EFFECTS OF PRACTICE ON INTERSEGMENTAL COORDINATION
AbstractINTRODUCTION Coordination has often been evaluated based on the timing and sequencing of segmental contributions. Highly skilled strikers employ a sequential pattern because more force can be applied by the transfer of momentum principle. Novice performers exhibit a simultaneous pattern (Kreighbaum & Barthels, 1990). The purpose of the study was to evaluate the changes over time in intersegmental coordination as a result of practicing a racquetball forehand drive serve. METHODS Novice female adult participants (N = 10) were videotaped before and after 10 rnin of practicing a racquetball forehand drive serve on day 1, and after practice on consecutive days 2 through 5. Coordination was evaluated based on analysis of the graphical displays of the angular velocities of the pelvis, upper torso, shoulder, elbow, and wrist. Because coordination patterns often fall somewhere between simultaneous and sequential, a method of categorization was adapted. Shared positive contribution (SPC) was assessed between each of the adjacent segments and then averaged. SPC was calculated as the time both segments were in positive propulsion divided by the total time either segment was in positive propulsion (Bird, Hills, & Hudson, 1991). Any value over 100% indicated a distal to proximal initiation of propulsion (an immature pattern of coordination). The following classifications were used: (a) sequential, 0%-33% SPC; (b) intermediate, 34%-66% SPC; (c) simultaneous, 67%- 100% SPC; and (d) jerky, 101%-200%. RESULTS Results of the 60 trials were categorized as follows; (a) 2 sequential, (b) 21 intermediate, (c) 30 simultaneous, and (d) 7 jerky. Most of the participants (6 of 10) exhibited the same pattern on trial 6 as on trial I. Of the 4 whose patterns changed, 3 moved to a better (more sequential) category and the 4th moved to an inferior (more simultaneous) pattern. CONCLUSIONS Although improvement in coordination over the 5 days was not documented, evidence that novice participants of a striking task generally employ a simultaneous pattern of coordination was observed. Three participants did make a positive categorical change. Perhaps with more practice, a higher number of participants would have advanced to a more sequential pattern of coordination. REFERENCES Bird, M., Hills, L., & Hudson, J. L. (1991). Intersegmental coordination: An exploration of context. In C. Tant, P. Patterson, & S. York (Eds.), Biomechanics in Sports IX: Proceedings of the 9th International Symposium on Biomechanics in Sports (pp. 233-237). Ames, IA: Iowa State University. Kreighbaum, E., & Barthels, K. M. (1990). Biomechanics: A qualitative approach for studying human movement (3rd ed.). New York: Macmillan.