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| 2. |
- Bergh, U, et al.
(författare)
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Maximal oxygen uptake and muscle fiber types in trained and untrained humans.
- 1978
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Ingår i: Medicine and science in sports. - 0025-7990. ; 10:3, s. 151-4
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Tidskriftsartikel (refereegranskat)abstract
- Maximal oxygen uptake (Vo2 max) was determined in 138 male and 41 female human subjects and muscle fiber composition (gastrocnemius and vastus lateralis) in 53 of the males. Highest values for Vo2 max were 7.38 1 x min-1 and 4.341 x min-1 in males and females, respectively. In relation to body weight the highest values were 94 and 77 ml x (kg x min)-1. Athletes participating in endurance events had very high Vo2 max and predominantly slow twitch (ST) fiber populations whereas weight lifters attained rather low values for Vo2 max and had a higher percentage of fast twitch (FT) fibers. Among subjects with the same fiber composition, Vo2 max was higher in the athletes than in the moderately trained. All groups taken together demonstrated a positive relationship between Vo2 max and the relative number of ST fibers (r = 0.67). For endurance and strength athletes r = 0.72 and for the moderately trained r = 0.34, both correlation coefficients being significant.
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| 3. |
- Ekblom, Björn, et al.
(författare)
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Effect of changes in arterial oxygen content on circulation and physical performance.
- 1975
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Ingår i: Journal of applied physiology. - 0021-8987. ; 39:1, s. 71-5
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the effect of different levels of arterial oxygen content on hemodynamic parameters during exercise nine subjects performed submaximal bicycle or treadmill exercise and maximal treadmill exercise under three different experimental conditions: 1) breathing room air (control); 2) breathing 50% oxygen (hyperoxia); 3) after rebreathing a carbon monoxide gas mixture (hypoxia). Maximal oxygen consumption (Vo2 max) was significantly higher in hyperoxia (4.99 1/min) and significantly lower in hypoxia (3.80 1/min) than in the control experiment (4.43 1/min). Physical performance changes in parallel with Vo2 max. Maximal cardiac output (Qmax) was similar in hyperoxia as in control but was significantly lower in hypoxia mainly due to a decreased stroke volume. A correlation was found between Vo2 max and transported oxygen, i.e., Cao2 times Amax, thus suggesting that central circulation is an important limiting factor for human maximal aerobic power. During submaximal work HR was decreased in hyperoxia and increased in hypoxia. Corresponding Q values were unchanged except for a reduction during high submaximal exercise in hyperoxia.
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| 4. |
- Grillner, S, et al.
(författare)
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Intra-abdominal pressure changes during natural movements in man.
- 1978
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 103:3, s. 275-83
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Tidskriftsartikel (refereegranskat)abstract
- The weight of the upper part of the trunk is partially transmitted to the pelvis via the vertebral column. If the muscle walls around the abdominal cavity are contracted, a high pressure can be generated within the cavity (greater than 200 mmHg). The abdominal space can them transmit part of weight to, e.g., the upper part of the body, Intra-abdominal pressure recordings have been performed during locomotion and other natural movements with intragastric pressure recordings. With each step, there is a phasic variation in pressure, with its peak coinciding with that of the peak vertical force exerted by the leg against the ground. The peak values increase progressively with the speed of walking/running up to a mean of 38 mmHg and with trough values of 16 mmHg. The phasic variations with each step is due to a phasic activation of the abdominal muscles, with an EMG activity starting 50 ms or more before foot contact. If an extra load is put on the back, the posture changes and at the highest speed of running the pressure values are significantly higher than without this additional load. After a jump down from a moderate height of 0.4 m, the average increase is 89 mmHg and can often exceed 100 mmHg. These pressure changes are large and will presumably act to unload the spine under the prevailing biomechanical conditions and, in addition, there will no doubt be an effect on the circulatory system.
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| 5. |
- Hultén, B, et al.
(författare)
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Relationship between isometric endurance and fibre types in human leg muscles.
- 1975
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 93:1, s. 135-8
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Tidskriftsartikel (refereegranskat)abstract
- Relationship between isometric endurance performance at 50% of maximal voluntary isometric contraction (MCV) and skeletal muscle fibre composition has been elucidated in 19 physical education students. This was found to be linear and the equation corresponded to: y=9.35 + 1.093x; r=0.70 (endurance time expressed in seconds and fibre composition as percent slow twitch muscle fibres (ST) of the vastus lateralis muscle). As it is assumed from previous studies that similar isometric tensions preferentially recruit fast twitch muscle fibres (FT) and that the muscle at the point of exhaustion exhibits maximal values for lactate accumulation, it is suggested that lactate formed in FT fibres is released and stored in nonrecruited ST fibres. The ability to sustain similar isometric tension would then be depending on how large the fraction of ST fibres is that can serve as a lactaterecipient for lactate producing FT fibres.
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| 6. |
- Karlsson, J, et al.
(författare)
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LDH isozymes in skeletal muscles of endurance and strength trained athletes.
- 1975
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 93:2, s. 150-6
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Tidskriftsartikel (refereegranskat)abstract
- Muscle biopsy samples were obtained from arm and leg muscles of endurance and strength trained athletes, respectively. Total LDH activity as well as occurrence and activity of LDH isozymes were determined. Comparing the results from the athletes with those from non-trained subjects with corresponding fibre compositions, it was found that the endurance athletes had a lower total LDH activity, a higher relative activity of the most heart-specific isozymes. LDH (1 + 2), and, on electrophoretic separation, a complete absence of LDH (4 + 5) in both arm and leg muscles. As compared to the untrained material the strength trained athletes tended to have a higher total LDH activity, a similar distribution of relative isozyme activities, and, in the leg muscles, a strong electrophoretic band corresponding to LDH 5, the most skeletal muscle specific isozyme.
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| 7. |
- Komi, P V, et al.
(författare)
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Skeletal muscle fibres and muscle enzyme activities in monozygous and dizygous twins of both sexes.
- 1977
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 100:4, s. 385-92
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Tidskriftsartikel (refereegranskat)abstract
- Significance of the genetic component in determining the interindividual variation observed in skeletal muscle fibre composition and enzyme activities was investigated in 31 pairs of male and female monozygous (MZ) and dizygous (DZ) twins, whose ages ranged in all but one pair (11 years) from 15 to 24 years. Percent distribution of slow twitch muscle fibres and activities of Ca2+ and Ng2+ stimulated ATPases, creatine phosphokinase, myokinase, phosphorylase, lactate dehydrogenase (LDH) and distribution of its isozyme LDH-1 were all analyzed in biopsy samples taken from the vastus lateralis muscle. The data disclosed that in contrast to DZ twins the MZ twins of both sexes had an essentially identical muscle fibre composition. Calculation of the heritability estimate for this parameter gave the values of 99.5% and 92.8%, respectively for males and females. In contrast to the fibre composition presence of a significant genetic component was not observed in any of the enzyme activities studied. It was concluded that there is a predominant genetic influence on the skeletal muscle fibre composition in man, and thus also on the potential capacity of the muscles to perform work.
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| 8. |
- Nilsson, Johnny, et al.
(författare)
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Fatigue and EMG of repeated fast voluntary contractions in man.
- 1977
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 101:2, s. 194-8
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Tidskriftsartikel (refereegranskat)abstract
- A fatigue test consisting of repeated fast maximal contractions of the left quadriceps muscle in an isokinetic apparatus was performed by 12 healthy male subjects (19-25 yrs). EMG signals recorded from the surface of the left vastus lateralis muscle, from which also biopsies were obtained for muscle fibre classification. Only minor changes were observed in the EMG variables despite a decrease in muscle strength performance, in terms of peak torque, work and power to about 50% of initial values after 100 contractions. The concomitantly obtained positive correlation between the increase in EMG/torque ratio and the individual percentage of fast twitch (FT) muscle fibres indicated that local factors in the muscle, primarily in FT fibres, were causing the development of fatigue during repeated dynamic contractions with high power outputs.
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| 9. |
- Sjödin, B, et al.
(författare)
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Effect of physical training on LDH activity and LDH isozyme pattern in human skeletal muscle.
- 1976
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 97:2, s. 150-7
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Tidskriftsartikel (refereegranskat)abstract
- Total lactate dehydrogenase (LDH) activity and LDH isozyme pattern were studied in muscle biopsies obtained from m. vastus lateralis after 1) "aerobic" training performed as interval and extreme distance running, respectively (3 subjects); and 2) "anaerobic" training for two months, carried out as repeated maximal bursts of approximately 1 min running (6 subjects). After the "anaerobic training" no changes in LDH properties could be detected, although running performance improved. The extreme distance running resulted in a decrease in total LDH activity and an increase in relative activity of the heart specific isozymes. A relationship was also shown between the relative activity of these isozymes and the training distance covered. The relatively more aerobic prevailing during distance running as compared to "anaerobic training" were proposed to decrease muscle specific subunits and/or increase synthesis of heart specific subunits in both muscle fiber types. This suggestion was supported by isozyme analysis of lyophilized and dissected single muscle fibres.
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| 10. |
- Tesch, P, et al.
(författare)
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Muscle fatigue and its relation to lactate accumulation and LDH activity in man.
- 1978
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 103:4, s. 413-20
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Tidskriftsartikel (refereegranskat)abstract
- The lactate concentration in different muscle fibre types was determined in biopsy specimens from human vastus lateralis muscle after 30 and 60 s of maximal dynamic leg exercise. In addition, muscle fibre type distribution, total lactate dehydrogenase (LDH) activity, and isozymes of LDH were determined. In accordance with previous studies (Thorstensson and Karlsson 1976, Nilsson et al. 1977) it was found that an increasing proportion of slow twitch (ST) fibres corresponded to better sustained muscle force. Lactate was found preferentially in fast twitch (FT) fibres after 30 s, but after 60 s this difference was abolished. Differences between the two main muscle fibre types in muscle lactate, total LDH activity, and M-LDH activity were correlated to muscle fatigue. It was concluded that lactate or associated pH changes primarily in FT fibres could be one factor responsible for the impaired muscle function.
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