Accuracy, Repeatability, and Test–Retest Reliability of a Pressure Algometer for Pain Threshold and Tolerance in Sports, Exercise, and Rehabilitation Settings

Background: Pressure algometry is commonly used in sports, exercise, and rehabilitation settings to assess pain sensitivity and monitor neuromuscular status. Reliable and accessible devices are required for consistent assessment. This study evaluated the accuracy, agreement, repeatability, and test–retest reliability of the AMF-500 digital pressure algometer. Methods: Three independent studies were conducted. Study A assessed the agreement between the AMF-500 and a three-axis AMTI force plate during 30 controlled pressure trials. Study B compared pressure pain thresholds (lumbar paravertebral muscles, tibialis anterior, and thenar eminence) and lumbar pressure pain tolerance between the AMF-500 and the MED.DOR algometer in 27 healthy adults. Study C (n = 27 healthy adults) evaluated test–retest reliability across two sessions separated by 48 h. Agreement was assessed using Bland–Altman analyses, and intraclass correlation coefficients (ICC) was also applied. Standard error of measurement (SEM) and minimal detectable change (MDC) were also calculated. All pressure values were expressed in N/cm2. Results: In Study A, the AMF-500 slightly overestimated pressure compared with the force plate (19.34 ± 2.44 vs. 18.71 ± 2.49 N/cm2), with a mean bias of 0.63 N/cm2 and limits of agreement from 0.21 to 1.05 N/cm2, corresponding to a mean difference of approximately 3.4%. Despite this small systematic bias, agreement between devices was excellent (ICC = 0.99; 95% CI: 0.96–0.99), and no proportional bias was detected, indicating a small and consistent overestimation of pressure by the AMF-500. In Study B, no significant differences were observed between AMF-500 and MED.DOR for lumbar threshold, lumbar tolerance, tibialis anterior threshold, or thenar eminence threshold (all p > 0.05). Agreement between devices was good to excellent (ICC = 0.82–0.91). Bland–Altman analyses showed small mean biases (1.05–7.51 N/cm2), with proportional bias detected only for lumbar tolerance. In Study C, test–retest reliability for the AMF-500 ranged from moderate to good across sites (ICC = 0.69–0.88), comparable to MED.DOR (ICC = 0.63–0.88). SEM values for the AMF-500 ranged from 9.31 to 25.15 N/cm2, with higher variability observed for lumbar tolerance. Conclusions: The AMF-500 demonstrated acceptable accuracy, agreement, and reliability when compared with a laboratory force plate and an established clinical algometer. These findings can support its use as a low-cost tool for pressure pain assessment in sports, exercise, and rehabilitation contexts.