Laboratory Testing and Field Performance in BMX Riders.

In June 2003, the International Olympic Committee decided to introduce BMX in the 2008 Olympic Games in Beijing (China). We can assume, as in a 200 m sprint in track cycling, that the maximal power output (PO) of the lower limbs contribute to the BMX performance. However , few studies like Herman et al. (2009) and Mateo et al. 2011 have studied the PO characteristics of the elite riders on the initial straight line. However, this analyze could contribute to know the key factors of the BMX performance. The first aim of this descriptive study was to measure the PO characteristics of national to elite level BMX riders during maximal exercises in the laboratory and in the field, and the second aim is to analyze the relationships between the PO and the chronometric performances. This analysis could help BMX coaches for example to orient their training programs. Two groups of BMX male riders volunteered to take part in this study: riders of national level (n = 17, age 20 ± 1 years; height 1.79 ± 0.10 m; body mass 74.7 ± 10.4 kg; and, mean body fat 13.6 ± 4.2 %) performing in the French championships and elite riders of the French national team (n = 9, 22 ± 4 years; height 1.80 ± 0.05 m; body mass 75.9 ± 5.7 kg) performing in European, world or Olympics championships (UCI ranking in first fifty with the best at the fourth place). All subjects provided written informed consent. All of the tests (laboratory and field) tests were performed on the same day. Only the riders of national level have performed the laboratory tests. The subjects performed two types of vertical jumps: squat jumps (SJ) and counter movement jumps (CMJ) and maximal cycling sprint tests on cyclo-ergometer (Cateye CS 1000, Osaka, Japan) of 8 s duration against three resis-tive load levels (0.4 N m·kg-1 , 0.6 N m·kg-1 , 0.8 N m·kg-1 applied on the crank axis) in seated (ST SEA) and standing positions (ST STA) with 6 min of active rest between tests (Bertucci et al., 2007). After 30 min of active rest, two Wingate tests of 30 s duration were performed in seated (WT SEA) and standing positions (WT STA) in randomized order (45 min of recovery between the Wingate tests). The PowerTap (CycleOps, Madison, USA) samples at a frequency of 0.8 Hz the PO measurements. After 3 hours of …