Rocker-profile design shoes improve pendular energy recovery in walking with no effects on total mechanical work

Rocker-profile design shoes are commonly used in clinical settings. Such footwear reduces in-shoe pressure over the forefoot area during the gait, and depending on the rocker-profile type (i.e., toe-only, heel negative, or double rocker), affects lower limb kinematics, kinetics, and muscle electromyographic activity. However, whether wearing rocker-profile shoes influence the dynamics of the body centre of mass (BCoM) is unknown. We used a mathematical procedure combining Lissajous contours and Fourier analysis to describe the 3D trajectory of the BCoM in walking with rocker-profile (RollingSole) and flat (Control) shoes at 0.97, 1.25, and 1.53 m s^-1 in 30 participants. Harmonics amplitude and phase were compared using linear and circular statistics, respectively. External (W_ext), kinematic internal (W_int,k) and total (W_tot) mechanical works, and the mechanical energy fraction recovered from a pendular exchange of potential and kinetic energy were also calculated. RollingSole shoes yielded greater W_ext (1-9 %; P < 0.05) and fractional pendular energy exchange (1-8 %; P < 0.01), with lower W_int,k (2-5 %; P < 0.05) and unchanged W_tot (P ≥ 0.30). RollingSole shoes led also to a greater mean height of the BCoM (1-3 %; P < 0.01), and amplitude of the anteroposterior and vertical symmetric, and mediolateral 2nd-to-5th harmonics (1-30 %; P < 0.01). No differences between shoes were found for the harmonics phase (P ≥ 0.14). Our results indicate that RollingSole shoes enhanced an inverted pendulum-like behaviour of the BCoM during walking with no alterations in total mechanical work. This may result from the combination of rocker-profile design and greater BCoM height (through thicker soles) with such shoes, increasing recovery of mechanical energy in step-to-step transitions and mid-stance.