Enter the grip dynamometer readings from a set of trials. This tool gives you the coefficient of variation and a plain reading of what that number does and does not prove about effort.
Type each trial reading, separated by commas or spaces. Any unit is fine, as long as they all match. Three or more trials.
Cut-off and diagnostic numbers from Shechtman O. The coefficient of variation as a measure of sincerity of effort of grip strength, Part II. J Hand Ther. 2001;14(3):188-194. PMID 11511013. The study tested 146 uninjured volunteers, and its author concludes CV should not be used to judge sincerity of effort.
Above the 15 percent cut-off is a reason to look closer. For a three trial grip test, specificity at this cut-off is 0.94: about 94 of every 100 people giving full effort stay under it. That does not make a flag usually right, and the paper's author concluded no cut-off is accurate enough to judge one person's sincerity of effort. Weigh it with the rest of the exam.
At or below the cut-off clears nobody. Sensitivity is only 0.55, so the test misses almost half of the people who are actually holding back. A tight, consistent set of readings is a weak rule-out, not a clean bill.
Trial count matters. The area under the curve is 0.79 for three trials and 0.87 for five, so more trials give a more reliable read. The published numbers come from set trial counts, so for any other count this reading is a rough guide. And the 15 percent cut-off with these numbers is specific to the grip dynamometer, not to every effort test.
Want the full walk through of where grip testing and single camera video both fall short? Read the research teardown.