Read an interesting article by Tim Cusick & Andy Coggan (Training Peaks Senior coaches) who did a simple but very effect analysis on the huge variance in results from bike computers which are set to capture data at frequency greater then 1 second intervals. See below

In short irregular/infrequent data sampling plays havoc with your normalised power algorithm and subsequently TSS especially for 5 second or greater sampling. So ensure your head unit is set to upload data every second and ensure that auto pause and for Garmin users, Smart Sampling is turned off. So no more stopping the clock at traffic lights or during ‘pit stops’.

Tim Cusick test results:
Every sample (i.e., every 1 s): normalized power = 266 W
Every other sample (i.e., every 2 s starting at 2 s): normalized power = 267 W
Every 5th sample (i.e., every 5 s starting at 5 s): normalized power = 271 W
Every 5th sample (i.e., every 5 s starting at 6 s): normalized power = 273 W
Every 5th sample (i.e., every 5 s starting at 7 s): normalized power = 274 W
Every 5th sample (i.e., every 5 s starting at 8 s): normalized power = 271 W
Every 5th sample (i.e., every 5 s starting at 9 s): normalized power = 274 W
Every 10th sample (i.e., every 10 s starting at 10 s): normalized power = 287 W
Every 15th sample (i.e., every 15 s starting at 15 s): normalized power = 320 W
Every 30th sample (i.e., every 30 s starting at 30 s): normalized power = 406 W (!!)

The essential user guide to prevent corrupt or incomplete data:

  • Charge head unit battery frequently. Ensure its carries enough charge for each workout.
  • Back up files to your PC and delete data files off head unit as a full memory capacity can prevent current workout data been saved correctly.
  • Calibrate power meter before every session/race. Refer to user manual for correct technique and frequency of calibration.
  • Before each work out make sure you have ‘stopped’ and ‘save’ the last workout and today’s training does not get added to the last workout.
  • Turn off auto pause and auto stop function.
  • On Head unit select System/data recording/data averaging and ensure ‘include zeros’ is active in power mode.
  • Make sure ‘Smart Recording’ (Garmin users) is turned off.

Ref Dr Fabiano Araujo FCA Sports

Follow these simple steps and you can be confident that the data your coach sees better reflects your training and racing.