Kuntz, Jon R.

Terauds, Juris

English

ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive

FORCE MEASUREMENTS IN JOGGING USING BIOMECHANICS CINEMATOGRAPHY Jon R. Kuntz University of Alberta Edmonton, Alberta, Canada Juris Terauds Research Center for Sports Del Mar, California 92014 In order to measure force generation during jogging outside a laboratory situation, biomechanics cinematography (BC) may be a useful procedure. However, as useful as it may be, precise and practical force measurement procedures through BC have not been developed. Cinematography, a non-invasive technique, eliminates the need for any physical limitations or laboratory-controlled experimental procedures for the acquisition of data. Through the use of cinematographical procedures, data is easily obtainable and, if so desired, without disturbing the subject in any way. This guarantees a true-life performance as compared to one in which alternate experimental procedures could very easily cause the subject's performance to be unnatural. The purpose of this study was to develop a method utilizing biomechanics cinematography (BC) exclusively for determining the vertical-force component of jogging. An attempt was made, via BC, to reproduce the vertical-force characteristics of jogging as recorded by a force platform. DEFINITION OF TERMS In order to produce clarity for this paper, several terms are defined below: Biomechanics cinematography (BC): The acquisition and sub­sequent analysis of data specific to biomechanics research through the use of cinematographical procedures and computer techniques. Jogging: A form of locomotion in which the gait is much slower than running, but faster than walking. (Walking is char­acterized by having no air-borne phase). Stride: A measurement taken from the initial contact of one foot to the subsequent contact of the same foot. 361 <Q < t-tl .......... 0""':1:11 a III 'tl 'tlt-o-aO'==~ ..... n,o ..... ~ ~ ~ ~::r ll>::rOrolll::l~ _~ "'...... ,.. -,. ---nt-tllll!TS' ... _~ ~ 465 12 m Timing Light Generator 1 Camera Tektronix Dsci lloscopc r--1 m a-( Camera 2 Phase-lock FIGURE 1 EXPERIMENTAL SETUP PCBt18CA Power Supply D Foe," Pl.tfoem 15 m Run-up L... r-Non-support phase: The period of a stride when the body is not in contact with the running surface. (A walking stride lacks a non-support phase). Support phase: The period of a stride when either foot is in contact with the running surface. Each stride is composed of two support phases (i.e. right-support phase and left-support phase) . Foot-strike phase: That period of the support phase from the initial contact to when the foot is firmly fixed or flat on the running surface. Mid-strike phase: That period of the support phase when the foot is firmly fixed until the instant the heel begins to rise off the surface. Takeoff phase: That period of the support phase from the instant the heel begins to rise until the toes break contact with the running surface. METHODS AND PROCEDURES Subjects The sUbjects in this study ranged in age from 27 to 62 years for the males, and 23 to 30 years for the females. Their weight ranged from 637.0 to 997.6 Newtons (N) and 517.4 to 570.4 N for males and females respectively. The subjects first performed barefooted, and then repeated the test using jogging shoes. Each subject was given as many trials as needed to contact the force plate without altering the stride or looking at the force-measuring device. The sUbject decided which foot to use for contacting the force plate. Apparatus Two Photo Sonics IPL 16mm (pin registered) cameras with Angenieux 12-120 zoom lenses were used. A phase-lock system was used to ensure synchronized data between the two cameras. Camera One, which recorded the side view of the subjects, was positioned with its optical axis bisecting the force platform and perpendic­ular to the joggers' plane of motion. The camera was leveled, 12 meters from the platform, at a height of 1.2 meters. Camera Two recorded the force platform output display from a Tektronix 465 oscilloscope. This .camera was positioned 1.0 meter from the oscilloscope and adjusted so the entire screen from the oscillo­scope encompassed the field of view of the camera 270 364 f ( t Both cameras operated at a frame rate of 100 FPS and with a w shutter angle of 30°; this produced an exposure time of 1/1200 S. h Ektachrome 7250 film with an ASA rating of 400 was forced one stop a to produce an equivalent rating of 800 ASA. A Pentax 1° Spotmeterf VI was used for all light measurements. c A timing-light generator was connected to both cameras. The timing-light generator was set at 10 Hz and switched to 100 Hz for roughly 0.1 seconds after the cameras reached operating speed. The marks produced on the film were used to determine the actual tJ camera-frame rate and also served as reference points for matchingpI of original frames on the two films. CC tc A Stoelting's Force-Sensitive Platform was modified by the 1] installation of a PCB208A04 piezoelectric-force transducer for mE measuring the vertical-force component. The transducer was me powered by a PCB480A DC power supply. A Tektronix 465 oscillo­de scope produced the analog force signal from the transducer. The me oscilloscope was operating with a sensitivity of 0.01 volts/div­ision. The force platform was fitted into a specially-constructed casing and leveled flush with the jogging surface. A 1.0 meter Ph area on the force platform in the plane of motion was marked for ti later computation of projected size to real-life size. PI an Calibration ma re The transducer used for vertical-force measurement was cal­Mo ibrated by the manufacturer and reported to be linear to within th 1% and to have a maximum compression of 4450N. The linearity was Da	 tested from 0.0 to l200N in 225N intervals and found to be consis­tent with the manufacturer's claims. The modified force platform was checked for uniformity of measurements. The area of homogen­th eity was carefully marked and any trial by a SUbject with the foot th, contacting outside the specified area was discarded. Data Analysis fit The two synchronized films were initially edited and matched according to the timing marks on the edges of the films. Film Oneval from Camera One, contained a record of the jogging activity while Film Two, from Camera Two, contained the force plate data from gr< the oscilloscope. A Triad VR/lOO pin-registered film analyzer was used to project the image onto a Bendix Digitizing Board (accuracy ±0.001 inch). A Bendix Cursor was utilized, via a Hewlett Packard 9864A digitizer, to enter a standard reference point and all sUbsequent coordinate points into a Hewlett Packard 9825B desk-top computer. ER TOPP-2 TAKEOFF PHASE TOPP-l I , I I MIO-SUPPORT PIIASE I I \ \ , . \ , I \ " \ \ I I ," I ,\1, '( F= ma + mg \ \ \ FIGURE 2 SCHEMATIC DIAGRAM OF CINEt1ATOGRAPIIICAL CALCULATIONS F= mv/t + mg rOOT STRIKE PIIASE , I I I =:", TIME (s) FORCE (N) 270 I I fc (: tl Wc hE ac fl I 366 The calculations of the vertical force components were for the three phases of the total support phase. These phases include: (1) foot-strike phase, (2) mid-support phase, and (3) takeoff phase (Figure 2). cr Foot-strike phase th pe co to li me The equation of uniformly-accelerated motion due to gravity was used to determine the velocity with which the sUbject was descending from the flight phase in jogging when foot contact occurred. The maximum height reached by the center of mass of the body during the flight period was determined. The height of the center of mass of the body at the instant of foot contact was also computed. The difference between the two heights represented the actual distance the body accelerated at 9.8 m/s 2 . ma. da ma; By the equation: v = 2gd where Phc ti~ Plc anc maE reE Mon thr DaI: thr the V= final velocity g= acceleration due to gravity d= displacement, the velocity at impact was determined. The length of time of the foot-strike phase, in relation to the total contact time with the force plate, was derived from calculating the mean percent for all subjects as determined in the temporal phase of this study. The force of impact, (foot-strike phase), was then calculated by the equation: F = mv/t + mg fie where vau F= force of impact gra m= v= mass of the velocity at body impact t= time of "foot-strike phase" g= acceleration due to gravity Mid-support phase The forces along the force-time curve during this phase were computed by F ma + mg where F=	 vertical force component m=	 mass a=	 vertical acceleration of the center of mass of the body g=	 acceleration due to gravity Takeoff phase In order to minimize the error within the cinematographical analysis of the takeoff phase of the jogging stride, a technique was devised which divided the takeoff phase into two parts, "TOPP-l" and "TOPP-2". "TOPP-l" is that portion of the takeoff phase which begins the instant the heel rises off the running surface; the end of the mid-support phase. "TOPP-2" originates at the termination of "TOPP-l" and continues until the toes break contact with the running surface (i.e. the end of the entire support phase). The point of differentiation between "TOPP-l" and "TOPP-2" is the point at which the angle between the force-time curve and the tangent at that point is largest, when the force­time curve begins to tail off as force values approach zero. Elapsed time for the "TOPP-2" portion was determined in the prelim­inary temporal study by computing the mean percent time of the "TOPP-2" portion of all sUbjects. The initial force value for "TOPP-2" was measured by the force plate, and that force, as a percent of total sUbject weight, served to find the initial "TOPP-2" force when BC procedures were used. The entire takeoff phase was then graphically represented by two straight lines; one line from the final point in the mid-support phase to the initi~l point of the "TOPP-2" portion, and the second line from the initial "TOPP-2" to the instant the toe breaks contact with the running surface. RESULTS The total elapsed time of the support phase ranged from 0.18 to 0.23 S with a mean of .21 S. The time of the "foot-strike" phase varied between 0.03 to 0.05 S. For all trials, the mean "foot­strike phase" time was 21% of the total support-phase time. The 367 re,r,CE I NI i:&Ju. Lie. -20 OJ. 0 (j -i400.0J -'-/.J0.00 -lilOO • GO -160iJ.00 ­H\Jtl.OO ­liUQ.LiD -Hi G;~ .0 J -bJO .00 ­&G0.00 ­400.GG ­200.0u -0.08- -------i----+-----+--....,--t----+-----i-----t--t----­ TIME (LOO 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.211 FIGURE 3 COMPARISON: CINEMATOGRAPHY(-) vs FORCE PLATFORt1(*) SUBJECT GS-3 "TOPP-2" portion of the takeoff phase ranged from 0.02 to 0.04 S. or a mean 14% of the total support phase. In other words, the "TOPP-2" portion of the takeoff phase began when 14% of total support-phase time remained. At this instant, vertical force turned out to be .33 of ~ach subject's weight. The calculations of the vertical-force measurements from BC resulted in an initial peak, the duration of which was assigned 21% of the total time of the support phase, followed by a second peak which descended gradually and tailed off toward zero. The final portion, "TOPP-2", of the cinematography measurements, was assigned 14% of the total time of the support phase, as mentioned in the previous paragraph. During the foot-strike phase, the mean maximum-vertical force measurements were 2419.3 and 2520.0 N for the force plate and BC respectively. This phase gives BC an error of 100.7 N, or .04. During the mid-support phase at .09 S from initial foot contact, the mean force plate measurement was 1840.3 N, while for BC, the calculations produced a mean force of 2015.9, or a mean error of 175.5 N. For the total mid-support phase, the error for BC was 62.5 N. 270 fOl': (19 the was hei acc fli cru the per col to lim men­man. dat. mane Pho1 timt Pla1 ana] masE resj: Mome thrc Dape thrc the tied vaul grav 368 The mean vertical force measurement during the takeoff phase at the start of "TOPP-2" was 218.0 N for the force plate, and 223.8	 N using BC; an error of 5.77 N, or .03. The above results indicate that, within the limitations of this study, it seems that biomechanics cinematography can be a precise and practical tool in the determination of vertical-force characteristics in jogging. Further, BC eliminates the need for any physical limitations or laboratory-controlled experimental procedures for the acquisition of data. This, of course, further suggests that with innovative adjustments in BC procedures, com­petitive events, where direct measurement is not possible, can benefit from indirect biomechanics cinematography. REFERENCES Adrian, M. and Kreighbaum, During Competition." 1973, pp. 354-358. E. "Mechanics of Distance-Running Biomechanics Ill, Karger, Switzerland, Cavagna, G.A. "Force Platforms as Ergometers." Journal of Applied Physiology, #39, 1975, pp. 174-179. Diffrient, N., Tilley, A.R. and Bardagjy, J.C. Humanscale 1/2/3. Massachusetts Institute of Technology, M.I.T. Press, Cambridge, Massachusetts, 1979. Doolittle, T.L. "Errors in Linear Measurement with Cinematograph­ical Analysis." Kinesiology Review, 1971, pp. 32-38. Elftman, H. "A-Cinematic Study of the Distribution of Pressure in the Human Foot." The Anatomical Record, Vol. 59, ·1934, pp. 481-487. Elliot, B.C. and Blanksby, B.A. "Optimal Stride Length Consider­ations for Male and Female Recreational Runners." British Journal of Sports Medicine, #13, 1979, pp. 15-18. Fenn,	 W.O. "Work Against Gravity and Work Due to Velocity Changes In Running." American Journal of Physiology, #93, 1930b, pp. 433-462. Gagnon, M. and Rodrigue, D. "Assessment of Smoothing and Diff­erentiation Methods for the Determination of Acceleration from Film Data." Canadian Journal of Applied Sports Sciences, #3, 1978, pp. 223-228. Gorozhanin, V.S. "Investigation of the Kinematics of Running in Man." Biophysics, #18, 1973, pp. 1171-1181. Hutton, W.C. and Drabb1e, G.E. "An Apparatus to Give the Distrib­ution of Vertical Load Unaer the Foot." Rheumatology and Physical Medicine, #11, 1972, pp. 313-317 369 Ismail, A.H. "Analysis of Normal Gaits Utilizing a Special Force Platform." Biomechanics I, Wartenweiler, Jokl and Hebbelinck lEd.), S. Karger, Switzerland, 1968, pp. 90-95. James, S.L. and Brubaker, C.E. "Biomechanics of Running." Ortho­pedic Clinics of North America, Vol. 4, #3, July, 1973, pp. 605-615. Kramer, J.F. "Electromyographical and Cinematographical Analysis of Walking Backwards." Ph.D. Dissertation, University of Alberta, 1979. Matake, T. "On the New Force Plate Study." Biomechanics V-B, Komi (Ed.), University Park Press, Baltimore, 1976, pp. 426-432. Miller, D.I. "Biomechanics of Running - What Should The Future Hold?" Canadian Journal of Applied Sports Sciences, #3, 1978, pp. 229-236. Payne, A.H. "A Comparison of the Ground Forces in Race Walking With Those in Normal Walking and Running." Biomechanics VI-A, Asmussen and Jorgensen (Ed.), University Park Press, Baltimore, 1978, pp. 293-302. Saito, M., Kobayashi, K., Miyashita, M. and Hoshikawa, T. "Temporal Patterns in Running." Biomechanics IV, Nelson and Morehouse lEd.), University Park Press, Baltimore, 1974, pp. 106-111. Yoneda, Y., Adrian, M., Walker, F. and Dobie, D. "Kinematic and Kinetic Analysis of Sprinting and Jogging." Science in Athletics, Terauds and Dales (Ed.), Academic Publishers, Del Mar, 1979, pp. 85-91. 

FORCE MEASUREMENTS IN JOGGING USING BIOMECHANICS CINEMATOGRAPHY

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FORCE MEASUREMENTS IN JOGGING USING BIOMECHANICS CINEMATOGRAPHY

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ISBS (International Society of Biomechanics in Sports): Conference Proceedings Archive