A consensus definition and rating scale for minimalist shoes

Area of Science:

• Biomechanics
• Sports Medicine
• Footwear Technology

Background:

• The term "minimalist running shoes" lacks standardization, potentially impacting biomechanics and injury rates.
• Existing definitions do not adequately capture the nuances of minimalist footwear.
• A need exists for a quantifiable measure of running shoe minimalism.

Purpose of the Study:

• To establish a consensus-based definition of minimalist running shoes.
• To develop and validate the Minimalist Index (MI) for quantifying shoe minimalism.
• To provide a reliable tool for classifying running shoes.

Main Methods:

• A modified Delphi study involving 42 international experts.
• Development of the Minimalist Index (MI) based on expert consensus.
• Validation of MI using subjective rankings and visual analog scales (VAS) with 85 participants.
• Assessment of construct validity and inter/intra-rater reliability (ICC, Gwet's AC1).

Main Results:

• A consensus definition of minimalist shoes was achieved: high flexibility, low heel-to-toe drop, low weight/stack height, and absence of motion control.
• The MI incorporates weight, flexibility, heel-to-toe drop, stack height, and motion control/stability devices (20% weighting each).
• MI demonstrated high correlation with VAS (r=0.91), significant discriminative validity, and excellent reliability (ICC=0.84-0.99).

Conclusions:

• A standardized definition and the Minimalist Index (MI) were developed by international experts.
• The MI is a valid and reliable tool for differentiating running shoes by their degree of minimalism.
• This standardization may enhance future research and clinical recommendations, potentially reducing footwear-related injuries.