A novel method for assessing added mass in front crawl swimming

Area of Science:

• Sports Science
• Biomechanics
• Fluid Dynamics

Background:

• Swimmers face non-constant velocity during starts and turns, encountering inertial forces beyond drag.
• Added mass (M_A,a) represents water accelerated by the swimmer, increasing resistance during acceleration phases.
• Accurate quantification of M_A,a is crucial for understanding and improving swimming performance.

Purpose of the Study:

• To introduce and validate a novel method for determining added mass in surface swimming (M_A,a).
• To compare M_A,a during active swimming with passive added mass (M_A,p).
• To investigate factors contributing to the variability of M_A,a.

Main Methods:

• A standing start maximal test was employed with 16 male swimmers.
• Instantaneous velocity was measured using an IMU on the sacrum.
• M_A,a was estimated using maximum velocity (v_max), acceleration time (τ), active drag coefficient (k_a), and mean propulsive force (F_P).

Main Results:

• The novel method yielded average values: v_max = 1.73 m/s, τ = 1.14 s, F_P = 146.8 N, and k_a = 47.9 kg/m.
• Average M_A,a was 28.7% of body mass (M₀), comparable to passive added mass (M_A,p = 25% M₀).
• A significantly larger variability in M_A,a was observed compared to M_A,p, not explained by the active to passive drag ratio (k_a/k_p).

Conclusions:

• The standing start maximal test provides a reliable method for quantifying added mass in swimming.
• Added mass in surface swimming is similar to passive conditions but exhibits greater inter-individual variability.
• Further research is needed to identify the sources of variability in active added mass.