Gymnastics tumbling has occurred on large spring floor apparatuses for several decades. The spring floors have used a variety of elastic materials and designs to provide an increased take-off velocity and a forgiving landing surface. The purpose of this study was to assess the efficacy of a standard cylindrical spring (10.7 cm x 5 cm diameter, 9 coils) and a modified spring (10.7 cm, 5 cm widening to 6.7 cm diameter, 9 coils) in tumbling take-offs. Specifically, take-off foot contact durations and center of mass (COM) velocities from female gymnasts (14.8±2.8 y, 159.0±7.2 cm, 49.3±7.1 kg) were measured. Gymnasts performed two trials each of a round off, flic flac, to a layout rearward somersault on each spring-type attached to a tumbling strip (12.19m x 2.41m). Data were acquired via a ViconTM kinematic system using 43 markers and 10 cameras at 200 Hz. Data were found to be reliable across trials. Analysis consisted of two, 2x3 repeated measures ANOVAs. The results showed no statistical differences between spring-types in terms of contact durations or COM component velocities. Spring-type design differences may lead to disparate spring constant and frequency effects, however, these effects of may be overwhelmed by the influences of gymnast skill, matting, carpet, and the wood and fiberglass laminate panels.

Optimization has been used to simulate human neural control and resulting movement patterns. The short term aim was to develop the methodology required for solving the movement optimization problem often arising when modelling human movements. A long term aim is the contribution to increased knowledge about various human movements, wherein postures is one specific case. Simulation tools can give valuable information to improve orthopeadic treatments and technique for training and performance in sports. In one study a static 3D model with 30 muscle groups was used to analyse postures. The activation levels of these muscles are minimized in order to represent the individual’s choice of posture. Subject specific data in terms of anthropometry, strength and orthopedic aids serve as input. The specific aim of this part was to study effects from orthopedic treatment and altered abilities of the subject. Initial validation shows qualitative agreement of posture strategies but further details about passive stiffness and anthropometry are needed, especially to predict pelvis orientation. Four studies dealt with movement optimization. The main methodological advance was to introduce contact constraints to the movement optimization. A freetime multiple phase formulation was derived to be able to analyse movements where different constraints and degrees of freedom are present in subsequent phases of the movements. The athletic long jump, a two foot high jump, a backward somersault and rowing were used as applications with their different need of formulation. Maximum performance as well as least effort cost functions have been explored. Even though it has been a secondary aim in this work the results show reasonable agreement to expected movements in reality. Case specific subject properties and inclusion of muscle dynamics are required to draw conclusions about improvements in the sport activity, respectively. / <p>QC 20120910</p>

Rotational falls, or somersault falls, have led to serious and fatal injuries during the cross-country phase of Eventing competitions. Research to improve the safety of the sport began in 2000 after five fatal injuries occurred in the 1999 Eventing season. These efforts led to safety devices such as air jackets, improved helmets, and frangible/deformable fences. The focus of this thesis is to develop a more complete understanding of the horse-fence interaction as the approach motion transitions to a rotational fall. To achieve this, a large distribution of inertial properties was compiled through the development of a cylinder-based inertia approximation and a citizen science effort to gather equine geometrical measurements through a survey distributed by the United States Eventing Association (USEA). Furthermore, fundamental kinematic properties of the horse and rider were gathered from the literature. These distributions were used to conduct a Monte Carlo analysis to examine if the approach conditions of the horse and rider would result in a transition to a rotational fall upon horse-fence contact. Through the analysis the sensitivity of the main control parameters was explored to determine the dominant variables in the transition.