I notice that if I work out after work (~6pm) and the intensity level is up, I sleep really poorly that evening. It's as if I can't relax in bed and I sleep very restlessly. What can I do to fall asleep soundly after working out in the evening?
This isn't an uncommon problem. Doing a short burst, high intensity workout can actually help keep you awake if you're trying to cram for an exam (for example). In your situation though, this side-effect is not desirable.
Various things can be going on in your body after exercising that can keep your body from properly relaxing so that you can get the rest and recovery you need. Various hormone levels change during exercise and your heart rate will obviously be high and need to return to its resting heart level.
Here are some of the more helpful ways of dealing with these changes after you exercise to help you return to more "normal" levels that I have come across:
- Meditate. Stretching, yoga, even low-intensity cardio can help your body return its heart rate and certain hormones to normal levels more quickly.
- Regular aerobic exercise. This will help improve your cardiovascular health and eventually your heart rate will lower to a resting rate more quickly after exercising.
- Diet. If you have a recovery meal or drink after your workout you may want to consider what's in it. Consuming low glycemic food/drink in the evening can help your body regulate certain hormones that are important for sleeping. In addition, if you are eating a heavy meal after your workout, this can also cause unrest.
- Hydrate. Exercising causes you to shed water and so does sleep. Make sure you have plenty of water for your body to replenish the amount it just used and the amount it will use while you sleep.
Other general tips for getting a good night's rest:
- Avoid screens (TV, phone, tablet, computer) for 30-60 minutes before bed. The eye strain and concentration can make it difficult for your body to quickly settle into rest.
- Avoid caffeine and sugars before bed. You've probably heard all the ways these two chemicals can mess with your energy levels so I won't bother repeating them.
- Stretch. Not just after your exercise but just before bed. A 15-30 period of stretching will help clear your mind and increase blood flow to various parts of your body that will aid in recovery and make it easier for your body to relax.
I would suggest consulting your doctor. Heart rate usually returns to normal after about 15 - 20 minutes after workout, even with no yoga or stretching. In Humans, pineal gland secretes melatonin to control the sleep–wake cycle. Blue light, around 460 to 480 nm suppress production of melatonin in your body.
This is exactly the reason why you don't feel sleepy if spend too much time with computers or tube lights in your house.
Melatonin supplements are available over the counter in most countries, but I think it would be a good idea to check with your doctor before you get on it.