Abstract
Background/Objectives: the purpose of this study was to determine the contributions of mechanical, neural, morphological, and muscle quality factors on individual differences in the maximal ankle dorsiflexion range of motion (ROM). Methods: A sample of 41 university students performed passive-dorsiflexion and morphological measurements. In the passive-dorsiflexion measurement, while the ankle was passively dorsiflexed, maximal dorsiflexion ROM was measured in addition to passive torque at a given angle and muscle-tendon junction (MTJ) displacement during the last 13° as mechanical factors, and stretch tolerance and muscle activation were measured as neural factors. In morphological measurements, the cross-sectional area, muscle thickness, muscle fascicle length, and pennation angle were measured. In addition, the echo intensity was evaluated as muscle quality. Subjects were divided into three groups (flexible, moderate, and tight) using the value of the maximal dorsiflexion ROM. Results: Maximal dorsiflexion ROM and stretch tolerance were greater in the flexible group than those in the moderate and tight groups. MTJ displacement was smaller in the flexible group than those in the moderate and tight groups. Stepwise multiple regression analysis revealed that stretch tolerance and passive torque at a given angle were selected as parameters to explain the maximal dorsiflexion ROM (adjusted R(2) = 0.83). Conclusions: these results indicate that individual differences in maximal ankle dorsiflexion ROM are primarily related to mechanical and neural factors.