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Biomedical subjects

B Saltin

Publications and source records attributed to B Saltin.

At least 199 records · Page 11Linked to original sources
PubMed1982

Significance of skeletal muscle oxidative enzyme enhancement with endurance training.

A theoretical model is proposed to explain how the increase in mitochondrial protein concentration, and therefore of the oxidative enzymes, that occurs with endurance training could operate to alter the choice of substrate during submaximal exercise in a manner such that the oxidation of fatty acids increases, glycogen depletion and lactate production are reduced, and work capacity is enhanced. The model is based on the control of enzyme activities both by enzyme and substrate concentrations. The effect of altering enzyme concentration on reaction velocities is presented on the basis of standard Henri-Michaelis-Menten kinetics. It is shown that the reaction velocity at a given substrate concentration is a function of total enzyme concentration. With an increase in total enzyme concentration there is a parallel increase in reaction velocity at the same substrate level. This would have its greatest impact at substrate levels below the Km of the enzyme. It would have an effect of enhancing fatty acid flux through the oxidative pathways while inhibiting the Embden-Meyerhof pathway. The model, as proposed, is consistent with known alterations in metabolism as they occur in man during submaximal exercise following endurance training.

Adenosine Diphosphate↗
PubMed1982

Morphology and enzymatic capacity in arm and leg muscles in 78-81 year old men and women.

Twelve men and twelve women 78-81 years of age were studied with muscle biopsies from the right vastus lateralis and biceps brachii and with measurements of isometric and isokinetic strength for knee-extention and isometric strength for elbow-flexion. Bicycle ergometry with determination of heart rate and oxygen uptake at submaximal (50 W) and "maximal" work loads was also performed. Body cell mass was estimated from measurements of total body potassium. Muscle fibre composition with respect to slow twitch (ST = type I) and fast twitch (FT = type II) fibres did not differ between the sexes and the younger subjects drawn from population studies. The mean fibre areas averaged in vastus lateralis 4.7 and 3.3 micrometers 2 X 10(3) in men and women, respectively. This is less than 10 up to 30% of values found in sedentary younger subjects. The decline dominated in FT fibres, especially FTb fibres. In contrast biceps brachii did not show any matched fibre size reduction. The number of atrophic fibres was high and so was the frequency of "enclosed" fibres and areas with type grouping (ST fibres), indicating denervation--reinnervation. Such abnormalities are rarely seen in younger ages. Correlation analysis showed that only a minor part of the reduction in body cell mass with age could be explained by a reduction in fibre areas and that a reduction with age of the number of muscle fibres of both fibre types must be assumed. Positive correlations were observed between muscle strength and mean fibre and FT fibre areas. Comparing the present findings of skeletal muscle morphology to those in younger age groups, it is apparent that during the 8th decade of life major changes do occur. The measurements of aerobic and anaerobic enzymatic activities and of muscle capillary supply showed that levels comparable to those of younger age groups are maintained. Thus, quantitative rather than qualitative changes may explain the reduction in work performance with age.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1982

Extra- and intracellular water spaces in muscles of man at rest and with dynamic exercise.

A method was established to analyze the extracellular water space (H2Oe) in small muscle tissue samples as [3H]inulin distribution space. After initial experiments on rats, the method was applied on 13 men and 6 women. Muscles with different fiber compositions (soleus, S; vastus lateralis, (VL; gastrocnemius, G; triceps brachii, TB) were studied at rest. The total water content was the same for all muscles, 320 (313-330) ml/100 g dry wt. However, differences were demonstrated for H2Oe, with 26-34 ml/100 g dry wt in VL and 38-54 ml/100 g dry wt in S, (P less than 0.05); the values for G and TB were in between those for VL and S. The differences in H2Oe were not related to the fiber composition of the muscles. During 3 x 3 min of intense bicycle exercise demanding about 120% VO2 max (6 men), total water content increased in VL from 313 to 359 ml/100 g dry wt and H2Oe increased from 34 to 60 ml/100 g dry wt (P less than 0.05), In TB, which is relatively inactive during bicycle exercise, no such changes occurred. The calculated intracellular lactate concentration increased in VL from 5.7 to 30.6 mmol/l H2Oi. The extracellular lactate concentration amounted to 13.6 mmol/l H2Oe at the end of exercise. The concentration gradient for lactate of 2 from intra- to extracellular space favored a flux of water to the intracellular space. The relative large increase in H2Oe may then be caused by a hydrostatic rather than an osmotic factor.U

Adult↗
PubMed1981

Muscle fibre recruitment and metabolism in prolonged exhaustive dynamic exercise.

The rather constant amount of glycogen found in all fibre types in human skeletal muscle provides an opportunity to study the pattern of glycogen depletion with exercise, which should give an indication of which fibres are activated to generate the force. In very light dynamic contractions repeated for hours there is a primary reliance on slow twitch (ST) fibres with no or very minor involvement of fast twitch (FT) fibres. At heavier work loads (greater than 50% Vo2max) ST fibres are depleted first but FT fibres begin to become depleted. Exhaustion at these work levels coincides with muscle fibres of all types being depleted of glycogen. The crucial role of muscle glycogen in both the metabolic response to exercise and work performance is apparent. It is more difficult to explain why extramuscular substrates (plasma free fatty acids) cannot be utilized at a high enough rate to accommodate the energy turnover needed in more intense dynamic exercise. A limitation on the uptake of free fatty acids by the muscle cell rather than its transport to the cell or oxidation within it appears to be the critical factor.

Fatty Acids, Nonesterified↗
PubMed1981

Daily physical activity, work capacity and glucose tolerance in lean and obese normoglycaemic middle-aged men.

Daily physical activity, work capacity, relative body weight and glucose tolerance were studied in 115 normoglycaemic 48 year old men selected from a health screening programme. In contrast to the reported physical activity at work, leisure time activity was significantly related to maximal oxygen uptake (p less than 0.05), glucose (p less than 0.05) and insulin values (p less than 0.05) during OGTT, but not to relative body weight. The number of men with impaired glucose tolerance (glucose at 120 min greater than 6.9 mmol) was significantly higher among those who were physically inactive during their leisure time. The insulin glucose ratio at 0 and 120 min during the OGTT was significantly higher in the obese unfit as compared to the obese fit subjects thus suggesting an influence of moderate leisure time physical activity on glucose tolerance.

Blood Glucose↗
PubMed1981

Skeletal muscle fibre types and sizes in anorexia nervosa patients.

Fibre type composition and fibre areas in skeletal muscle of anorexia patients were studied on biopsies from the m. quadriceps femoris in five male and five females, whose body weight was 2-3.5 SDs less than expected from the normal weight/height relationship. In two of the males, the muscles studies were also made after rehabilitation. A higher than normal percentage of type I fibres was found in the patients (male, 62 +/- 12, female, 69 +/- 7) whereas the percentage of type IIA fibres did not differ from normal individuals (male, 38 +/- 12, female 24 +/- 15). Of note was the observation that no type IIB fibres were found and some patients had an increased occurrence of the normally rare type IIC fibres. All muscle fibres were markedly atrophied with the mean cross-sectional area of type IIA fibres being significantly smaller (male, 26.1 +/- 3.7, female, 21 +/- 10.3, micrometers2 x 10(-2)) than the mean area of type I fibres (male, 34.1 +/- 4.7, female, 35.3 +/- 7.4), micrometers2 x 10(-2)). In the two males studied after rehabilitation (body weight increased 12 and 19 kg), mean fibre area increased by 40%. Our results suggested that a predominant part of the reduction in body weight and lean body mass, seen in adolescent children suffering from anorexia nervosa, could be accounted for by a loss of skeletal muscle mass. In the six subjects where marker enzymes of glycolytic (TPDH, LDH) and mitochondrial pathways (CS, HAD) were assayed, the former were 50% and the latter 10-20% below sedentary controls. Maximal oxygen uptake was only 35 (males) and 29 (females) ml/kg min-1; this contrasted with the physical activity pattern of these patients, yet was in line with their small muscle mass with its low oxidative potential.

Adolescent↗
PubMed1981

Blood pressure and heart rate response to static exercise in relation to electromyographic activity and force development.

5 healthy men performed static knee extension (90 degree knee angle) with one leg for 5 min. In one series of experiments the force was held constant at 20% of the isometric maximal voluntary contraction. In the other the initial force development was also 20%, but the smoothed, rectified electromyographic activity, (SREMG) recorded after 5 s of contraction was kept constant. Heart rate (HR), arterial mean blood pressure (MBP) (measured 20 cm proximally to the elbow in a. brachialis), EMG (surface electrodes) from the lateral portion of m. quadriceps femoris, and force were continuously recorded. HR and MBP increased approximately 40% in the force-constant experiments and approximately 20% in the SREMG-constant experiments. The greatest increase occurred during the first two minutes of contraction. In the force-constant experiments SREMG doubled, with the most marked increases occurring during the very early and late parts of the contraction. SREMG correlated with both HR (r = 0.85) and MBP (r = 0.98). In the SREMG-constant experiments force declined quickly during the first minute and remained at about 12% MVC thereafter. The observed cardiovascular responses to static contraction can best be explained as the result of the combined action of central and peripheral drives, the central drive being related to the central activity for the recruitment of motor units, and the peripheral drive being mediated through chemoreceptors in the exercising muscles.

Adult↗
PubMed1981

Body weight, skeletal muscle morphology, and enzyme activities in relation to fasting serum insulin concentration and glucose tolerance in 48-year-old men.

Tissue samples were taken from the gastrocnemius muscle of 26 randomly selected, glucose-tolerant, 48-yr-old men. Hexokinase, phosphorylase, lactate dehydrogenase (LDH), succinate dehydrogenase, and lipoprotein lipase activity (LPLA), as well as the area per fiber type and capillary density, were determined. Mean fiber area correlated positively with relative body weight (r equals 0.53, P less than 0.01), but capillary density did not. The result is that, in cases of high body weight, each capillary supplies a larger muscle fiber area. Serum insulin concentration in the fasting state correlated positively with body weight (r equals 0.77, P less than 0.001) and with mean fiber area per capillary (r equals 0.87; P less than 0.001). Only during the latter part of an oral glucose tolerance test (OGTT) did blood glucose concentrations correlate with relative body weight and mean fiber area per capillary (r equals 0.42, r equals 0.51, P less than 0.05). A stepwise multiple regression analysis showed that the different muscle morphology measurements could account for 3/4 of the variation in the fasting serum insulin concentration, the fasting insulin/glucose ratio, and the blood glucose concentration at 120 min in the OGTT. Of the intracellular enzymes, only LDH (r equals -0.71, P less than 0.001) correlated with the mean fiber area per capillary. LPLA correlated with capillary density (r equals 0.66, P less than 0.001), and, long with the muscle morphology measurements, could account for 3/4 of the variation in serum triglyceride concentrations. The results show that a large mean muscle fiber area/capillary ratio indicates a morphologic imbalance, which is related to both glucose tolerance and various degrees of insulin sensitivity.

Blood Glucose↗
PubMed1981

Response of arterial blood pressure to static exercise in relation to muscle mass, force development, and electromyographic activity.

In young men, the arterial blood pressure response during static exercise at 40% of maximal voluntary contraction (MVC) and the response after the contraction with a cuff inflated both were increased when a greater mass of skeletal muscle was involved. Also in men with a previously injured leg, the arterial systolic pressure and the smoothed, rectified electromyographic activity (EMG) were greater during static contraction of the large, strong leg than during static contraction of the small, weak leg at the same percent MVC. However, the arterial systolic pressure and the EMG were almost the same during contraction of either leg when the same force was developed. Finally, in young men, either the force developed was held constant at 20% MVC or the level of the initial EMG at 20% MVC was held constant for 5 minutes. During the force-constant experiments, the EMG doubled and correlated with the 40% increase in mean arterial pressure (r = 0.89). In the EMG-constant experiments, force declined to about 12% MVC with an increase of only 20% in mean arterial pressure. These studies of the response of arterial blood pressure to static muscular contractions can best be explained by both central and peripheral control mechanisms. The central control mechanism "central command" is probably related to the central activity for recruitment of motor units and the peripheral control mechanism is probably mediated by muscle afferents which are excited by metabolic changes in the contracting skeletal muscle.

Arteries↗
PubMed1980

Two years' follow-up of asthmatic boys participating in a physical activity programme.

Eleven boys with bronchial asthma, mean age 11.2 years, particpated in a 20-month long physical activity programme. The training was performed in an ordinary indoor gymnasium for one hour twice a week. No drugs were given prior to the training sessions. Cardiorespiratory function and dimensions and maximal aerobic capacity were determined before, during and after the training period. The respiratory and circulatory dimensions increased as expected during and after the training period. The respiratory and circulatory dimensions increased as expected during the observation period and after correction for the influence of growth no changes were seen in the variables studied. Nor did the training group differ significantly in any respect from a group of nine asthmatic boys not trained. There was only a slight but not significant increase in the maximal exygen uptake and the ventilatory coefficient in the training group as compared to the non training group. After a one-week winter-camp with high exercise intensity there was a rise in the total ventilation, the ventilatory coefficient and the maximal work performed but the maximal oxygen uptake was not affected. All boys showed a very good ability to participate in the physical activity programme at approximately the same level as the physical education given at school.

Adolescent↗
PubMed1980

The role of muscle mass in the cardiovascular response to static contractions.

1. Eleven men performed static contractions with the fingers (digits II and III), forearm (handgrip) and the knee extensors (knee angle 90 degrees ) at 40% maximal voluntary contraction (MVC) for 2 min. In seven of the subjects handgrip and knee extension were combined, both contractions held at 40% MVC. At the end of the contraction, cuffs were inflated to 250 mmHg for 3 min around the extremity which had been contracting. Continuous measurements were performed of force, heart rate and intra-arterial blood pressure (a. brachialis; 20 cm proximally), before and during contraction as well as during the recovery with and without cuffs inflated.2. Heart rate and blood pressure increased momentarily with the onset of a contraction whereafter a gradual further increase took place. This pattern of response was similar for all muscle groups studied. The increases during the contractions were in the order: fingers, forearm, knee extensors and combined forearm-knee extensors, with the difference between each muscle group contraction being significant.3. In the recovery period from a contraction with the cuff(s) inflated, heart rate returned to control level. Blood pressure also dropped, but remained elevated above pre-contraction level until the cuff(s) was released.4. The present data during contraction are at variance with earlier observations showing that the cardiovascular response to a static contraction is proportional to the% MVC regardless of the muscle mass involved in the contraction. Our findings are in line with the traditional concept of central and peripheral nervous inputs playing a role in the cardiovascular adjustments to exercise, with both the central and the peripheral factors being related to the mass of the muscles engaged in the exercise.

Adult↗
PubMed1980

Functional adaptations to physical activity and inactivity.

Rather than focusing on the performance criteria accompanying adaptation to physical activity, this paper emphasizes the magnitudes of alteration in the function of the circulatory, respiratory, and metabolic systems with adaptation. It is our opinion that the limitation of maximal aerobic power resides in the transport of oxygen to working muscle by the circulation. Increases in maximal aerobic power that accompany physical conditioning are attributed primarily to increased maximal muscle blood flow and muscle capillary density. The increase in the oxidative potential of skeletal muscle after training is presented as the mechanism by which capacity for submaximal work is augmented.

Adaptation, Physiological↗
PubMed1980

Solvent-induced occupational myopathy.

Serum creatine kinase (CK) was significantly higher (p < 0.02) in 69 patients examined for occupational intoxication from solvents than in 96 non-exposed control subjects. A needle muscle biopsy was performed in nine patients randomly selected from the patients with elevated levels of serum CK. A higher activity of muscle lactate dehydrogenase (LDH) (p < 0.05) and a lower activity of muscle succinate dehydrogenase (SDH) (p < 0.01) was found in the patients when compared with 16 non-exposed control subjects. No histological abnormalities were observed using light microscopy. The elevated serum CK represented the serum CKM isoenzyme fraction. It is concluded that skeletal muscles should be added to the list of organs involved in intoxication from solvents and that serum CK should be analyzed in solvent-intoxicated patients as an indicator of myopathy.

Adolescent↗
PubMed1979

Myopathy in bone loss of ageing: improvement by treatment with 1 alpha-hydroxycholecalciferol and calcium.

1. Eleven patients with the bone loss of ageing were treated with the vitamin D analogue 1 alpha-hydroxycholecalciferol and calcium for 3--6 months. 2. Muscle biopsies were taken from the vastus lateralis before and after the treatment and the activity of several enzymes was measured. Succinate dehydrogenase and total phosphorylase activities, which are a measure of the oxidative capacity, were low and increased significantly with the treatment. The lactate dehydrogenase activity, which can be taken as a measure of the anaerobic metabolism, was normal and did not change with treatment. The phosphagen stores, ATP and creatine phosphate were low and increased to normal with treatment. 3. Histochemical classification of the fibre composition revealed that the treatment induced an increase in the relative number of fast-twitch a (FTa or type II A) fibres accompanied by a reduction of the fast-twitch b (FTb or type II B) fibres. The cross-sectional area of the FTa fibres also increased with the treatment. 4. The present findings indicate that treatment with the active vitamin D analogue, 1 alpha-hydroxycholecalciferol, and calcium improves the myopathy associated with the bone loss of ageing.

Aged↗