The influence of palmaris longus agenesis on upper limb muscle function in healthy adult men and women

• Grant number: 24/20486-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Health Sciences - Physical Education
• Principal Investigator: Leonardo Coelho Rabello de Lima
• Grantee: Jenniffer Licio Antonicelli
• Host Institution: Escola de Educação Física e Esporte de Ribeirão Preto (EEFERP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

The palmaris longus muscle (PL) functions as a wrist flexor and tightens the palmar aponeurosis. Agenesis of this muscle is observed in approximately 10-15% of the population and does not impact quality of life. Although various studies indicate that PL agenesis does not compromise muscle function as assessed by handgrip strength, to our knowledge, no studies have investigated its impact on wrist proprioception or, in particular, wrist flexor muscle function, especially with regard to different manifestations of muscle strength (i.e., maximal strength, explosive strength, and localised muscular endurance). This study aims to address this gap by investigating whether PL agenesis affects wrist proprioception and/or the various manifestations of wrist flexor strength. The study will include healthy adult men and women with no experience in strength training or manual work and no recent upper limb injury. Participants' forearms will undergo indirect tests to identify the presence of the PL muscle, which will then be confirmed by ultrasound. Forearms with and without the PL muscle will be allocated to the occurrence (OC) and agenesis (AG) groups, respectively. Dynamometric evaluations of strength (maximal, explosive, and endurance) and proprioception (passive and active position sense) will then be conducted on all included forearms. The independent variables will be compared between groups using Student's t-tests for unpaired samples (if normally distributed) or Mann-Whitney non-parametric tests (if non-normally distributed). The significance level will be set at p < 0.05. (AU)