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  • 1
    Electronic Resource
    Electronic Resource
    A method for assessing muscle fatigue during sprint exercise in humans using a friction-loaded cycle ergometer (1998)
    Springer
    European journal of applied physiology 78 (1998), S. 231-235 
    Details
    ISSN: 1439-6327
    Keywords: Key wordsFatigue ; Sprint repetition ; Force-velocity ; Friction-loaded cycle ergometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study investigated the mechanical changes induced by muscle fatigue caused by repeated sprints and determined whether a friction-loaded cycle ergometer has any advantages for assessing muscle fatigue. Nine subjects performed 15 sprints, each of 5 s with a 25-s rest, on a friction-loaded cycle ergometer. The averaged force, power and velocity of each push-off were calculated. Maximal power decreased by 17.9%, with a concomittent slowing of muscle contraction, but without any change in the maximal force. These results demonstrated that repeated sprints slow down muscle contraction, leading to a fall in maximal power without any loss of force. This would suggest that fast twitch fibres are selectively fatigued by repeated sprints. However, the ergometer used in the present study made it difficult to evaluate the relative influences of contraction velocity and sprinting time. This was certainly the most important limitation. On the other hand, it showed the advantage of measuring instantaneous power and total work dissipated in the environment simultaneously. It also permitted a force-velocity relationship to be obtained from a single sprint and this relationship is known to be closely related to the muscle fibre composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050412
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  • 2
    Electronic Resource
    Electronic Resource
    Optimal velocity for maximal power production in non-isokinetic cycling is related to muscle fibre type composition (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 114-118 
    Details
    ISSN: 1439-6327
    Keywords: Friction loaded cycle ergometer ; Optimal velocity ; Fast-twitch fibres ; Maximal power
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To determine whether power-velocity relationships obtained on a nonisokinetic cycle ergometer could be related to muscle fibre type composition, ten healthy specifically trained subjects (eight men and two women) performed brief periods of maximal cycling on a friction loaded cycle ergometer. Frictional force and flywheel velocity were recorded at a sampling frequency of 200 Hz. Power output was computed as the product of velocity and inertial plus frictional forces. Force, velocity and power were averaged over each down stroke. Muscle fibre content was determined by biopsy of the vastus lateralis muscle. Maximal down stroke power [14.36 (SD 2.37)W·kg−1] and velocity at maximal power [120 (SD 8) rpm] were in accordance with previous results obtained on an isokinetic cycle ergometer. The proportion of fast twitch fibres expressed in terms of cross sectional area was related to optimal velocity (r = 0.88, P 〈 0.001), to squat jump performance (r = 0.78, P 〈 0.01) and tended to be related to maximal power expressed per kilogram of body mass (r = 0.60, P = 0.06). Squat jump performance was also related to cycling maximal power expressed per kilogram of body mass (r = 0.87, P 〈 0.01) and to optimal velocity (r = 0.86, P 〈 0.01). All these data suggest that the nonisokinetic cycle ergometer is a good tool with which to evaluate the relative contribution of type II fibres to maximal power output. Furthermore, the strong correlation obtained demonstrated that optimal velocity, when related to training status, would appear to be the most accurate parameter to explore the fibre composition of the knee extensor muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376503
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Relationships between postcompetition blood lactate concentration and average running velocity over 100-m and 200-m races (1994)
    Springer
    European journal of applied physiology 68 (1994), S. 508-513 
    Details
    ISSN: 1439-6327
    Keywords: Sprint running ; Blood lactate ; Performance ; Energy cost of running
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relationships between anaerobic glycolysis and average velocity (ν) sustained during sprint running were studied in 12 national level male sprinters. A blood sample was obtained within 3 min of the completion of semi-finals and finals in the 100-m and 200-m Cameroon national championships and blood lactate concentration ([la−]b) was measured. The 35-m times were video-recorded. The 100-m and 200-m [la−]b were 8.5 (SD 0.8) and 10.3 (SD 0.8) mmol·l−1, respectively. These were not correlated with the performances. Over 200 m [la−]b was correlated with the ν sustained over the last 165 m (r=0.65,P〈0.05). In the 9 athletes who participated in both the 100-m and 200-m races, the difference between the [la−]b measured at the end of the two races was negatively correlated to the difference in v sustained over the two races (r=0.76,P〉0.02). Energy expenditure during sprint running was estimated from the [la−]b values. This estimate was mainly based on the assumption that a 1 mmol·l−1 increase in [la−]b corresponds to the energy produced by the utilization of 3.30 ml O2·kg−1. The energy cost of running was estimated at 0.275 (SD 0.02) ml O2·kg−1·m−1 over 200-m and 0.433 (SD 0.03) ml O2·kg−1·m−1 over 100-m races. These results would suggest that at the velocities studied anaerobic glycolysis contributes to at least 55% of the energy expenditure related to sprint running. However, the influence of both mechanical factors and the contribution of other energy processes obscure the relationship between [la−]b and performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00599521
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    Paper (German National Licenses)
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