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All force data was processed and analysed using Ballistic Measurement System (BMS) Software (v2012.3.7). Only related force data were normalised to body weight after analysing all of the test variables (force related variables were peak RFD, peak force, peak power, impulse at 100 ms, 200 ms, 250 ms, and 300 ms) by dividing the final results by body weight. The concentric phase was the only phase analysed throughout all of the tests. After recording results from the three successful trials for each participant, the mean value over the three trials was calculated and reported. For the 10 consecutive hops test, the mean value of the resultant 10 successful hops from each trial was calculated, and then the final mean value of the three trials was reported. It was taken into consideration that the first provided force in the 10 hops force-time data was not analysed, as it was a countermovement hop which had different force- time characteristics to the rest of the nine hops. The software identifies the onset of movement with a threshold set at 40 N. A detailed analysis of each of the individual tests is explained in the following sections:

68 2.2.4.1 Squat Hop Data Analysis

The data resulting from the data collection did not include eccentric phase in force-time curve (concentric phase only) (see Figure 2.13). The onset of movement for the concentric phase in the squat hop test was set with thresholds of movement at 40 N. The instants of take-off and touchdown were defined as the instants at which vertical force had fallen below and above, respectively, a threshold equal to five times the standard deviation of the residual force which was calculated during the first 200 milliseconds of flight phase of the hop (i.e. when the force plate was unloaded). The 200 millisecond timeframe for this residual force threshold calculation is in line with previous suggestions (Moir, 2008). The dependant variables analysed included peak force, peak velocity, peak power, and peak instantaneous RFD. Dependant variables were calculated from the force-time data during the concentric phase, as described below.

Peak force was identified as the highest force achieved over the force-time trace during the activity prior to take off. Centre of mass velocity for squat hop was determined by dividing vertical force data (minus body weight) by body mass and then integrating the product using the trapezoid rule (Moir, 2008). Instantaneous power was then calculated by multiplying vertical force and velocity data at each time point, with the highest resultant value representing peak power.

Peak instantaneous RFD was calculated as the difference between two adjacent force samples divided by the intersample time interval 0.00167 second (1 / 600 Hz = 0.00167) in order to calculate the instantaneous RFD. The peak instantaneous RFD was calculated as the maximum value achieved over the first derivative of the force-time trace.

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2.2.4.2 Countermovement Hop Data Analysis

The final collected data on force generation included the eccentric and concentric work phases in a force-time curve. In CMJ, there is an eccentric action of agonist muscles followed by a concentric action, and jump performance results, generally, from the use of the elastic energy generated in the stretch shortening cycle (SSC) (Pupo et al., 2012). The unweighting phase is considered to occur between the onset of countermovement hop movement and the instant of peak negative centre of mass velocity (which is equal to body weight). The eccentric phase of the countermovement hop is defined as occurring between the instants of peak negative centre of mass velocity and zero centre of mass velocity. The onset of movement for the concentric phase in the countermovement hop test was set with thresholds of movement at 40 N. The instants of take-off and touchdown were defined as the instants at which vertical force had fallen below and above, respectively, a threshold equal to five times the standard deviation of the residual force, which was calculated during the first 200 milliseconds of the flight phase of the hop (i.e. when the force plate was unloaded). The 200 millisecond timeframe of this residual force threshold calculation is in line with previous suggestions (Moir, 2008).

The dependant variables analysed included peak force, peak velocity, peak power, and peak instantaneous RFD during the concentric phase. Dependant variables were calculated from the force-time data, as explained abovein the squat hop data analysis.

2.2.4.3 Ten Consecutive Hops Data Analysis

The final data collected for the ten consecutive force generations included ten eccentric and concentric phases in a force-time curve. Here, the analysis was done over the proportion of the whole phase (e.g. concentric phaseonly) for each of the individual forces, and not for the overall phase, which included the landing force and eccentric phase. The unweighting phase was considered to have occurred between the peak landing vertical force and the instant of peak negative centre of mass velocity (which is equal to body weight). The eccentric phase was defined as occurring between the instants of peak negative centre of mass velocity and zero centre of mass velocity. The onset of movement for the concentric phase was set with thresholds of movement at 40 N. The instants of take-off and touchdown were defined as the instants at which vertical force had fallen below and above, respectively, a threshold equal to five times the standard deviation of the residual force, which was calculated during the first 200 milliseconds of flight phase of the hop (i.e. when the force plate was unloaded). The 200 millisecond timeframe of this residual force threshold calculation is in line with previous suggestions (Moir, 2008).

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The dependant variables analysed included peak force, peak velocity, peak power, and peak instantaneous RFD during the concentric phase. Dependant variables were calculated from the force-time data, as explained abovein the squat hop data analysis.

2.2.4.4 Isometric Mid-Thigh Pull Data Analysis

The final collected force generation data included only the isometric phase in a force-time curve. In this test, peak force was known as the greatest recorded instantaneous force on the body during an IMTP test, so the peak force was performed at the beginning of the trial, otherwise it was considered a failed trial (see Figure 2.14). The start of each trial was determined as increase in force greater than 40 N. The dependant variables analysed included peak force, peak instantaneous RFD, impulse 0-100 milliseconds (ms), impulse 0-200 ms, impulse 0-250 ms, and impulse 0-300 ms. Dependant variables were calculated from the force-time data, as described below:

Peak force and peak instantaneous RFD data were calculated from the force-time data as previously explained above in the squat hop data analysis. For the calculation of impulse at 100, 200, 250, and 300 ms, the vertical force-time curve was integrated over 100-, 200-, 250- and 300-millisecond windows from the onset of force production, when the vertical force increased above a threshold of 40 N, (Comfort et al., 2015).

Figure 2.14. Illustrates the analyses of the IMTP data