Assessing Shoulder Proprioceptive Sense of Force: Hand-Held Dynamometer Reliability and Comparison with Isokinetic Protocols.

Background: Proprioception is crucial for shoulder stability, yet clinical methods for assessing all aspects, particularly the sense of force (SOF) -the ability to perceive, interpret, and reproduce force at a joint-are limited. The purpose of this study was to test a new SOF protocol with a handheld dynamometer (HHD) and examine its agreement with an isokinetic dynamometer (IKD), as well as its reliability and the effect of contraction intensity. Design: Cross-sectional measurement study. Methods: Fifty-one healthy participants were assessed for SOF using an Isokinetic dynamometer (IKD) and a HHD to evaluate the agreement between the two methods. Of the initial sample, 25 participants completed a second session with the HHD, enabling the evaluation of the protocol's reliability exclusively with this device. Error score were also compared between three different contraction intensities: 10%, 30% and 50% of maximal voluntary isometric contraction (MVIC). Intra-class correlation coefficients (ICCs), standard error of measurement (SEM), and minimal detectable change (MDC) for intra-rater (within-day and between-day) and inter-rater (within-day) reliability while agreement between the tools was assessed using regression line method. Results: Agreement between devices was low with a poor correlation observed between measurements. The HHD SOF protocol showed low to moderate reliability for intra-rater between-day assessments, with ICCs from 0.44 to 0.64. The absolute reliability MDC95 ranged from 12% to 42%. Inter-rater within-day reliability was low, with ICCs from 0.007 to 0.43. Significant differences in error scores were observed between the HHD and IKD at 30% and 50% MVIC, and higher error scores were noted at Target 10% MVIC compared to 30% and 50%. Conclusions: The SOF protocol using HHD demonstrates moderate reliability but low inter-rater reliability. Different tools yield varying results, with force intensity impacting SOF error scores, while rotation does not. Level of evidence: 2b.