Motions at the knee and hip joints were remarkably similar during both the springboard and platform jumps. Range of motion at the hip was identical during both dives (83�), and there was only a 3� difference in range of motion at the knee. A major difference, however, was that lower leg segment velocity was 121 deg/sec greater during the ascent phase of the platform jump. Maximum angular velocity occurs at approximately 76% of total movement time for both dives. When comparing the ascent phase of both movements, maximum angular velocity of the lower leg occurred at 57% on springboard, and 86% on platform.
The similarity in range of motion is due to several factors. First, our subject has had extensive diving experience and competes on a national level. Another invariant feature was that the subject performed the same movement during each trial. The variable for the two movements was the type of diving surface. At the onset of the platform dive, hip angle decreases while the knee remains fully extended. This creates a "sitting" motion which helps move the diver away from the platform. At the end of the movement, the sitting motion results in a decoupling of knee and hip joint movement, where the knee is fixed in full extension and the hip continues to extend. The most significant difference between the two movements was lower leg angular velocity. It was an important factor in platform diving because it projected the diver vertically and away from the platform. Lower leg angular velocity was slower during the ascent phase of the springboard dive because the subject could rely on the elasticity of the board to project him vertically and horizontally. This is the reason a diver bends his/her knees deeply and loads the diving board. When the board is pushed down it reacts by pushing up on the diver. The angle at which the diver loads the board is the angle at which the diver leaves the board. Therefore, the motion of the board plus the movement of the diver contributes to the resultant vertical and horizontal motion.
We chose to focus our study on the lower extremity and were unable to account for specific back press techniques used by other athletes. A larger video frame would have allowed for greater compression of the springboard and thus increased height during the springboard jump. A next area of research could be to determine which press creates greater force at the knee and hip joint and maximum performance. In addition, motions of the upper extremity could be investigated to determine what impact they have on overall diving performance.
Kooi, B.W. and Kuipers, M. (1994). The Dynamics of Springboards. Journal of Applied Biomechanics. 10, 335-351.
Billingsley, Hobie. (1965). Diving Illustrated. Portland, CT: Taylor Publishing.