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  • 201. Westing, Stephen
    et al.
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Karlson, Eddy
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man1988In: European Journal of Applied Physiology and Occupational Physiology, ISSN 0301-5548, E-ISSN 1432-1025, Vol. 58, p. 100-104Article in journal (Refereed)
    Abstract [en]

    The primary purpose of this investigation was to study the eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man using a recently developed combined isometric, concentric and eccentric controlled velocity dynamometer (the SPARK System). A secondary purpose was to compare the method error associated with maximal voluntary concentric and eccentric torque output over a range of testing velocities. 21 males (21-32 years) performed on two separate days maximal voluntary isometric, concentric and eccentric contractions of the quadriceps femoris at 4 isokinetic lever arm velocities of 0 degree.s-1 (isometric), 30 degrees.s-1, 120 degrees.s-1 and 270 degrees.s-1. Eccentric peak torque and angle-specific torques (measured every 10 degrees from 30 degrees to 70 degrees) did not significantly change from 0 degrees.s-1 to 270 degrees.s-1 (p greater than 0.005) with the exception of angle-specific 40 degrees torque, which significantly increased; p less than 0.05). The mean method error was significantly higher for the eccentric tests (10.6% +/- 1.6%) than for the concentric tests (8.1% +/- 1.7%) (p less than 0.05). The mean method error decreased slightly with increasing concentric velocity (p greater than 0.05), and increased slightly with increasing eccentric velocity (p greater than 0.05). A tension restricting neural mechanism, if active during maximal eccentric contractions, could possibly account for the large difference seen between the present eccentric torque-velocity results and the classic results obtained from isolated animal muscle.

  • 202. Westing, Stephen
    et al.
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Effects of electrical stimulation on eccentric and concentric torque-velocity relationships during knee extension in man1990In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 140, p. 17-22Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to examine the effects of electrical stimulation on torque output during knee extension. Nine well-trained males (19-43 years) performed maximal voluntary, electrically evoked and superimposed eccentric and concentric knee extensions at velocities of 60, 180 and 360 degrees s-1, plus an isometric test (torque was always recorded at a 60 degree knee angle). Fifty-hertz stimulation was applied percutaneously at the maximum tolerated voltage (140-200 V). By superimposing electrical stimulation, eccentric torque could be increased by an average of 21-24% above the voluntary level (P less than 0.05). No corresponding differences were observed between superimposed and voluntary torques under isometric or concentric conditions. Electrically evoked torque also exceeded voluntary torque under eccentric conditions (11-12%, P less than 0.05), but was less under isometric and concentric conditions (-10 to -52%, P less than 0.05). Within the limitations of the study, it was concluded that eccentric knee extension torque under maximal voluntary conditions does not represent the maximal torque-producing capacity. The action of a neural inhibitory mechanism was proposed as an explanation for this finding. If active, this mechanism may protect against the extreme muscle tension that could otherwise develop under truly maximal eccentric conditions.

  • 203. Westing, Stephen
    et al.
    Seger, Jan
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Thorstensson, Alf
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Laboratory for Biomechanics and Motor Control.
    Isoacceleration: a new concept of resistive exercise1991In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 23, no 5, p. 631-635Article in journal (Refereed)
    Abstract [en]

    This study presents the concept of constant (iso-) accelerative and decelerative exercise and compares concentric and eccentric torque output during isoaccelerative and isodecelerative movements with that during comparable constant velocity (isokinetic) conditions. Twelve men (19-42 yr) performed maximal voluntary concentric and eccentric knee extensions at velocities of 120 and 240 degrees.s-1 (isokinetic) and at accelerations of 180 and 720 degrees.s-2 (both isoaccelerative and isodecelerative) between 10 degrees and 90 degrees knee angles. At 50 degrees, the 180 and 720 degrees.s-2 tests had velocities of 120 and 240 degrees.s-1, respectively, and thus torque comparisons could be made at a corresponding position and velocity. No difference was seen among the isoaccelerative, isodecelerative, or isokinetic angle- and velocity-specific torques for either the concentric or eccentric tests (P greater than 0.05). The results demonstrated that, under conditions of maximal voluntary effort, movement speed as such (within the range studied) was the essential determinant of muscle force--not whether this speed was attained during accelerative, decelerative, or constant velocity movements. As a testing and training modality, the controlled acceleration technique, particularly eccentric deceleration and concentric accleration, appears to offer advantages as compared with existing methods, since it more faithfully reflects the contraction conditions during natural strength-requiring movements.

  • 204.
    Wichardt, Emma
    et al.
    Idrottsmedicin, Umeå universitet.
    Mattsson, C. Mikael
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Ekblom, Björn
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Björn Ekblom's research group.
    Henriksson-Larsén, Karin
    Swedish School of Sport and Health Sciences, GIH.
    Rhabdomyolysis/myoglobinemia and NSAID during 48-hours ultra-endurance exercise (adventure racing)2011In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 111, no 7, p. 1541-1544Article in journal (Refereed)
    Abstract [en]

    Purpose: To determine if rhabdomyolysis with myoglobinemia exists during a 48+ hour adventure race and if there is a correlation with NSAID use, race time and perceived pain or exertion. Method: Blood samples for analyses of myoglobin (Mb) were collected, and perception of exertion and pain registered on the Borg-RPE and CR scales, from 20 subjects (3 female, 17 male) Pre, Mid and Post race. Subjects were asked about NSAID use at each sampling and within 12 hours pre race. Result: A significant rise in Mb was observed throughout the race, with the NSAID group (n=6) having significantly lower Mb-Post than the no-NSAID group (n=14). High Mb-Pre and Post correlated to shorter race time and high Mb-Pre to lower Pain-Post. Race time also correlated to NSAID use, with the NSAID group having significantly longer race time than the no-NSAID group. Conclusion: Rhabdomyolysis with myoglobinemia, which might be reduced with NSAID use, exists during a 48+ hour adventure race. Indications that high Mb-levels correlate with shorter race time and less pain, and the reasons for the NSAID groups longer race time, need further investigation.

  • 205. Yu, M
    et al.
    Blomstrand, Eva
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences, Eva Blomstrand's research group.
    Chibalin, A V
    Krook, A
    Zierath, J R
    Marathon running increases ERK1/2 and p38 MAP kinase signalling to downstream targets in human skeletal muscle.2001In: Journal of Physiology, ISSN 0022-3751, E-ISSN 1469-7793, Vol. 536, no Pt 1, p. 273-82Article in journal (Refereed)
    Abstract [en]

    1. We tested the hypothesis that long-distance running activates parallel mitogen-activated protein kinase (MAPK) cascades that involve extracellular signal regulated kinase 1 and 2 (ERK1/2) and p38 MAPK and their downstream substrates. 2. Eleven men completed a 42.2 km marathon (mean race time 4 h 1 min; range 2 h 56 min to 4 h 33 min). Vastus lateralis muscle biopsies were obtained before and after the race. Glycogen content was measured spectrophotometrically. ERK1/2 and p38 MAPK phosphorylation was determined by immunoblot analysis using phosphospecific antibodies. Activation of the downstream targets of ERK1/2 and p38 MAPK, MAPK-activated protein kinase-1 (MAPKAP-K1; also called p90 ribosomal S6 kinase, p90rsk), MAPK-activated protein kinase-2 (MAPKAP-K2), mitogen- and stress-activated kinase 1 (MSK1) and mitogen- and stress-activated kinase 2 (MSK2) was determined using immune complex assays. 3. Muscle glycogen content was reduced by 40 +/- 6 % after the marathon. ERK1/2 phosphorylation increased 7.8-fold and p38 MAPK phosphorylation increased 4.4-fold post-exercise. Prolonged running did not alter ERK1/2 and p38 MAPK protein expression. The activity of p90rsk, a downstream target of ERK1/2, increased 2.8-fold after the marathon. The activity of MAPKAPK-K2, a downstream target of p38 MAPK, increased 3.1-fold post-exercise. MSK1 and MSK2 are downstream of both ERK1/2 and p38 MAPK. MSK1 activity increased 2.4-fold post-exercise. MSK2 activity was low, relative to MSK1, with little activation post-exercise. 4. In conclusion, prolonged distance running activates MAPK signalling cascades in skeletal muscle, including increased activity of downstream targets: p90rsk, MAPKAP-K2 and MSK. Activation of these downstream targets provides a potential mechanism by which exercise induces gene transcription in skeletal muscle.

  • 206.
    Åstrand, Per-Olof
    Swedish School of Sport and Health Sciences, GIH. Department of Physiology, Kungliga Gymnastiska Centralinstitutet, Stockholm.
    Experimental studies of physical working capacity in relation to sex and age1952Doctoral thesis, monograph (Other academic)
  • 207.
    Åstrand, PO
    et al.
    Swedish School of Sport and Health Sciences, GIH, Department of Sport and Health Sciences.
    Bergh, U
    Kilbom, A
    A 33-yr follow-up of peak oxygen uptake and related variables of former physical education students.1997In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 82, no 6, p. 1844-52Article in journal (Refereed)
    Abstract [en]

    In 1949, 27 female and 26 male physical education students were studied at a mean age of 22 and 25 yr, respectively. They were restudied in 1970 and 1982. Measurements included oxygen uptake, heart rate, and pulmonary ventilation during submaximal and maximal exercise on a cycle ergometer and treadmill. After 21 yr, peak aerobic power was significantly reduced, from 2.90 to 2.18 l/min and from 4.09 to 3.28 l/min for women and men, respectively. After another 12 yr, the 1970 maxima were not reduced further. From 1949 to 1982 there was a decrease in peak heart rate from 196 to 177 beats/min in women and from 190 to 175 beats/min in men (P < 0.05). Highest pulmonary ventilation did not change significantly. At an oxygen uptake of 1.5 l/min, the heart rate was the same in 1949 as in 1982. In conclusion, the physical fitness level of the subjects was well above average for these ages. From 1970 to 1982 there was no decline in the average peak aerobic power, a finding possibly related to increased habitual physical activity.

2345 201 - 207 of 207
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