Changes in internal mechanical cost during overground running to exhaustion.
OBJECTIVE
The purpose of this study was to determine, during an overground supra-threshold run, whether a change in the internal mechanical cost could occur during an exhaustive run and whether this change was related to the increase in the energy cost of running (C(r)).


METHODS
The Cr of 14 endurance runners was measured from pulmonary gas exchange using a breath-by-breath portable gas analyzer (Cosmed K4b, Rome, Italy), at the third and the last minute of an exhaustive exercise performed at their velocity corresponding to 95% of the maximal oxygen uptake (4.88 +/- 0.38 m.s(-1)). At the same time, potential, kinetic, and internal mechanical costs (C(pe), C(ke), and C(int)) were measured with a 3D motion analysis system (ANIMAN3D).


RESULTS
C(int) and C(r) increased significantly within the third minute and the end of the supra-threshold exercise (respectively, 0.55 +/- 0.07 vs 0.60 +/- 0.07 J.kg(-1).m(-1) and 4.10 +/- 0.39 vs 4.32 +/- 0.42 J.kg(-1).m(-1); P < or = 0.03). However, the percentage of variation of C(int) and C(r) were not correlated (r = 0.06; P = 0.84). Contrary to C(int), C(ke) and C(pe) remained constant during the exercise (respectively, 1.33 +/- 0.33 vs 1.38 +/- 0.29 J.kg(-1).m(-1) P = 0.79 and 0.47 +/- 0.11 vs 0.48 +/- 0.10 J.kg(-1).m(-1); P = 0.67), but both parameters were significantly correlated with C(r) (r = 0.43; P = 0.03 and r = 0.40; P = 0.03).


CONCLUSIONS
During overground running to exhaustion, a significant increase in C(int) occurred, but this did not account for the increase in C(r). Moreover, the increase in C(int) has yet to be explained.
Slawinski
Jean S
JS
Department STAPS, UFR of Fundamental Applied Science University of Evry-Val d'Essonne, Building of Sciences, Evry, France. jeanslawinski@yahoo.fr
Billat
Veronique L
VL
D000328:Adult; D001696:Biomechanical Phenomena; D004734:Energy Metabolism; D005221:Fatigue; D005260:Female; D005602:France; D006801:Humans; D008297:Male; D011659:Pulmonary Gas Exchange; D015656:Respiratory Mechanics / Q000502:physiology*; D012420:Running / Q000502:physiology*