# Effects of Core Stabilization Exercise Programs on Changes in
## 4 Discussion and Limitation  
This study presented basic data for facilitating the development of an effective exercise intervention program for preventing musculoskeletal disorders caused by a lengthy sedentary lifestyle. We determined the effects of a 7-week core stabilization exercise program on the mechanical and neuromuscular properties of the erector spinae and the isokinetic muscle function of the trunk in adult females who perform \(\geq 7\) h of sedentary work per day. Regarding the mechanical and neuromuscular properties of the erector spinae muscle, there was a significant post-exercise increase in the Dm and Vc90, but not Tc, values. Tc showed higher and lower values in type I and II muscle fibers, respectively; specifically, Tc has a strong correlation with type I muscle fibers [37; 38]. Given the nature of the erector spinae muscle, type I muscle fibers, which have strong fatigue resistance, are more dominant than type IIa or IIx muscle fibers in maintaining lumbar stability through continued contraction [39; 40]. Furthermore, it is difficult to convert type I muscle fibers into type IIa and type IIx muscle fibers through training [41]. Consistent with this evidence, we observed no significant post-exercise change in the Tc of the erector spinae muscle. Consistent with our hypothesis, there was a significant post-exercise increase in Dm. Dm is considered a scale for muscle stiffness; specifically, it is negatively correlated with muscle stiffness [42; 43; 44]. A lengthy sedentary lifestyle causes microdamage and spasms in muscle connective tissue, which increases muscle stiffness by restricting muscle tissue microcirculation [45; 46]. Moreover, muscle stiffness showed a strong positive correlation with isometric contraction [47]. [PERSON] et al. [8] reported a significant increase in lumbar muscle stiffness after 4-5 h of sedentary work and a significantly reduced muscle stiffness after an 8 min roller massage. Because roller masses break down the cross-bridges between the actin and myosin filaments that were previously formed by the prolonged sitting period, muscle stiffness is significantly reduced. Moreover, the effect of relaxing muscle tension and reducing muscle stiffness owing to self-facial relaxation using a foam roller is known to have long-term effects [48]. Muscle stiffness increases immediately after exercise, which is relieved with repeated exercise [49]. Accordingly, erector spinae stiffness was reduced in participants through repeated exercise and self-facial relaxation using a foam roller. As a result, there was a post-exercise increase in Dm. Consistent with our hypothesis, Vc90 showed a significant post-intervention increase. This suggests a post-exercise increase in the contraction velocity of the erector spinae muscle. Core stabilization exercise can effectively stimulate the sensory receptors and motor control of core muscles and increase neuromuscular control and stability [23], with a concomitant increase in the core muscle activation [21; 50]. Specifically, [PERSON] et al. [51] reported that stabilization exercise for \(\geq\)3 weeks is required to activate the erector spinae muscle in patients with non-specific chronic low-back pain. Accordingly, there was a post-exercise increase in core muscle activation and neuromuscular control; specifically, TMG measurement revealed an increased contraction velocity through the activation of the erector spinae muscle. This indicated that core stabilization was achieved through enhanced muscle function, which allowed lumbar stabilization during activities of daily living and sports activities, while changing appropriately to maintain proper postural control [40; 52]. Regarding the isokinetic muscle function of the trunk, there was no significant post-exercise change in maximum and relative flexor muscle strength at an angular velocity of 60\({}^{\circ}\)/s, as well as maximum and relative flexor muscle strength at an angular velocity of 90\({}^{\circ}\)/s.