The biomechanical difference between running with traditional and 3D printed orthoses.

Running-related injuries have been associated with excessive foot pronation and high vertical loading rates. Traditional plaster-molded (TPM) foot orthoses are commonly prescribed to minimize these atypical biomechanical patterns. Recently, 3D printed (3DP) orthoses have become popular, yet the functional difference between these two types of orthoses remains unknown. Therefore, this study compared running biomechanics and perceived comfort during treadmill running in three orthotic conditions: 3DP orthoses, TPM orthoses, and a no-orthoses control condition (CON). Thirteen female asymptomatic runners with excessive foot pronation were recruited. Rearfoot eversion angle and velocity (at initial contact and peak) during stance, vertical loading rates, and perceived comfort were compared. Results showed lower peak rearfoot eversion angles during running with TPM (p=0.001, d=0.38) or 3DP orthoses (p=0.002, d=0.24) than CON. No differences were observed in other biomechanical parameters among the three conditions (p>0.05). Running with TPM (p≤0.001, d=1.74-1.82) and 3DP orthoses (p<0.003, d=1.06-1.34) resulted in better perceived comfort in "medial-lateral control" and "heel cushioning" than CON. There were no statistical differences in all parameters between TPM and 3DP orthoses. The present findings indicate improved comfort during running with TPM or 3DP orthoses, which hinted 3DP orthoses could be a viable alternative to TPM orthoses for clinical practice.

Measurement agreement between a newly developed sensing insole and traditional laboratory-based method for footstrike pattern detection in runners.

This study introduced a novel but simple method to continuously measure footstrike patterns in runners using inexpensive force sensors. Two force sensing resistors were firmly affixed at the heel and second toe of both insoles to collect the time signal of foot contact. A total of 109 healthy young adults (42 males and 67 females) were recruited in this study. They ran on an instrumented treadmill at 0°, +10°, and -10° inclinations and attempted rearfoot, midfoot, and forefoot landings using real time visual biofeedback. Intra-step strike index and onset time difference between two force sensors were measured and analyzed with univariate linear regression. We analyzed 25,655 footfalls and found that onset time difference between two sensors explained 80-84% of variation in the prediction model of strike index (R-squared = 0.799-0.836, p<0.001). However, the time windows to detect footstrike patterns on different surface inclinations were not consistent. These findings may allow laboratory-based gait retraining to be implemented in natural running environments to aid in both injury prevention and performance enhancement.

Effects of training in minimalist shoes on the intrinsic and extrinsic foot muscle volume.

BACKGROUND: Minimalist shoes have gained popularity recently because it is speculated to strengthen the foot muscles and foot arches, which may help to resist injuries. However, previous studies provided limited evidence supporting the link between changes in muscle size and footwear transition. Therefore, this study sought to examine the effects of minimalist shoes on the intrinsic and extrinsic foot muscle volume in habitual shod runners. The relationship between participants' compliance with the minimalist shoes and changes in muscle õvolume was also evaluated. METHODS: Twenty habitual shod runners underwent a 6-month self-monitoring training program designed for minimalist shoe transition. Another 18 characteristics-matched shod runners were also introduced with the same program but they maintained running practice with standard shoes. Runners were monitored using an online surveillance platform during the program. We measured overall intrinsic and extrinsic foot muscle volume before and after the program using MRI scans. FINDINGS: Runners in the experimental group exhibited significantly larger leg (P=0.01, Cohen's d=0.62) and foot (P<0.01, Cohen's d=0.54) muscle after transition. Foot muscle growth was mainly contributed by the forefoot (P<0.01, Cohen's d=0.64) but not the rearfoot muscle (P=0.10, Cohen's d=0.30). Leg and foot muscle volume of runners in the control group remained similar after the program (P=0.33-0.95). A significant positive correlation was found between participants' compliance with the minimalist shoes and changes in leg muscle volume (r=0.51; P=0.02). INTERPRETATION: Habitual shod runners who transitioned to minimalist shoes demonstrated significant increase in leg and foot muscle volume. Additionally, the increase in leg muscle volume was significantly correlated associated with the compliance of minimalist shoe use.