The purpose of this work was to test the hypothesis that the lower energy cost in highly trained runners is associated with a lower mechanical cost. To test this hypothesis, C, Cke, Cpe, and Cint were measured in runners who differ in training status. The results showed that contrary to our hypothesis, the energy cost of running was not different for runners with different training status. However, the mechanical cost is different for runners with different training status. Indeed, the mechanical cost associated to the vertical movements of the center of mass (Cpe) was smaller in highly trained runners. Inversely, the mechanical cost associated with the movement of the segments around the center of mass (Cint) and the step rate (SR) were greater.
Following this hypothesis, the present results show that the mechanical cost of the vertical movements of the CM (Cpe) is smaller in highly trained runners. This result is in accordance with the generally acknowledged principle which states that smaller verticals oscillations of the body center of mass are associated with a high level of training (28,37). However, there was no relationship observed between Cpe and C (Fig. 4). According to the training status, the variation in Cpe is not associated with the variation in C. Similarly, the kinetic mechanical cost (Cke) or the mechanical cost of the movements of the segments around the center of mass (Cint) were not correlated with C (Fig. 4). These results agree with numerous studies, which have demonstrated that the relationships between C and the mechanical cost are both weak and inconsistent (11,28,37). The mechanical cost reflects a global and indirect expression of the muscular effort, which explains why a low correlation is observed between C and the mechanical cost. Other mechanical parameters should be correlated with C. Indeed, it has been shown that less economical runners possess a more compliant running style during ground contact (11,24,27).
Collectively, the results reported here do not confirm our primary hypothesis and suggest that the mechanical cost (Cpe and Cint) is not correlated with C but with V̇O2max. The mechanism that explains the modifications of the mechanical parameters (SR, Cpe, and Cint) is in relation with the level of training of the runners rather than their energy cost. However, this mechanism has to be elucidated.
If humans are self-optimizing machines, the minimal cost, being an optimally criterion, may be identified that governs the kinematic and kinetic detail of the performance. For example, it has been shown that adult and children tend to walk or run at frequencies that are determined by the oxygen cost (10). However, it is unlikely that the metabolic cost is the only optimality criteria adopted for human activity. The potential for injury may also result in the development of optimal criteria. Farley and Taylor (19) reported that horses naturally switch from a trot to a gallop actually increasing their metabolic cost but reducing the peak of forces on the muscles, tendons, and bones. They suggest that this mechanism reduces the chance of injury for the horse. During human running, the body is subjected to high impact loads during the initial portion of the support phase of the stride. These impacts have magnitudes up to 2.3 times body weight (BW) with an impact load rate of 113 BW·s−1 (29). Increases in impact shock can result from an increase in running speed (21), from running downhill (22), from an increase in stride length (15,23) or fatigue (35). It would appear, therefore, that impact shock attenuation may be an important factor on which individuals optimize. In a same way, Zamparo et al. (38) have recently demonstrated that the self selected speed of running depends not only on cardiovascular factors but also on biomechanical factors.
To conclude, highly trained runners did not display a lower C. However, Cpe was 20% lower and Cint was 30% greater in highly trained runners. The endurance training leads to an increase of Cint and a decrease in Cpe without any modification of C. These mechanical adjustments may be associated with the same self-optimizing mechanisms that contribute to reduce the impact loads during the initial portion of the support phase of the stride.
The authors gratefully acknowledge the Fédération Franç aise de Ski and Michel Tavernier for their assistance during the experiment.
1. BAILEY, S., and S. MESSIER. Variation in stride length and running
economy in male novice runners subsequent to a seven-week training
program. Int. J. Sports. Med.
2. BARSTOW, T., and P. MOLE. Linear and nonlinear characteristics of oxygen uptake
kinetics during heavy exercise. J. Appl. Physiol.
3. BERNARD, O., F. MADDIO, S. OUATTARA, et al. Influence of the oxygen uptake
slow component on the aerobic energy cost of high-intensity submaximal treadmill running
in humans. Eur. J. Appl. Physiol.
4. BILLAT, V. L., R. RICHARD, V. M. BINSSE, J. P. KORALSZTEIN, and P. HAOUZI. The V(O2) slow component for severe exercise depends on type of exercise and is not correlated with time to fatigue. J. Appl. Physiol.
5. BILLAT, V., B. FLECHET, B. PETIT, G. MURIAUX, and J. P. KORALSZTEIN. Interval training
effects on aerobic performance and over-training
markers. Med. Sci. Sports Exerc.
6. BILLAT, V., A. DEMARLE, J. SLAWINSKI, M. PAIVA, and J. P. KORALSZTEIN. Physical training
characteristics of top-class marathon runners. Med. Sci. Sports Exerc.
7. BORRANI, F., R. CANDAU, G. MILLET, S. PERREY, J. FUCHSLOCHER, and J. ROUILLON. Is the V̇O2max
slow component dependent on progressive recruitment of fast-twitch fibers in trained runners?J. Appl. Physiol.
8. BOURDIN, M., A. BELLI, L. ARSAC, C. BOSCO, and J. R. LACOUR. Effect of vertical loading on energy cost and kinematics of running
in trained male subjects. J. Appl. Physiol.
9. CANDAU, R., A. BELLI, G. Y. MILLET, D. GEORGES, B. BARBIER, and J. D. ROUILLON. Energy cost and running
mechanics during a treadmill run to voluntary exhaustion in humans. Eur. J. Appl. Physiol. Occup. Physiol.
10. CAVANAGH, P. R., and K. R. WILLIAMS. The effect of stride length variation on oxygen uptake
during distance running
. Med. Sci. Sports Exerc.
11. DALLEAU, G., A. BELLI, M. BOURDIN and J. R. LACOUR. The spring-mass model and the energy cost of treadmill running
. Eur. J. Appl. Physiol. Occup. Physiol.
12. DANIELS, J. Physiological characteristics of champion male athletes. Res. Q. Exerc. Sport
13. DANIELS, J., R. YARBROUGH, and C. FOSTER. Changes in VO2 max and running
performance with training
. Eur. J. Appl. Physiol. Occup. Physiol.
14. DANIELS, J., and N. DANIELS. Running
economy of elite male and elite female runners. Med. Sports Sci. Exerc.
15. DERRICK, T., J. HAMILL, G. CALDWELL. Energy absorption of impacts during running
at various stride lengths. Med. Sports Sci. Exerc.
16. DERRICK, T., F. DEREU, and S. MCLEAN. Impacts and kinematic adjustments during an exhaustive run. Med. Sports Sci. Exerc.
17. DI PRAMPERO, P. Energetics of muscular exercise. Rev. Physiol. Biochem. Pharmacol.
18. DI PRAMPERO, P. The energy cost of human locomotion on land and in water. Int. J. Sports Med.
19. FARLEY, C., and C. TAYLOR. A mechanical trigger for the trot-gallop transition in horse. Science
20. FARLEY, C., and O. GONZALEZ. Leg stiffness and stride frequency in human running
. J. Biomech.
21. HAMILL, J., B. BATES, K. KNUTZEN, and J. SAWHILL. Variation in ground reaction force parameters at different running
speeds. Hum. Mov. Sci.
22. HAMILL, C., T. CLARKE, E. FREDERICK, L. GOODYEAR, and E. HOWLEY. Effect of grade running
on kinematics and impact force. Med. Sci. Sports Exerc.
23. HAMILL, J., T. DERRICK, and K. HOLT. Shock attenuation and stride frequency during running
. Hum. Mov. Sci.
24. HEISE, G., and P. MARTIN. “Leg spring” characteristics and the aerobic demand of running
. Med. Sci. Sports Exerc.
25. LAKE, M., and P. CAVANAGH. Six weeks of training
does not change running
mechanics or improve running
economy. Med. Sci. Sports Exerc.
26. MCFARLANE, D. Automated metabolic gas analysis system. Sports Med.
27. MCMAHON, T., G. VALIANT, and E. FREDERICK. Groucho running
. J. Appl. Physiol.
28. MORGAN, D., P. MARTIN, and G. KRAHENBUHL. Factors affecting running
economy. Sports Med.
29. MUNRO, C., D. MILLER, and A. FUGLEVAND. Ground reaction forces in running
: a re-examination. J. Biomech.
30. PAAVOLAINEN, L., K. KAKKINEN, I. HAMALAINEN A. NUMMELA, and H. RUSKO. Explosive strength training
improves 5-km running
time by improving running
economy and muscle power. J. Appl. Physiol.
31. PETRAY, C., and G. KRAHENBUHL. Running training
instruction on running
technique, and running
economy in 10 year-old males. Res. Q. Exerc. Sport
32. SLAWINSKI, J., A. DEMARLE, J. P. KORALSZTEIN, and V. BILLAT. Effect of supra-lactate threshold training
on the relationship between mechanical stride descriptors and aerobic energy cost in trained runners. Arch. Physiol. Biochem.
33. SMITH, T., L. MCNAUGHTON, and K. MARSHALL. Effects of 4-week training
using Vmax/Tmax on V̇O2max
and performance in athletes. Med. Sci. Sports Exerc.
34. TAVERNIER, M., P. COSSERAT, A. EMMENDOERFFER, et al. A 3D motion analysis system using a numerical human model. In:Proceedings of the International Society of Biomechanics Congress
, Vol. 19, Tokyo, 1997, pp. 406.
35. VERBITSKY, O., J. MIZRAHI, J. VOLOSHIN, J. TREIGER, and E. ISAKOV.Shock transmission and fatigue in human running
. J. Appl. Bio-mech.
36. WILCOX, A., and R. BULBULIAN. Change in running
economy relative to V̇O2max
during a cross-country season. J. Sports Med. Phys. Fitness
37. WILLIAMS, K., and P. CAVANAGH. Relationship between distance running
economy, and performance. J. Appl. Physiol.
38. ZAMPARO, P., R. PERINI, C. PEANO, and P. E. DI PRAMPERO. The self selected speed of running
in recreational long distance runners. Int. J. Sports Med.