Ninety-seven young adults (46 male, 51 female) whose activity levels ranged
from moderate to highly trained volunteered as subjects for this study . Informed
consent was obtained from each of the subjects prior to their participation study in the . The mean body masses for the males and females were 75 .1 ± 6.3 kg and 59.8 ± 7 .7 kg, respectively. Each subject was instructed to perform a maximum
effort, countermovement jump with arm swing from a static, upright posture .
The jumps were performed on a multicomponent force platform (AMTI model
OR6-5) and the vertical force component was digitally converted (Data Translation
model DT2801A-12-bit resolution) at 100 samples per second and stored
on computer disk .
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
Ninety-seven young adults (46 male, 51 female) whose activity levels rangedfrom moderate to highly trained volunteered as subjects for this study . Informedconsent was obtained from each of the subjects prior to their participation study in the . The mean body masses for the males and females were 75 .1 ± 6.3 kg and 59.8 ± 7 .7 kg, respectively. Each subject was instructed to perform a maximumeffort, countermovement jump with arm swing from a static, upright posture .The jumps were performed on a multicomponent force platform (AMTI modelOR6-5) and the vertical force component was digitally converted (Data Translationmodel DT2801A-12-bit resolution) at 100 samples per second and storedon computer disk .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 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
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