Your own guessAcross 141 lifters, experienced trainees underestimated their reps left by 1–2. Newer lifters missed by 4–5.Steele et al., 2017
Wrist rep countersFour Garmin watches tested on simple dumbbell circuits were not accurate enough. The researchers recommended counting by hand.Int. J. of Exercise Science, Garmin validity study
Heart rateMeasures heart and lungs, not the working muscle, and climbs late. Most wearables track only this cardio strain during lifting.
Bar speedRep speed tracks effort closely: a −0.88 correlation with rated effort in experienced squatters. It slows on the exact rep the muscle tires.Zourdos et al., 2016
Day oneStarts from a speed curve built from published velocity research, so it reads your reps left from the first set.
Your curveAs you train at different loads, it maps how your own speed falls on each exercise. Personal curves predict reps left within 1–2 reps, and within about one on machines.Int. J. Sports Physiol. Perform., 2025 · J. Sports Sciences, 2025
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BuddycoreTwo reps left. Rack it, or push one more.
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Today
RepsLat Pulldown040 kgSet 3
Reps leftIn reserve—Out of 8Tap at 2
Bar speedRep by rep—m/sFastSlow
This weekEvery setMonSun
EffortClose to failure
Heart rateApple Watch108bpm
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Buddycore
Your training buddy for every lift. It counts your reps, logs your weight, and knows when you are close to failure.