We calculated mechanical power for each sample by multiplying the vertical
force by the vertical velocity of the subject's center of gravity . We determined
these velocities by subtracting body weight from the force-time curve, dividing
by body mass, and integrating with respect to time using the trapezoidal rule for numerical integration (Hornbeck, 1967). Vertical impulse was calculated by
subtraction of body weight and integration of the force-time curve . We normalized
all force values to units of body weight (BW) by dividing the ground reaction
forces by the subject's body weight in Newtons . Similarly, all power values were
normalized to WattsBW, and all impulse values were normalized to BWs . This
normalization was performed to control for the confounding effects that mass
may have had on the relationships between certain variables . An example of a
typical force-time curve is shown in Figure 1 and of a typical power-time curve
in Figure 2 .
The instant of takeoff was defined as the instant that ended the takeoff
phase and began the flight phase. The low point was defined as the instant that
the center of gravity had zero velocity and was at a minimum height during the
takeoff phase . The temporal variables are labeled with uppercase letters and the
kinetic variables are labled with lowercase letters in Figures 1 and 2 and are summarized in Table 1 . Ensemble averages were plotted of the five highest and
the five lowest jumps to allow qualitative examination of the characteristics of good and poor performances . We performed an independent t test comparing the
means of the height attained by jumps that had a single maximum peak of force
with the height attained by jumps that had two or more peaks in the takeoff phase .
In addition to the 15 variables identified in Figures I and 2, four additional
calculations were made . The average slope from the minimum force to the
maximum force (p) was calculated as
We calculated mechanical power for each sample by multiplying the verticalforce by the vertical velocity of the subject's center of gravity . We determinedthese velocities by subtracting body weight from the force-time curve, dividingby body mass, and integrating with respect to time using the trapezoidal rule for numerical integration (Hornbeck, 1967). Vertical impulse was calculated bysubtraction of body weight and integration of the force-time curve . We normalizedall force values to units of body weight (BW) by dividing the ground reactionforces by the subject's body weight in Newtons . Similarly, all power values werenormalized to WattsBW, and all impulse values were normalized to BWs . Thisnormalization was performed to control for the confounding effects that massmay have had on the relationships between certain variables . An example of atypical force-time curve is shown in Figure 1 and of a typical power-time curvein Figure 2 .The instant of takeoff was defined as the instant that ended the takeoffphase and began the flight phase. The low point was defined as the instant thatthe center of gravity had zero velocity and was at a minimum height during thetakeoff phase . The temporal variables are labeled with uppercase letters and thekinetic variables are labled with lowercase letters in Figures 1 and 2 and are summarized in Table 1 . Ensemble averages were plotted of the five highest andthe five lowest jumps to allow qualitative examination of the characteristics of good and poor performances . We performed an independent t test comparing themeans of the height attained by jumps that had a single maximum peak of forcewith the height attained by jumps that had two or more peaks in the takeoff phase .In addition to the 15 variables identified in Figures I and 2, four additionalcalculations were made . The average slope from the minimum force to themaximum force (p) was calculated as
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