KHP415Lab2

KHP 415 - Biomechanics of Human Movement Laboratory Lab 2 –Linear Kinematics (running kinematics) Reading Assignment : Enoka, R.M. (1994). Neuromechanical Basis of Kinesiology , 2 nd ed. Champaign, IL: Human Kinetics, pp. 14-16 (available on Canvas). Introduction : In running events, a competitive athlete's goal is to cover a given distance in the shortest possible time. From a biomechanics perspective, the goal is to cover the distance with the highest possible average velocity or speed. By describing various kinematic aspects of running we can gain information about strengths and weaknesses in an athlete's performance that may lead to better running times or a reduced potential for injury. This laboratory focuses on some of the most basic descriptors of running performance—velocity, step length, step time, and step rate. The lab consists of two parts, the first focusing on distance running kinematics and the second on sprinting kinematics. Several students will be asked to run. Please come to class wearing appropriate clothing and footwear for running. Purposes : 1) To examine the association between step length, step rate, and velocity during running, and 2) to examine the velocity profile for a 25 m sprint. Equipment and supplies needed : Please bring a calculator, graph paper, and a ruler so that you can plot results from your analyses. All other equipment needs will be provided. Definitions and Equations : Stride –the basic unit of motion for walking and running reflecting one complete cycle of motion; commonly defined as the motion occurring between successive contacts of the same foot (i.e., right foot contact to next right foot contact) Step –one half of a complete stride (e.g., right foot contact to left foot contact) Step length (SL) – the distance traveled per step Step time (ST ) – the time required to complete one step Step rate (SR) – the frequency at which steps are taken (i.e., number of steps per unit of time); inverse of step time = d / t (1) running velocity = step length / step time = SL / ST (2) running velocity = step length × step rate = SL × SR (3) Part 1 – Association between step length, step rate, and running velocity Data Collection : · Establish groups of approximately 8-10 students: one volunteer runner, one starter, 3-4 step counters, 2-3 timers, 1 data recorder. · A 25-meter running course will be established for the tests. The starter will be positioned at the starting line. Step counters will be positioned in the middle of the 25 meter measurement zone. Timers and data recorder will be positioned at the finish line. · The volunteer runner from each group will run through the 25 meter course two times at each of five self- selected speeds--very slow (slow jogging speed) ,slow, medium (comfortable distance running speed), fast (fast distance running speed), and very fast (at or just below maximum sprinting capability). Be careful! No injuries, please! For each trial, the speed should be constant through the 25 m measurement zone. This will require the runner to start his or her run approximately 10 m before the starting line. · As the runner passes the starting line, the starter signals the timers to begin timing the run and the step counters

to begin to count the number of foot strikes over the 25 m course. As the runner crosses the finish line, the timers stop their stop watches, compute an average of their times to the nearest 0.01 s, and supply the average time for the run to the recorder. Similarly, the step counters report to the recorder an average of the number of foot strikes (to the nearest 0.1 footstrikes) taken over the 25 m distance. These results, which will be shared with all group members, are recorded initially on the data recorder's data sheet in Table 1 that follows. TABLE 1. Raw data for 25 m run times and footstrike counts Subject: Velocity/Trial Distance (m) Time (s) Footstrikes (#) Steps (footstrikes – 1) Very slow (trial 1) 25 7.8 22.4 21.4 Very slow (trial 2) 25 7.9 22.6 21.6 Very slow (Avg.) 25 7.85 22.5 21.5 Slow (trial 1) 25 7.0 18.2 17.2 Slow (trial 2) 25 7.1 20 19 Slow (Avg.) 25 7.05 19.1 18.1 Medium (trial 1) 25 5.8 15.6 14.6 Medium (trial 2) 25 5.7 17 16 Medium (Avg.) 25 5.75 16.3 15.3 Fast (trial 1) 25 4.6 14.2 13.2 Fast (trial 2) 25 4.7 14.4 13.4 Fast (Avg.) 25 4.65 14.3 13.3 Very fast (trial 1) 25 3.3 12.4 11.4 Very fast (trial 2) 25 2.8 13.4 12.4 Very fast (Avg.) 25 3.05 12.9 11.9 Data Analysis: Using the distance traveled (25 m), time, and step information for each speed condition from the table above, compute: a) average running velocity over the 25 m course, b) average step length (SL), c) average step time (ST), and d) average step rate (SR). Record the results below in Table 2. TABLE 2. Average results for velocity, step length, step time, and step rate Velocity condition Ave. velocity (m/s) Ave. SL (m) Ave. ST (s) Ave. SR (steps/s) Very slow 3.18 1.16 .37 2.74 Slow 3.55 1.38 .39 2.57 Medium 4.35 1.63 .38 2.66 Fast 5.37 1.88 .35 2.86 Very fast 8.2 2.1 .26 3.9 Part 2--Velocity Profile of Sprinting Performance Data Collection : Establish a group of approximately 12 students: one volunteer sprinter, a starter, 10 timers Establish a 25 m sprint course with cones positioned at the start line and at 5, 10, 15, 20, and 25 m points. The starter will be positioned at the starting line. Two timers will be positioned 5, 10, 15, 20, and 25 m from the start line (i.e., 2 timers at each 5 m location). The volunteer sprinter will complete three 25 m sprinting trials, beginning each trial from a standing start . For each trial, the starter, facing toward the timers, will give a loud "ready-set-go" sequence of verbal commands at which time the runner will initiate his or her sprint to the finish line and all timers will start their stopwatches. As the runner passes any given 5 m position, the timers at that location stop their stopwatches. A data recorder for the group will then record in Table 3 below the average times (nearest 0.01 s) recorded at each 5 m position.