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  • 11
    Electronic Resource
    Electronic Resource
    Glycolytic intermediates in human muscle after isometric contraction (1981)
    Springer
    Pflügers Archiv 389 (1981), S. 277-282 
    Details
    ISSN: 1432-2013
    Keywords: Lactate ; Glycogenolysis ; Muscle contraction ; Glycogen ; Human muscle ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Isometric contraction of the quadriceps muscle sustained to fatigue with a force of 66% of the maximum voluntary contraction force resulted in a mean glycogen utilization of 80.4 (S.D. 58.4) mmol glucosyl units/kg dry muscle (d.m.) and an accumulation of glycolytic intermediates and glucose corresponding to 82.9 (S.D. 17.5) mmol glucosyl units/kg d.m. Accumulation of hexose phosphates (principally glucose 6-phosphate) accounted for 35.4% (S.D. 4.1) of the total increase and lactate for 59.3% (S.D. 2.8). During a 4 min recovery period glucose 6-[hosphate content showed a linear decrease with a half time of 2.0 min and lactate decreased exponentially with a half time of 2.5 min. The rate of lactate disappearance from the muscle was approximately 4 times as fast as that observed previously after maximal bicycle exercise. This was probably due to a lower lactate concentration in blood after isometric contraction resulting in a larger muscle-blood gradient for lactate. Muscle content of free glucose was increased after contraction and increased further during recovery. It is concluded that the glucose increase is confined to the intracellular pool and is an effect of hexokinase inhibition by accumulated glucose 6-phosphate. Occlusion, of the local circulation after the contraction inhibited the recovery processes for lactate and glucose 6-phosphate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584790
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  • 12
    Electronic Resource
    Electronic Resource
    Lactate content and pH in muscle samples obtained after dynamic exercise (1976)
    Springer
    Pflügers Archiv 367 (1976), S. 143-149 
    Details
    ISSN: 1432-2013
    Keywords: Hydrogen ion ; Lactate ; Pyruvate ; Exertion ; Muscle ; Blood ; Man ; Recovery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Analyzes were made on muscle samples taken from the lateral part of the m. quadriceps femoris of man (lactate, pyruvate, and pH) on venous blood (lactate, pyruvate) and on capillary blood (pH). Samples were taken at rest, immediately after termination of dynamic exercise and during 20 min recovery from exhaustive dynamic exercise. Muscle pH decreased from 7.08 at rest to 6.60 at exhaustion. Decrease in muscle pH was linearly related to muscle content of lactate + pyruvate. The relationship was slightly different from what has been obtained after isometric exercise and this difference was ascribed to acid-base exchange with the blood during dynamic exercise. Lactate content was highly elevated in muscle after exercise and the concentration was 2–3 times higher than in blood. Pyruvate content was, however, only slightly higher than that at rest. During recovery lactate content of muscle decreased exponentially with respect to time, whereas pyruvate content increased. The half-time of lactate decrease was 9.5 min. From the lactate dehydrogenase equilibrium relative values on NADH/NAD ratio could be calculated. It was found that NADH/NAD was highly increased after exercise and that it had not returned to the basal value after 20 min recovery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585150
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  • 13
    Electronic Resource
    Electronic Resource
    Evaluation of methods for electrical stimulation of human skeletal muscle in situ (1983)
    Springer
    Pflügers Archiv 398 (1983), S. 139-141 
    Details
    ISSN: 1432-2013
    Keywords: Electrical stimulation ; Human muscle ; Curarization ; Contraction force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A comparison was made between three different techniques for electrical stimulation of human skeletal muscle: percutaneous stimulation via large aluminum foil electrodes or via ordinary ECG-electrodes and intramuscular stimulation via platinum-coated wires.—The relationship between voltage and duration of the stimulating pulses and the evoked force of contraction is described.—A series of experiments on surgical patients who were curarized showed that these electrical stimulation techniques selectively activate nerve-endings within the muscle, and not the muscle fibres directly.—In a group of male volunteers there were linear relationships between body weight and maximum voluntary contraction force (MVC) of the knee extensors and between body weight and the stimulating voltage needed to produce 50% of MVC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581062
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  • 14
    Electronic Resource
    Electronic Resource
    Contraction characteristics of the human quadriceps muscle during percutaneous electrical stimulation (1990)
    Springer
    Pflügers Archiv 417 (1990), S. 136-141 
    Details
    ISSN: 1432-2013
    Keywords: Electrical stimulation ; Fatigue ; Force ; Frequency ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Percutaneous electrical stimulation was used to study the force response of the quadriceps muscle. The normal frequency dependence of force was investigated in muscles at rest and after fatiguing contractions. A comparison between force response during fatigue induced by electrical stimulation at different frequencies and by voluntary work suggested equal changes in contractility, irrespective of the fatigue-inducing procedure. In fresh muscle we found a linear relation between stimulation period (10–100 ms) and force. At fatigue the relation changes with maximal deviation from linearity at a 50-ms period (20 Hz). There is a rapid recovery of high frequency force whereas the low frequency response remains low even after 30 min rest. At very low frequencies there is initially unexpectedly high force in fatigued muscle. This could be a result of increased fusion of twitches with initially prolonged relaxation time. To study the twitch summation we compared experimental results in a wide frequency range with computer-simulated twitch summations and present the frequency dependence of summation processes in human quadriceps muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370690
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  • 15
    Electronic Resource
    Electronic Resource
    Relaxation and force during fatigue and recovery of the human quadriceps muscle: relations to metabolite changes (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 153-160 
    Details
    ISSN: 1432-2013
    Keywords: ATP ; Electrical stimulation ; Force ; Phosphate ; Phosphocreatine ; Relaxation ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Force and relaxation were measured during electrical stimulation of the quadriceps muscle of 14 volunteers. Stimulation produced 51.2 s of intermittent ischaemic contractions either as 16 3.2-s tetani or as 64 0.8-s tetani. Changes during recovery were followed for 180 s. On 8 subjects muscle biopsies were taken during work and after the rest period for determination of ATP, phosphocreatine and intermediates in glucolysis. The stimulation using 0.8-s contractions gave more pronounced fatigue and slowing of relaxation. There was a good correlation between force and relaxation during work but this relation changed during recovery, indicating that no general relation exists between these two contraction characteristics. In the 0.8-s stimulation more ATP was utilized and there were more profound changes in metabolite levels. We found a correlation between estimated [H2PO 4 − ] and relaxation covering both work and recovery and hypothesize that inorganic phosphate and its removal by phosphocreatine resynthesis during recovery might be important. Since stimulation patterns differ in force and relaxation even after the recovery period we suggest that additional factors, such as pH, are of importance in this work model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370464
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  • 16
    Electronic Resource
    Electronic Resource
    Adenine nucleotide and IMP contents of the quadriceps muscle in man after exercise (1978)
    Springer
    Pflügers Archiv 374 (1978), S. 193-198 
    Details
    ISSN: 1432-2013
    Keywords: Man ; Muscle ; Exertion ; Recovery ; Adenine nucleotide ; Inosine 5-monophosphate ; Inorganic phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Subjects performed submaximal and maximal bicycle exercise. Work time was between 2 and 15 min. Muscle biopsies were taken from m. quadriceps femoris at rest, immediately after termination of exercise and in some cases during the recovery period. Samples were analyzed for lactate, ATP, ADP, AMP, inorganic phosphate, creatine phosphate, creatine and IMP. The decrease in creatine phosphate and ATP/ADP ratio, as well as the increase in lactate were similar to previous investigations. Total adenine nucleotide content (TAN=ATP+ADP+AMP) decreased after maximal exercise with about 15% but was unchanged after submaximal exercise. The decrease in TAN after maximal exercise was corresponded by a similar increase in muscle IMP content. After 30 min of recovery TAN was restored to the basal value and IMP had decreased correspondingly. The physiological importance of adenine nucleotide degradation and IMP accumulation is discussed as well as the regulatory properties of the involved enzymes. The amount of energy which is liberated when 1 mol of ATP is hydrolysed to ADP has been calculated to decrease from 54 kJ at rest to 50 kJ after exhaustive exercise. It is suggested that the energy yield in the hydrolysation of ATP, rather than the amount of available ATP, is limiting for muscle contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581301
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  • 17
    Electronic Resource
    Electronic Resource
    Muscle glycogen resynthesis rate in humans after supplementation of drinks containing carbohydrates with low and high molecular masses (2000)
    Springer
    European journal of applied physiology 81 (2000), S. 346-351 
    Details
    ISSN: 1439-6327
    Keywords: Key words Carbohydrate ; Osmolality ; Glycogen ; Insulin ; Glucose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The rate of muscle glycogen synthesis during 2 and 4 h of recovery after depletion by exercise was studied using two energy equivalent carbohydrate drinks, one containing a polyglucoside with a mean molecular mass of 500 000–700 000 (C drink), and one containing monomers and oligomers of glucose with a mean molecular mass of approximately 500 (G drink). The osmolality was 84 and 350 mosmol · l−1, respectively. A group of 13 healthy well-trained men ingested the drinks after glycogen depleting exercise, one drink at each test occasion. The total amount of carbohydrates consumed was 300 g (4.2 g · kg−1) body mass given as 75 g in 500 ml water immediately after exercise and again 30, 60 ad 90-min post exercise. Blood glucose and insulin concentrations were recorded at rest and every 30 min throughout the 4-h recovery period. Muscle biopsies were obtained at the end of exercise and after 2 and 4 h of recovery. Mean muscle glycogen contents after exercise were 52.9 (SD 27.4) mmol glycosyl units · kg−1 (dry mass) in the C group and 58.3 (SD 35.4) mmol glycosyl units · kg−1 (dry mass) in the G group. Mean glycogen synthesis rate was significantly higher during the initial 2 h for the C drink compared to the G drink: 50.2 (SD 13.7) mmol · kg−1 (dry mass) · h−1 in the C group and 29.9 (SD 12.5) mmol · kg−1 (dry mass) · h−1 in the G group. During the last 2 h the mean synthesis rate was 18.8 (SD 33.3) and 23.3 (SD 22.4) mmol · kg−1 (dry mass) · h−1 in the C and G group, respectively (n.s.). Mean blood glucose and insulin concentrations did not differ between the two drinks. Our data indicted that the osmolality of the carbohydrate drink may influence the rate of resynthesis of glycogen in muscle after its depletion by exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050053
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  • 18
    Electronic Resource
    Electronic Resource
    Glycogen degradation during isometric exercise at low contraction force (1988)
    Springer
    European journal of applied physiology 58 (1988), S. 225-227 
    Details
    ISSN: 1439-6327
    Keywords: Glycogen degradation ; Low contraction force
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The glycogen content was measured in biopsy samples of human vastus lateralis muscle during prolonged isometric contraction with low force generation. In the first experiment 15% of the maximum voluntary contraction force (MVC) was held for 10 min. Glycogen utilization was 68.1 mmol glucosyl units · kg−1 dry muscle (d.m.). The study was continued by intermittent contractions of 50 s duration and 10 s rest repeated for 50 min. This resulted in a total glycogen utilization of 167.5 mmol glucosyl units · kg−1 d.m. The study was repeated with a force set to 7.5% MVC starting with 20 min continuous contraction followed by the same intermittent contractions for a further 100 min. The glycogen decrease was 15 mmol after the continuous contraction and totally 50 mmol after 2 h with the lower force. Thus the glycogen degradation rate even at low contraction force was related to the force level, being 6 times higher when the force was increased from 7.5 to 15% MVC. With prolonged isometric work periods at work loads corresponding to 15% MVC or higher depletion of the glycogen store can limit work performance capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417253
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  • 19
    Electronic Resource
    Electronic Resource
    Muscle glycogen consumption during cross-country skiing (the Vasa ski race) (1973)
    Springer
    European journal of applied physiology 31 (1973), S. 71-75 
    Details
    ISSN: 1439-6327
    Keywords: Ski-Race ; Exercise ; Muscle Glycogen ; Diet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The glycogen content in muscle tissue of the quadriceps femoris and the deltoid muscles was examined in four healthy subjects, performing a ski race of 85 km. Muscle samples were obtained before, after 45 km, and at the end of the race. The glycogen content before was above the normal range in all the subjects due to a special training and diet program. The decrease of glycogen in the leg muscles was most pronounced during the first part of the race and also at the end there was a sufficient amount of glycogen in the leg muscles. In the arm muscles, on the other hand, practically complete exhaustion of the glycogen store was found at the end of the race. The subjects experienced a marked feeling of tiredness in the arm muscles during the last kilometers of the race. The result can partly be explained by the topographical profile of the race.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693727
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  • 20
    Electronic Resource
    Electronic Resource
    The effect of repeated muscle biopsy sampling on ATP and glycogen resynthesis following exercise in man (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 186-190 
    Details
    ISSN: 1439-6327
    Keywords: Recovery ; Adenine nucleotides ; Trauma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study investigated the effect of repeated biopsy sampling on muscle adenosine 5′-triphosphate (ATP) and glycogen resynthesis following prolonged submaximal exercise. In one group of subjects (Ia, n = 7), biopsy specimens were obtained from the vastus lateralis immediately and 48 h after exhaustive one-legged cycling from both the non-exercised (control) and exercised legs. Additional samples were obtained from the exercised leg at 3, 10 and 24 h post-exercise. In a second group of subjects (Ib, n = 6), biopsy specimens were obtained immediately after exercise from both the control and exercised legs and at 48 h post-exercise from the exercised leg. All muscle biopsies were separated by a distance of 2.5 cm. In group Ia, ATP in the exercised leg was still lower after 48 h of recovery compared with the control leg (P 〈 0.05), but complete restoration had occurred in group Ib (P 〉 0.05). Glycogen super compensation was not observed in group Ia. However, at the end of recovery, in group Ib glycogen in the exercised leg was 42% greater than in the control leg (tP 〈 0.01) . Thus, following exhaustive dynamic exercise, repeated muscle biopsy sampling impaired ATP and glycogen resynthesis for several days, which may have been a result of the distance separating each biopsy site. The inhibition of ATP resynthesis appeared to be associated mainly with type II muscle fibres. The finding that, in contrast to muscle glycogen, ATP did not return to the basal level during the 48 h of recovery, suggests that the measurement of ATP may be a more sensitive measure of muscle damage than that of glycogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262830
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