Background: Behavioural data indicate the existence of a complementary “upper body strategy” for postural control, especially during challenging dynamic balance tasks; however, information about joint kinematics associated with this strategy is limited, leaving a gap in our understanding of the underlying movement patterns.

Objective: The objective was to investigate the influence of free vs. restricted arm movement strategies on balance outcomes and joint kinematics during challenging dynamic balance tasks.

Methods: Dynamic balance performance was assessed in 25 healthy young adults (13 females, mean age: 24.5 ± 3.1 years) using the Y Balance Test–Lower Quarter (YBT–LQ) and the 3-m Beam Walking Backward task with two difficulty levels (beam width: 4.5 cm vs. 3.0 cm). Participants performed the balance assessments under two different arm positions: free and restricted arm movements. Reach distance, step number, and joint range of motion (ROM) were compared between test conditions.

Results: Free compared to restricted arm movements led to significantly greater joint ROM, particularly in upper body segments such as the shoulder (p ≤ .001 to.002). Increased task difficulty also resulted in higher ROM across conditions (e.g., shoulder joint: p = .040 to.043), especially during free arm movements.

Conclusions: The increased joint ROM with free arm movements, particularly under increased task difficulty indicates an active engagement of the upper body segments during dynamic postural control. This highlights the importance of free arm movements to enhance balance control through greater joint mobility.