Effect of Eccentric and Concentric Contraction Mode on Myogenic Regulatory Factors Expression in Human Vastus Lateralis Muscle

Background: Skeletal muscle contractions are caused to release myokines by muscle fiber. This study investigated the myogenic regulatory factors, as MHC I, IIA, IIX, Myo-D, MRF4, Murf, Atrogin-1, Decorin, Myonection, and IL-15 mRNA expression in the response of eccentric vs. concentric contraction. Methods: Eighteen healthy men were randomly divided into two eccentric and concentric groups, each of 9 persons. Isokinetic contraction protocols included maximal single-leg eccentric or concentric knee extension tasks at 60°/s with the dominant leg. Contractions consisted of a maximum of 12 sets of 10 reps, and the rest time between each set was 30 seconds. The baseline biopsy was performed four weeks before the study, and post-test biopsies were taken immediately after exercise protocols from Vastus Lateralis muscle. The gene expression levels evaluated using Real-Time PCR methods. Results: A significant difference in MyoD, MRF4, Myonection, and Decorin mRNA, were observed following eccentric or concentric contractions (P≤0.05). The MHC I, MHC IIA, IL-15 mRNA has been changed significantly compared to the pre-exercise in the concentric group (P≤0.05). While only MHC IIX and Atrogin-1 mRNA changed significantly in the eccentric group (P≤0.05). Additionally, the results showed a significant difference in MyoD, MRF4, IL-15, and Decorin were observed at the follow-up values between eccentric or concentric groups (P≤0.05). Conclusion: Our findings highlight the growing importance of elucidating the different responses of muscle growth factors associated with a myogenic activity such as MHC IIA, Decorin, IL-15, Myonectin, Decorin, MuRF1, and MHC IIX mRNA in following to various types of exercise.

Development of a Rehabilitation and Training Device Considering the Ankle Degree of Freedom

While the number of people who need rehabilitation has been increasing because of the aging population, there are only a limited number of physical therapists engaged in rehabilitation, making it difficult to perform rehabilitation at a sufficient level. In this situation, various devices have been developed to replace physical therapists. However, no rehabilitation devices that can respond to the complicated degrees of freedom of an ankle joint complex (AJC) are commercially available. In the present study, we developed an AJC rehabilitation device using a Stewart platform parallel link mechanism. Using the device, we aim to measure and control the AJC with six degrees of freedom so that complicated composite motions of the AJC can be realized. To evaluate the device’s usefulness, we investigated how the composite motion generated by moving the AJC along the trajectory the device reproduced could influence a crural muscle. Muscular activities of the anterior tibial, soleus, and gastrocnemius muscles, generated by a composite motion of plantar flexion and inversion, had a similar feature to those generated by plantar flexion. However, the muscular activity of the peroneus longus muscle generated in the composite motion was significantly different from that generated only in plantar flexion. In the composite motion of plantar flexion and inversion, based on the knowledge that activity to develop only back muscles while suppressing muscular activities of the anterior tibial and peroneus longus muscles is possible. Based on the knowledge, the device was used to perform isokinetic contraction for evaluating the device’s usefulness for muscular training. We found a difference between the combination of active muscles during the composite motion and that during plantar flexion. A load can be applied to different muscles depending on the composite motion, which indicates that the device can be suitable for rehabilitation or training with high degrees of freedom.

The Effect of the Cranial Electrotherapy on the Muscle Motor Function in Different Operating Modes

The aim of the present study was to analyze the effect of cranial electrotherapy stimulation on muscle function analysis indicators. Instrumental assessment of muscle function (on a REV9000, Technogym, Italy) was performed before and after cranial electrotherapy stimulation, assessments of the muscle function was performed during knee extension maximum voluntary, isometric contraction (MVIC), angle velocity with load 45Nm isotonic contraction and maximum pick torque in isokinetic contraction on 30°/s, 200°/s and 300°/s and neuromuscular efficiency measurements. To analyze data was used Excel program Statistics 3.1. Subjects of our study were twenty healthy athletes of sport fitness. 1 minute after cranial electrotherapy application the indicators of the analysis in 80% of cases are lower than before the cranial electrotherapy. After the application of the cranial electrotherapy the inhibition phase. 10 minutes after the cranial electrotherapy application the activation phase begins. During this phase the indicators of maximum voluntary isometric contraction increase in 41% of cases, the indicators of angle velocity with load 45Nm in isotonic contraction increase in 78% of cases and maximum peak torque indicators in isokinetic contraction on 30°/s increase in 25% of cases, on 200°/s increase in 80% of cases and on 300°/s indicators increase in 25% of cases. The results obtained in the research prove that the 20 minute effect of cranial electrotherapy stimulation partly influenced by the maximum isometric muscle strength, angular velocity and peak torque. The study results could be partially useful to optimize the different modes of operation of sports.

β-Alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters

Carnosine (β-alanyl-l-histidine) is present in high concentrations in human skeletal muscle. The ingestion of β-alanine, the rate-limiting precursor of carnosine, has been shown to elevate the muscle carnosine content. We aimed to investigate, using proton magnetic resonance spectroscopy (proton MRS), whether oral supplementation with β-alanine during 4 wk would elevate the calf muscle carnosine content and affect exercise performance in 400-m sprint-trained competitive athletes. Fifteen male athletes participated in a placebo-controlled, double-blind study and were supplemented orally for 4 wk with either 4.8 g/day β-alanine or placebo. Muscle carnosine concentration was quantified in soleus and gastrocnemius by proton MRS. Performance was evaluated by isokinetic testing during five bouts of 30 maximal voluntary knee extensions, by endurance during isometric contraction at 45% maximal voluntary contraction, and by the indoor 400-m running time. β-Alanine supplementation significantly increased the carnosine content in both the soleus (+47%) and gastrocnemius (+37%). In placebo, carnosine remained stable in soleus, while a small and significant increase of +16% occurred in gastrocnemius. Dynamic knee extension torque during the fourth and fifth bout was significantly improved with β-alanine but not with placebo. Isometric endurance and 400-m race time were not affected by treatment. In conclusion, 1) proton MRS can be used to noninvasively quantify human muscle carnosine content; 2) muscle carnosine is increased by oral β-alanine supplementation in sprint-trained athletes; 3) carnosine loading slightly but significantly attenuated fatigue in repeated bouts of exhaustive dynamic contractions; and 4) the increase in muscle carnosine did not improve isometric endurance or 400-m race time.