0000000000190984
AUTHOR
Alain Belli
Biomechanical factors affecting running economy.
KYROLAINEN, H., A. BELLI, and P. V. KOMI. Biomechanical factors affecting running economy. Med. Sci. Sports Exerc., Vol. 33, No. 8, 2001, pp. 1330 -1337. Purpose: The present study was designed to investigate kinematics, kinetics, and muscle activity for explaining running economy at different running speeds. Methods: A total of 17 young endurance runners ran at 12-13 different running speeds. Respiratory gases were collected. Kinematic records were obtained by a high-speed video camera, and 3-D ground reaction forces (GRF) were measured simultaneously with telemetric EMG recordings of the selected leg muscles. In the analysis, joint moments and power were calculated by inverse dynamic meth…
Effect of 5% body weight forward pulling on dynamics of treadmill running
Forward pulled running on a treadmill is known to increase mechanical and decrease metabolic constrains relative to normal running. This experimental situation was used to investigate the variations of the mechanical parameters induced by the pulling. Ten subjects ran during 3 min at individually predetermined constant speeds of 16.4 ± 1.4 km · h-1 on a treadmill while being forward pulled by a load equal to 5% of their body weight. Ground reaction forces were recorded during the last 30 s of the run. Kinematic parameters of the stride as well as impulses and mechanical work were then calculated. Stride frequency did not change, while horizontal impulses were highly modified (+38% and -28%,…
Mechanical efficiency in athletes during running.
The purpose of this study was to compare the external mechanical efficiency (ME) between power-trained athletes (n = 5) and endurance-trained athletes (n = 5). The relationships between biomechanical variables and metabolic cost were also investigated. The subjects ran at 3 different speeds (2.50 m.s-1, 3.25 m.s-1 and 4.00 m.s-1) both on the treadmill and on the track. The external work of the subjects was determined by a kinematic arm, and energy expenditure was determined by measuring oxygen consumption and respiratory exchange ratio. Biomechanical parameters included ground reaction forces, angular displacements of the knee and ankle joints and electromyography (EMG) of the selected musc…
Mechanical step variability during treadmill running.
The present study was designed to study intra-individual step variability measured both on vertical displacement of the body (delta Z) and on step time (delta t) parameters by means of a kinematic arm and during treadmill running. A group of 17 subjects ran successively at 60%, 80%, 100% and 140% of their maximal aerobic velocity (Vamax). The total number of steps analysed was 6116. The absolute delta Z step variability (sigma delta Z) ranged between 5 mm and 21 mm while the absolute delta t variability (sigma delta t) ranged between 6 ms and 40 ms. Step variabilities were due to step asymmetry (from 38.5% to 48.5% of the step variability) and to stride variability. For submaximal velocitie…
Optic fibre as a transducer of tendomuscular forces
Direct in vivo tendon force measurements open up new possibilities for understanding of muscle-tendon loads during natural locomotion. The present report presents a new optic fibre method for such applications. The method is based on light intensity modulation by mechanical modification of the geometric properties of the optic fibre. A special optic fibre with a plastic covering buffer and with a total diameter of either 265 microns or 500 microns was carefully prepared at both ends for receiving and transmitting light. The fibre was inserted through the rabbit common calcaneal tendon with a 20 gauge needle. By removing the needle the optic fibre remained in situ. Static loading demonstrate…