Want to run further, lift heavier or nail your first pull-up? Each month, we put your questions to our team of the finest fitness brains to give you the tools you need to make good on your goals
Q I often struggle to sleep. Is working out in the evenings to blame?
Alice Liveing says: You’re not wrong to draw a line between late-night workouts and poor sleep, with multiple studies suggesting the former could be responsible for the latter. While some studies blame the cognitive consequences of an elevated heart rate, others believe that the stress hormone cortisol, produced during exercise, can inhibit the production of melatonin (the hormone that makes you feel sleepy before bedtime).
What’s the common thread running through this research? The exercise was high-intensity. One study* compared the sleep onset (how long it takes you to drop off) and sleep quality in a group of active and non-active adults who performed a session of moderate evening exercise. Not only did steady exercise have no impact on their sleep, it helped participants fall asleep faster and spend more time in deep sleep. When researchers upped the intensity, however, they found that when participants performed high-intensity workouts, such as interval training, less than an hour before bedtime, it not only took them longer to fall asleep, but their sleep was lower quality.
This means that if your training sessions fall into the high-intensity category – anything that gets your heart rate above 75% of your max for 10 minutes or more – it’s worth getting them done earlier in the day. If they don’t, there may be other factor
