Mechanical and Contractile Properties of Knee Joint Muscles Measured by the Method of Tensiomyography in Differently Trained Men and Women.

ABSTRACT: Toskic, LD, Dopsaj, MJ, Markovic, MR, Toskic, DR, Ignjatovic, AM. Mechanical and contractile properties of knee joint muscles measured by the method of tensiomyography in differently trained men and women. J Strength Cond Res 36(6): 1532-1539, 2022-The aim of this study was to investigate the differences in mechanical and contractile properties of knee joint flexor and extensor muscles between differently trained men and women, using tensiomyography (TMG). The sample consisted of 159 subjects (84 men and 75 women), who were assigned to one of 5 groups according to the following levels and types of their physical activity: physically inactive, physically active nonathletes, strength and power athletes, endurance athletes, and team sports athletes. Measurements were performed on the following knee flexor and extensor muscles of the dominant leg: rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus. The results showed significant differences in contraction time-Tc (F = 1.911, p = 0.010) and delay time-Td (F = 1.989, p = 0.007) parameters between differently trained men and women, whereas in other TMG parameters, there were no differences between groups. It is indicated that physical activities characteristic of strength and power sports (combat sports and sprint disciplines) could lead to an increased speed of twitch force generation and fast twitch muscle fibers, and that almost any regular, systematic, and planned physical activity leads to increased muscle responsiveness. Obtained results also indicated that TMG parameters do not have enough specific discriminatory power for detecting differences between differently trained young adults.

Melatonin modulates acute cardiac muscle damage induced by carbon tetrachloride - involvement of oxidative damage, glutathione, and arginine and nitric oxide metabolism.

The present study was designed to evaluate the cardioprotective effects of melatonin (a single dose of 50 mg·kg-1), a naturally occurring polypharmacological molecule, in Wistar rats acutely exposed to carbon tetrachloride (CCl4). This was done for the first time by tracking different biochemical parameters that reflect rat heart antioxidative and oxidative capacities, nitric oxide and arginine metabolism, and the glutathione cycle. Additionally, the extrinsic apoptosis pathway related parameters were studied. Acute exposure to CCl4 led to an increase in the studied tissue oxidant parameters (hydrogen peroxide, malondialdehyde, and carbonylated protein content), as well as the activity alteration of antioxidant (catalase, superoxide dismutase, and peroxidase) and glutathione-metabolizing (glutathione peroxidase, S-transferase, and reductase) enzymes. Furthermore, CCl4 caused a disturbance in the tissue myeloperoxidase, nitric oxide, citrulline, arginase, and inducible nitric oxide synthase content and activities and in two apoptosis-related parameters, caspase-3 and FAS ligand. Melatonin as a post-treatment prevented the changes induced by CCl4 to a differing extent, and in some cases, it was so potent that it completely abolished any tissue disturbances. This study is a promising starting point for further research directed to the development of melatonin treatment in cardiac tissue associated diseases.

Aerobic capacity as an indicator in different kinds of sports.

Physical capacity of athletes is an important element of success in sports achievements. Aerobic capacity has been accepted as its major component. Maximal oxygen uptake (VO2max) has been regarded by majority of authors as the best indicator of aerobic capacity of an organism, and at the same time, the best indicator of an athlete's physical capacity. The aim of the investigation was to analyze the aerobic capacity as an indicator of physical capacity of athletes, differences in their aerobic capacity with regard to the kind of sport they are practicing, as well as the differences obtained when compared to physically inactive subjects. The investigation included the determination of absolute and relative VO2max in the total of 66 male examinees. The examinees were divided into two groups of active athletes (football players (n=22) and volleyball players (n=18) of different profiles, while the third group of non-athletes served as control group. Maximal oxygen uptake was determined by performing the Astrand 6 minute cycle test. Peak values of VO2 max were recorded in the group of football players (4,25+/-0,27 l/min), and they were statistically significantly higher (p<0,001) compared to other examined groups. In the group of volleyball players the oxygen uptake was 3,95+/-0,18 l/min, while statistically significantly lower values were reported in the group of non-athletes compared to the groups of athletes (p<0,01). A similar ratio of VO2 max values was also shown by the analysis of values expressed in relative units. Our results showed that peak values of VO2 max were obtained in football players, and that football as a sport requires higher degree of endurance compared to volleyball. Having considered the morphological and functional changes which are the consequence of the training process, it can be concluded that VO2 max values are statistically significantly higher in the groups of athletes compared to the group of non-athletes.