The Garmin Forerunner 235 is a smart watch which can calculate your VO2 Max from its wrist-based heart rate monitor and can predict race times.
Garmin Forerunner 235 GPS Running Watch Review - Cotswold Trekker - Visit Cotswolds
Garmin Forerunner 235 Review
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Garmin Forerunner 235 review: The best watch for casual and serious runners - CNET
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Garmin Forerunner 235 review: The best watch for casual and serious runners - CNET