What data comes in
Weight (kg), body fat %, fat mass, muscle mass, bone mass, hydration, visceral fat index, blood pressure (systolic/diastolic), heart rate. From Withings smart scales (Body, Body Comp, Body Scan) and BPM devices.
What Withings is good at
The only consumer integration that provides body composition data. Automatic daily weigh-ins. Trends over weeks and months. Blood pressure monitoring for overtraining detection. Hydration tracking.
What it misses
Training load. Recovery signals — no HRV, no sleep staging from scales alone. How you feel. Your training plan. Body composition changes slowly — it’s a background signal, not a daily decision driver.
How Rudder uses it
Withings feeds the Body composition channel — separate from Recovery and Load. Rudder uses it for:
- ·Power-to-weight ratio (calculated automatically when Strava power data exists)
- ·Weight trends over 30 days
- ·Body fat trends
- ·Dehydration detection (weight up + hydration down = water, not fat)
- ·Morning BP elevation as potential overreaching signal
Best for
Athletes tracking race weight, power-to-weight ratio, or body composition changes across training blocks. Cyclists and triathletes who weigh daily.
Example decision
Your weight went up 1.5kg this week but hydration is down and body fat is unchanged.
Rudder: “Weight gain is likely dehydration recovery, not fat. Your power-to-weight ratio improved from 3.2 to 3.4 W/kg this month as CTL rose. The training is working.”
Frequently asked
- What data does Rudder read from Withings?
- Weight, body fat percentage, muscle mass, and bone mass from Withings smart scales. Used for body composition trends and power-to-weight tracking.
- Do I need a Withings scale?
- No. Withings data is optional. It adds body composition context but the training decision works without it.
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