Definição de valores de referência para o comprimento do músculo gastrocnêmio por meio de um aplicativo de inclinômetro para smartphone

Abstract

Background: Gastrocnemius tightness has been associated with several musculoskeletal disorders and can be quantified using the ankle-foot dorsiflexion index (ADI). However, normative reference values obtained under weight-bearing conditions using smartphone-based inclinometry remain unavailable. Aim: To establish clinically applicable reference values to gastrocnemius muscle length in healthy individuals using a smartphone-based inclinometer. Methods: This cross-sectional study included healthy adults (N = 189) assessed using a weight- bearing lunge test. Ankle dorsiflexion was measured with the knee flexed and extended using a smartphone-based inclinometer, and the ADI was calculated as the difference between these measurements. Reference values were established using pooled limb data, with the 97.5th percentile used to define the upper reference limit. Results: ADI values demonstrated substantial physiological variability, with a mean of 6.5°. The 97.5th percentile corresponded to 13.1°. No clinically meaningful differences were observed between limbs, sex, or limb dominance. ADI was not significantly associated with age, height, sitting time, stretching habits, or ankle mobility exercises. Weak negative correlations between ADI and both body weight (rs = −0.164, p = 0.024), and BMI (rs = −0.159, p = 0.029) and ADI in the non-dominant limb only. Conclusions: ADI values demonstrated substantial interindividual variability in healthy adults. An upper ADI reference limit of 13.1° may support a more evidence-based interpretation of gastrocnemius tightness during weight-bearing assessment. Body weight and body mass index showed only weak negative correlations with ADI, with limited clinical relevance.