Évolution des erreurs techniques et de quelques variables physiologiques pendant la course d'orientation

Abstract

Lors de la compétition de course d'orientation (CO), l'accumulation des erreurs techniques (ET) peut représenter un handicap important à l'arrivée. Dix compétiteurs nationaux masculins ont effectué une course d'orientation dans les conditions de la compétition sur un circuit constitué de quatre boucles qui se recoupaient en un point central. La nature, le nombre et le moment auquel survenaient les ET ont été comptabilisés à partir des relevés cartographiques et des temps de course de chaque sujet. Parallèlement les facteurs de la capacité physique des sujets (vitesse de course, fréquence cardiaque, lactatémie et glycémie) ont été évalués à chaque passage au point central des boucles. Nos résultats ont montré que les ET étaient plus fréquentes dans le premier quart d'heure de CO et à la fin de la course. Bien qu'il soit difficile de mettre en parallèle des facteurs objectifs de la capacité physique et les éléments décisionnels liés au comportement des sujets, notre étude a confirmé que le nombre d'ET (reflet de la dégradation de la performance mentale), était lié à la vitesse d'installation de la diminution des capacités physiques; dans ces conditions le rôle joué par un échauffement insuffisant et/ou une recharge énergétique inappropriée pendant la course est évoqué. During orienteering, the accumulation of technical errors (TE) can be an important factor of handicap at the arrival. In the same conditions of championships, ten voluntary national runners (age: 29.2 ± 3 years, height: 176.8 ± 3.5 cm, body mass: 65.0 ±6.8) participed to the study. Firstly in laboratory the subjects performed a treadmill test in order to study their physical capacity (aerobic fitness and oxygen consumption). The initial speed (12 km·h −1 ) increased by 1 km·h −1 every 4 minutes. During the last minute of each step a blood sample (50 μ l) was taken on a finger for lactate analyze (Kontron). Two days later the subjects participed in an orienteering race (OR) of four loops (Bi 1 , B 2 , B 3 , B 4 ) stepping in a central point; the first and third loops (B 1 , B3) were technical orienteering while the second and the fourth (B 2 , B 4 ) were rough orienteering. During the race the heart rate (HR) was recorded by means of a Sport Tester PE 4 000. The nature, the number and the moment of TE were determined with the help of the map area of each subject and time keeping. During OR the subject's physical capacity (running speed, HR, lactates, carbohydrate) was evaluated when the runners arrived at the crossing point of the loops. The results give some evidence that the anaerobic threshold quickly is reached during technical orienteering (B 1 ) and stay at a level hihger than 4 mmoles.l −1 during the whole field test, suggesting that the energy expenditure was very high. It is difficult to compare the physical capacity and the psychological behavior of the subjects during OR yet two distinctive critical pediods have been observed for TE in OR (B 3 , B 4 ); nevertheless our study confirms that the number of TE (which is a picture of the mental performance) is linked to the decrease of the physical capacity. Indeed the increase of HR (HRmax-HRmin) during OR stabilized in the first three loops (B 1 , B 2 , B 3 ) at 25 beats, min −1 , then the increase of HR was about 31 beats.min −1 in B4. This increase of HR (HRmax-HRmin), is due to the muscular fatigue, the subjects must have some rest and they run slowly because the carbohydrates decrease, excepted for the best runners. Thus the consequences of an insufficient warm-up in the first quarter of the race and/or supply of energetics substrates during the whole OR has been brought to attention.