Evaluating the Influence of Gravity on Shoulder Strength Measures Assessed via Handheld Dynamometry.

Abstract

Handheld dynamometry is a feasible, reliable, and cost-effective method for assessing shoulder strength. One limitation to this tool is the lack of standardized testing protocols and specified shoulder strength test positions. Although it is recommended that strength tests be performed in a gravity-eliminated position, this may not always be a feasible or practical testing protocol. There is limited research on the influence of gravity on strength measures; to our knowledge, no study has compared handheld dynamometry shoulder strength assessments based on body position and gravity. Therefore, the purpose of this study was to compare shoulder flexion, extension, and abduction strength assessed via handheld dynamometry between a gravity-eliminated and a gravity-influenced test position. This study was a comparison of shoulder strength based on test position. The test position was the independent variable, and the dependent variables were shoulder flexion, extension, and abduction strength. Supine (gravity-eliminated) and seated (gravity-influenced) strength measures were assessed in 20 healthy adults (19.4 [1.2]y) on the dominant arm. Paired t tests were used to determine differences between body positions for each test. Significance was accepted at P ≤ .05. There were no differences between supine and seated flexion and extension measures. Absolute supine shoulder abduction scores (152.5 [58.4]N) were significantly higher than seated scores (139.9 [55.6]N). Findings show that gravity should be considered when using handheld dynamometry scores as indicators of abductor shoulder strength and function.