Effect of vertical loading on energy cost and kinematics of running
in trained male subjects.
Bourdin, M., A. Belli, L. M. Arsac, C. Bosco, and J. R. Lacour.
Laboratoire de Physiologie -GIP Exercice, Facult[acute]e de
M[acute]edecine. Lyon-Sud, BP : 12, F 69921 Oullins Cedex, France
APStracts 2:0339A, 1995.
This investigation examined the effect of vertical loading during
level treadmill running on net energy cost of running expressed per
kg of body mass per m of distance covered (Cr) and some concomitant
kinematic and neuromuscular adaptations. The tested hypothesis was
that running with a vertical load increases the use of muscle elastic
capacity, thus improving efficiency. The studied group consisted of
ten trained male runners (height: 177.2 +/- 6.5 cm; body mass: 70.7
+/- 5.4 kg and Cr: 3.78 +/- 0.17 J. kg-1.m-1). It was first observed
that at a given velocity (5 m.s-1), a low Cr was significantly
associated with a low external work of the center of mass of the body
(Wext., expressed in J.kg-1.m-1) and a high eccentric to concentric
ratio of integrated electromyographic activity (RECC/CON) for VL.
These results indicated that both Wext. and RECC/CON for VL could
explain a large part of the inter individual variations in Cr. Then
secondly, the intra individual variation in Wext. and RECC/CON due to
vertical loading were explored for subjects running at 5 m.s-1 with a
weight jacket containing 9.3% of their body mass. A comparison with a
non parametric paired test showed that in loaded (L) condition, net
metabolic power (, expressed in W) increased significantly (P <
0.01) by 4.6%, but not in direct proportion to body mass increase. As
a result, Cr was significantly reduced by 5.1% (P < 0.01). While
in L condition, Wext. expressed in J.kg-1.m-1 decrease significantly
(P < 0.05) by 4%. The results of the linear regression showed
that the variations in Cr and Wext. due to vertical loading were
significantly and positively correlated (r = 0.75; P < 0.01).
Net positive external efficiency as defined by the ratio of Wext./Cr
was the same for UL and L conditions suggesting that movement
efficiency did not change with trunk loading. Since RECC/CON could be
a good index of effectiveness in stretch - shortening cycle (SSC),
the results observed in this study did not give conclusive evidence
that SSC for Gastrocnemius Lateralis and Vastus Lateralis was an
important factor for the improvement of energy cost of running due to
vertical loading. It was then concluded that the significant
improvement of Cr observed when the load was added was mainly due to
the fact that Wext. was significantly decreased.
Received 14 June 1994; accepted in final form 24 July 1995.
APS Manuscript Number A588-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 August 1995.