Musculoskeletal responses to intensity-specific resistance training : multiple studies executed on a multifunctional dynamometer for application in space

Abstract

This thesis focuses on an interdisciplinary investigation of different exercise intensities and methods, used for the maintenance of the musculoskeletal system in the microgravity of space. Especially for weight bearing structures, such as muscles and bones, the ruling weightlessness in the cosmos causes enormous changes that threat or even prevent long-term missions. Various exercise devices try to counteract this problem and allow astronauts an earth-like stimulus for a selective resistance training to reduce muscle and bone atrophy. After previous developments have repeatedly pointed out various weaknesses in microgravity and do not meet the requirement so far, the demand for new machines or methods for this purpose is large. An interesting promising development is represented by the "Multifunctional Dynamometer for Application in Space" (MDS), which was developed at the Technical University of Vienna and was already tested successfully in the 520-day isolation project "Mars 500" (June 2010 - November 2011). To underline a future application of the MDS, a study was called out in cooperation with Bernhard Gmeiner, which should research the impact dynamics of this device on critical regions of the lower limb system during single-legged leg press and calf raise exercises. By using the data obtained from a motion analysis, it was aim of this thesis to develop a suitable biomechanical model of the lower structures, in order to draw conclusions about forces onto muscles and joints. Thereby forces were calculated that partially load the internal structures with twelve times body weight. Furthermore, the results emphasize especially the importance of calf raises as a training exercise for the soleus muscle. In another procedure, a complete training study on several subjects was conducted to examine the issue of microgravity completely contrary to the previous study. While not examining the principle of optimum load from a biomechanical point of view, but rather at the biochemical level and specifically related to the problem of fluid shift in weightlessness. After new findings suggest that muscle and bone atrophy greatly depend on the changed blood pressure gradient in these structures, due to the relocation of the blood from the lower body in the upper, a long-term research study including eleven students which trained up to six weeks under vascular blood flow reduction on the MDS was carried out. The final results show significant strength increases, where between individual isometric maximum strength tests, within two weeks, partly an increase of 5-8% of isometric maximum force was measured. Finally, all findings obtained in this thesis should support a better basic understanding of specific load capabilities of the lower musculoskeletal system and also help to enhance the MDS in general.