I can't sleep! I know, some exercise will tire me out!

A friend recently said to me that she struggles to get to sleep after doing some exercise, particularly a run. She asked me if this was something many people suffer. Now I certainly haven't seen too many people who have this problem, I for one don't suffer so I thought I would do some research on this. As a physiotherapist, I firmly believe that regular exercise can aid with many conditions and prevention of more sinister conditions later in life. In addition, we as a profession administer treatment based on up to date, evidenced based research that has been critically and peer reviewed. I have spent the past few days trying to do just this and sure enough, all of the evidence I have found is what has worked for someone on a chat forum. This is always a real danger sign when trying to give advice to the many based on a few. However, I did find a few published articles pertaining to this, but they are ranging from 15-30 years old now! In our profession, they are deemed unreliable due to their age of publication. I also stumbled across several websites that are dedicated primarily to sleep or lack of sleep generally. With this, there seems to be conflicting information as to what and when during the day you should exercise. The National Sleep Association suggest not performing exercise at least 3 hours before you go to sleep. However, they do not publish any evidence to substantiate this. Additionally, they have not been clear as to what they define as exercise. Some other internet sites suggest no exercise at least 2 hours before trying to go to sleep. Again, there is no similarity or definition of what exercise they have measured this against. They also stated that this small study was performed on people who suffer from insomnia, therefore not necessarily generalisable to a wider public audience. The reason I stress this is because there is suggestions that some people find that walking in an evening helps them go to sleep whereas performing higher impact exercises, for example weight training and running inhibits sleep patterns. They suggested that intense exercise should be performed in the earlier stages of the day. But this study was performed on existing, trained runners. Not exactly the general population I did happen to come across a more recently published study by Glazer-Baron (2013) who performed a randomised controlled trial on a group of sedentary people. She split the group evenly between a control group and a group asked to perform 30 - 40 minutes of moderate intensity exercise, 3 - 4 times a week over a period of 16 weeks. The group who performed the exercises for the 16 week period were shown to gain on average an extra night's sleep, but this took more than 2 months to take effect. On the down side, this study was performed on small (n=12) group of over 60's. Again, not necessarily generalisable to the wider population. To add the confusion, an outdated systematic review of the evidence says more studies are needed into this! Helpful hey!? So, does this answer your question? Probably not. The evidence points to not exercising for 2 - 3 hours before trying to sleep but the studies are outdated and not robust enough to be generalised to the wider public. I personally think this down to individuality and other extrinsic factors have to be considered: Are you eating later? Are you checking your phone more to see if anyone else has liked your strava run? (White screen syndrome) Are you showering too late before bed, re-invigorating you? Are your endorphins and adrenaline running sky high? The consensus between friends appears to be mixed too. Maybe we should perform our own study?