- Email: [email protected]
Peak power in jumping, cycling & running
654
Abstracts-International Society of Biomechanics XIV Congress 1993
PEAK POWER IN JUMPING, CYCLING & RUNNING Laurent M. ARSAC, Alain BELLI, Jean R. LACOUR Laboratoire de Physiologie de l’exercice musculaire, GIP exercice, Univ. LYON I, BP12,69921 Oullins, France. Jumping, cycling and running are basic movements making it possible to evaluate muscular ability to produce the maximal power output performed by human leg. Twenty trained male subjects were successively involved in allout jumping (CMJ), cycling and sprint running by using respectively a force plate, a cycle ergometer and a sprint treadmill. The mechanical power output was computed from the force and the velocity sampled (200 Hz) from the sensors of the ergometers. Movements were identified by electrogoniometers and EMG recordings (six muscles). Although the same muscle groups were activated, significant differences in maximal power outputs per push-off were observed. The maximal power output, averaged during a push-off phase in cycling is significantly lower (926 watts, p
AEROBIC AND ANAEROBIC ENERGY CONTRIBUTION IN LONG HIGH-INTENSITY BICYCLE ERGOMETER TESTS Christa M.C. Bakker, Gert de Groot and Gerrit Jan van Ingen Schenau Faculty of Human Movement Schiences, Vrije Universiteit, Amsterdam, The Netherlands. Simulation of human performance in endurance sports requires detailed information about the kinetics of the energy producing systems, as well as knowledge about the ultimate capabilities of man in maximal exercise of different duration. A study was designed to determine whether the capacity to deliver energy anaerobically is limited in long efforts of high intensity. Second aim was to mndel the kinetics of aerobic and anaerobic energy contribution in maximal performances of different duration. To this end 11 national level speed skaters performed a 30 sec. all-out test, a 60 sec. and a 7 min. high intensity test, and 4 performed an additional 14 min. test on a cycle ergometer. Power output and ventiiatory variables were recorded. Aerobic power was described by an exponential function for 002 values obtained from the 60 sec. test. Total power output minus aerobic power yielded anaerobic power, which was modelled for the 30 sec. test by an exponential relation. Results indicate that both actually realised and modelled anaerobic energy contributions to long tests are of similar magnitude (realised: 422.6 W/kg in 7 min., 446.4 W/kg in 14 min., modelled: 459.5 W/kg in 7 min., 486.1 W/kg in 14 min.). Thus, it is concluded that a fixed amount of anaerobic energy can be released in maximal efforts of different duration. This anaerobic capacity can be estimated with reasonable accuracy from a short 30 sec. supra maximal test. The aerobic model resulted in a slight overestimation, possibly caused by using a constant efficiency value for each exercise intensity.
AERODYNAMICS OF THE CRICKET BALL: UNDERSTANDING THE REVERSE SWING PHENOMONA Rodnev S. Barrett and David H. Wood Human Movement Studies, University of Technology, Sydney, Australia Lateral deviation of a cricket ball during traiectory is known to occur due to pressure assymetries caused by the action of the seam and/or the surface roughness of the bail. Conventional swing is characterised by a seam induced late separation of the turbulent boundary layer on one side of the ball compared with a relative laminar flow on the other. This produces a side force in the direction of the seam side. However, under certain conditions this side force is known to occur in the opposite direction and is known a reverse swing. The negative side force that a cricket ball experiences occurs at Reynolds numbers greater than those associatedwith conventional swing. This causesthe turbulent separation of the boundary layer on the seam or rough side of the ball to occur earlier than on the smooth side. The mechanism for this effect appears to be associatedwith the action of the seam as a tripping wire or boundary fence that causes a thickening of the turbulent boundary layer flowing over it. The extra thickness reduces the effectiveness of the turbulence in mixing with the surrounding air and so the thickened boundary layer will separate earlier than the unthickened one. This effect would appear to be enhanced by the surface roughness associated with older balls becauseroughness on the non-seam side will assist in the transition to turbulent flow. Claims that an uneven weighting of the ball (such as is achieved by rubbing moisture into one side) can influence swing are unfounded as swing is produced by forces acting only in the horizontal plane. It is worth noting however that moistening the surface of a cricket ball may have some effect on its own other than increasing the weight.
Abstracts-International Society of Biomechanics XIV Congress 1993
PEAK POWER IN JUMPING, CYCLING & RUNNING Laurent M. ARSAC, Alain BELLI, Jean R. LACOUR Laboratoire de Physiologie de l’exercice musculaire, GIP exercice, Univ. LYON I, BP12,69921 Oullins, France. Jumping, cycling and running are basic movements making it possible to evaluate muscular ability to produce the maximal power output performed by human leg. Twenty trained male subjects were successively involved in allout jumping (CMJ), cycling and sprint running by using respectively a force plate, a cycle ergometer and a sprint treadmill. The mechanical power output was computed from the force and the velocity sampled (200 Hz) from the sensors of the ergometers. Movements were identified by electrogoniometers and EMG recordings (six muscles). Although the same muscle groups were activated, significant differences in maximal power outputs per push-off were observed. The maximal power output, averaged during a push-off phase in cycling is significantly lower (926 watts, p
AEROBIC AND ANAEROBIC ENERGY CONTRIBUTION IN LONG HIGH-INTENSITY BICYCLE ERGOMETER TESTS Christa M.C. Bakker, Gert de Groot and Gerrit Jan van Ingen Schenau Faculty of Human Movement Schiences, Vrije Universiteit, Amsterdam, The Netherlands. Simulation of human performance in endurance sports requires detailed information about the kinetics of the energy producing systems, as well as knowledge about the ultimate capabilities of man in maximal exercise of different duration. A study was designed to determine whether the capacity to deliver energy anaerobically is limited in long efforts of high intensity. Second aim was to mndel the kinetics of aerobic and anaerobic energy contribution in maximal performances of different duration. To this end 11 national level speed skaters performed a 30 sec. all-out test, a 60 sec. and a 7 min. high intensity test, and 4 performed an additional 14 min. test on a cycle ergometer. Power output and ventiiatory variables were recorded. Aerobic power was described by an exponential function for 002 values obtained from the 60 sec. test. Total power output minus aerobic power yielded anaerobic power, which was modelled for the 30 sec. test by an exponential relation. Results indicate that both actually realised and modelled anaerobic energy contributions to long tests are of similar magnitude (realised: 422.6 W/kg in 7 min., 446.4 W/kg in 14 min., modelled: 459.5 W/kg in 7 min., 486.1 W/kg in 14 min.). Thus, it is concluded that a fixed amount of anaerobic energy can be released in maximal efforts of different duration. This anaerobic capacity can be estimated with reasonable accuracy from a short 30 sec. supra maximal test. The aerobic model resulted in a slight overestimation, possibly caused by using a constant efficiency value for each exercise intensity.
AERODYNAMICS OF THE CRICKET BALL: UNDERSTANDING THE REVERSE SWING PHENOMONA Rodnev S. Barrett and David H. Wood Human Movement Studies, University of Technology, Sydney, Australia Lateral deviation of a cricket ball during traiectory is known to occur due to pressure assymetries caused by the action of the seam and/or the surface roughness of the bail. Conventional swing is characterised by a seam induced late separation of the turbulent boundary layer on one side of the ball compared with a relative laminar flow on the other. This produces a side force in the direction of the seam side. However, under certain conditions this side force is known to occur in the opposite direction and is known a reverse swing. The negative side force that a cricket ball experiences occurs at Reynolds numbers greater than those associatedwith conventional swing. This causesthe turbulent separation of the boundary layer on the seam or rough side of the ball to occur earlier than on the smooth side. The mechanism for this effect appears to be associatedwith the action of the seam as a tripping wire or boundary fence that causes a thickening of the turbulent boundary layer flowing over it. The extra thickness reduces the effectiveness of the turbulence in mixing with the surrounding air and so the thickened boundary layer will separate earlier than the unthickened one. This effect would appear to be enhanced by the surface roughness associated with older balls becauseroughness on the non-seam side will assist in the transition to turbulent flow. Claims that an uneven weighting of the ball (such as is achieved by rubbing moisture into one side) can influence swing are unfounded as swing is produced by forces acting only in the horizontal plane. It is worth noting however that moistening the surface of a cricket ball may have some effect on its own other than increasing the weight.