european college of sport science

Wednesday, June 24th, 2009
Fukuda, K., Ito, A. (2004) Relationship between sprint running velocity and changes in the horizontal velocity of the body’s center of gravity
during the foot contact phase. Japan J. Phys. Educ. Hlth. Sport Sci. 49: 29-39 (in Japanese).
INITIAL ROTATIONAL VELOCITY OF HIPS IS A KEY FACTOR IN DISCUS THROW
YAMAMOTO, D., ITO, A.
OSAKA UNIVERSITY OF HEALTH AND SPORT SCIENCES
The purpose of this study was to investigate relationships between the official discus throwing distance and the movements of discus
throw or the release conditions of discus. The throwing movements of 18 male discus throwers were recorded by two digital video cameras
(60 Hz) in the 11th World Championships in Athletics in Osaka and the Japan Track and Field National Championships, and also in
experimental trials. From the video data of trials when each athlete had thrown the longest distance, real-life three-dimensional coordinates
of their body landmarks and the center of the discus were calculated with the direct linear transformation method. The throwing
movements were divided into six instants and analyzed.
The initial velocity and the height of discus at the moment of release showed a positive correlation with the throwing distance. The throwing
distance had no relation with the release height normalized by the body height and the release angle. These results suggested that
the initial velocity and the release height of discus must be important to take longer throws, however the release height was dependent
on the body height. At the right-foot takeoff (R-off) and the left-foot touchdown (L-on), both discus velocity and rotational velocity of hips
indicated positive correlations with the throwing distance. Positive relations were shown between the discus velocity at R-off and rotational
velocity of shoulders and hips at the same instants. The discus velocity at L-on had a positive relationship with the rotational velocity
of shoulders at that time. The higher discus velocity at R-off of longer-distance throwers suggested that increase of rotational velocity of
the whole body at the beginning of throwing movements is important. The translational velocity of the center of mass including thrower
and discus (CM) at left-foot takeoff (L-off), right-foot touchdown (R-on) and L-on were recognized as a negative correlation with the official
distance. The translational velocity of CM showed a negative relation with the rotational velocity of hips at L-off, and also velocity of CM
indicated a negative correlation with torsion angle of trunk at R-on. These results suggested that longer-distance throwers might keep
lower translational velocity of CM to obtain lager torsion angle of trunk during the flight phase.
These findings were concluded as follows. Differences in movements which determine throwing distance appeared from the beginning
of throwing movements. That is, it is necessary for throwers to increase discus velocity with rotational velocities of shoulders and hips
from the initial phase of throwing. At the middle phase, to maintain a lower translational velocity of CM must obtain higher rotational
velocity of hips, and thus a larger torsion angle of trunk is produced by the higher rotational velocity of hips. The increase of rotational
velocity of hips, shoulders and arm swing occurred in order during the final phase before discus release.
FOOT STRIKE PATTERNS OF HIGH LEVEL MALE 800M RUNNERS
HAYES, P.R., CAPLAN, N.
NORTHUMBRIA UNIVERSITY
Recently Hasegawa et al (2007) investigated the foot strike patterns and ground contact times during a half marathon. They found that
foot strike patterns were related to running speed with forefoot and midfoot strikers exhibiting shorter ground contact times and faster
running speeds. The purpose of this study was to conduct a similar analysis in male 800m runners. Ten seeded sub-elite races were
filmed on one evening at a British Milers Club meeting. Seventy one runners were filmed by a 100-Hz video camera at a height of 15 cm
placed 15 m from the start / finish line. All runners completed their race and were captured on both laps of the race. Average race time
showed a range of 14.46 s from 107.53 to 121.99 s with a mean 115.21 +/- 3.41s and coefficient of variation of 3.0%. The mean contact
time for lap 1 was 156 +/- 12 ms and for lap 2 it was 168 +/- 16 ms. On lap 1 35%, 48% and 17% of runners made initial ground contact
with the forefoot, midfoot and heel respectively. For lap 2 these values were 34%, 51% and 15%. Two way ANOVA s comparing ground
contact time across the different races for lap 1 and lap 2 revealed significant main effects for both lap (F1,61 = 46.315; P < 0.000) and race
(F9,61 = 2.766; P = 0.009). Those runners who displayed the same foot strike pattern on both laps (N = 48) were entered in to a 2x3
ANOVA comparing ground contact times by lap and foot strike position. This showed significant main effects for both lap (F1,45 = 32.600;
P < 0.000) and foot strike position (F2,45 = 12.779; P < 0.000). Post-hoc analysis revealed significant differences between the heel and
both other contact points. The shortest ground contact times were for the forefoot (156 ms) followed by midfoot (161 ms) and heel (177 ms).
For each contact point there was a significant increase (forefoot – t15 = 2.782, P = 0.014; midfoot – t24 = 3.501, P = 0.002; heel – t8 =
5.292, P = 0.001) in ground contact time between lap 1 and lap 2. Linear regression revealed a significant relationship between average
running speed and ground contact time for both lap 1 and lap 2, however only a small portion of average running speed was accounted
for (10.3% lap 1 and 11.9% lap 2). This study found that foot strike patterns were related to running speed. The relationship between
ground contact time and running speed supports the notion of a spring-mass model of locomotion. Over the course of an 800m race
ground contact time increased irrespective of foot strike position. This implies an element of fatigue, with runners presumably requiring
longer to generate the same impulse. Alternatively, this may have been a reflection of the pacing strategy during the races, with all races
adopting a first lap that was quicker than average race speed.
References
Hasegawa, H., Yamauchi, T., and Kraemer, W.J. (2007) Foot strike patterns of runners at the 15-km point during an elite level half marathon.
Journal of Strength and Conditioning Research 21(3): 888-893.
FOOT STRIKE PATTERNS OF HIGH LEVEL FEMALE 800M RUNNERS
HAYES, P.R., CAPLAN, N.
NORTHUMBRIA UNIVERSITY
Recently Hasegawa et al (2007) investigated foot strike patterns and ground contact times during a half marathon. They found foot strike
patterns were related to running speed with forefoot and midfoot strikers exhibiting shorter ground contact times and faster running
speeds. The purpose of this study was to conduct a similar analysis in female 800m runners. Five seeded sub-elite races were filmed on
one evening at a British Milers Club meeting. The runners (N = 34) were filmed by a 100-Hz video camera at a height of 15 cm placed 15
m from the start / finish line. All runners completed their race and were captured on both laps of the race. Average race time showed a
range of 15.85 s with a mean 132.84 +/- 4.43 and CV of 3.3%. Mean contact time for lap 1 and lap 2 were 163 +/- 14 ms and 179 +/- 16
ms. On lap 1 27%, 44% and 29% of runners made initial ground contact with the forefoot, midfoot and heel respectively. These values
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