KINESIOLOGIASLOVENICA 1995; 2 (1) : 5- 10 5 Milan Čoh• Branko Škof• Otmar Kugovnik • Aleš Dolenec• Tomaš lampmiller• • Eugen laao• • ROIIICI• Holček* • Peter šeliager• • KINEMATIC-DYNAMIC CHARAaERISTICS OF MAXIMAL VELOCITY OF YOUNG SPRINTE RS KINEMATIČNO-DINAMIČNE ZNAČILNOSTI NAJVEČJE HITROSTI MLADIH v SPRINTERJEV ABSTRACT Sprinting speed is a complex abi lity whose physio- logical base is mostly genetically defined. Top com- petition results are therefore asa rule attainab le on- ly for a srna II, select numberof individuals. The purpose of this study was to find the most im- portant kinematic-dynamic parameters, their de- velopmental trend and their influence on the effi- ciency in maximal sprinting speed for you ng sprint- ers of both sexes, from eleven to eighteen years of age. We recorded kinematical and dynamical pa - rameters with a locomometer. The vertical pressure on the surface was calcu lated by biomechanical modelling of running steps. We ca lculated the cor- relation between maximal sprintingspeed and kine- matical and dynamical parameters. The results show, for both sexes, that the structure of the sprint stride changes drastically in connection to the stride length and frequency, the ratio between the contact and the flight phases and the vertical pressure on the surface. The correlation coefficients show that the duration of contact {R=0.71), the relative stride frequency (R=0.52) and the vertica l pressure on the su rface (R = 0.89} are good indicators of the sprinting poten- tial of young runners. Keywords: sprint, kinematics, dynamics, diagnostics •r.,n,lty ,,i Spori , ljublj,ln.l, Sl<1 vl'n i,1 .. F,Kult y o f Physic.11 [duc,,t ion and Sport . Br,1t isl,w,1. Sluv,,ki,, IZVLEČEK Namen študije je bil ugotoviti kinematično-d ina­ mične parametre, njihov trend razvoja in vpliv na učinkovitost v maksimalni šprinterski hitrosti pri mladih šprinterjih in šprinterkah starih od 11 do 18 let. Študi ja je nasta la kot plod sodelovanja laboratorija za biomehaniko Fakultete za šport v Ljubljani in Fakultete za telesno vzgojo in šport (Fakulta telesnej vychovy a sportu) v Bratislavi. Rezultati študije kažejo, da se pri mladih šprinterj ih obeh spolov izrazito spreminja struktura šprin- terskega koraka kot posledica dolžine in frekvence korakov, razmerja kontaktno-letnih faz in ver- tikalnega pritiska na podlago. Glede na velikost korelacijsk ih koeficientov so kon- taktni časi (R=0.71), relativna frekvenca (R=0.52) in vertikalni pritisk na podlago (R= 0.89) naj- pomembnejši dejavniki uspešnosti mladih špri nter- jev. Ključne besede: šprint , kinematika, dinamika , dia- gnostika 6 Milan Čoh, Branko Škof, Otmar Kugovnik, Aleš Dolenec, Tomaš Kampm,lle E Laczo. R man Holček . Peter Šelinger KINEMATIC-DYNAMIC CHARACTERISTICS OF MAXIMAL VELOCITY OF YOUNG SPRINTERS INTRODUCTION Maximal sprinting speed, no doubt the most impor- tant factor of competitive sprinting efficiency, is mostly dependenton the neuromuscular processes, the histologic structure of the muscles, explosive power potential, dynamic flexibility, biochemical processes and the level of proficiency in the motor stereotype - technique. Different emphasis is given to the individual factors atdifferentstages in the de- velopment process of the sprinter. The basic prob- lem in the methodics of sport training is without doubtconnected with the choice of relevanttraining methods - formi ng a suitable and efficient training process. Mastery of an efficient technique is one of the priority goals in the early phase of the develop- ment of youngsprinters. Other factors namely man- ifest themselves through the technical model of sprint (Gambetta, 1991 ). Although that in running, as the most elementary mode of movement, a high degree of movement standardisation is present, significant differences in the execution efficiency of the technique appear, es- pecially in sprinting. According to Tabachnik (1991 ) the most appropri ate biological age for masteri ng ef- ficient technique is from 7 to 13. A programmed training process is decisive for future results in sprint running. Maximal sprintingspeed is manifested through two basic parameters : stride length and frequency. Both components are closely correlated. Their relation is very individually conditioned and automated in the centra l regulation of movement according to the sprinter's motor abilitifS and morphological charac- teristics (Ionov and Cernjajev, 1968)_ Stride fre- quency and length as well as the factors which influ- ence their size, change significantly with the sprint- er 's development. In fact, the training process is, fun- damentally, oriented toward fi nding an optimal pro- portion between the two components. The purpose of this study isto fi nd the kinematic-dy- namic parameters, their dynamics and degree of correlation w ith maximal sprinting speed of young male and female sprinters aged from 11 to 18. METHODS Subjects The subject sample consisted of 2 7 young male and 35 you ng fema le spri nters, members of six Slovene track and field teams. According to age they were grouped into four categories: - male sprinters, 11 -14 years of age (n= 15) (height 162.7 ± 12.6 cm, mass 49.7 ± 12.5 kg) - male sprinters, 15-18 ear oi age (n = 1 2) (height 174.8 ± 4.1 cm, mas 66.4 ± 6.6 kg) - female sprinters, 11-13 ear of a e (n= 15) (height 159.3 ± 9.6 cm, mass 46.2 ± 5.1 kg) - female sprin ters, 14-1 7 years o age (n= 20) (height 166.9 ± 5.8 cm, mass 52.9 ± 5.1 k Procedures The project for measuring maximal sprinting speed parameters emerged from cooperation between the Institute for Kinesiology of the Faculty of Sport in Ljubljana and the Faculty of Physical Education and Sport (Fakulta telesnej vychovy a sportu) in Bratislava. The primary instrument used to register kinematic variables was the LOCOMOMETER (Fig . 1 ), (Kampmiller et al. , 1991 ). Figure J: MEA VREM E T -TN TR ME T LOCOMOMETER COMPUTER TRIDE-LE GTH MEASURFR + DRUM ,.......,. AMPLIFIER CONDUCTOR Variables The following kine matic variables were used in these procedures: Kinematic variables : Duration of contact with the surface (ms) Flightduration (ms) Stride frequency (number of strides/sec.) Stride length (cm) Activity (flight duration/contact duration) Relative stride length 1 (stride length/body height) Relative stride length 2 (stride length/leg length) Relative frequency (frequency x body height) Vertical pressure (N) Relative vertical pressure Morphologic variables: Body height (cm) Body weight (kg) Leg length (cm) Criterion variable : 20 m sprintwith a runningstart (m/s) Milan Čoh , Branko Škof, Otmar Kugovnik, Aleš Dolenec, Tomaš Kampmiller, Eugen Laczo, Roman Holček, Peter Šelinger KINEMATIC-DYNAMIC CHARACTERISTICS OF MAXIMAL VELOCITY OF YOUNG SPRINTERS 7 The procedure for generating the kinematic vari- ables is based on the functioning of the LOCO- MOMETE~ (authors: T. Kampmiller, E. Laczo, R. Holček, P. Selinger) . It uses a closed circuit (12 V), where the runner pulling a steel reel (d iameter 0.005 mm) represents one pole of the circuit. The velocity of the rope is measured by a digital counter which sends impulses via a scanner and amplifier to the computing unit. The second pole of the circuit is the contact platform on which the sprinter runs. This platform was moistened with an electrolyte (sodi um chloride - NaCl). The individual touches of the sprinter's shoes on the platform defined the contact and flight phases of the stride, the length and the fre- quency of the strides were also computed. In sprint running we proceeded from the fact that running is a series of jumps in the horizontal plane. In individual jumps we have the following values: length of jump (D), horizontal component of flight speed (Vx), flight duration (T), contact duration(t) and body mass of runner (m}. The duration of con- tact with the surface is composed of amortisation (com pensation) and extension. In regard to some previous studies (Ozolin, 1986), the extension phase (t1) is 60 o/o of the complete contactduration. S (to) is the marked duration of amortization. The following equations are valid in this case: D = 2 * Vx * tgalpha (1) g where alpha is the flight angle of the centre of gra- vity Vy = Vx * tgalpha (2) where vy is the vertical component of flight speed Fram the above equations we can calculate the speed Vy: Dg Vy = 2Vx (3) The vertical component of the pressure of surface at the tirne of the push-off is marked by Fp by the fol- lowing equation: t f fp * (t) - mg)dt = m * vy (4) to We mark the force Fp by an integral with the limited average value of Fp and have the following depen- dence : tf;: Vx JFp * dt = m(- + g) to t1 (5) For the calculation of the relative value of vertical pressure the following equation holds: (~ )1 _ D _ D m -g g - 2Vx * t1 - 1.2 * t * Vx (6) By further procedure the basic statistical parameters were calculated for al i variables, the differences be- tween the subject sam ples in kinematic-dynamic variables were defined, also the correlations be- tween the variables and the criterion were calcula- ted . Table 1 : Kinematic-dynamic parameters of maximal speed for male and female sprinters of differentages (X: mean value, SO: stan- dard deviation). Sprinters MALE FE MALE Age 11-14 15-18 11 -13 14-1 7 n=15 n=12 n= 15 n=20 Parameters X so X so X so X so Bod~heitt 162.7 12.6 174.8 4.1 ** 159.3 9.6 166.7 5.8 ** Leg engt 93 .1 8.9 100.3 2.8 * 92.5 5.1 95.8 3.4 * Boayweight 49.7 12.5 66.4 6.6 ** 46.2 8.3 52.9 5.1 * Ouration of contact 128 13.3 107 7.5 ** 123 7.3 118 12.8 Ouration of flight 11 7 15.6 127 9.3 128 12.4 128 12.4 Stride frequency 4.1 0.2 4.3 0.2 4 .00 0.2 4.08 0.2 Stride length 179 21.5 205 13.2 ** 181 15 .1 188 9.2 Speed 7.32 0.7 8.80 0.6 ** 7.23 0.4 7.65 o.s * Activity 0.93 0.1 1.20 0.1 ** 1.04 0.2 1.09 0.2 Rel. stride length 1 1.10 o.o 1.18 O.O ** 1.14 0.1 1.12 0.1 Rel. stride length 2 1.92 0.1 2.06 0.1 ** 1.95 0.1 1.96 0.1 Relative frequency 6.64 5.8 7.50 2.9 ** 6.34 3.8 6.78 4.3 * Vertical pressure 1285 35 .6 1853 9.8 ** 1236 24.3 1436 14.9 * Rel. vertical pressure 15.88 16.1 18.1 1 10.5 ** 16.97 11 .0 17.33 16.9 ** P< 0.01 * P< 0.05 8 Milan Čoh, Branko Škof, Otmar Kugovnik, Aleš Dolenec, Tomaš Kampmiller, Eugen Laczo, Roman Holček, Peter Šelinger KINEMATIC-DYNAMIC CHARACTERISTICS OF MAXIMAL VELOCITY OF YOUNG SPRINTERS TABLE 2: Correlation coefic ients of kinem atical and dynamica l parameters with maximal sprinting speed Sprinters MALE Parameters Age: 11 - 14 n= l S Body height .84 * Leg length .78 * Bodyweight .84 * Duration of contact -.4 1 Duration of flight .33 Stride frequency .01 Stride length .78 * Activity .83 * Rel. stride length 1 .49 Rel. stride length 2 .53 * Relative frequency .43 Vertical pressure .89 * Rel. vertical pressure .5 8 • * P<0.05 RESULTS Statistically significant differences exist between the age groups of sprinters (Table 1) in all the used pa- rameters, except the absolute stri de frequency and the duration of the flight phase. The groups differ chiefly in the following parameters: absolute and rel - ative vertical pressure, contact duration and stride length, as well as relative frequency. The presented parameters have a common basis in the neuromus- cular efficiency, which is manifested mostly in the push-off pressure. Changed relations between the duration of contacts and flight phases (activity- 78%) point to this. Differences in maximal speed among female sprint- ers (Table 1) occur mostly on account of the differ- ences in morphologic measures and less asa conse- quence of differences in the ki nematic-dynamic pa- rameters, with the exception of vertical pressure and relative frequency. For male spri nters (11-14 years old) the contact phase is longer than the flight phase, far female sprinters of the same age category this relation is just the opposite. The tendencyfor further development is toward shortening the contact phases and length- ening the flight phases, both for males and females. Th is is most evident for male sprinters from 15 to 18 years of age. The proportion of the contact phase in the duration of the running stride is 52% for the 11 - 14 year old male sprinters and only 46% for the 15-18 year group. With female sprinters no signifi- cant changes were noted in the duration of the con- tact phase. Alongside quantitati ve changes, also structural - or rather the relation between the con- tact and the fl ight phases occur with young spri nters. The process of training youngsprinters should be ori- FEMALE Age : 15-18 Age: 11 -13 Age: 14- 17 n=l2 n=15 n=20 .08 .50 .56 * .03 .36 .45 . .40 .22 .33 -.71 * -.69 * -.67 . .19 .09 .04 .56 * .63 * .65 . .61 * .68 * .82 * .56 * .53 * .60 * .34 .51 * .46 .49 .22 .28 .52 * .30 .32 .56 • .74 + .so * .41 .38 .43 + ented precisely into changing the qual ity of the spri nting stri de and approach i ng the modality of top sprinters, where the re lation of contact-flight phase is 43% against 57% far male sprinters and 45% against 55% for female sprinters (Lopez, 1990). The change in the quali ty of the ru nn ing stride be- tween the age categories can be seen also in para- meters of frequency and especially stride length. The latter increases for male sprinters by an average of 24 cm and by 11 cm for female sprinters . The stri de length is connected both with the development of motor and morphologic factors. Body height, or bet- ter leg length, indisputably decisively forms the run- ningstride. The index of relative stride length shows the extent to which the stride length is optimised to the body height. An optimal index for top male sprinters is 1.20 - 1.25 (Gambetta, 1991 ), in our da- ta it is the male sprinter group 15- 18 years of age that is closest to these values. Stride length is without doubt connected with the vertical pressure developed on the surface by the runner. The mean value of the vertical pressure of the foot on the surface for the 11 - 14 year old male sprinters group is 1285 N and a massive 1853 N for the older male group, representing almost three times the mean body weight of the sprinters. The va- lue is 1236 N for the younger female sprinters and 1436 N for the older group, being about two and a half times their mean body weight. Top sprinters de- velop a reaction force of the surface in the order of 2800-3100 N (Ozolin, 1986). In light of the results in Table 2, we can state that the morphological parameters: body height, leg length and body weight have a high positive corre lation with maximal speed in the 11 - 14 year old male Milan Čoh , Branko Škof, Otmar Kugovnik, Aleš Dolenec, Tomaš Kampmiller, Eugen Laczo, Roman Holček , Peter Šelinger KINEMATIC-DYNAMIC CHARACTERISTICS OF MAXIMAL VELOCITY OF YOUNG SPRINTERS 9 sprinters group. Both longitudinal measures are also positively corre lated with maximal speed in 14-17 female sprinters group, but this correlation is less evi- dent. The importance of the longitudinal measures, especially leg length, should be treated in context with the stride length parameter, which is in high cor- relation with maximal speed for ali runners . The variability of results in the maximal sprinti ng speed was connected mostly by relative frequency, stride length, duration of contact and vertical pres- sure, this being valid for sprinters of both sexes and ali categories. DISCUSSION Sprinting is a continuous series of "jumps" in the ho- rizontal plane, where there is a demand for devel- oping as much pressure on the surface as possible. Beside the degree of this pressure, also its frequency of occurrence by contact of feet with the track is sig- nificant. The duration of the contact phase and of the flight phase varies significantly in different qual- ity categories of sprinters. There is a general rule that with better sprinters the duration of contact is short- er, wh ile the duration of the flight phase is longer. This is just the opposite with poorer sprinters. Sprinters of top international quality have a 85 or less millisecond contact duration, while the flight phase lasts up to 130 milliseconds, that is from 55% to 60% of the duration of the complete stride cycle (Gambetta, 1991 ). The contact phase of the sprint stri de consists of two parts : forward support phase - amortisation and back support phase - extension. The execution of the contact phase is connected with the excentric- concentric mode of muscle contraction. In the first phase (amortisation) a stretching of the extensors of the jump, knee and hip rings occurs, due to external pressure, which is greater than the strength of the mentioned muscle groups. Amortisation is followed by the concentric mode, that is the sprinters push- off from the surface. The regulation of muscle activity in excentric and concentric contraction is based on the physiological laws of muscle strength develop- ment. In excentr ic-concentric contractions it was found that a greater efficiency of the push-off occurs due to the exploitation of elastic energy which is saved during excentric contraction (Bosco et al. , 1976, Bosco, 1985). Most of the elastic energy can be saved in the muscles, this depends on the speed of extension of external pressure and on the number of active transversal bridges. Far the occurrence of the transfer of elastic energy into concentric con- traction , the duration of stretchingand switch should be shorter or the same as the duration of the life- span of each transversal bridge (30-40 milliseconds), in the opposite case the elastic energy is lost (Bosco, 1985). These fi ndings are also confirmed by the contempo- rary sprint practice. The model of the sprinting stride technique is directed toward the shortest possible amortisation phase (contact with foot must be per- formed close to the center-point) and a relatively short active knee phase of the push-off leg which is 25 to 30 degrees (Ballreich, 1986). Beside the size of the contraction force and its speed (with best sprinters the tirne a muscle needs to fully relax is less than 70 ms), the relaxation dynamics of an individual muscle, actively participating in the running stri de, is even more significant for sprinting efficiency. A short relaxation period (with bestsprint- ers the value of half of the relaxation tirne of the leg extensor muscle is less than 35 ms) (Doraevic: et al., 1988) enables a faster re-introduction of agonists and in this way a higher stride frequency and espe- cially a better co-ordination among i ndividual mus- cle groups. The frequency and the length of the stride are signi- ficantly correlated with maximal speed of sprinters of al I categories with the exception of 11 - 14 years male group. This is logical enough, as these are the two basic components that, in the physical sense, generate the results in the maximal locomotoric speed and on the basis of which the youngsprinters had been indirectly chosen for sprint running. The correlations of both variables point to a both-sided mutual significance, where the result in maximal speed depends on the optimal correlation of both components. Most probably correlations point to the factthat fre- quency is not an independent and decisive deter- minant of speed, buta parameter which is, in greater part, dependent on the factors of the efficiency of the push-off action (contact du ration, vertical pres- sure). Quite evidently, the frequency, by use of a suit- able train ing process, "adapts " to the degree of strength of the strategically most significant muscle groups. We know of examples of "forcing" the fre- quency during maximal speed tra iningof the sprint- ers with the support of special methods (downhill running - the Petrovski method, running by pulling- the Hammel method, horizontal puli by help of a rubber band - the Vittorio method, the system of horizontal and vertical puli with the help of an elec- tromotor - the Kuznjecov method), but such inter- ventions into the change of proportions between the stri de length, push-off pressure and frequency have not been successful (Bosco, 1986). 10 Milan Čoh. Branko Škof. Otmar Kugovnik. Aleš Dolenec. Tomaš Kampmiller, Eugen Laczo. Roman Holček, Peter Šelinger KINEMATIC-DYNAMIC CHARACTERISTICS OF MAXIMAL VELOCITY OF YOUNG SPRINTE RS Stride frequency, especially of young sprinters, should be dealt with in closest relation to other kine- matic and dynamic parameters. Apart from the for- mation of strength of strategically important muscle groups, also the training process should be directed toward perfecting movementstructures- movement technique, which enables an efficient transforma- tion of strength into the speed of locomotion in such a way as to get an opti mal ratio between stri de length and stride frequency. Relative frequency is an important parameter in which body height is also implied. The variable has, in ali four groups, high positive correlation values with the absolute speed. Better results in sprinting can evidently be expected from those individuals who have, next to somewhat above-average body height, also a high stride frequency. Contact du ration of spri nters is positively correlated with frequency. In the duration of contact, frequen- cy as well as efficiency of the push-off action are im- plied. This is reflected in the magnitude of the kine- matic parameter that has, with ali sub-samples of sprinters, a general positive correlation with maxi- mal speed. For the transfer of elastic energy from ex- centric contraction (forward support phase) into concentric contraction (back support phase) to oc- cu r, the stretching of extensors of the push-off leg must be short enough (30% to 40% milliseconds). The phase of forward support (from the placing of the push-off foot on the surface to the vertical posi- tion) can only last from 40% to 45% of the complete contact tirne (Ozolin 1986). Among the 62 subjects of our sample only 3 young male and 1 female sprinters had the duration of contact shorter than 100 milliseconds. Tabachnik (1991 ) namely states that one of the basic indicators of high sprinting po- tential of young sprinters is the duration of contact which must be 100 milliseconds or less. Vertical pressure is the third parameter that has a high positive correlation with maximal speed in ali four sub-samples of subjects. Absolute pressure, where body mass of the subject is not taken into ac- count and is an indication of push-off quantity, as well as relative pressure, which considers body mass and is an indicator of push-off quality, are both sig- nificant. Correlation is especially high with the ab- solute vertical pressure of younger boys (R=0.88) and also of younger girls (R=0.84). Correlation co- efficients of relative ground reaction force with the criterion are lower. Regarding the correlation of contact duration and vertical pressure, which is negative, we can draw the following rules: Faster runners develop greater sur- face pressure during shorter duration of contact, which in consequence influences the absolute and the relative stride length. The correlation of surface pressure and stri de length is, in all subject groups, highly positive. The production of greatsurface pres- sure during a short tirne interval (90 - 100 millise- conds) is thus a basic genetic ability that undoubt- edly indicates sprinting talent of beginners. REFERENCES 1. Ballreich R, Kuhlow A. Biomechanik der Leichtathletik. Stuttgart: Enke Verlag, 1986 2. Bosco C, Komi V, Locatelli E. Physiologische Betrachtungen zum Tiefsprung. Leistungssport 1976; 2: 434-439 3. Bosco C. Stretch-shortening cycle in skelet muscle function and physiological considerations on explosive power in man. Atleticastudi 1985; 7-113 4. Bosco C, Vittori C. Biomechanical characteristics of sprint running during maximal and supra maximal speed. New Studies in Athletics 1986; 1 : 36-42 S. Bruggemann P, Lopez V. Time analysis of the sprint events. NewStudies in Athletics 1990; S: Suppl. 11-66 6. 0 ordevicS, StefanovskaA, Karba R, Strojnik V, Podlogar V. Spremembe kontraktilnih lastnosti mišice vastus lateralis s pomočjo električne stimulacije. Ljubljana: Inštitut za kinezi- ologijo, 1988. 7. Gambetta V. Essential consideration for the development of a teaching model for the 100 meters sprint. New Studies in Atletics 1991 ; 6(1-2): 27-32. 8. Ionov D, ČernjajevG. Zavisimostskorosti bega otdliny i čas­ toti šaga. Legkaja atletika 1968; (3): 18-19 9. Kampmiller T, Koštial J, Sedlaček J, Laczo E, Šelinger P, Holček R. Razvoj špecialnych schopnosti supramaximalnou rychlostou. Telesna vychova & sport 1991 ;2: 4-7 1 O. Kampmiller T, Holček R, Koštial J, Šelinger P. Kinematicka charakteristika begu 7 až 18 ročnej maldeže. Acta Facultatis Educations Physique Universitatis Comenianae. Bratislava: Univerzita Komenskoho, 1993 11. Ozolin E. Sprinterskij beg. Moskva: Fizkultura i sport, 1986 12. Tabachnik B. Choosing your sprinters. Scholastic Coach 1991; 60(9): 88-92