Weight set on your Stryd is important for power calculations. If your actual weight is different than what is on the device, power readings will no longer accurately reflect your power.
Power changes linearly with weight. For example, your weight is 70 kg and your power at 5 min/km is 250 watts. If you carry a 5 kg backpack on your run, your total weight is 75 kg (an increase of 7.1%. If running at the same pace, your power at 5 min/km will be about 268 watts (and your Stryd will still indicate 250 watts if the weight setting is unchanged).
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