Thus, don't leave anything to chance regarding your strategy on marathon day. Use all training runs as opportunities for experimentation. There's no worse feeling in a marathon than realizing that your socks are a contributing factor to the development of blisters. Some experts claim that they can't penetrate deep enough to relieve muscular discomfort. Others say that are effective in reducing pain and inflammation.
Some research suggests that drinking caffeinated products spares glycogen early in a marathon.
The flip side is that caffeine is a diuretic and thus may lead to dehydration. The bottom line is that if you choose to consume caffeine, be sure to also drink other fluids to avoid dehydration. The key is finding the particular product that works for you.