Muscles

(1) Background: The naked mole-rat (Heterocephalus glaber) survives hypoxia–reoxygenation stresses by utilizing metabolic rate depression, achieved in part by downregulating nonessential genes and processes to conserve endogenous cellular resources and prevent buildup of toxic waste byproducts. Tight molecular control of protein degradation (specifically the ubiquitin–proteasome system) is a potent regulatory tool for maintaining muscle integrity during hypoxia, but how this system is regulated in the heart of hypoxia-tolerant species is poorly understood. (2) Methods: The protein expression levels of cullin-RING E3 ligases (specifically CRL4 architecture), deubiquitinating enzymes, and proteasomal activity were assayed in cardiac tissues from H. glaber exposed to 24 h of normoxia or hypoxia in vivo. (3) Results: Overall, the protein expression of E3 ligases decreased, whereas expression of deubiquitinating enzymes increased during hypoxia, all of which play roles in themes of oxidative stress, heightened DNA damage repair, and the HIF-1-VHL-NFκB axis. Proteasomal activity was elevated during hypoxia, which conceivably links to the oxidative stress theory of aging and longevity of H. glaber. (4) Conclusions: Taken together, our results expand current research into protein degradation and extreme environmental stress responses, with a specific focus on cardiac mechanisms related to oxidative stress resistance along the hypoxia-longevity axis.

Muscular strength plays a crucial role in sports performance and is often evaluated using vertical jump tests such as the Squat Jump (SJ) and Countermovement Jump (CMJ). Measurements based on flight time (FT) assume that takeoff and landing postures are identical, yet differences in ankle position can introduce systematic errors. This study examined whether dorsiflexion (DF) or plantarflexion (PF) of the ankle during the flight phase affects jump height. Forty-three active university students completed four repetitions each of SJ and CMJ under DF and PF across two sessions. Jump heights were recorded using a Chronojump-Boscosystem platform. No significant difference was observed in SJ between DF and PF, while CMJ heights were consistently higher under DF (DF: 28.29 cm ± 7.7 cm vs. PF: 27.08 cm ± 7.03 cm, p = 0.001; d = 0.16). Notably, the effect of DF appeared more pronounced in CMJ, suggesting that higher jumps are more sensitive to postural variations. These findings could suggest that DF can artificially increase jump heights as measured on a jump platform, without reflecting true improvements in force production. Coaches and practitioners should interpret FT-derived data with caution, particularly for higher jumps. Future research combining precise motion capture with force platforms could directly track center-of-mass changes and validate this mechanism.

Background: The study examined sex differences in countermovement jump (CMJ) force plate metrics and neuromuscular responses to a standardized dynamic warm-up in physically active college students. Methods: Forty-one participants (21 males, 20 females) completed pre- and post-warm-up assessments of CMJ performance using a dual force plate system. Body composition was measured via bioelectrical impedance analysis, and performance metrics included force, velocity, power, and other jump metrics. Percent change scores were calculated for all metrics. Results: Males demonstrated significantly greater improvements in braking force metrics compared to females, including force at minimum displacement (11.4% Δ male vs. 5.7% Δ female, p = 0.043), average braking force (10.6% Δ male vs. 5.0% Δ female, p = 0.043), and peak braking force (11.5% Δ male vs. 5.7% Δ female, p = 0.043). No significant sex differences were found in velocity, power, propulsive force, or other general CMJ performance variables. Hierarchical regression analyses revealed that sex was a significant (p ≤ 0.043 for all) predictor of changes in braking force metrics, while lean body mass did not enhance model fit or independently predict force changes. The addition of lean body mass slightly attenuated the sex effect but did not contribute meaningfully to the models. Conclusions: Findings suggest males may experience greater braking force adaptation to a dynamic warm-up, while other performance outcomes appear similar between sexes. These results may inform sex-specific warm-up strategies targeting neuromuscular readiness and braking force development.