Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

2004 - 200912010 - 20191

Settings

Has files: YesSubject: search.filters.subject.Ground reaction force (Biomechanics)

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Ground reaction forces and electromyography in a parkour obstacle course : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Sport and Exercise Science at Massey University, Wellington, New Zealand
    (Massey University, 2019) Austmann, Marcel
    Parkour is a physical discipline that involves athletes, also known as traceurs, using specific skills and movements to overcome obstacles in an urban environment. A typical parkour landing involves an ever-changing combination of variables such as speed, agility, and multiple movement skills that in turn may affect the forces placed on the body. The purpose of the present study was to design a field- based protocol that measured and compared the forces athletes are exposed to in their natural training environment. Methods: A parkour specific obstacle course was designed and five experienced traceurs completed the series of obstacles in succession. Between obstacle comparisons were made for ground reaction force (GRF), time to maximal ground reaction force (TTP), and rate of force development (RFD). Additionally, electromyography was assessed to help better describe underlying mechanisms associated with differences in landing forces. Electrodes were placed bilaterally on the vastus lateralis (VL), gastrocnemius (GM), and the tibialis anterior (TA) and area (%MVIC) was used to represent muscle activation. Results: GRF was highest in obstacles with larger drop heights as well as increased momentum from previous obstacles which includes obstacles 2a-floor, 4-floor, and 2c-floor. The lowest TTP values were associated with obstacles involving short landing contact time due to limited space which includes obstacles 3-4, 2c-floor, and 1-floor. RFD was greatest in obstacles 2a- floor, 3-4, 4-floor, 9-floor, and 2c-floor which all required explosive power upon landing in order to complete subsequent obstacles. EMG data showed that the GM and VL had greater activation on obstacles requiring either a change in direction such as 6b-7 and/or a rapid descent such as obstacles 7-8 and 8-floor. TA showed higher activations on obstacle 9-floor and 2b-2c, but activations were similar across most obstacles. The activation of the TA may be due to its role in eccentrically contracting during initial foot strike during landing. Conclusion: Due to the dynamic nature of parkour, athletes are often exposed to a variety of landings which would produce diverse kinetic demands. By using a parkour specific course, this study provided force data that was a close representation of the forces traceurs are exposed to in a typical parkour run.
  • Thumbnail Image
    Item
    Effect of foot orthoses on GRF in running gait : a thesis presented in partial fulfillment of the requirements for the degree of Masters of Philosophy, Massey University
    (Massey University, 2004) Sloane, John
    For many years foot orthoses have been used to treat injuries of the feet, lower limb and back. Much of the evidence for their use has been anecdotal and measurement of kinematic or kinetic effects has been inconclusive. A single subject was selected for this case study to test the effect of orthoses on ground reaction forces during running. The subject was a competitive multi-sports athlete, and a heel strike runner (characterized as a runner who's heel is the first part of the foot to contact the ground). The experiment was conducted in a hall on a 40m curved running track with a force plate on one side. Timing lights were placed 5m from each end of the plate to measure speed and a video camera recorded the foot strike on the plate. The subject was asked to run at constant speed while wearing shoes and shoes with foot orthoses, at two self-selected speeds. Data from left and right foot was combined for analysis. The results showed a significant decrease in the magnitude of the vertical impact peak and the maximum vertical peak while the time to vertical impact peak was increased when wearing foot orthoses. Significant reductions were also seen in the peak posterior shear with both the time to peak and magnitude of the peak being changed by wearing foot orthoses. The mediolateral force was characterized by a medial impact followed by larger lateral impulse. It is the lateral force in the absorption phase of stance that is responsible for pronation, however no changes were seen in the mediolateral ground reaction force with the use of foot orthoses. This indicates that there is no acute effect in the shear forces, that act at approximately right angles to the subtalar joint axis. If orthoses have an acute effect on the lower limb it is likely to be complex and highly patient specific.