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Biomedical subjects

B Essén

Publications and source records attributed to B Essén.

9 recordsLinked to original sources
PubMed1978

Regulation of glycolysis in intermittent exercise in man.

1. Seven healthy male volunteers performed intermittent exercise (15 sec work--15 sec rest) at a high work load for 60 min and six subjects performed continuous exercise at an equally high load to exhaustion, which occurred after 4--6 min. 2. Muscle biopsies were obtained from the lateral portion of the quadriceps muscle before intermittent exercise and after the end of a work period and the end of the subsequent rest period at 5, 15, 30 and 60 min of exercise, as well as before, immediately after and about 15, 30, 60 and 180 sec after continuous exercise. 3. The reduction in glycogen content was smaller and glucose-6-phosphate, glycerol-1-phosphate, lactate and malate contents were lower after both work and rest periods in intermittent compared with continuous exercise, indicating a lower rate of glycolysis. 4. ATP and CP levels had decreased at the end of work periods in intermittent exercise but increased to slightly below basal in the subsequent rest periods. A still larger decrease in ATP and CP levels was found after continuous exercise to exhaustion and a progressive increase occurred over the 3 min of recovery. 5. In each rest period during intermittent exercise citrate levels increased to reach above basal. They increased also in the recovery phase after continuous exercise, although more slowly. 6. The findings support the assumption that ATP, CP and citrate act as regulatory factors of glycolysis in human muscle by retarding certain rate limiting steps. The increase in G-6-P/F-1-6-P2 ratio in rest periods of intermittent intense exercise and in the recovery phase of continuous intense exercise suggests that glycolysis is retarded at the phosphofructokinase reaction. 7. The factors mentioned may therefore contribute to the relative increase in lipid utilization during intense intermittent compared to continuous exercise.

Adenosine Triphosphate↗
PubMed1977

Intramuscular substrate utilization during prolonged exercise.

Large stores of intramuscular substrates are found in the different fiber types of human skeletal muscle, and with prolonged exercise both glycogen and triglyceride stores are utilized. The contribution from intramuscular glycogen stores is greatest at higher work intensities while triglyceride stores are utilized at moderate intensities. In man all fiber types have a similar glycogen content whereas the highest lipid content is found in the more oxidative fibers. The muscle metabolism is well adapted to the supply of substrate as well as to the demand for energy. Among several regulatory mechanisms, changes in citrate concentration seems to be an important factor in the interplay between carbohydrate and lipid metabolism.

Diet↗
PubMed1977

Utilization of blood-borne and intramuscular substrates during continuous and intermittent exercise in man.

1. Substrate utilization in the legs during bicycle exercise was studied in five subjects when performing intermittent intense exercise (15 sec work--15 sec rest) as well as continuous exercise during 60 min, with an almost identical average power output and oxygen uptake in both situations. 2. Muscle biopsies were obtained from vastus lateralis at rest, during, and after exercise in order to determine intramuscular lipid and carbohydrate utilization. The contribution from blood-borne substrates to total oxidative metabolism was determined by arterial-femoral venous (a-fv) differences for oxygen, FFA, glucose, and lactate and leg blood flow. 3. Intermittent and continuous exercise revealed a similar glycogen depletion and the intramuscular lactate accumulation was rather small. A similar uptake of blood-borne substrate (FFA, glucose) was found in both situations whereas a release of lactate only was observed in intermittent exercise. 4. ATP and CP levels oscillated between work and rest periods in intermittent exercise but were not resynthesized to resting levels at the end of the rest periods. The mainly aerobic energy release during each work period in intermittent exercise is partly caused by myoglobin functioning as an oxygen store; this factor was calculated to be more important than ATP and CP or lactate level oscillations. 5. The metabolic response to intermittent exercise was found to be similar to that found in continuous exercise with approximately the same average power output and oxygen uptake. This indicates that some factor in the intermediary metabolism, for instance citrate, functions as a regulator retarding glycolysis and favouring lipid utilization and an aerobic energy release in intermittent exercise.

Adenosine Triphosphate↗
PubMed1976

Glycogen phosphorylase activity in biopsy samples and single muscle fibres of musculus quadriceps femoris of man at rest.

Glycogen phosphorylase activity in biopsy samples of the quadriceps muscle of man taken at rest was measured in the direction of glycogen breakdown. The conditions of assay used were pH 6.8 and 35 degrees C. Mean phosphorylase activity per kg fresh muscle in 8 male volunteers was: phosphorylase a - 259 U, and total phosphorylase - 627 U, where 1 U is the production of 1 mumol glucose-1-phosphate/s under the conditions of assay. The mean value of total activity, transposed to the in vivo condition, is sufficient to support a maximum rate of glycogen degradation calculated as glucosyl units utilized per kg fresh muscle, of 627 mumol/s. This is approximately the rate at which glycolysis occurs during a maximum voluntary isometric contraction. The mean ratio of phosphorylase a activity to total activity at rest was 0.40. Estimates of the mean total phosphorylase activity in type I ('slow') muscle fibres isolated from the quadriceps of 9 volunteers ranged from 210-385 U/kg fresh muscle, and in type II ('fast') muscle fibres from 493-934 U/kg fresh muscle. The average ratio of activity in type II fibres compared with that in type I fibres was 2.5.

Adolescent↗
PubMed1976

The nature of the training response; peripheral and central adaptations of one-legged exercise.

13 male subjects were studied and placed in 3 groups. Each group exercised one leg with sprint (S), or endurance (E) training and the other leg oppositely or not at all (NT). Oxygen uptake (Vo2), heart rate and blood lactate were measured for each leg separately and for both legs together during submaximal and maximal bicycle work before and after 4 weeks of training with 4-5 sessions per week. Muscle samples were obtained from the quadriceps muscle and assayed for succinate dehydrogenase (SDH) activity, and stained for myofibrillar ATPase. In addition, eight of the subjects performed after the training two-legged exercise at 70% Vo2 max for one hour. The measurements included muscle glycogen and lactate concentrations of the two legs as well as the blood flow and the a-v difference for O2, glucose and lactate.

Adaptation, Physiological↗
PubMed1975

Metabolic characteristics of fibre types in human skeletal muscle.

Muscle biopsy samples were obtained from healthy subjects in order to evaluate quantitative differences in single fibres of substrate (glycogen and triglyceride) and ion concentrations (Na+ and K+) as well as enzyme activity levels (succinate-dehydrogenase, SDH; phosphofructokinase, PFK; 3-hydroxyacyl-CoA-dehydrogenase, HAD; myosin ATPase) between human skeletal muscle fibre types. After freeze drying of the muscle specimen fragments of single fibres were dissected out and stained for myofibrillar-ATPase with preincubations at pH's of 10.3, 4.6, 4.35. Type I ("red") and II A,B, and C ("white") fibres could then be identified. Glycogen content was the same in different fibres, whereas triglyceride content was highest in Type I fibres (2-3 X Type II). No significant differences were observed for Na+ and K+ between fibre types. The activity for the enzymes studied were quite different in the fibre types (SDH and HAD, Type I is approximately 1.5 X Type II; PFK Type I is approximately 0.5 X Type II, Myosin ATPase Type I is approxiamtely 0.4 X Type II). The subgroups of Type II fibres were distinguished by differences in both SDH and PFK activities (SDH, Type II C is greater than A is greater than B; PFK, Type II B is greater than A is approximately C). It is concluded that contractile and metabolic characteristics of human skeletal fibres are very similar to many other species. One difference, however, appears to be than no Type II fibres have an oxidative potential higher than Type I fibres.

Adenosine Triphosphatases↗