| 1. |
- Thorstensson, Alf, et al.
(författare)
-
Effect of strength training on EMG of human skeletal muscle.
- 1976
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 98:2, s. 232-6
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of an 8 weeks period of systematic progressive strength training on the EMG activity of the leg extensor muscles (vastus lateralis and rectus femoris) were investigated in 8 healthy male subjects (22-31 yrs). After training there were indications (n.s.) of a decline in integrated EMG (IEMG) during maximal isometric knee extension as well as in the IEMG vs isometric force relationship. The averaged motor unit potential (AMUP) did not demonstrate any significant changes due to the strength training regimen. In conformity with earlier findings no or only minor alterations were observed in anthropometrics, muscle enzyme activities and fibre composition. The fibre area ratio indicated a specific effect of the training stimuli on the fast twitch muscle fibres. Thus, EMG-analyses, as employed in the present study, did not provide any conclusive additional explanation as to the mechanisms behind the well established gains in muscle strength performance induced by the applied strength training program.
|
|
| 2. |
- Komi, P V, et al.
(författare)
-
Skeletal muscle fibres and muscle enzyme activities in monozygous and dizygous twins of both sexes.
- 1977
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 100:4, s. 385-92
-
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.
|
|
| 3. |
- Tesch, P, et al.
(författare)
-
Muscle fatigue and its relation to lactate accumulation and LDH activity in man.
- 1978
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 103:4, s. 413-20
-
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.
|
|
| 4. |
- Thorstensson, Alf, et al.
(författare)
-
Actomyosin ATPase, myokinase, CPK and LDH in human fast and slow twitch muscle fibres.
- 1977
-
Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 99:2, s. 225-9
-
Tidskriftsartikel (refereegranskat)abstract
- The enzyme activities of Mg2+ stimulated ATPase, creatine phosphokinase (CPK), myokinase (MK) and lactate dehydrogenase (LDH) were determined in pooled fast twitch (FT) and slow twitch (ST) human skeletal muscle fibers, dissected out from freeze-dried muscle biopsy material. All enzymes investigated demonstrated higher activities in FT fibres. The ratio in enzyme activity between fibre types was greatest for Mg2+ stimulated ATPase (3:1) and smallest for CPK (1.3:1). In addition, the isozyme patterns of CPK, MK and LDH were studied by means of isoelectric focusing (CPK and MK) and discelectrophoresis (LDH). A difference was observed between fibre types with respect to the isozyme distribution of MK and LDH, whereas the CPK isozyme pattern was similar in both fibre types. These results on separated human FT and ST fibres were essentially in conformity with what has earlier been indicated from experiments on mixed muscle homogenates.
|
|
| 5. |
- Thorstensson, Alf, et al.
(författare)
-
Muscle strength and fiber composition in athletes and sedentary men.
- 1977
-
Ingår i: Medicine and science in sports. - 0025-7990. ; 9:1, s. 26-30
-
Tidskriftsartikel (refereegranskat)abstract
- Members of Swedish national teams in track and field events (sprinting and jumping), downhill skiing, race walking, orienteering, and a group of sedentary men were studied to examine the relationship between muslce fiber characteristics in needle biopsy samples form m. vastus lateralis and muscle strength measured as peak torque during isokinectic knee extensions. In comparison with the sedentary group the following differences were found: a) percentage fast twitch fibers was lower in the endurance athetes, b) fast to slow twitch muscle fiber area ratio was higher in the track athletes, c)track athletes and downhill skier attained higher peak torque values at all angular velocities examined. The track athletes had, however, higher torque values at the fastest angular velocity as compared to the downhill skiers, whereas there was no differnce under isometric conditions. The proportion of fast twitch fibers was related to torque produced, especially at high motion velocity. The training also appeared to affect the force-velocity relationship.
|
|
