If you are serious about your training, you may want to invest in a sport watch. It has a built-in sleep tracker so you can measure your sleep quality. It weighs 49 g.
From Ultimate Outdoors
Garmin Forerunner 255 Gps Running Watch - Grey, Grey
The product is available from £262.26 at international stores.
Chain Reaction Cycles
Garmin Forerunner 255 GPS Running Watch AW22 - Slate Grey, Slate Grey
The product exists on 5 additional merchants that don't have an agreement with PriceRunner.
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