Fitness Glossary
Definitions for the fitness terms that show up across our tools and guides — what they mean, how they're measured, and what's changed in recent research.
Strength
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One-Rep Max (1RM)
1RM, or one-repetition maximum, is the heaviest load you can lift correctly for a single rep of a given exercise. It is the reference point that every percentage-based strength program — 5×5, 5/3/1, conjugate, RPE charts — pivots around, and the cleanest single number for tracking strength over time.
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Wilks Score (Wilks Coefficient)
The Wilks coefficient is a body-weight scaling factor that normalizes a powerlifting total — squat plus bench plus deadlift — so lifters at different bodyweights and across sexes can be compared on the same scale. Published by Robert Wilks in 1994, it ran the sport's cross-bodyweight scoring for 25 years. The IPF replaced it with IPF GL Points in 2020, but Wilks is still the most-quoted strength score in casual lifting communities.
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Working Weight (Working Set Weight)
Working weight is the load on the bar during the main, performance-driving sets of a lift — the sets that actually drive adaptation, separate from warm-ups and cool-down sets. It's usually expressed as a percentage of your one-rep max (typically 70–85% for hypertrophy, 80–95% for strength) or chosen by RPE/RIR target. Coaches use working weight to dose intensity, plan progression, and tell beginners apart from seasoned lifters who know that the warm-up bar doesn't count.
Cardio
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Heart Rate Zones (Training Zones)
Heart rate zones are intensity bands — usually expressed as percentages of maximum heart rate or heart rate reserve — that map a workout's bpm to a specific physiological adaptation. The standard 5-zone model runs from very-easy recovery (Zone 1) to all-out VO2max work (Zone 5). Coaches use zones to dose volume, structure polarized training, and target the metabolic adaptations behind aerobic base, lactate threshold, and top-end fitness.
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Resting Heart Rate (RHR)
Resting heart rate (RHR) is the number of times your heart beats per minute when you're awake but fully at rest. Typical adult range is 60–100 bpm; trained endurance athletes often sit at 40–60 bpm. RHR is one of the cheapest, most informative single numbers in fitness — it tracks aerobic fitness, signals over-reaching when it drifts up, and independently predicts cardiovascular mortality across large cohorts.
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VO2max (Maximal Oxygen Uptake)
VO2max is the maximum rate at which your body can take in, deliver, and use oxygen during all-out exercise, expressed in millilitres per kilogram per minute. It is the most reliable single number for cardiorespiratory fitness, the ceiling that paces every endurance performance, and one of the strongest known predictors of all-cause mortality in adults.