Ankle joint flexibility affects undulatory underwater swimming speed

Area of Science:

• Biomechanics
• Sports Science
• Human Locomotion

Background:

• Undulatory underwater swimming (UUS) mimics whale fin movements but is limited by human anatomy.
• Ankle joint flexibility, specifically plantar flexion, is hypothesized to be crucial for efficient UUS.

Purpose of the Study:

• To investigate the impact of ankle joint flexibility on swimming velocity and kick efficiency during UUS.
• To compare UUS kinematics with reduced, normal, and enhanced maximum plantar flexion angles.

Main Methods:

• Ten trained swimmers performed UUS trials with normal, restricted, and increased ankle flexibility.
• Plantar flexion was manipulated using tape (restricted) and stretching (increased).
• Two-dimensional motion analysis captured kinematics, and swimming velocity and kick efficiency were measured.

Main Results:

• Restricted plantar flexion significantly decreased swimming velocity and kick efficiency compared to normal and increased flexibility.
• Increased plantar flexion did not significantly improve velocity or efficiency over normal flexibility.
• A significant positive correlation was found between body height normalized swimming velocity and plantar flexion angle.

Conclusions:

• Impaired plantar flexion negatively affects UUS velocity.
• Swimmers with limited ankle flexibility may benefit from targeted flexibility programs to enhance UUS performance.
• Ankle joint flexibility is a key factor for optimizing undulatory underwater swimming.