ABSTRACT
Objective:To analyze the contractile properties of the lumbar erector spinae in patients with chronic nonspecific low back pain (CNLBP), and to explore their correlation with pain and dysfunction. Methods:From January to June, 2020, 24 patients with CNLBP in the outpatient and the ward of geriatric rehabilitation medicine department and 26 asymptomatic volunteers were included. Their contractile properties of the lumbar erector spinae were measured with tensiomyography, including maximum radial muscle displacement (Dm), contraction time (Tc), delay time (Td), sustain time (Ts), half-time relaxation (Tr) and lateral symmetry (LS). The contraction velocity (VC) was calculated. Potential associations of tensiomyography parameters to Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) were assessed using correlation analysis. Results:No significant differences were found in Td, Ts, Tc, Tr and LS between two groups (P > 0.05). Dm and Vc were significantly lower in both sides of CNLBP group than in the control group (t > 2.058, P < 0.01). Dm or Vc were not correlated with VAS and ODI (P > 0.05). Conclusion:Erector spinae are stiff and fatiguable in patients with CNLBP, however, they are not associated with pain and dysfunction. Tensiomyography could be used for accurate diagnosis and treatment of CNLBP.
ABSTRACT
Objective To investigate the effects of creatine supplement on contractile properties of soleus (SOL) and extensor digitorum longus (EDL) in elder rat. Methods 20 male Sprague-Dawley rats were randomly divided into control group and creatine supplement group with 10 rats in each group. After 6 weeks, the content of creatine and phosphocreatine were detected by high performance liquid chromatog-raphy, and contractile properties were examined in SOL and EDL in vitro at 30℃. Results The content of creatine and phosphocreatine both in SOL and EDL were higher in the creatine supplement group than in the control group (P0.05). Creatine supple-ments significantly increased the fatigue resistance of the SOL and there was no significant effect on EDL. The force potentiation which oc-curred in EDL during the initial 20~30 s of the fatigue test significantly increased (P<0.05). Conclusion Creatine supplement is effective on the contractile properties of SOL and EDL in elder rats, but the effect is dependent on the fiber types.
ABSTRACT
The purpose of this study was to determine the change in elbow flexor isometric torque at different phases of the menstrual cycle in humans. The subjects were six eumenorrheic females (age 22.0±3.5yr ; height 156.5±3.3cm ; body mass 50.2±4.9 kg) . The serum luteinizing hormone (LH), estradiol and progesterone levels, maximal voluntary contraction (MVC), integrated electromyographic activity (iEMG), interpolated twitch torque, evoked contractile properties, anthropometric parameters and Profile of Mood States (POMS) were measured at three different phases of the menstrual cycle, i. e., the menstrual, ovulatory and luteal phases. The MVC was significantly higher in the ovulatory phase than in the menstrual and luteal phases (P<0.05) . The iEMG, calculated voluntary activation and anthropometric parameters did not change significantly over the menstrual cycle. The MVC/iEMG ratio (electromechanical efficiency) and the evoked peak torque were also significantly higher in the ovulatory phase than in the menstrual and luteal phases (P<0.05, P<0.01) . In the menstrual phase, the fatigue and anger subscale score of POMS were significantly higher (P<0.05) and the vigor subscale score was significantly lower than in the other phases (P<0.05) . These results indicate that the variation in MVC observed over the menstrual cycle may be related to the intrinsic contractile properties rather than neural or psychological factors.
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The effects of chronic overload by synergist ablation (SA) on fiber type, myosin heavy chain (MyoHC) isoforms, and contractile properties in the rat plantaris muscle were studied. Plantaris muscle was overloaded by bilateral removal of its synergist of gastrocnemius muscle in Fischer 344 female rats (aged 8 weeks) . Muscles of sham-operated legs served as controls.<BR>The overloaded plantaris was 20% heavier than control 3 weeks after SA. Overload by SA resulted in remarkable increases in cross-sectional areas of muscle fibers of all types ; however, the percentage increase was less in type II b fibers. Twitch contraction and half-relaxation time before and after tetanus did not change, but fatigue resistance increased significantly with overload. The percentage of area occupied by type II b fibers, which have lower oxidative capacity, decreased while the percentage of area occupied by other type II fibers, but not type I fibers, increased. Analysis of MyoHC isoforms with gradient sodium dodecylsulfate polyacrylamide gel electrophoresis revealed a decrease in II b isoforms and an increase in II d isoforms.<BR>These results suggest that chronic overload produces changes in muscle fiber type and MyoHC isoform compositions which partly account for increased fatigue resistance in overloaded muscles.
ABSTRACT
The effects of testosterone on the structural and contractile properties of the denervated rat skeletal muscles that were not influenced by neurotrophic-effects were investigated. Male Wistar strain rats (3-week-old, n=28) were used in the present study. All rats were divided into four (n=7, for each) groups; control (C), testosterone control (TC), denervated (DN), and denervated with testosterone (DNT) groups. Sciatic nerves of DN and DNT groups' rats were resected at the 4-week-old after birth. Testosterone that was melted in corn-oil was administered (40 mg/kg body weight/week) for the TC and DNT groups. At the end of breeding period (15-week-old), soleus (SOL) and extensor digitorum longus (EDL) muscles were dissected from both hindlimbs and contractile profiles were analyzed in vitro. Relative weight (muscle weight/body weight) of SOL muscle in the DNT group was significantly (p<0.01) higher than that of the DN group. There is no significant difference in EDL muscle between the DN and DNT groups. Time to peak tension and half relaxation time in EDL muscle of the DNT group was significantly (p<0.05) higher than those of the DN group. Maximum twitch tension was prone to decrease following denervation, and significantly (p<0.01) difference between the DN and DNT groups in both muscles regarding the maximum twitch tension was observed. There is no significant difference of myosin and actomyosin ATPase activities comparison of each group in SOL muscle, however, the TC group were significantly higher than those of the C group in EDL muscle. These results suggested that the effects of testosterone for the hypertrophy in skeletal muscles were not synergistic effects with the neurotrophiceffects, however, for the ATPase in fast muscle act synergistically with the neurotrophic effect to change of myosin ATPase. Moreover, it was also suggested that the sensitivity to the testosterone was different in each type of fiber.