%0 Journal Article %A P Jiménez-Reyes %A M Molina-Reina %A J González-Hernández %A Juan González-Badillo %T METABOLIC AND MECHANICAL RESPONSES TO 200–400 M RACES IN HIGH LEVEL SPRINTERS %D 2013 %R 10.1136/bjsports-2013-093073.18 %J British Journal of Sports Medicine %P e4-e4 %V 47 %N 17 %X The 400 m run is one of the most demanding athletic events. In 400 m, muscle acidosis decreases force production. A large number of both biochemical and biophysical changes occur at the same time that fatigue is developing (Nummela et al. JSS 1992;10:217–228). The aim of this study was to investigate relationships between changes in CMJ height pre-post and blood lactate and ammonia concentrations observed during real competition. Sixteen high level sprinters (age 23±4 y, body mass 72.6±3.7 kg, height 181.2±5.3 cm; body fat 7.4±2.7%) performed six competitions (including National Track and Field Championships). Mechanical responses (i.e. height performance in CMJ and speed loss) and metabolic responses (i.e. blood lactate and ammonia concentrations) were measured before and at 1, 3, 5, 7 and 9 minutes after exercise. The main result of this study was a highly significant correlation between CMJ height loss pre-post competition and metabolic responses (r=0.86–0.94). The decrease in jump capacity pattern was mainly related to higher blood lactate and ammonia responses. These losses were about 17% for 200 m and 27% for 400 m. Fatigue, measured as CMJ height loss, increased with performance level of athletes, and, was strongly correlated to lactate (r=0.87) and ammonia (r=0.91). Gorostiaga et al. JSCR 2010;24:1138–1149) which examined CMJ height loss following typical sprint-training workouts in 400 m elite runners (60–300 m), although were not performed at maximal intensity or real competition. Metabolic stress developed during the effort in real competition can be estimated by measuring the CMJ because of the high correlation between CMJ and blood lactate and ammonia concentrations (Jiménez-Reyes et al. MSSE 2012;44(5):582), without the necessity of measuring blood metabolites.  %U https://bjsm.bmj.com/content/bjsports/47/17/e4.10.full.pdf