Sex-Differences in the Oxygenation Levels of Intercostal and Vastus Lateralis Muscles During Incremental Exercise

This study aimed to examine sex differences in oxygen saturation in respiratory (SmO2-m.intercostales) and locomotor muscles (SmO2-m.vastus lateralis) while performing physical exercise. Twenty-five (12 women) healthy and physically active participants were evaluated during an incremental test with a cycle ergometer, while ventilatory variables [lung ventilation (V.E), tidal volume (Vt), and respiratory rate (RR)] were acquired through the breath-by-breath method. SmO2 was acquired using the MOXY® devices on the m.intercostales and m.vastus lateralis. A two-way ANOVA (sex × time) indicated that women showed a greater significant decrease of SmO2-m.intercostales, and men showed a greater significant decrease of SmO2-m.vastus lateralis. Additionally, women reached a higher level of ΔSmO2-m.intercostales normalized to V.E (L⋅min–1) (p < 0.001), whereas men had a higher level of ΔSmO2-m.vastus lateralis normalized to peak workload-to-weight (watts⋅kg–1, PtW) (p = 0.049), as confirmed by Student’s t-test. During an incremental physical exercise, women experienced a greater cost of breathing, reflected by greater deoxygenation of the respiratory muscles, whereas men had a higher peripheral load, indicated by greater deoxygenation of the locomotor muscles.

The Evolution of Appendicular Muscles During the Fin-to-Limb Transition: Possible Insights Through Studies of Soft Tissues, a Perspective

The evolution of the appendages during the fin-to-limb transition has been extensively studied, yet the majority of studies focused on the skeleton and the fossil record. Whereas the evolution of the anatomy of the appendicular musculature has been studied, the changes in the muscular architecture during the fin-to-limb transition remain largely unstudied, yet may provide important new insights. The fin-to-limb transition is associated with the appearance of a new mode of locomotion and the associated shift from pectoral to pelvic dominance. Here, we propose ways to investigate this question and review data on muscle mass and muscle architecture of the pectoral and pelvic muscles in extant vertebrates. We explore whether changes in appendage type are associated with changes in the muscular architecture and the relative investment in different muscle groups. These preliminary data show a general increase in the muscle mass of the appendages relative to the body mass during the fin-to-limb transition. The locomotor shift suggested to occur during the fin-to-limb transition appears supported by our preliminary data since in “fish” the pectoral fins are heavier than the pelvic fins, whereas in tetrapods, the forelimb muscles are less developed than the hind limb muscles. Finally, a shift in the investment in different muscle groups with an increase of the contribution of the superficial groups in tetrapods compared to “fish” appears to take place. Our study highlights the potential of investigating quantitative features of the locomotor muscles, yet also demonstrates the lack of quantitative data allowing to test these ideas.

Exercise Training-Induced Extracellular Matrix Protein Adaptation in Locomotor Muscles: A Systematic Review

Exercise training promotes muscle adaptation and remodelling by balancing the processes of anabolism and catabolism; however, the mechanisms by which exercise delays accelerated muscle wasting are not fully understood. Intramuscular extracellular matrix (ECM) proteins are essential to tissue structure and function, as they create a responsive environment for the survival and repair of the muscle fibres. However, their role in muscle adaptation is underappreciated and underinvestigated. The PubMed, COCHRANE, Scopus and CIHNAL databases were systematically searched from inception until February 2021. The inclusion criteria were on ECM adaptation after exercise training in healthy adult population. Evidence from 21 studies on 402 participants demonstrates that exercise training induces muscle remodelling, and this is accompanied by ECM adaptation. All types of exercise interventions promoted a widespread increase in collagens, glycoproteins and proteoglycans ECM transcriptomes in younger and older participants. The ECM controlling mechanisms highlighted here were concerned with myogenic and angiogenic processes during muscle adaptation and remodelling. Further research identifying the mechanisms underlying the link between ECMs and muscle adaptation will support the discovery of novel therapeutic targets and the development of personalised exercise training medicine.

Mechanisms of adaptation of motor «fast» and «slow» locomotor muscles in mice under conditions of allergic reorganization of the body

The state of the contractile function of transversely striated locomotor muscles under conditions of allergic reorganization remains relevant for modern sports medicine. In particular, it is known that the mandatory vaccination of athletes before the competition leads to changes in the state of the muscular system. The mechanisms of these changes are not fully understood. In the presented work, the following research methods were used: the registration of: a) the contractile function of various locomotor «fast» and «slow» muscles of the mouse in vitro on humoral initiators of contraction — carbacholine (CCh) and potassium chloride (KCI); b) indicators of the systems of pro- and antioxidant balance in the blood and in the tissues of these muscles and the determination of the level of malondialdehyde (MDA) in them. The differences in the ratios of the dynamics of the contraction force and the MDA level in both muscles demonstrate the degree of their resistance to oxidative stress, which determines the differences in the mechanisms of their adaptation to allergic reorganization. The materials of the article can be used to correct the function of locomotor muscles during vaccination, as well as to determine the strategy of therapeutic action, taking into account their fiber composition. The purpose of the article is to determine the mechanisms of adaptation of skeletal muscles (SM) of the mouse («fast» (m.EDL) and «slow» (m.Soleus)) during allergic reorganization.

Myoglobin Concentration and Oxygen Stores in Different Functional Muscle Groups from Three Small Cetacean Species

Compared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g−1 muscle), enhancing their onboard oxygen (O2) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O2 stores have been often determined by measuring Mb concentration from a single muscle sample (longissimus dorsi) and multiplying that value by the animal’s locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O2 stores calculations. For that, body muscles from three delphinid species: Delphinus delphis, Stenella coeruleoalba, and Stenella frontalis, were dissected and weighed. Mb concentration was calculated from six muscles/muscle groups (epaxial, hypaxial and rectus abdominis; mastohumeralis; sternohyoideus; and dorsal scalenus), each representative of different functional groups (locomotion powering swimming, pectoral fin movement, feeding and respiration, respectively). Results demonstrated that the Mb concentration was heterogeneously distributed, being significantly higher in locomotor muscles. Locomotor muscles were the major contributors to total muscle O2 stores (mean 92.8%) due to their high Mb concentration and large muscle masses. Compared to this method, previous studies assuming homogenous Mb concentration distribution likely underestimated total muscle O2 stores by 10% when only considering locomotor muscles and overestimated them by 13% when total muscle mass was considered.

Adaptive Mechanisms of a Mouse Locomotor Muscles "M. Soleus" and "M. Edl" the Conditions of the Allergic Modification of the Organism

The relevance of the problem discussed in the article is connected to the fact that mandatory athletes’ vaccination before competitions leads to the change in the function of the muscular system, the mechanisms of which have not yet been fully clarified. The purpose of the article is to determine the mechanism of a mouse skeletal muscles adaptation (SM) ("fast" (in case of m.edl) and "slow" (in case of m.soleus) in case of allergic alteration. The following research methods were used in the presented work: registration of the constrictive function of the abovementioned muscles in vitro to the humoral constriction initiators (carbacholinum and KCI) and determination of malonyldialdehyde (MDA) level in them, just as the indicators of the oxidant and antioxidant equilibrium. It has been demonstrated that the change in the “slow” muscle strength correlates with the MDA level dynamics, evidently, reflects the adaptation processes during the allergic modification. "Fast" muscles turn out to be more sustainable to oxidative stress which is most probably achieved by the work of compensatory mechanisms and is expressed in quite minor changes in the MDA dynamics. The article can be used in the search of the new possibilities for the correction of the locomotor muscles function in the conditions of the allergy, аnd also while the therapeutic impact strategy is determined, taking into account their fiber composition.

Combined influence of inspiratory loading and locomotor subsystolic cuff inflation on cardiovascular responses during submaximal exercise

Reflexes arising from the respiratory and locomotor muscles influence cardiovascular regulation during exercise. However, it is unclear how the respiratory and locomotor muscle reflexes interact when simultaneously stimulated. Herein, we demonstrate that stimulation of the respiratory and locomotor muscle reflexes yielded additive cardiovascular responses during submaximal exercise.