Weiss, L. W., Schilling, B. K., Fry, A. C., Chiu, L. Z., & Moore, C. A. (2009). Expressions of strength and average rate of dynamic force development: Are these measures related? ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 2764.

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"Average rate of force development may be calculated as DF / DT. The elapsed time for force is based upon operationally-defined starting and ending points. Specific time segments of RFD have been proposed as being unique for each individual with implications for both performance and training. These segments consist of the first and second halves of the total elapsed time for RFD. The first half is referred to as the “start gradient” (SG), and the second half, the “acceleration gradient” (AG). It has been reported that RFD and SG have little association with peak force (PkF). Although often associated with isometric force, RFD might also be considered for dynamic performance (DRFD). Dynamometers exist that measure only dynamic actions, so associations between the analogous segments of DRFD may be examined."

This study determined the association between various aspects of strength and dynamic performance for two “explosive” lifts to ascertain if they represent unique characteristics. Ss (N = 48) who had systematically weight-trained for at least three months performed three practice sessions. Testing took place during two identical sessions in which 30% 1 RM parallel jump squats and 90% 1 RM hang-power cleans were performed in duplicate.

For the squat, dynamic performance was associated with the start gradient (R = .73), acceleration gradient (r = 1.00), peak force (r = .66), peak power (r = .82), 1 RM (r = .44), and relative 1 RM (r = .44). For the hang-power clean, dynamic performance was associated the start gradient(r = .98), acceleration gradient (r = 1.00), peak force (r =.88), peak power (r =.82), 1 RM (r =.61), and relative 1 RM (r =.59). The degrees of association in these relationships varied considerably.

Implication. For squats and hang power cleans, dynamic performance appears to be directly related to the acceleration gradient, highly related to the start gradient, peak force, and peak power, and moderately related to 1 RM and relative 1 RM. The change in performance of a strength activity does not necessarily mean that other aspects of the performance will be altered along traditional expectations.

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