31 Skinny Secrets from the World's Sexiest Women

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And even if you are able to get to sleep initially, you struggle to stay asleep and fail to have a restful night. What gives? How can an exhausting event leave you sleepless? Exercise ramps up your heart rate, core temperature, and sweat rate. It also has an excitatory effect on your nervous and endocrine systems. The more strenuous the exercise and the longer the workout or competition, the longer you have been in this excited or aroused state.