Backpack loading position and self-selected foot position as measured by foot tracings

Area of Science:

• Biomechanics
• Human postural control

Background:

• Maintaining postural stability is crucial for backpack wearers, even under static conditions.
• Limited research exists on how foot positioning adjustments affect stability with varying backpack loads.

Purpose of the Study:

• To investigate the effect of altering backpack load position on postural stability variables.
• To analyze changes in foot tracings (Base of Support, Feet Width, Feet Opening Angle) in response to backpack loads.

Main Methods:

• 150 healthy participants stood in a natural stance with a backpack under four conditions: unloaded, and loaded at 0cm, 20cm, and 40cm from the posterior midline.
• Foot tracings were collected for each condition.
• Base of Support (BoS), Feet Width (FW), and Feet Opening Angle (FOA) were calculated from the tracings.

Main Results:

• A significant decrease in Base of Support (BoS) was observed in all loaded conditions compared to the unloaded condition.
• Participants significantly reduced Feet Width (FW) and Feet Opening Angle (FOA) when the backpack was loaded.
• These results indicate a trend to bring the feet closer together and reduce 'toeout' with added load.

Conclusions:

• The observed reduction in BoS and FOA in response to backpack load appears counterintuitive and may be a maladaptive strategy.
• Further research is needed to understand this response and inform strategies to enhance postural stability for backpack wearers.
• Understanding and potentially counteracting this instinctive response could improve safety and comfort for individuals carrying backpacks.