Forces acting on a foot at an upward jump

V diplomski nalogi obravnavamo navpični skok z rokami ob telesu. Skok izvedemo iz rahlega počepa in se posebej posvetimo silam, ki delujejo na stopalo pri odrivu. Diplomska naloga je sestavljena iz teoretičnega in eksperimentalnega dela. V teoretičnem delu obravnavamo sile, ki delujejo na stopalo med navpičnim skokom. Predpostavimo, da na stopalo delujejo podlaga, Ahilova tetiva ter mečnica in golenica. Odriv razdelimo v dve fazi: v prvi fazi je stopalo v celoti na podlagi, v drugi fazi pa se peta odlepi od podlage. Izpeljemo velikosti sil Ahilove tetive ter mečnice in golenice na stopalo v odvisnosti od lege stopala pri odrivu. V eksperimentalnem delu predstavimo računalniško podprt eksperiment za merjenje sil na stopalo pri navpičnem skoku. Z Vernierjevo odrivno ploščo in merilnikom gibanja izmerimo časovni potek sile podlage in odmik temena glave od začetne lege med navpičnim skokom. Navpični skok posnamemo tudi s kamero, posnetek pa nato analiziramo s programom Quintic Biomechanics, s katerim je mogoče določiti vrednosti kota med stopalom in golenico ter stopalom in podlago v različnih trenutkih navpičnega skoka. Iz meritev lahko izračunamo časovno odvisnost sile Ahilove tetive in golenice pri navpičnem skoku. Rezultati meritev kažejo, da sta sili golenice in mečnice ter Ahilove tetive ves čas večji od sile podlage na stopalo. V prvi fazi odriva sili Ahilove tetive ter golenice in mečnice dosežeta 2-kratno vrednost glede na velikost na dnu počepa, iz katerega se odrinemo. Sila podlage na stopalo je na koncu prve faze večja za okrog 70 %. V drugi fazi sila podlage na stopalo še narašča, tako da je sila podlage na stopalo na koncu druge faze za 90 % večja v primerjavi s silo podlage na stopalo v izhodiščnem položaju. Sili golenice in mečnice ter Ahilove tetive se na začetku druge faze povečata za približno 50 %, nato ostaneta konstantni in sta 3-krat večji od njune izhodiščne vrednosti. Maksimalna sila golenice in mečnice, ki deluje na stopalo pri odrivu, je (2,3 +- 0,3)kN in pri doskoku (5 +- 2)kN. Največji navor v gležnju pa znaša (0,20 +- 0,05)kNm. Izmerjene in izračunane velikosti sil in navorov so primerljive z vrednostmi, ki smo jih pridobili iz literature.In my diploma work I have studied a vertical jump with arms along the body. The jump is preformed from the knees-bend and the main goal was to study forces acting on a foot during the push up. Diploma work consists of the theoretical and experimental part. In the theoretical part we focus on the forces acting on the foot during the vertical jump. We assume that there are only three forces acting on the foot: the normal force, force of the Achilles tendon and the forces of bones tibia and fibula. The push up is divided into two phases: during the first phase the whole foot is on the floor, the second phase starts when the heel starts to rise. We deduce the size of forces of the Achilles tendon and tibia/fibula depending on the position of the foot during the push up. The experimental part introduces a computer-based experiment for measuring the forces on the foot during the vertical jump. With the Vernier force plate and motion sensor we measure the normal force and the position of the head during the vertical jump. The vertical jump is recorded by a camera, and the video analysis is performed by the software Quintic Biomechanics, which allows for determination of the magnitudes of the angles between the foot and tibia and the foot and the ground at different times during the vertical jump. From the measurements we can calculate the time dependence of the force of the Achilles tendon and tibia during the vertical jump. The results show that the forces of the tibia/fibula and Achilles tendon are always larger than the normal force. During the first phase of the push up the magnitude of the forces Achilles tendon and tibia/fibula doubles, while the normal force increases by 70 %. During the second phase the normal force is still increasing and it finally reaches 190 % of its initial value (at the beginning of the jump). During the first part of the second phase forces Achilles tendon and tibia/fibula increase by about 50 %, then remain constant at a value which is approximately three times higher than their initial values. The maximum force of the tibia/fibula on the foot when we are rising is (2,3 +- 0,3)kN and at the landing it is (5 +- 2)kN. The peak value of the torque acting on an ankle is (0,20 +- 0,05)kNm. The measured and calculated values of the forces and torques are comparable with the values obtained from the literature