**1. Introduction**

Motorcycle racers ride on speed tracks with multiples curves, moving their bodies by taking different postures as they attempt to minimize their lap times. Motorcycle riders take aerodynamic positions, flexing their hips and knees, and also changing to a braking posture. In different phases of cornering, a rider shifts his mass around the center of mass of the motorcycle from one footpeg to another footpeg. Leaning the motorcycle into corners improves the rider's performance. To achieve

this, centrifugal forces have to be balanced and the rider must make rapid changes of lateral, medial, and anteroposterior movements [1].

Lower limb muscles play a relevant role in motorcycling performance through the forces produced by the feet and footpeg. Studies show the importance of motorcycle riders being in good physical shape to reduce muscle fatigue from the large loads to which they are exposed and thereby improve their performance [2]. Thus, motorcycle riders show an increase in the reactive forces of the joints during riding and the associated activity patterns of the LLM related to footwear and the footpeg. These forces and activity patterns may produce various musculoskeletal conditions, such as (1) Achilles tendinopathy, (2) alterations in plantar pressures, (3) muscle strains, (4) knee pain, (5) ligament sprains, (6) metatarsalgia, (7) patellofemoral syndrome, (8) plantar fasciitis, (9) tendon injuries, and (10) paresthesia [3–6].

These injuries suggest a variety of potential causes: (1) abnormality of LLM, (2) biomechanical dysfunction, (3) characteristics of the riding environment, (4) male gender, (5) type of boot or shoes, and (6) foot pedal force. These factors are complex and related, and their precise roles in causing injury are not clear [7–12].

No prior investigation has evaluated electromyography (EMG) activity patterns of LLM or the effects of customized foot insoles (CFI) on such patterns during sport motorcycling. Previous reports have recorded significant variations in the EMG activity patterns of LLM during cycling [13–15].

In this study, we evaluated the effects of four types of CFI in the activity patterns of the LLM in healthy people during sport motorcycling. We hypothesized that participants wearing different types of CFI might vary in their EMG function patterns of the LLM. Our main goal was to determine which material of CFI limits the EMG patterns the most.
