To give you a taste of the eclectic array of thesis topics that I've considered for the past year or so, let me list them for you.
The effects of an in-season training program on certain physiological variables in female collegiate volleyball players.
The effects of a vegan or lacto-ovo-vegetarian diet on skeletal muscle mass accumulation as compared to an omnivorous diet. (human study)
The same as above but as a rat study.
The effects of whey protein versus soy protein in combination with an acute bout of resistance exercise on the phosphorylation of p70S6K, a cell-signaling molecule with a role in skeletal muscle protein synthesis. (human study)
The relationship between adolescents' perceptions of worth and their physical activity levels, percent body fat, aerobic fitness levels, etc.
In each instance something came up which prevented the feasibility of the study. My thesis chair says that is normal and that I have learned some valuable lessons in the process. I only wish I didn't have to learn those lessons in a manner that took so much precious time.
Currently, I'm working on the literature review for my latest (and hopefully final) topic: Developing a submaximal jogging treadmill test to predict aerobic fitness in adolescents. I can only hope that this one is a winner.