Background and Objectives: Weight-bearing activities exacerbate pain and fatigue in functional flat foot, with uphill walking presenting additional challenges due to increased external loads. The current study investigates whether 3D-printed customized arch-support insoles can enhance gait variables and ankle alignment during uphill walking. Materials and Methods: Twenty healthy young adults, divided into two groups (normal foot condition (control, n = 10), functional flat foot (FF, n = 10)), walked on a treadmill at a 10% incline under two conditions: wearing shoes alone (shoe) or wearing shoes with 3D-printed customized arch-support insoles (SI). Gait pattern, center of force (COF), and ankle joint angles were analyzed by OptoGait, Tekscan, and Kinovea, respectively. Results: The foot flat phase of the gait pattern was prolonged in individuals with FF compared to the control under both shoe and SI conditions, whereas the propulsive phase was shortened with the SI. Medial deviation of the COF during the propulsive phase, observed in individuals with FF under the shoe condition, was corrected to a more lateral alignment with the SI, resembling the COF alignment of the control. Additionally, individuals with FF under the shoe condition exhibited increased ankle pronation compared to the control, whereas the SI moderated pronation, achieving alignment closer to that of the control. Conclusions: These findings indicate that the 3D-printed customized arch-support insoles can improve gait mechanics and ankle alignment in individuals with FF, particularly under challenging conditions such as uphill walking.

Background/Objectives: Functional flat foot (FF) is associated with altered lower limb biomechanics, leading to inefficient load transfer and potential overuse injuries. Customized orthoses, such as 3D-printed insoles and toe spreaders, may mitigate these deficits, but their combined biomechanical and neuromuscular effects remain unclear. The current study investigated the immediate effects of 3D-printed arch support insoles (SI) and toe spreaders (Toe) and their combination (SI+Toe) on gait pattern, center of force (COF), ankle alignment, and lower limb muscle activation in young adults with FF. Methods: Ten FF individuals and ten matched controls performed level walking under four randomized conditions: shoe-only, SI, Toe, and SI+Toe. Gait was analyzed using OptoGait, COF trajectory via F-Scan, ankle angles using Kinovea, and muscle activity (semitendinosus, biceps femoris, tibialis anterior, peroneus longus, gastrocnemius, and soleus) via surface EMG. Results: Compared to controls, FF individuals exhibited medial COF deviation, increased ankle eversion, and altered muscle activity. In the FF group, SI+Toe reduced medial COF deviation, decreased eversion, and prolonged foot flat while shortening the propulsive phase. Semitendinosus and tibialis anterior activity increased under SI+Toe, while gastrocnemius and soleus remained reduced during propulsion. Conclusions: The combined utilization of 3D-printed insoles and toe spreaders produced immediate measurable improvements in foot alignment and muscle activity patterns in FF individuals. These findings support that integrating customized orthotic designs with toe spreader elements may provide a practical, non-invasive approach for improving lower limb biomechanics. Such strategies may help improve foot mechanics and reduce compensatory muscle activation in a clinical setting.

Background and Objectives: Scapular muscles are crucial in controlling scapular movement, ensuring proper alignment, and preventing injuries during shoulder joint motion. The shoulder abduction angle is one of the most important factors when performing exercises to improve scapular movement control. The Pilates reformer arm work (AW) movement can be performed with different shoulder abduction angles. Therefore, this study analyzed the differences in scapular muscle activation depending on the shoulder abduction angle during the AW movement. Materials and Methods: Twenty-six healthy adult males performed the AW movement under four shoulder abduction angle conditions (0°, 90°, 135°, 160°). When performing the AW in the four conditions, surface electromyography analyzed the muscle activation of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), serratus anterior (SA), posterior deltoid (PD), and levator scapulae (LS), and the muscle activation ratios of the UT/LT, LS/LT, UT/SA, and LS/SA. Results: The UT, LT, and SA muscle activation increased proportionally with the increasing shoulder abduction angle (p < 0.001). The LT showed the highest muscle activity at the shoulder abduction angle of 135° (p < 0.001). The MT and PD showed the highest muscle activities at the shoulder abduction angle of 90° (p < 0.001). The muscle activity ratios of the UT/LT and LS/LT were the lowest at the shoulder abduction angles of 90° and 135° (p < 0.001). The muscle activity ratio between the UT/SA and LS/SA was the lowest at the 135° and 160° shoulder abduction angles (p < 0.001). Conclusions: Our findings highlight the impact of the shoulder abduction angle on scapular muscle activation, suggesting that different angles may be used to engage specific muscles during Pilates reformer arm work exercises selectively. This insight can guide exercise interventions for individuals aiming to improve their scapular control and stability.

Background and Objectives: The back squat is widely used in resistance training, performance enhancement, and rehabilitation, and barbell position and squat depth are key modifiable variables that may influence neuromuscular demand. This study investigated the effects of barbell position and squat depth on trunk and lower-extremity muscle activation during the back squat. Materials and Methods: Twenty-two adult men with at least 2 years of back-squat experience performed high-bar and low-bar back squats to knee-flexion angles of 50°, 90°, and 130° using a standardized external load corresponding to 80% of each participant’s habitual one-repetition maximum (1RM). Conditions were presented in randomized order. Surface electromyography was used to record the rectus femoris, vastus medialis, vastus lateralis, gluteus maximus, semitendinosus, biceps femoris, rectus abdominis, and erector spinae. Electromyographic activity was analyzed separately for eccentric and concentric phases and normalized to maximal voluntary isometric contraction (%MVIC). Results: Increasing squat depth most consistently increased quadriceps and erector spinae activation, indicating greater knee extensor and trunk extensor demand at deeper positions. Rectus abdominis activation showed a depth-related effect during the concentric phase, with only isolated pairwise differences during the eccentric phase, whereas gluteus maximus activation showed limited modulation. Barbell position produced selective phase- and depth-dependent responses: the low-bar squat showed greater hamstring and erector spinae activation in specific comparisons, whereas the high-bar squat showed greater knee-extensor activation at selected depths, most clearly in the rectus femoris. Conclusions: Barbell position and squat depth modify relative neuromuscular demand during the back squat and may be used to adjust the emphasis on knee extensor, trunk stabilizer, and posterior-chain demands rather than to target a single muscle group in isolation.