Number of successive cycles necessary to achieve stability of selected ground reaction force variables during continuous jumping

Ments,such as walking, running and jumping, data collectedacross a single cycle might be atypical and potentially unable torepresent an individualپfs generalized performance. the studydescribed here was designed to determine the number of successivecycles due to continuous, repetitive countermovementjumping which a test subject should perform in a single experimentalsession to achieve stability of the mean of the correspondingcontinuously measured ground reaction force (grf)variables. seven vertical grf variables (period of jumpingcycle, duration of contact phase, peak force amplitude and itstiming, average rate of force development, average rate of forcerelaxation and impulse) were extracted on the cycle-by-cyclebasis from vertical jumping force time histories generated bytwelve participants who were jumping in response to regularelectronic metronome beats in the range 2-2.8 hz. stability ofthe selected grf variables across successive jumping cycleswas examined for three jumping rates (2, 2.4 and 2.8 hz) usingtwo statistical methods: intra-class correlation (icc) analysisand segmental averaging technique (sat). results of the iccanalysis indicated that an average of four successive cycles(mean 4.5 پ} 2.7 for 2 hz; 3.9 پ} 2.6 for 2.4 hz; 3.3 پ} 2.7 for2.8 hz) were necessary to achieve maximum icc values. exceptfor jumping period, maximum icc values took values from0.592 to 0.991 and all were significantly (p . 0.05) differentfrom zero. results of the sat revealed that an average of tensuccessive cycles (mean 10.5 پ} 3.5 for 2 hz; 9.2 پ} 3.8 for2.4 hz; 9.0 پ} 3.9 for 2.8 hz) were necessary to achieve stabilityof the selected parameters using criteria previously reported inthe literature. using 10 reference trials, the sat required standarddeviation criterion values of 0.49, 0.41 and 0.55 for 2 hz,2.4 hz and 2.8 hz jumping rates, respectively, in order to approximatethe icc results. the results of the study suggest thatthe icc might be a less conservative but more objective methodto evaluate stability of the data. based on these considerations, itcan be recommended that a force time history due to continuous,repetitive countermovement jumping should include minimumof four (the average from the icc analysis) and possibly asmany as nine successive jumping cycles (the upper limit of theicc analysis) to establish stable mean values of the selectedgrf data. this information is important for both experimentalmeasurements and analytical studies of grf signals due tocontinuous, repetitive countermovement jumping.