Seasonal fluctuations of force production in high jumpers.

To investigate the influence of training on the isometric force-time (f-t) characteristics and on dynamic force production, eight Finnish male high jumpers were tested six to seven times during a twelve month period. The variations in the isometric maximal force, in the rate of isometric force development (RFD), as well as in the vertical jumping height during the follow-up period were compared to the respective changes in the high jump result. The RFD and vertical jumping heights were found to show their highest values relative to the other seasons during the competitive seasons in January and July-August. The changes in the maximal isometric strengths did not coincide with the changes in the high jump results. The rate of the isometric force development was concluded to be a rather good indicator of the momentary high jumping condition, even though it was realized that in such a technical sport event as the high jump the prediction of the jumping performance by some physical performance variables is approximate.