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Sökning: WFRF:(Tesch P.A)

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  • Berg, H E, et al. (författare)
  • Involvement of eccentric muscle actions in giant slalom racing.
  • 1995
  • Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 27:12, s. 1666-70
  • Tidskriftsartikel (refereegranskat)abstract
    • Joint angular movements and muscle activation (EMG), were determined in male elite racers while performing the giant slalom. Movement cycles averaged 3.5 +/- 0.6 s (left plus right turn), and knee angle ranged 66-114 degrees (180 degrees = straight leg). Knee extensor muscle use was dominated (rectified EMG; P < 0.05) by the leg controlling the outside (downhill) ski during the turn. Time spent while decreasing knee angle (eccentric muscle action) of outside leg averaged 1.0 +/- 0.2 s. This phase was longer (P < 0.05) than the average push-off (concentric muscle action) phase of 0.5 +/- 0.1 s. Moreover, EMG activity of the outside leg during eccentric muscle actions exceeded (P < 0.05) that of concentric actions and was similar to that attained during maximum isometric knee extension in laboratory tests. Knee and hip angular movement ranged 20-50 degrees. Average joint velocities equalled 20-40 degrees.s(-1) during the turning phase. Thus, competitive giant slalom skiing is dominated by slow eccentric muscle actions performed at near maximum voluntary force. Because of their greater ability to generate force, eccentric muscle actions may be warranted or even required to resist the G-forces induced during the turn phase.
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  • Eiken, Ola, et al. (författare)
  • Effect of nitrous oxide on human skeletal muscle function
  • 1996
  • Ingår i: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 40:4, s. 486-488
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Nitrous oxide (N2O) is commonly administered in conjunction with parturition, which requires the performance of repeated high-force voluntary muscle actions. Therefore, we examined the effect of a subanesthetic dose of N2O on the force-velocity relationship of the quadriceps femoris muscle. METHODS: Nine healthy subjects performed maximal voluntary muscle actions once while breathing air and once while breathing a normoxic gas mixture containing 35% (N2O). Peak torque of the knee extensors was measured during concentric muscle contractions at different angular velocities (30, 60, 90, 150 and 210 degrees s-1), and eccentric (30, 60, 90, and 150 degrees s-1) and isometric (knee-joint angle approximately equal to 60 degrees) muscle actions. Maximal angular velocity was determined during unloaded knee extensions. RESULTS: N2O decreased peak torque at any given angular velocity. The overall decrease in peak averaged 4.8 +/- 2.2% (P < 0.0001). Likewise, N2O decreased maximal angular velocity by 5.7 +/- 4.3% (P < 0.01). Thus, the impairment in muscle function induced by a 35% N2O is only minute and hence most likely of little significance in clinical practice.
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  • Eiken, Ola, et al. (författare)
  • Effects of hyperoxia and hypoxia on dynamic and sustained static performance of the human quadriceps muscle
  • 1984
  • Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 122:4, s. 629-633
  • Tidskriftsartikel (refereegranskat)abstract
    • The influence of variations in inspired PO2 on dynamic and static muscle performance of the left quadriceps muscle was studied. Eight subjects performed (1) 60 maximal consecutive dynamic contractions and (2) one sustained exhaustive static contraction at 27% of maximal voluntary contraction (MVC). Breathing mixtures containing 11%, 21% or 99% O2, were administered. Peak torque as an average of the 60 knee extensions was higher (p less than 0.01) during hyperoxia (mean +/- SE = 104 +/- 4 Nm) than during normoxia (98 +/- 4 Nm), but did not differ significantly between hypoxia (95 +/- 5 Nm) and normoxia. Peak torque of individual extensions declined more rapidly during hypoxia than during normoxia, differing in the final 12 extensions by 11% from normoxic values. Static endurance time was reduced (p less than 0.02) during hypoxia (152 +/- 12 s) as compared to normoxia (189 +/- 13 s) and hyperoxia (169 +/- 11 s). No significant difference in endurance time was demonstrated between hyperoxia and normoxia. Thus, hypoxia impaired muscle performance in both dynamic and sustained static exercise, whereas acute hyperoxia improved dynamic but not static muscle performance. The results are interpreted in terms of differences in rate of intramuscular H+ accumulation.
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  • Eiken, Ola, et al. (författare)
  • Human skeletal muscle function and metabolism during intense exercise at high O2 and N2 pressures
  • 1987
  • Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 63:2, s. 571-575
  • Tidskriftsartikel (refereegranskat)abstract
    • The maximal contractile force (peak torque) of the quadriceps femoris was studied during 60 repeated unilateral dynamic knee extensions in nine subjects under three different conditions, viz., during air breathing at normal (1 ATA) and raised (6 ATA) ambient pressures and during O2 breathing at 1.3 ATA. In six subjects the electromyographic (EMG) activity of the working muscle was recorded. Muscle biopsies were obtained from the vastus lateralis before, immediately after, and 1 min after exercise. Tissue specimens were subsequently assayed for various muscle metabolites. Peak torque, as an average of the 60 knee extensions, was higher (P less than 0.05) at 1.3 ATA than at 6 or 1 ATA. Peak torque of the exercising muscle declined more rapidly at 1 ATA than at 1.3 ATA, differing in the final 24 contractions by 14%. At 6 ATA peak torque of the initial 12 contractions was 6% lower (P less than 0.05) than at 1 ATA but equaled 1-ATA values in the latter third of the exercise bout. Although the EMG activity at 1 ATA increased relative to that at 6 ATA as exercise proceeded, the rate of force decline was greater at 1 ATA. Despite greater total work produced at 1.3 ATA than at 1 ATA, the metabolic response to exercise was not substantially altered at increased O2 pressure. However, the restitution rate of energy-rich phosphagens and the elimination of lactate during recovery were greater (P less than 0.05) at 1.3 ATA. These results suggest that hyperoxia may enhance the rate of energy release, whereas high N2 pressure and/or high hydrostatic pressure seem to interfere with neuromuscular activity.
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