Decoding Backward Walking Neuromechanics: An Integrated Linear and Fractal EMG-Kinematic Analysis Revealing...

Walking is a fundamental activity with distinct neuromuscular and biomechanical characteristics in forward (FW) and backward walking (BW). While FW is well-studied, BW offers unique advantages for rehabilitation and athletic training. This study comprehensively analyzed linear and nonlinear (using Higuchi's Fractal Dimension) electromyographic (EMG) features across five frequency bands, and linear and nonlinear kinematic features for the hip, knee, and ankle joints across all three movement planes at three controlled speeds (2, 2.5, and 3 km/h). Results demonstrated significant increases in muscle activity and neuromuscular control during BW, particularly in Vastus Lateralis and Rectus Femoris. Linear EMG features showed significant increases. Nonlinear EMG features revealed heightened neuromuscular complexity in mid-and high-frequency bands during BW. The Gastrocnemius Medialis exhibited consistent activity reductions. Concurrently, BW significantly altered joint kinematics, with speed-dependent effects. The ankle consistently exhibited increased variability and complexity in frontal and sagittal planes. Conversely, the hip showed reduced variability and range. The knee predominantly acted as a stabilizer. Nonlinear kinematic features provided additional insights into joint-specific dynamics, highlighting distinct speed- and joint-dependent adaptations. The frequency-specific EMG analysis showed distinct recruitment strategies, with low frequencies supporting stability and higher frequencies indicating force generation. These kinematic and neuromuscular findings highlight the intricate biomechanical demands of BW, emphasizing its relevance for rehabilitation and athletic training to enhance strength, adaptability, neuromuscular control and agility.