Your fresh 1RM overestimates your fatigued max by 9.5 kg
In short
Twenty-seven resistance-trained men (hexagonal-bar deadlift 1RM 176.8 kg on average) repeated a full 1RM test after rest, moderate fatigue, or high fatigue (five sets at 70% 1RM). The pre-session 1RM overestimated the actual post-fatigue 1RM by 9.5 ± 9.4 kg, with the error growing as fatigue increased. Velocity-based estimates stayed stable across fatigue levels, and using bar velocity measured at 90% of 1RM was the most accurate method, with an absolute error of 4.7 ± 3.7 kg.
Your 1RM is not one number across a session. After five sets at 70% of 1RM, the heaviest weight these lifters could actually pull sat an average of 9.5 kg below what they had tested at the start — in trained men averaging a 176.8 kg max.
What was measured?
Twenty-seven resistance-trained men completed three experimental sessions, each built around full incremental loading tests before and after a 30-minute intervention: rest (control), moderate fatigue (5 sets at 70% 1RM for half the possible reps), or high fatigue (the same sets taken to failure). The lift was the hexagonal-bar deadlift, and the study ran at Istanbul Gelisim University. The pre-session 1RM and five velocity-based estimates were then compared against a directly re-measured post-session 1RM.
How percentage-based training drifts
Keep prescribing loads from the pre-session max and the 80% on paper becomes a heavier real intensity as fatigue builds — and the overestimation was larger under high fatigue than moderate. Velocity-based estimates, by contrast, held steady regardless of fatigue level. Bar velocity measured at a heavy load (90% of 1RM) was the most accurate method at an absolute error of 4.7 kg, while velocity at a light load (50%) underestimated by 13.4 kg — worse than just using the pre-session max (9.5 kg).
If reading intensity from bar speed is new to you, bar speed tells you your percentage covers the principle.
When to test your max
The Big 3 numbers behind your Muscle Index obey the same physics. A max attempted after your accessory work will log below what you can actually lift — close to 10 kg below, on this data. Test personal records as the first lift of a session, after a proper warm-up. The best time to test your max and tapering before a max attempt pick up from here.
The lift was the hexagonal (trap) bar deadlift and the sample was 27 trained men. Error magnitudes may differ for straight-bar deadlifts or squats, and the velocity-based methods require a device that measures bar speed.
Frequently asked questions
How much lower is a 1RM tested late in a session?
In this trial, after five sets at 70% of 1RM, the real max sat an average of 9.5 kg below the value tested at the start of the session — in trained men averaging a 176.8 kg deadlift — and the gap widened with more fatigue.
How should percentage-based programs account for fatigue?
Assume percentages anchored to a pre-session 1RM run heavier than planned as the session goes on. In this study, estimating the day's 1RM from bar velocity at a heavy load stayed accurate regardless of fatigue.
What is velocity-based 1RM estimation?
You measure mean bar velocity at a submaximal load and map it onto your personal load-velocity relationship to back-calculate that day's 1RM. Here, velocity measured at 90% of 1RM gave the most accurate estimate, with a 4.7 kg absolute error.
When should you test the 1RM you log for your strength score?
As the first lift of the session, after a full warm-up. An attempt made after accessory work can record close to 10 kg below your actual ability.
Source: PubMed