A PORTABLE SET-UP FOR COLLECTING TRIPLE
JUMP GROUND REACTION FORCES

Budapest-Siofok, Hungary, July 2-6, 1994

Presentation Abstract Below

Clifford Larkins,
The University of Michigan, USA and

While ground reaction forces (GRFs) have been commonly assessed during running and some single take-off activities such as the long jump and the high jump, little is known about these forces during the triple jump. The purpose of this study was to design, build, and test a portable triple jump runway that could be used to collect  data for all three takeoffs in succession. Previous studies have used only one or two plates. The portable runway was designed to house three Bertec force plates and was built out of compressed ply wood. The force plate housing holes were spaced 3 meters (10 feet) apart which can accommodate a minimum hop-step ratio of 3m:3m (10ft:10ft). The runway was also designed so that the sections housing the force plates can be 'telescoped' out in 30.48 cm (1 foot) increments. Given these incremental increases, the maximum hop-step ratios possible are 4.52m:4.52m (15ft:15ft). Because the force plates were not rigidly mounted to the ground, a number of precautions were taken to eliminate possible measurement errors. In order to eliminate sliding, the runway structure was precision made so that when the force plates were set into their housing, the bottom of the plates fit snugly against the walls of the structure while allowing the top plate to float freely. In order to eliminate the possibility of rocking, a flat formica surface was placed under the plates. Both the floor and the formica surface were tested with a leveler and determined to be flat. Testing of the portable forceplate setup was done using three Bertec force plates (40cm x 60cm) spaced using the minimum hop-step ratios, 3m:3m. One subject performed 15 triple jumps (using a six step approach), each jump 9 meters total distance (3m:3m:3m). This procedure is appropriate because this is a typical practice session for the collegian female jumpers coached by the researcher. The final landing was onto gymnastics mats (not typical). The study showed that accurate ground reaction force data can be collected for the triple jump for all three takeoffs in succession. This type of setup would be very useful to scientifically oriented coaches for use during practice sessions. It would also be useful for researchers interested in modeling ground reaction forces in the triple jump. However, it probably would not be useful for collecting data for jumps using a full approach. The most noticeable finding related to the force-time curves was that each takeoff phase has its own characteristic force-time curve. This has not been completely documented in previous studies that used only one or two force plates.

REFERENCES

Amadio, A.C. (1985). Biomechanische analyse des dreisprungs. Doctoral dissertation, Deutsche Sporthochschule, Koln.

Hay, J. G. (1993). Citius, altius, longius (faster, higher, longer): The biomechanics of jumping for distance. Journal of Biomechanics 26:7-21.

Ramey, M.R. and Williams, K.R. (1985). Ground reaction forces in the triple jump, International Journal of Sport Biomechanics 1:233-239.