Evaluating Muscle Strength and Fiber CSA

After 24-week CS exposure, the grip force test was performed to evaluate the muscle strength of limbs using a grip strength meter (unibiolab, Beijing, China) as reported previously (Kehl et al., 2000 (link)). The researchers were blinded to group allocation. In brief, the mouse was grasping a mesh bar connected to a force transducer with all four limbs and was being pulled back by the tail at a constant speed until its grip was released. The peak force (g) produced during the process was recorded using the transducer. The mean of three attempts was recorded as grip strength. The cross-sectional area (CSA) of muscle fibers was measured as described previously (Chiu et al., 2018 (link)). Transversal gastrocnemius muscle sections (10 µm thick) were cut from paraffin-embedded muscle tissues using a cryostat (Leica, Solms, Germany) and stained with hematoxylin–eosin (H&E). Muscle sections were photographed and tiled using the Leica CTR 6500 microscope equipped with the Leica DFC 420 camera and Image Pro Plus software (Media Cybernetics, Maryland, United States). The CSA of muscle fibers was analyzed (n ≥ 3 mice per group).