PURPOSE: Muscle overuse is characterized by inflammation, reduced strength and muscle damage. It has been proposed that calcium (Ca2+) accumulation during muscle contraction, is responsible for muscle damage. Muscle contractile properties are regulated by calcium regulatory excitation contraction coupling mechanisms. Therefore, the main aim of the present study was to investigate the effects of voluntary repetitive tasks during six weeks on the rate of sarcoplasmic reticulum (SR) Ca2+-uptake, and Ca2+-release, in young female Sprague-Dawley rats. Secondly, this study aims to evaluate the effect of the training on muscular strength and the relationship between SR Ca2+-kinetics and grip strength test performance. METHODS: Six rats were trained (EXP), using a well-established model of reaching and handle pulling with the upper extremities (2 hr/day, 3days/week, 6 weeks), six control rats (KON) were included that were not exposed to the task. Grip strength were evaluated using a grip strength meter for rodents, two weeks prior the training was initiated, and two days after the training period was concluded. Tissue samples were obtained from the supraspinatus and trapezius muscle, and the rate of SR Ca2+-uptake and SR Ca2+-release were analysed using the fluorescent Ca2+ indicator indo 1. RESULTS: The analysis revealed that EXP had a significant higher rate of SR Ca2+-uptake, in both supraspinatus (33%, P < 0,05) and trapezius (14%, P < 0,05), compared to KON. However, no significant differences in SR Ca2+-release rate were found between groups, in neither of the muscles. A decline in grip strength were found in both EXP and KON, with no significant differences between groups. No significant correlation between grip strength and the Ca2+ release uptake variables could be found. CONCLUSION: The present results suggests that repetitive voluntary reaching and handle pulling with the upper extremities during six weeks, induce extant changes in SR Ca2+-uptake rate in rats.

Mesoporous materials constitute a promising class of nanomaterials for a number of applications due to their tunable pore structure. The synthesis of most mesoporous materials involves a surfactant liquid crystal structure to form the pores. As well as the many advantages associated with this method of synthesis, there are disadvantages such as high production costs and a substantial environmental impact which limit the possibilities for large scale production. Therefore there is a need for other synthesis routes. The aim of the work described herein was to contribute to this field by developing a synthesis route that does not rely on surfactants for pore formation. A mesoporous magnesium carbonate material was therefore formed by self-assemblage of the particles around carbon dioxide gas bubbles, which functioned as pore templates. It was also possible to vary the pore diameter between 3 and 20 nm. The biocompatibility of the formed magnesium carbonate material was evaluated in terms of in vitro cytotoxicity and hemocompatibility, in vivo skin irritation and acute systemic toxicity. The results from the in vitro cytotoxicity, in vivo skin irritation and acute systemic toxicity test using a polar extraction vehicle showed that the material was non-toxic. While signs of toxicity were observed in the acute systemic toxicity test using a non-polar solvent, this was attributed to injection of particles rather than toxic leachables. In the in vitro hemocompatibility test, no hemolytic activity was found with material concentrations of up to 1 mg/ml. It was further shown that the material had anticoagulant properties and induced moderate activation of the complement system. The anticoagulant properties were ascribed to uptake of Ca2+. Finally, the ability of the material to increase the dissolution rate of the poorly soluble drug itraconazole was analyzed.  Itraconazole was dissolved up to 23 times faster from the magnesium carbonate pores than when the free drug was used. The release rate from the delivery vehicle was dependent on the pore diameter. The work presented herein is expected to be useful for the development of alternative synthesis routes for mesoporous materials and also for encouraging the development of biomedical applications for these materials.