Spring-Mass Behaviour during the Run of an International Triathlon Competition
Résumé
We investigated the changes in step temporal
parameters and spring-mass behaviour during
the running phase of a major international
triathlon competition. 73 elite triathletes were
followed during the 2011 World Championships
Grand Final. The running speed, ground
contact and fl ight times were assessed over a
30 m fl at section at the beginning of the 4 running
laps and towards the fi nish line, by using
a high-frequency camera (300 Hz). The leg and
vertical stiff ness, and vertical displacement of
the mass centre were calculated from step temporal
characteristics. A concomitant decrease
in running speed, vertical stiff ness and leg stiff -
ness was reported during the four running laps,
except towards the fi nish line, where these
parameters increased. Running biomechanics
was not aff ected between the beginning
and the end of the 10 km run, when triathletes
were compared for the same running speed
(1.68 ± 0.16 m vs. 1.70 ± 0.17 m for step length,
3.18 ± 0.11 Hz vs. 3.16 ± 0.15 Hz for step rate,
12.87 ± 3.14 kN.m − 1 vs.12.76 ± 3.05 kN.m − 1 for
Kleg, 31.18 ± 4.71 kN.m − 1 vs.30.74 ± 3.88 kN.m − 1
for Kvert, at lap1 and fi nish, respectively). Independent
of the cofounding eff ect of speed and
despite the neuromuscular fatigue previously
shown after a long-duration event, the lower
limb mechanical stiff ness and the overall springmass
regulation were not altered over the 10 km
triathlon run in elite competitors. This study
showed also that step length explained, to a
greater extent than step frequency, the running
speed variance in elite triathletes.