Analysis 4

Kin 355 Lab #4: Jumping Lab Data Analysis Fall 2009 You will first need to identify the cell when two events occur: (A) initiation of movement and (B) take-off. The vertical ground reaction forces (VGRF) were sampled for 3 seconds at 1000 Hz. Part One: Jumping Impulse 1. Calculate the jumping impulse (JI) by finding the area under the curve using the trapezoidal rule from the initiation of movement until take-off. The initiation of movement (point A) will be when the force curves goes below zero for the countermovement or when the force curve goes above zero for the squat. The body weight (BW) has been subtracted already, so the force will be –BW when the individual leaves the ground (point B). Trapezoidal rule = 0.5*b*(h1 + h2). This formula will be used to calculate each area between frames (b = 1/1000 seconds). You will then sum these impulses to get the total jumping impulse between points A and B for the countermovement and squat jumps. Step-by-step for each subject: * Graph VGRF for the countermovement jump. Use the cursor to determine the following points: A = initiation of movement (deviates below 0 for countermovement, above 0 for squat); B = take-off (= -BW, low point on graph). Repeat for the squat jump. * To determine the actual frame number for A (the initiation of movement), search the values in this area of the data column for the zero crossing (-10 N is a safe indicator) before the movement starts. For frames B (take off), search for when the values hit their minimum (may fluctuate ~3 N, but basically constant). * In column C enter the trapezoidal rule formula to calculate the area under the curve for each time point. The base is equal to the time between data samples. The heights are the vertical ground reactions of each time point. Copy and paste this equation down the entire column for columns C and D. * Sum the areas under the curve for the cells between point A and point B for the squat and countermovement in cells F3 and G3. This sum is the total jumping impulse. 2. Calculate the take-off velocity using the impulse-momentum relationship in cells F4 and G4. Divide the jumping impulse by the subject mass to calculate velocity. 3. Calculate the height of jump using equations of constantly accelerated motion with the takeoff velocity (an example is given in your notes) in cells F5 and G5. Jumping height = v2/2a. Part Two: Complete results section Prepare one graph comparing the jump heights calculated for the squat and countermovement jump. Use two tails and a type 1 paired t-test to determine statistical significance (p < 0.05). Include a plot of a representative countermovement trial in your lab report that indicates when points A and B occur. Make sure you take a look at your lecture notes. This analysis can be much simpler if you look at the information in the lecture. The linear kinetics notes have information specific to vertical jumping and impulse-momentum analysis.