To examine the differences between men with and without scapular winging in the electromyographic (EMG) amplitude and activity ratio between the pectoralis major (PM) and serratus anterior (SA) during 3 push-up plus exercises: (a) the standard push-up plus (SPP), (b) the knee push-up plus (KPP), and (c) the wall push-up plus (WPP), and to determine which exercise induced the lowest PM/SA ratio in each group. Twenty-eight men participated in this study (13 scapular winging group: age, 21.8 ± 2.1 years; 15 control group: age, 23.3 ± 2.0 years). Surface EMG of the PM, SA, and activity ratio between the PM and SA were collected during 3 push-up plus exercises, and the EMG data were expressed as a percentage of the reference voluntary contraction (%RVC). The normalized PM activity for subjects in the scapular winging group was significantly greater than that in the control group (79.16 ± 6.65 %RVC vs. 39.66 ± 6.19 %RVC, p ≤ 0.05). The normalized SA activity was significantly lower in the scapular winging group compared with the control group (39.80 ± 4.09 %RVC vs. 56.28 ± 3.81 %RVC, p ≤ 0.05) and was significantly decreased in the following order: SPP > KPP > WPP; 77.09 ± 5.12 %RVC > 39.48 ± 3.38 %RVC > 27.55 ± 3.07 %RVC, p < 0.016). The PM/SA EMG ratio was significantly greater in the scapular winging group compared with that in the control group across all exercises and was significantly lower during SPP than that during KPP and WPP in both groups (1.13 ± 0.58 vs. 0.53 ± 0.25 for SPP, 3.50 ± 2.07 vs. 0.92 ± 0.63 for KPP, 4.04 ± 3.13 vs. 1.19 ± 0.66 for WPP, p < 0.016). Greater PM activity was found in the scapular winging group, and the SPP is an optimal exercise for subjects with scapular winging, where maximum SA activation with minimal PM activation is desired.

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Residual stresses occur in frequency-selective surface (FSS)-embedded composite structures after co-curing due to differences between the coefficients of thermal expansion between composite skins and FSSs. Furthermore, the electromagnetic characteristics may be affected by the deformation of the FSS pattern by residual stresses. Therefore, we studied the changes in electromagnetic characteristics due to the deformation of FSS, using residual stresses to deform loop-type FSS-embedded hybrid composites. We considered the effects of loop-type FSS patterns of equal dimension as well as the stacking sequences of composite laminates on the electromagnetic characteristics of FSSs: Square loop, triangular loop and circular loop. The stacking sequences of composite laminates considered in this study were [0] 8 , [0/90] 4 , [±45] 4 and [0/±45/90] 2 . The FSS was located between composite laminates in the middle plane. To determine the residual stresses and deformations in the FSS embedded laminate structures, the thermal loading condition in the finite element analysis was induced by cooling the hybrid structures from 125°C to 20°C based on the cure cycle of the composite. Also, the electromagnetic reflection characteristics of the hybrid structures were predicted using deformed models by residual stresses, considering the effects of stacking sequence of composite laminates. The results showed that the maximum residual stresses and deformations were produced in the [0] 8 composites with all three loop-types of FSS pattern. However, the maximum resonance frequency shifts occurred in the square and triangle loop-types with stacking sequence of [0] 8 , while the maximum resonance frequency shift occurred in the circular loop-type with stacking sequence of [0/±45/90] 2 .