PURPOSE Previous research has rarely examined foot segment motion and muscle activity simultaneously in relation to foot type. Therefore, this study aimed to investigate how foot type influences segmental foot kinematics and lower limb biomechanics during walking. METHODS Fifty-eight healthy adults were sorted into normal group (NG), pes planus group (PPG), or pes cavus group (PCG) using the Foot Posture Index, navicular drop, normalized navicular height, and normalized instep height. Furthermore, three-dimensional foot kinematics and lower limb muscle activity were recorded during 12-meter, self-paced walking using an optical motion capture system and surface electromyography. Kinematic analysis during the stance phase included measurement of joint angles and ranges of motion (ROM) for the following segments: foot relative to the shank, forefoot relative to the midfoot, lateral forefoot relative to the midfoot, medial forefoot relative to the midfoot, and hallux relative to the medial forefoot. Moreover, muscle activity analysis included the tibialis anterior, peroneus longus, and medial and lateral heads of the gastrocnemius. RESULTS Compared with the NG and PPG, the PCG exhibited greater ROMs in the frontal plane for the forefoot relative to the midfoot and medial forefoot relative to the midfoot. Additionally, the PPG exhibited a greater ROM in the frontal plane for the hallux relative to the medial forefoot compared with the NG. The intersegmental angles according to foot type demonstrated distinct kinematic differences between the PPG and NG in the transverse plane, specifically in the forefoot relative to the midfoot and medial forefoot relative to the midfoot relationships. However, no significant differences were observed in lower limb muscle activity during the stance phase. CONCLUSIONS This study provides insights into kinematic changes according to foot type during walking. Moreover, the findings of this study may deepen our understanding of the intrinsic risk factors for lower extremity injuries and tissue stress associated with variations in foot type.
PURPOSE This study aimed to identify the lower limb muscle activity based on direction prediction presence or absence and gender during side cutting in healthy college students. METHODS The study participants included 14 healthy males and females (8 males; 6 females). All participants ran at full speed for a distance of 12m, and side-cutting was carried out at 45 degrees in a randomly indicated direction and in a fixed direction. Simultaneously, data regarding vastus medialis, vastus lateralis, semitendinosus, and biceps femoris muscle activity of the dominant leg were collected using an electromyography sensor, and data regarding vertical acceleration were collected using an inertial sensor attached to the pelvis. A sync webcam was used for obtaining the initial contact of side cutting and the stance period time. During the 10 milliseconds (pre-activation) prior to the initial contact and 50% of the stance phase (loading phase), vastus medialis, vastus lateralis, semitendinosus, and biceps femoris average muscle activity and hamstring to quadriceps ratio included as variables. RESULTS During the pre-activation and loading phase, the vastus medialis muscle activity of the male group was higher in the unexpected condition than in the expected condition. Furthermore, hamstring to quadriceps ratio was confirmed to be lower under unexpected condition compared to under expected condition during on loading phase. CONCLUSIONS The study results suggest that the risk of anterior cruciate ligament injury may increase with side cutting under unpredictable conditions. It is expected to provide useful information for identifying factors related to knee injury in the general population.
