi­vidual's resistance to pathogenic factors. In tum, resistance depends on the effec­tiveness of specific homeostatic regulation and the mechanism of general adaptation. Through the change in adaptivity, health may be increased or reduced. While it is difficult to predict which specific homeostatic mechanism will be necessary in various stages of life in the individual, it is more reliable to try to improve health, thereby increasing the effectiveness of the mechanism of general adaptation.

Physical training results in a variety of changes in individuals. There are sev­eral changes which are essential both for increased exercise performance and for increasing adaptivity, by favouring the effectiveness of the mechanism of general adaptation. These changes: improve central nervous regulation and central nerv­ous system functions; increase endocrine system capacity; increase energy po­tential ; improve the capacity of the oxygen transport system; improve oxidation processes; increase metabolic and functional economy; increase functional sta­bility; and increase the number of Na +,K+-pumps.

The influence of these changes on adaptivity is accomplished by the influence of exercise training on immunoactivities, and by the antisc1erotic effect of train­ing. The latter may be considered to be metabolic (actualised through the training

124 Viru & Smirnova

effect on lipoprotein metabolism and aging-related calcium distribution) or me­chanical (protection of tissues from sclerotic changes by their activities) effects.

The training effects are specifically dependent upon performed exercises. En­durance exercise is considered to be the most important and widely recommended form of exercise for health improvement. Most of the training benefits (listed above) for increased adaptivity are induced by aerobic endurance training. Gym­nastic exercises are indispensable in regard to mechanical anti sclerotic effect. They are also essential influences on the central nervous system. Aerobic dance or aerobic rhythmic gymnastics are ways by which the positive effects of endur­ance and gymnastic exercise can be combined.

The World Health Organization defines health

as a state of complete physical, mental and social

welfare.[1) Amosov[2) defines health as the sum of

reserve capacities of the main functional systems of an organism. Karvonen[3) emphasises that the

term health must include not only the current state,

but also a direction and a potential to move in that

direction. Accordingly, it was affirmed by Kaznatcheyev[4) that human health is a dynamic

state (process) of maintaining and developing bio-

Changes to maintain or res10re the

level of rigid constants

Cons1antlevel of 1emperature pH. p02' osmolic pressure. contents of ions and water

Fig. 1. Homeostatic regulation. The rigid constants are those which determine the conditions for optimal enzyme activity.

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logical, physiological and psychic functions, opti­mal working capacity and social activity during a maximal life span.

Therefore, health is determined not only by the absence of disease but also by an individual's resis­tance to pathogenic factors. In turn, resistance de­pends on the effectiveness of specific homeostatic regulation and the mechanism of general adaptation.

Adaptation to life conditions, change in the ex­ternal environment and any kind of bodily activity are always directed towards maintaining or restor­ing the constancy of the internal milieu of the body. Accordingly, certain specific reactions are intro­duced by any alteration of the body's internal en­vironment. The integrated aim of these reactions was defined by Cannon[5) as homeostasis or homeo­static regulation.

Some of the parameters of the internal milieu are very rigid, with a very narrow range of fluctu­ation between the basal state and activity levels, deviation from which cannot be associated with maintenance of life. The rigid constants are those which determine the conditions for optimal en­zyme activity (fig. 1). A shift in these conditions disturbs or excludes the possibility for enzymatic metabolic reactions and, hence, for normal life.

In many cases, adaptation is characterised by nonspecific responses, independent of the specific nature of the actions. An extensive study of non­specific adaptive responses enabled Selye[6) to es­tablish the stress reaction as the sum of nonspecific changes, or as the nonspecific response of the body to any demands made upon it.

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Health Promotion and Exercise Training

In situations that require the activation of adap­tation processes, the main events within an individ­ual can be described in the following manner: the agent (stressor) acts, by various pathways, on the structures of the central nervous system. If the re­quired intensity of the homeostatic reactions is high, or if it is necessary to maintain them for a prolonged duration, the mechanisms of general ad­aptation will be activated (see fig. 2). This means overall mobilisation of the body's energy reserve and protein reserves, as well as activation of de­fence faculties, e.g. the immune system.[7)

Consequently, health depends on the adaptivity of the individual, and, hence, through the change in adaptivity, health may be increased or reduced. There are opportunities for improving the capacity for homeostatic regulation and for the mechanism of general adaptation. However, it is difficult to predict which specific homeostatic mechanism will be necessary in various stages of life in indi­viduals. Therefore, it is more reliable to try to im­prove health and thereby increase the effectiveness of the mechanism of general adaptation.

1. Genotype and Phenotype

Genotype determines the 'reaction norm'. By summing up the reaction norms of the main func­tional systems, the genetically possible limits of adaptivity and thereby of individual health can be determined. The degree to which these genetically possible limits are utilised depends on the individ­ual phenotype which is formed in the course of a person's life. Various positive and negative influ­ences affect the individual's adaptivity to living conditions. The result of these influences and the person 's lifestyle will determine health.

In everyday life, the need for the activation of adaptation processes depends on the genotypic ad­aptation of each individual to climatic and geo­graphic conditions. In this wayan 'ecoportrait' may be predicted for each person,(8) determining the amount of the adaptation activity necessary. The larger the difference between the ecoportrait (genotypic adaptation) and life conditions, the greater the daily expenditure of adaptation ca-

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125

I Adaptation to Exercise 1

~ 1 Mobilisation Mobilisation Activation

of energy of protein of defence reserve resources faculties

I Adaptive synthesis I of proteins

I Improved functional I possibilities

Fig. 2. Mechanism of general adaptation.

pacities. Increased daily expenditure of adaptation capacities reduces the reserve for adaptation to extraordinary influences.

Many studies demonstrate the influence of mus­cular activity on the individual and their health (for recent reviews, see Blair,[9) Bouchard et aI.,llO.ll)

Leon,(12) US Centers for Disease Control and Pre­vention and the American College of Sports Med­icine(13) . Positive influences on health can be ach­ieved by cold and altitude acclimatisation,D4) or by a number of other factors. However, in these cases the effect is not as extensive as with physical ac­tivity because the improvement in adaptivity is re­lated to the specific homeostatic mechanism and to a lesser extent to the mechanism of general adap­tation. There is no medicine or drug which actually increases adaptivity. Nutritional factors may be es­sential in avoiding or reducing the influence of negative factors,IIS.17) but they are not able to aug­ment health.

2. Effects of Physical Training on Health

Physical training results in a variety of changes in individuals, including changes in the shape of the body, the size of organs, the functional capaci­ties of cardiovascular and respiratory systems. There are also changes in metabolic resources, cel­lular structures and metabolic processes, as well as in the molecular, autoregulatory, humoral, hor-

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Table I. Exercise training benefits and increasing adaptivity

Improvement of nervous regulation and functions of the central nervous system Increased capacity of endocrine systems and aHered sensitivity to hormones

Increased energy potential of the organism

Improved capacity of oxygen transport system

Improved oxidation processes

Increased metabolic and functional economy

Increased functional stability

Increased number of Na+,K+·pumps

Influence on immunoactivity

Antisclerotic effect of training

monal and nervous mechanisms. There are several changes whose effect is not limited to improved exercise performance and are important for building up resistance against pathogenic factors (table I).

2.1 Improvement and Regulation of the Central NeNous System

With physical training, formation of various new coordinations is typical.[l8.19) Besides improved motor coordination, regulation of autonomic func­tion may be improved in a trained individuals by the following manifestations:[20.23] • change in autonomic balance • more rapid adjustments and labilisation of

regulatory influences • more precise accordance between activity and

autonomic responses • increased sensitivity to regulatory influences.

In trained animals, the density of synapses of dendritic spikes in the cerebellum[24) and the spinal neuron size[25) were found to be greater than in un­trained animals. The training effects on the brain tissue also include the elevated activity of various (mainly oxidative) enzymes,[26.27) an increased num­ber of capillaries per area of cross-section of the brain,[28) and an increased content of endorphins and encephalins in various structuresP9,30)

The influence of exercise on mental health is considered to consist of a reduced state of anxiety, a decreased level of mild to moderate depression, a reduction in neuroticism and anxiety and a de­crease in various psychosocial stress indices, as

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Viru & Smirnova

well as beneficial emotional effects,l3I·33) Data from 56 000 individuals[34) has led to the conclu­sion that the level of physical activity is positively associated with good mental health (positive mood, general well-being, relatively infrequent symp­toms of anxiety and depression) in the household population of the US and Canada.

2.2 Increased Capacity of Endocrine Systems

Typical training effects include reduced hor­monal responses to submaximal exercise,[35.36) as well as to various other stimuli.[37) However, supra­maximal exercise tests demonstrated extremely pro­nounced responses of catecholamines,[38.39) corti­cotropin,[40) cortisol,[4I) somatotropinf41 ,42) and p-endorphin[40,42) in trained athletes. The increased capacity to secrete glucocorticoids and epinephrine (adenaline) is related to hypertrophy of both the adrenal cortex[43) and the adrenal medulla,[44) as well as to the increased number of mitochondria, their vesicular cristae, elements of endoplasmic re­ticulum, polysomes on adrenocorticocytes of the fascicular zone and to the elevated content of cyto­chrome a-a3 in the adrenal cortex.[45)

A prominent effect of training on hormonal reg­ulation originates from the altered sensitivity of tissues to hormones, due to changes both in the density of cellular hormone receptors and in post­receptory processes.[38,46) Results indicated that training also influences hormone metabolism and tumover.l47) In addition, these changes make the regulation more labile.

2.3 Increased Energy Potential

Exercise training results in increased glycogen stores in skeletal muscle,[27.48.49)liver[27) and myo­cardium. [27.50.51) Increased phosphocreatine content in skeletal muscle is indicated by some studies[27] but not confirmed by others,f48] The increased en­ergy stores are associated with an enzymatic adap­tation, making their mobilisation and restoration more effectiveP7.48) As a result of training, the ac­tivities of the enzymes catalysing both the break-

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Health Promotion and Exercise Training

down and resynthesis of energy stores increase si­multaneously.l52)

2.4 Improved Capacity of the Oxygen Transport System

Training-induced heart hypertrophy[53-55) is associated with a number of changes which make the heart functionally stronger and increase its efficiency. The increased thickness of the myo­cardium[56-60) and the cross-sectional area of myo­cardial fibres(61) are associated with increased con­tractility[62.63) and enlarged heart cavities.[55.58.60)

The latter is considered to be a regulative cardiac dilatation,[55) because there is an augmented resid­ual blood volume in the heart in the resting condi­tion which is almost completely utilised for the in­crease of stroke volume during exercise.[55) The increased capillarisation and capillary-to-fibre ra­tio of the myocardium is typical for endurance trained animals. [61.64-67)

Additionally, increased capillary diffusion ca­pacity,[64) precapillary vascularity[68) and total size of the coronary tree have been established.l69] The development of extra coronary collaterals[7o.7I) and increased coronary artery lumina[70] were ob­served. The cardiac sarcoplasmic reticulum has a greater capacity to sequester and bind calcium in swim-trained versus sedentary rats.[72] In small ro­dents, training in treadmill running increased the myofibrillar ATPase levels.[73.74] Within an exten­sive heart rate (HR) range, the heart of a trained rat exerts a higher level of left ventricular pressure than that of an untrained rat.[75) Consequently, adaptive mechanisms to economise cross-bridge cycling of protofibrils may be necessary to buffer the high degree of contractile activation that can be achieved at high exercise intensity levels in the trained state.l75) In dogs, endurance training im­proved the stroke volume potential in association with increased left ventricular relaxation rate.[76.77]

These changes constitute the foundation for in­creased cardiac performance as a result of endur­ance training in humans[78-80] and in experimental animals,l23.8I) Accordingly, the major adaptation to endurance training is the generation of a greater

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127

maximal stroke volume at any given level of exer­cise, as well as a greater maximal stroke volume. Whereas with submaximal exercise the heart rate is lower in trained individuals, the cardiac output may be on the same level or even lower than in untrained individuals. During maximal and supra­maximal exercises, the rise in HR is almost the same, and the higher maximal stroke volume al­lows maximal cardiac output 1.5 to 2.0 times higher in endurance athletes than in sedentary humans.

Additional benefits will be provided to the oxy­gen transport system by the increased capillarisa­tion of lung alveolae[82) and skeletal muscle,[66.83)

altered conditions for alveolar ventilation and gas diffusion across alveolar and capillary mem­branes,[84) increased activity of oxidative en­zymes,[85.86) increased glycogen content[87) and capillarisation[85] of the diaphragm, stimulation of erythropoietic processes in the bone marrow[88] and rises in blood volume[88-90] and total haemo­globin content.[89) The integral expression of these changes is the maximum oxygen uptake (Y02max). The values of YO 2m ax in endurance athletes exceed twice the corresponding level of sedentary individ­uals.l91 .92] Training-induced vagotonia has been shown to avoid fibrillation of the heart.l93]

2.5 Training and Oxidation Processes

Training increases the oxidation capacity of tis­sues as well as improving control of oxidation pro­cesses. The foundation for augmented oxidation potential is the increase in the activity of enzymes which catalyse the key reactions both in the Krebs cycle and in the oxidation chain.[48.94) In tum, the increased activity of oxidation enzymes is related to the mitochondria. A typical result of endurance training is the increased number and total volume of mitochondria in active muscles.l48)

These changes are absent in the myocardium.l48] Obviously, the oxidative potential of myocardio­cytes is sufficiently high without training.

The increased oxidation potential is reflected by an elevated anaerobic threshold, allowing the per-

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formance of exercises of higher intensity without accumulation of lactate. [92.95-97]

The increased activity of oxidation enzymes seems to be related to an increase in enzyme levels, allowing a better control of the oxidation pro­cesses. With high enzyme levels it is possible to attain a high rate of substrate fluxes at low substrate levels.l48]

In a trained individual it is possible to increase both lipolysis and fatty acid oxidation despite the accumulation of lactate.l27,48] A greater use of fat as a fuel following endurance training might be related to a more rapid translocation of the ADP (adenosine diphosphate) generated during contrac­tion into the mitochondria. The consequence of this is a tighter control over the glycolytic process, cre­ating more favourable conditions for the entry of acetyl units derived from ~-oxidation offatty acids into the Krebs cycle. [98]

As a result of endurance training, the activation of free radical oxidation becomes less pronounced during exercise,[99] and probably also during other stressful situations, due to an increase in activi­ties of enzymes participating in antioxidant sys­tems.[IOO,IOI]

2.6 Increased Metabolic and Functional Economy

In 1956, the principle of increased economy as a result of training was established by Mellero­wicz.l 102] The expressions of increased economy in body functions and metabolism in a trained indi­viduals are: • decreased functional activity in resting condi­

tions (e.g. training bradycardia) in association with an enhanced ability to intensify the func­tions (fig. 3); this combination results in an in­creased functional reserve

• moderate functional responses to submaximal exercise and accelerated recovery after exercise

• increased mechanical efficiency during exer­cise, related to (i) better coordination, (ii) ac­complished control of oxidation processes, and (iii) use of economical metabolic pathways

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Viru & Smirnova

Untrained people ,. ,." Athletes

, ----

Resting state

--/

/

/ /

/

Exercise intensity

Fig. 3. Functional response to exercises of various intensity in trained and untrained people and athletes.

• more rational adjustments (e.g. heart function is intensified more on account of inotropic than chronotropic influences). [21 ,78-80]

According to Raab,[103] autonomic balance de­termines the ratio between functional and energy expenditure in the myocardium both in a resting state and in a stress situation. Raab[103] assumed that the increased cholinergic influences in an en­durance trained individual prevent the harmful prevalence of sympathetic action, which, together with a high functional activity, leads to exaggerated oxygen uptake causing a decreased mechanical ef­ficiency of the heart contraction, unequal distribu­tion of available oxygen between myocardial cap­illaries, and (due to the latter) to necrotic changes that occur in people with hypokinesia. However, this theory has not found recognition. Anyway, the more economical function of the myocardium pres­ents an opportunity to avoid harmful conse­quences. At the same time, it means that a reserve exists for a further rise in functional activity as well as for a stable function during a prolonged period of activity.

2.7 Increased Functional Stability

During prolonged exercise, the cardiorespira­tory function gradually transfers from the most ra­tional pathway of adjustment to a less rational one: lung ventilation increases without the concomitant elevation of alveolar ventilation (the 'dead space' expands), HR increases in conjunction with a de­crease in the stroke volume and blood pressure; and

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Health Promotion and Exercise Training

cardiac output is not maintained at steady­state.[I04] AS-month training regimen considerably reduced the alterations in cardiorespiratory func­tion during exercise.[105] These data are consistent with an exponential decrease in the % 'V02max which it is possible to maintain during long-lasting exercise.

In endurance-trained individuals, the slope of this exponential curve is less steep than in the un­trained.[911 Evidently, the functional capacity ofthe cardiovascular system is determined by the highest possible level of oxygen transport to tissues (mainly to working muscles) and by opportunities to maintain the necessary level of oxygen trans­port. The term 'functional stability' describes the ability of the body to maintain those levels of func­tional activities for a prolonged period which are necessary for effective performance and for avoid­ing disturbances in the rigid constants of the inter­nal milieu of the individuaP I061

Functional stability is required not only for oxy­gen transport, but for all systems to work actively during prolonged exercise or other long-lasting stressor influences. Studies on endocrine functions during prolonged exercise indicate that hormonal regulation may also change, causing disturbances in cellular functions) 1071

2.8 Increased Number of Na+,K+-Pumps

Experiments on rats[1081 and biopsy studies with humans,D091 including elderly people, indicate that exercise training increases the number of ouabain binding sites. Consequently, training results in an increased density of sodium, potassium (Na+,K+) pumps in the cellular membrane of muscle fibres. This change increases possibilities for restoration of the intracellular ionic composition after each ac­tivity cycle, and thereby creates favourable condi­tions for the functioning of cells. During prolonged exercise in rats it has been found that the activity of Na+,K+-ATPase decreases in the microsomal fraction of the skeletal and heart muscle tissues, together with intracellular accumulation of Na and water)1101 However, in trained rats the activity of this enzyme was maintained even during swim-

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129

ming for 18 to 24 hours. Obviously, training ele­vates the functional stability of Na+,K+-pump function.

2.9lmmunoactivity

The relationship between the training effect on immunoactivity and improvement in exercise per­formance is unclear. Exercise alters many aspects of immune function, both positively and neg a­tively)1111 Studies have indicated that systematic physical activity can cause changes related to in­creased efficiency of immunoregulation.[l12-114] The increased activity of natural killer (NK) cells was demonstrated in highly trained racing cyclists, which resulted in better resistance to infectious dis­eases)115] In marathon runners, the activity of NK cells increased and susceptibility to infections de­creased during 6 to 15 weeks of moderate train­ing. [1161 Other results have indicated the opposite, showing that a pronounced drop in immunoactivity may follow exhaustive training and competi­tion.l 1l21 Whereas moderate training reduces risk of upper respiratory tract infections, heavy exer­cise increases the athlete's risk because of negative changes in immune function)11 7] Reduced cellular immune reactivity was detected in female athletes with menstrual disorders. [I 18]

An impairment of the immune system was found in athletes from the preparatory period to the end of the competition season.l1l9] The most pro­nounced changes (impaired differentiation of im­munocompetent cells and decreased humoral im­munity) were observed in swimmers exhibiting electrocardiographic signs of overexertion of the myocardium during exercise)119] A study of 130 sportsmen (rowers, wrestlers, skiers and swim­mers) showed a decrease in the indices of secretory immunity during preparation for international competition, down to the almost complete disap­pearance of several classes of immunoglobins and normal antibodies. This was associated with a low antiviral immune defence and the inefficiency of anti-influenza vaccination. [I 20] A more extensive study (350 participants) distinguished 4 stages of the immune system (activation, compensation, de-

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compensation and recovery) during a year of train­ing in highly qualified sportsmen.l 121]

While decreased morbidity has been found in trained people in population studies,[122-124] in­creasing susceptibility to infections is a frequent phenomenon among outstanding athletes, and oc­curs particularly during the peak performance pe­riod.[125,126] This increased susceptibility is related to suppression of the immune activity. However, the suppression is followed by recovery of normal immune activity in sportsmen during the rest from training.l121 ] This is comparable to changes in the immune system during and after acute exercise. The following phases were discriminated in the ac­tivity of NK cells: a short term phase of increased cytotoxic activity; a decrease in cytotoxic activity I to 2h after exercise; and then recovery to normal levels within 20 to 24h after exercise. [I 16,127]

Currently, there is some evidence suggesting that physical activity may protect against some forms of neoplasm.[I11,1I2,128-131] Moderate run-ning training has been found to suppress the tu­mour growth and its metastatic spread within the body.l132,133] Influences of training on the immune system may be attributed to this effect of physical activity. Here, an essential factor can be the exer­cise-induced increase in the number and activity of NK cells.l 134] It has been assumed that exercise is a complex stimulus for macrophages that, at least in part, triggers their cytotoxic activity against tu­mour cells.l 135]

Physical activity increases both the production of mutagenic free radicals and the activity of those enzymes that break down mutagens[136] which may be a benefit of a more active lifestyle.l131]

3. Training and Adaptivity

It is assumed that training effects occur because of adaptive protein synthesis resulting from the in­fluence of specific inductors on the cellular genetic apparatus and protein synthesis mechanism.[I37-139] Consequently, the increased number of protein molecules synthesised makes it possible to substi­tute physiologically exhausted protein structures with new ones, to increase the size of the most ac-

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Viru & Smirnova

tive cellular structures in the organs most respon­sible during training, and to raise the number of molecules of enzymes catalysing the most active metabolic pathways during exercise. However, the question of whether the systematical and frequent unidirectional stimulation of protein synthesis leads to the development or to the exhaustion of the mechanism of adaptive protein synthesis remains open. In other words, the problem is whether train­ing reduces or increases the possibilities for protein synthesis needed simultaneously for other aims and adaptation to exercise.

Trained rats were found to be more resistant to the influences of hypoxia, irradiation, high or low environmental temperatures, and the action of var­ious toxins or poisons (fig. 4). However, with a forced training regimen, the resistance of experi­mental animals was lower than in sedentary con­trols. [140]

The above discussion (section 2.9) on the sup­pression of immune activity and the increase in sus­ceptibility to infections in athletes reaching the top levels of performance, suggest that sportsmen ex­haust their adaptivity in order to achieve a high performance level. However, these are transitory changes. After the competition season is over, a rest period is necessary for the recovery of adaptivity. Otherwise, it would be impossible for athletes to maintain a training condition during preparation for the following season.

The morbidity in former sportsmen is deter­mined not only by sports training but also by the lifestyle after the end of training. A substantial in­fluence may be exerted by changes in the regimen of physical activity. Detraining means not only a decrease in the performance capacity and physical abilities, but also adaptive changes in the individ­ual. For example, in comparison with active sports­men, former sportsmen revealed an increased basal rate of lipolysis and a reduced sensitivity to the lipogenic action of insulin.l 141 ] These findings sug­gest that, in the detraining period, changes occur in lipid metabolism which avoid an increase of adipose tissue after a decrease in energy expenditure.[141]

Sports Med. 19 (2) 1995

Health Promotion and Exercise Training

100

80

~ ~ 60

'0

~ 40 ~ :::l

CIJ

20

0

0

: .... " :-:' :. :. ',I."

-- Daily swimming for 1 h

-- Daily swimming for 3.5h •••• . Daily swimming for 4.5h

- - - _. Daily clambering on a vertical bar for 1 h Sedentary rats

~ ~.;.~::.:.:.:.:.:.:.:.:~~~.~ ........ ........ .... ~ ................. .

5 10

......... _-_ .. ---------

15 20 25 30 Days of irradiation

Fig. 4. Survival of trained and sedentary rats during a period of daily irradiation. The trained rats performed daily exercises dur­ing 2 months before the first irradiation.

4. Antisclerotic Effect of Training

Results from a number of studies indicate that exercise causes a change in the blood lipoprotein content[142-145) that is considered to be essential for slowing down the development of atherosclerosis and avoiding ischaemic coronary disease. These changes include decreases in total and low density lipoprotein (LDL) cholesterol levels, and increase in high density lipoprotein (HDL) cholesterol, mainly HDL2 cholesterol. Also, increased levels of apolipoprotein-AI and decreased apolipoprotein­B[146,147) were found. Lipoprotein lipase increased in muscle and adipose tissue[148,149) in trained per­sons, and lipase decreased in the liver[87) of trained animals. A training-induced increase in cholesterol degradation was found in the liver.l 150,15l) Physical activity stimulates cholesterol degradation in the adrenals as well.[I52) These changes are related to

the protective effect of physical activity against heart disease. [153-157) The changes in blood lipopro­

tein content may have significance also in training­induced alterations in blood pressure.[158)

During prolonged exercise, calcitonin activity increases and the calcium level concomitantly de­creases in the blood plasma,[I59) Further studies are

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131

needed to clarify whether these changes also influ­ence the anti sclerotic effect of training. Intensive physical training can result in up to 45% higher bone mineral density than the average of untrained people aged between 40 and 60 years.l l60)

A mechanical anti sclerotic effect of exercising has also been suggested. This is related to protec­tion of tissues from sclerotic changes by their ac­tivity. The protection of muscle, tendon and liga­ment tissues from sclerotic changes is revealed by the level of flexibility in physically active elderly men and women. When exercise involve alter­ations in body position or with movement, rapid changes in the vascular tone of peripheral vessels are necessary in order to ensure the normal blood supply to various parts of the body. Accordingly, gymnastic exercises cause gymnastics of blood vessels, thereby mechanical anti sclerotic influence may be assumed.

5. Effects of Different Types of Training

It is widely argued that the effects of training on muscle fibre structure and the metabolism depend strongly on the type of exercise.[27,48,49) Sirnilarily, the type of exercise (endurance, sp~int or high­resistance training) will specifically affect the cardiovascular system,[56-60,68,161,162] Y02max[9l)

or blood lipoprotein content.l 142,163) Generally, the most positive changes in aerobic working capacity, cardiovascular functions and blood lipoprotein content are induced by endurance exercise. Only more dynamic forms of resistance exercises (e.g. circuit weight-training) which involve light to moderate resistance and are performed with many repetitions and short rest intervals may improve insulin sensitivity, lipoprotein content and blood pressure and raise HDLcholesterol.l l641 A decrease in LDL cholesterol levels and an increase in HDL cholesterol levels were also found as a result of isokinetic exercises. [165)

Endurance exercise is considered to be the most important and widely recommended form of exer­cise for health improvement.[166-168) Gymnastic ex­ercises are considered indispensable for a mechan­ical anti sclerotic effect. It is possible to suggest

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132

that the foundation for the supporting/stimulating action of muscular activity on brain function and

mental activities is related to proprioceptive charges from contracting muscles to the brain stem reticular formation (the arousal effect). Accord­ingly, the arousal effect of exercise depends on the force of applied muscle contractions. In gymnastic

exercise this is stronger than in endurance exer­cises. Strong but short term influence is exerted by

sprint and weight exercises. Aerobic exercise reduces state and trait anxiety

and decreases various psychological stress indi­cesJ31.l69,170] Training with both aerobic and non­

aerobic forms of exercises is also associated with reduced depression.[171]

Strength and gymnastic exercises help to avoid muscular weakness (and thereby loss of support to the joints) in the elderly. In older individuals, effi­cient muscular function brings independence in daily activities and eventually improves an individ­ual's quality of life.l 172]

Aerobic dance or aerobic rhythmic gymnastics is an attempt to combine the positive effects of endurance and gymnastic exercises. Indeed, the increase in V02max[173,174] and HDL cholesterol lev­els[173, 175] are evidence of the improvement of aer­obic working capacity together with the metabolic antisc1erotic effect. The association of these changes with maintaining or improving flexibility demon­strates the benefits of these forms of exercise.

Viru & Smirnova

Results of longitudinal studies have emphasised the significance of exercise intensity as well as the nonstop nature of the aerobic dance component of rhythmic gymnastics. Improvement in V02max was obtained when exercise intensity caused a heart rate of 140 to 175 beats/min during training ses­sions.l 175] However, when exercise intensity was higher (a mean heart rate of 180 beats/min or higher) with anaerobic exercise, no increase was found in V02max . Increased levels of HDL choles­terol were observed when heart rate was 140 to 150 beats/min during a training session.[175] When the gymnastic exercises were the same (as in the case of nonstop, rhythmic gymnastics) but there were rest intervals between exercises, improvement was not found either V02max or in the blood lipoprotein content.

A 8-week period of continuous running in­creased V02max when the heart rate was 165 to 175 beats/min during exercise. The increase in HDL cholesterol levels appeared when HR was 140 to 150 beats/min.[176]

6. Conclusions

Exercise training, depending on the exercises used (table II), induces changes in individual, in­creasing health and well being. The improved ad­aptivity of the individual is the background for health promotion by exercise training with benefits dependant to an extent on the changes in the im­mune system.

Table II. Influence of continuous aerobic exercise and gymnastics on the individual capacities determining adaptivity

Influence

Improvement of nervous regulation and functions of the central nervous system

Increased capacity of endocrine systems and altered sensitivity to hormones

Increased energy potential of the organism

Improved capacity of oxygen transport system

Improved oxidation processes

Increased metabolic and functional economy

Increased functional stability

Increased number of Na,K-pumps

Influence on immunoactivity

Metabolic anti sclerotic effect

Mechanic antiscierotic effect

© Adis International Limited. All rights reserved.

Aerobic endurance Gymnastics' exercises

Modest Pronounced

Pronounced Negligible

Strong No

Strong Negligible

Strong No

Pronounced Negligible

Pronounced No

Pronounced Questionable

Pronounced Questionable Pronounced No

Negligible Strong

Sports Med. 19 (2) 1995

Health Promotion and Exercise Training

In athletes, training for top performance in­creases a risk of injuries)177] At the same time, positive health changes are most pronounced in athletes. When individuals exercise for health im­provement there is a limited risk of injuries. How­ever, this minimal risk for health impairment is many times lower than that in sedentary persons with hypokinesia.

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Correspondence and reprints: Dr Atko Viru, University of Tartu, 18 Ylikooli Street, Tartu EE-2400, Estonia.

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