Muscle Contractile Properties Research Articles

Effects of post activation potentiation on electromechanical delay

Electromechanical delay (EMD) presumably depends upon both contractile and tensile factors. It has recently been used as an indirect measure of muscle tendon stiffness to study adaptations to stretching and training. The aim of the present study was to investigate whether contractile properties induced by a 6 s maximum voluntary isometric contraction (MVIC) could affect EMD without altering passive muscle tendon stiffness or stiffness index. Plantar flexor twitches were evoked via electrical stimulation of the tibial nerve in eight highly trained male sprinters before and after a 6 s MVIC in passive isometric or passively shortening or lengthening muscles. For each twitch, EMD, twitch contractile properties and SOLM-Wave were measured. Passive muscle tendon stiffness was measured from the slope of the relation between torque and ankle angle during controlled passive dorsal flexion and stiffness index by curve-fitting the torque angle data using a second-order polynomial function. EMD did not differ between isometric, lengthening or shortening movements. EMD was reduced by up to 11.56 ± 5.64% immediately after the MVIC and stayed depressed for up to 60 s after conditioning. Peak twitch torque and rate of torque development were potentiated by up to 119.41 ± 37.15% and 116.06 ± 37.39%, respectively. Rising time was reduced by up to 14.46 ± 7.22%. No significant changes occurred in passive muscle tendon stiffness or stiffness index. Using a conditioning MVIC, it was shown that there was an acute enhancement of contractile muscle properties as well as a significant reduction in EMD with no corresponding changes in stiffness. Therefore, caution should be taken when using and interpreting EMD as a proxy for muscle tendon stiffness.

Acute effects of bi-hemispheric transcranial direct current stimulation on the neuromuscular function of patients with chronic stroke: A randomized controlled study

BackgroundMuscle weakness in patients with chronic stroke is due to neuromuscular disorders such as muscle atrophy, loss of voluntary activation or weak muscle contractile properties which are majored by the imbalance of interhemispheric inhibition following stroke. In patients with chronic stroke, unilateral transcranial direct current stimulation improved the maximal isometric strength of paretic knee extensors, but bilateral transcranial direct current stimulation failed to improve concentric strength. This study aimed to assess if a bilateral current stimulation improves isometric maximal strength, voluntary activation and contractile properties of knee extensors in patients with chronic stroke. MethodsThirteen patients with chronic stroke and eight young healthy individuals participated in this randomized, simple-blinded, crossover study that included two experimental sessions: one with sham bilateral transcranial direct current stimulation and another with effective bilateral transcranial direct current stimulation (20 min, 2 mA). In the stroke patients, the anode was placed over the primary motor cortex of the affected hemisphere and the cathode over the contralateral primary motor cortex. In healthy participants, the brain side targeted by the anode and the cathode was randomly assigned. In each session, participants performed three assessments of strength, voluntary activation and contractile properties: before, during and after effective/sham bilateral transcranial direct current stimulation. FindingsBilateral transcranial direct current stimulation had no effect on any neuromuscular assessments in both groups (All P values > 0.05, partial eta-squares varied from 0.02 to 0.06). InterpretationA single session of bilateral transcranial direct current stimulation did not compensate muscular weakness of knee extensors in patients with chronic stroke.

Functional Requirements of a Mathematical Model of Muscle Contraction.

Muscle modeling has a long history. Models typically belong to the class of lumped models built around Hill's contractile element, or to crossbridge models at the ultrastructure level. Lumped models built on the contractile element are not sufficiently dynamic, since the muscle's contractile properties are set a priori by the force-velocity relation. We have shown that the force-velocity relation is not a unique descriptor of muscle's contractile state [1]. Alternatively, description of muscle as a time and length dependent force generator may be used to model muscle dynamics. This paper defines the functional requirements of a mathematical model of muscle contraction and evaluates how closely a lumped model based on ultrastructural dynamics resembles muscle. This single model was found able to describe isometric and isotonic contractions, the force-length relation, the force-velocity relation, and changes in contractile state and contraction rate. This approach may help link macro contractile properties, such as the force-velocity relation, to micro dynamics of crossbridge bonds. It may also be useful as a component of larger physiological models and simulations.

Body Composition and Muscle Contractile Properties in Male Professional Soccer Players

Body Composition and Muscle Contractile Properties in Male Professional Soccer Players

Testosterone and Resistance Training Improves Muscle Quality Following Spinal Cord Injury

Spinal cord injury (SCI) adversely effects muscle quality and testosterone levels. Following SCI, resistance training (RT) has been shown to increase muscle cross-sectional area (CSA). Testosterone replacement therapy (TRT) in other populations has also been shown to improve muscle quality. PURPOSE: To examine if the combination of RT and TRT (TRT+RT) can maximize the beneficial effects to muscle quality following SCI. METHODS: Twenty-two SCI subjects were randomized into two intervention groups for 16-weeks: TRT+RT (n = 11), or TRT (n = 11). Muscle quality was assessed by measuring peak torque at speeds of 0, 60, 90, and 180°/sec (PT-0°, PT-60°, PT-90°, PT-180°), knee extensor CSA (KE-CSA), specific tension (ST), and contractile speeds (rise time [RTi], and half-time to relaxation [½TiR]) for each limb prior to testing and following the intervention. 2x2 mixed models with subject identifiers added as random effects and post-hoc Tukey-Kramer HSD tests identified pairwise differences within interactions (P < 0.05). RESULTS: Following the intervention period, participants in the TRT+RT group increased PT-0° (48.4%, P = 0.017), KE-CSA (30.8%, P < 0.001), ST (8%, NS), and RTi (17.7%, P = 0.012). PT-0° decreased (17%, NS), KE-CSA slightly increased (10%, NS), ST decreased (20%, NS), and RTi also slightly decreased (9%, NS) in the TRT group. Changes to PT-60°, PT-90°, PT-180°, and ½TiR for each group were similar following the 16-week intervention. CONCLUSION: Mechanical stress induced via RT combined with TRT maximizes enhancements of muscle quality when compared to TRT interventions alone in men with complete SCI. Our study shows that TRT+RT increases both muscle size, strength, and also improves muscle contractile properties.

Residual force enhancement and force depression in human single muscle fibres

Residual force depression (rFD) and residual force enhancement (rFE) are intrinsic contractile properties of muscle. rFD is characterized as a decrease in steady-state isometric force following active shortening compared with a purely isometric contraction at the same muscle length and level of activation. By contrast, isometric force is increased following active lengthening compared to a reference isometric contraction at the same muscle length and level of activation; this is termed rFE. To date, there have been no investigations of rFD and rFE in human muscle fibres, therefore the purpose of this study was to determine whether rFD and rFE occur at the single muscle fibre level in humans. rFD and rFE were investigated in maximally activated single muscle fibres biopsied from the vastus lateralis of healthy adults. To induce rFD, fibres were activated and shortened from an average sarcomere length (SL) of 3.2–2.6 μm. Reference isometric contractions were performed at an average SL of 2.6 μm. To induce rFE, fibres were actively lengthened from an average SL of 2.6–3.2 μm and a reference isometric contraction was performed at an average SL of 3.2 μm. Isometric steady-state force was lower following active shortening (p < 0.05), and higher following active lengthening (p < 0.05), as compared to the reference isometric contractions. We demonstrated rFD and rFE in human single fibres which is consistent with previous animal models. The non-responder phenomenon often reported in rFE studies involving voluntary contractions at the whole human level was not observed at the single fibre level.

The Effect of Vitamin D Supplementation on Skeletal Muscle in the mdx Mouse Model of Duchenne Muscular Dystrophy.

Vitamin D (VitD) has shown to be beneficial in reversing muscle weakness and atrophy associated with VitD deficiency. Duchenne muscular dystrophy is characterized by worsening muscle weakness and muscle atrophy, with VitD deficiency commonly observed. This study aimed to investigate the effect of VitD supplementation on dystrophic skeletal muscle. Eight-week old female control (C57BL/10; n = 29) and dystrophic (C57BL/mdx; n = 23) mice were randomly supplemented with one of three VitD enriched diets (1000, 8000 & 20,000 IU/kg chow). Following a four-week feeding period, the extensor digitorum longus (EDL) and soleus muscles contractile and fatigue properties were tested ex vivo, followed by histological analysis. As expected, mdx muscles displayed higher mass yet lower specific forces and a rightward shift in their force frequency relationship consistent with dystrophic pathology. There was a trend for mdx muscle mass to be larger following the 20,000 IU/kg diet, but this did not result in improved force production. Fiber area in the EDL was larger in mdx compared to controls, and there were higher amounts of damage in both muscles, with VitD supplementation having no effect. Four weeks of VitD supplementation did not appear to have any impact upon dystrophic skeletal muscle pathology at this age.

Clinical utility of tensiomyography for muscle function analysis in athletes.

An exhaustive review has been made to filter the studies that have analyzed muscle function though tensiomyography (TMG) with elite or well-trained athletes. The results of this review indicate that the several protocols used in athletes to find the displacement-time curve with greater maximum radial muscle displacement showed a good-excellent reliability. TMG has been used to characterize athletes’ muscles contractile properties from specific sports disciplines, although there are very few sports that have been deeply analyzed. TMG seems to be useful to determine changes in muscles contractile properties after stimuli of competition, training or recovery. These changes have been strongly related with the fatigue produced after an effort. In addition, TMG parameters could be used to control training effects during a specific period or throughout the season being also a very useful tool to individualize athletes training loads. In this sense, it also seems to provide sports performance information in cyclic sports by relating some TMG parameters with performance indicators. On the other hand, the TMG-BCM algorithm has been used as a lateral and functional symmetry measure and as a monitoring tool for injury prevention and recovery. However, it seems to be no clear criterion that determines asymmetry degree, nor established contractile properties values as a reference to prevent or recover sports injuries. Despite the utility shown in these fields, there are still very few sports analyzed and it is really necessary to continue advancing in the knowledge of the contractile properties behavior, such as the effects of athletes’ training, competitions and injuries and even in the parameters interpretation obtained with the TMG.

Muscle fiber dysfunction contributes to weakness in inclusion body myositis

Atrophy and fatty infiltration are important causes of muscle weakness in inclusion body myositis (IBM). Muscle weakness can also be caused by reduced specific force; i.e. the amount of force generated per unit of residual muscle tissue. This study investigates in vivo specific force of the quadriceps and ex vivo specific force of single muscle fibers in patients with IBM. We included 8 participants with IBM and 12 healthy controls, who all underwent quantitative muscle testing, quantitative MRI of the quadriceps and paired muscle biopsies of the quadriceps and tibialis anterior. Single muscle fibers were isolated to measure muscle fiber specific force and contractile properties. Both in vivo quadriceps specific force and ex vivo muscle fiber specific force were reduced. Muscle fiber dysfunction was accompanied by reduced active stiffness, which reflects a decrease in the number of attached actin-myosin cross-bridges during activation. Myosin concentration was reduced in IBM fibers. Because reduced specific force contributes to muscle weakness in patients with IBM, therapeutic strategies that augment muscle fiber strength may provide benefit to patients with IBM.

Testosterone and Resistance Training Improve Muscle Quality in Spinal Cord Injury.

Spinal cord injury (SCI) negatively impacts muscle quality and testosterone levels. Resistance training (RT) has been shown to increase muscle cross-sectional area (CSA) after SCI, whereas testosterone replacement therapy (TRT) has been shown to improve muscle quality in other populations. The purpose of this pilot study was to examine if the combined effects of these interventions, TRT + RT, may maximize the beneficial effects on muscle quality after SCI. Twenty-two SCI subjects randomized into either a TRT + RT (n = 11) or TRT (n = 11) intervention for 16 wk. Muscle quality measured by peak torque (PT) at speeds of 0°·s (PT-0°), 60°·s (PT-60°), 90°·s (PT-90°), and 180°·s (PT-180°), knee extensor CSA, specific tension, and contractile speed (rise time [RTi], and half-time to relaxation [½TiR]) was assessed for each limb at baseline and postintervention using 2 × 2 mixed models. After 16 wk, subjects in the TRT + RT group increased PT-0° (48.4%, P = 0.017), knee extensor CSA (30.8%, P < 0.0001), and RTi (17.7%, P = 0.012); with no significant changes observed in the TRT group. Regardless of the intervention, changes to PT-60° (28.4%, P = 0.020), PT-90° (26.1%, P = 0.055), and PT-180° (20.6%, P = 0.09) for each group were similar. The addition of mechanical stress via RT to TRT maximizes improvements to muscle quality after complete SCI when compared with TRT administered alone. Our evidence shows that this intervention increases muscle size and strength while also improving muscle contractile properties.

Top-down Mass Spectrometry of Sarcomeric Protein Post-translational Modifications from Non-human Primate Skeletal Muscle.

Sarcomeric proteins, including myofilament and Z-disk proteins, play critical roles in regulating muscle contractile properties. A variety of isoforms and post-translational modifications (PTMs) of sarcomeric proteins have been shown to be associated with modulation of muscle functions and the occurrence of muscle diseases. Non-human primates (NHPs) are excellent research models for sarcopenia, a disease associated with alterations in sarcomeric proteins, due to their marked similarities to humans. However, the sarcomeric proteins in NHP skeletal muscle have not been well characterized. To gain a deeper understanding of sarcomeric proteins in NHP skeletal muscle, we employed top-down mass spectrometry (MS) to conduct a comprehensive analysis on isoforms and PTMs of sarcomeric proteins in rhesus macaque skeletal muscle. We identified 23 protein isoforms with 46 proteoforms of sarcomeric proteins, including 6 isoforms with 18 proteoforms from fast skeletal troponin T. Particularly, for the first time, a novel PDZ/LIM domain protein isoform, PDLIM7, was characterized with a newly identified protein sequence. Moreover, we also identified multiple PTMs on these proteins, including deamidation, methylation, acetylation, tri-methylation, phosphorylation, and S-glutathionylation. Most PTM sites were localized, including Asn13 deamidation on MLC-2S; His73 methylation on αactin; N-terminal acetylation on most identified proteins; N-terminal tri-methylation on MLC-1S, MLC-1F, MLC-2S, and MLC-2F; Ser14 phosphorylation on MLC-2S; and Ser15 and Ser16 phosphorylation on MLC-2F. In summary, a comprehensive characterization of sarcomeric proteins including multiple isoforms and PTMs in NHP skeletal muscle was achieved by analyzing intact proteins in the top-down MS approach.

Does Dietary-Induced Obesity in Old Age Impair the Contractile Performance of Isolated Mouse Soleus, Extensor Digitorum Longus and Diaphragm Skeletal Muscles?

Ageing and obesity independently have been shown to significantly impair isolated muscle contractile properties, though their synergistic effects are poorly understood. We uniquely examined the effects of 9 weeks of a high-fat diet (HFD) on isometric force, work loop power output (PO) across a range of contractile velocities, and fatigability of 79-week-old soleus, extensor digitorum longus (EDL) and diaphragm compared with age-matched lean controls. The dietary intervention resulted in a significant increase in body mass and gonadal fat pad mass compared to the control group. Despite increased muscle mass for HFD soleus and EDL, absolute isometric force, isometric stress (force/CSA), PO normalised to muscle mass and fatigability was unchanged, although absolute PO was significantly greater. Obesity did not cause an alteration in the contractile velocity that elicited maximal PO. In the obese group, normalised diaphragm PO was significantly reduced, with a tendency for reduced isometric stress and fatigability was unchanged. HFD soleus isolated from larger animals produced lower maximal PO which may relate to impaired balance in older, larger adults. The increase in absolute PO is smaller than the magnitude of weight gain, meaning in vivo locomotor function is likely to be impaired in old obese adults, with an association between greater body mass and poorer normalised power output for the soleus. An obesity-induced reduction in diaphragm contractility will likely impair in vivo respiratory function and consequently contribute further to the negative cycle of obesity.

Characterization of torque generating properties of ankle plantar flexor muscles in ambulant adults with cerebral palsy.

Weakness of plantar flexor muscles is related to reduced push-off and forward propulsion during gait in persons with cerebral palsy (CP). It has not been clarified to what an extent altered muscle contractile properties contribute to this muscle weakness. Here, we investigated the torque generating capacity and muscle fascicle length in the triceps surae muscle throughout ankle range of motion (ROM) in adults with CP using maximal single muscle twitches elicited by electrical nerve stimulation and ultrasonography. Fourteen adults with CP (age 36, SD 10.6, GMFCS I-III) and 17 neurological intact (NI) adults (age 36, SD 4.5) participated. Plantar flexor torque during supramaximal stimulation of the tibial nerve was recorded in a dynamometer at 8 ankle angles throughout ROM. Medial gastrocnemius (MG) fascicle length was tracked using ultrasonography. Adults with CP showed reduced plantar flexor torque and fascicle shortening during supramaximal stimulation throughout ROM. The largest torque generation was observed at the ankle joint position where the largest shortening of MG fascicles was observed in both groups. This was at a more plantarflexed position in the CP group. Reduced torque and fascicle shortening during supramaximal stimulation of the tibial nerve indicate impaired contractile properties of plantar flexor muscles in adults with CP. Maximal torque was observed at a more plantarflexed position in adults with CP indicating an altered torque-fascicle length/ankle angle relation. The findings suggest that gait rehabilitation in adults with CP may require special focus on improvement of muscle contractility.

Test-retest reliability of elbow flexor contraction characteristics with tensiomyography for different elbow joint angles

Tensiomyography (TMG) has gained popularity as a tool to quantify muscle contractile properties. However, it is unclear whether joint angle and inter-stimulus interval influence the test-retest reliability of TMG. Fifteen participants (13M/2F; 29.5 ± 7.4 y) underwent TMG recording of the biceps brachii (BB) at 10°, 45° and 90° of elbow flexion with 10 and 20 s inter-stimulus rest intervals in a randomised order on two separate days. The intra-class correlation coefficient (ICC2,1) and 95% confidence interval (95%CI) were calculated for delay time (Td), contraction time (Tc), sustain time (Ts), relaxation time (Tr) and maximal displacement (Dm). Additionally, the standard error of measurement (SEM), coefficient of variation (CV) and minimal detectable change (MDC) were obtained. Across conditions the ICC2,1 varied for each parameter (Td:0.465–0.947, Tc:0.452–0.831, Ts:0.717–0.918, Tr:0.841–0.935, Dm:0.646–0.900). CV was low for Td (2.1–3.0%), Tc (4.4–7.7%) and Ts (5.5–6.9%) but greater for Tr (10.0–15.3%) and Dm (5.8–13.1%) across conditions. Ts (∼210 ms, P < 0.001) and Dm (∼17 mm, P < 0.001) were greatest at 10° and 90°, respectively, while Td was shortest (∼22.9 ms, P = 0.002) at 10° compared to other angles. No differences were observed between inter-stimulus intervals or day. The findings are expected to help shape best practice methods for TMG use in field and research based settings.

Effect of magnetic field exposure on muscle contractile properties and morphology in spinal cord transected rats: A non-invasive therapeutic approach

Introduction:Spinal cord injury (SCI) is an insult to spinal cord resulting either complete or partial loss of movements, muscular coordination and endurance. Antigravity slow type muscles are more vulnerable to disuse-induced atrophy. Aim of present study was to investigate the effect of magnetic field (MF) exposure on soleus muscle contractility and morphology following SCI.

The influence of added mass on muscle activation and contractile mechanics during submaximal and maximal countermovement jumping in humans.

Muscle contractile mechanics induced by the changing demands of human movement have the potential to influence our movement strategies. This study examined fascicle length changes of the triceps surae during jumping with added mass or increasing jump height to determine whether the chosen movement strategies were associated with relevant changes in muscle contractile properties. Sixteen participants jumped at sub-maximal and maximal intensities while total net work was matched via two distinct paradigms: (1) adding mass to the participant or (2) increasing jump height. Electromyography (EMG) and ultrasound analyses were performed to examine muscle activation, fascicle length and fascicle velocity changes of the triceps surae during jumping. Integrated EMG was significantly higher in the added mass paradigm with no difference in mean or maximal EMG, indicating that the muscle was activated for a significantly longer period of time but not activated to a greater intensity. Fascicle shortening velocity was slower with added mass compared than with increasing jump height; therefore, intrinsic force-velocity properties probably enabled increased force production. Improved fascicle contractile mechanics paired with a longer activation period probably produced a consistently larger fascicle force, enabling a greater impulse about the ankle joint. This may explain why previous research found that participants used an ankle-centred strategy for work production in the added mass paradigm and not in the jump height paradigm. The varied architecture of muscles within the lower limb may influence which muscles we choose to employ for work production under different task constraints.

EFFECTS OF 8-WEEK ELECTRICAL MUSCLE STIMULATION ON THE MUSCLE CONTRACTILE PROPERTIES IN ADOLESCENT GIRLS

The study aimed to determine the effect of 8-week unilateral electrical muscle stimulation (EMS) training of leg muscles: vastus lateralis, vastus medialis and biceps femoris with the same number of muscle contractions in comparison to controls. Contractile properties were monitored by measuring the maximal voluntary isometric contraction (MVC) and the rate of force development in first 50 ms (RFD50) of knee extensors and flexors and tensiomyography of stimulated muscles. In addition, we also investigated the retained effect after 8 weeks without EMS training. Nineteen healthy young female athletes aged 15 to 18 years (average 16.4 ± .9 years) were randomly divided in a control group (CG; N=8) and experimental group (EG; N=11). CG performed maximal unilateral voluntary contractions while the EG performed also EMS training of the same leg by stimulating both vasti muscles and biceps femoris. There were no changes in CG after 8-weeks of maximal unilateral voluntary training; however, EG improved MVC in knee extensors (12.6%; P =.085) and RFD50 (142.1%; P =.049) where RFD50 retained increased also 8 weeks after EMS training (73%; P =.090). Tensiomyography revealed decreased amplitude (13.2%; P=.011) only in EG, representing higher muscle tone after 8-weeks of EMS in comparison to CG. Our findings indicate that EMS training has a positive effect on muscle contractile properties in young female athletes even after comparing to matched controls by the number of contractions.

Exercise-induced muscle damage on the contractile properties of the lumbar paraspinal muscles: a laser displacement mechanomyographic approach.

This study investigated whether laser displacement mechanomyography (MMG) could detect acute injury of low back muscles following strenuous eccentric exercise. Sixteen healthy adults (10 females, 6 males, mean ± standard deviation, age 21 ± 2.90years, BMI 21.63 ± 1.99kg/m2), without low back pain or low back resistance training, were recruited. Strength [maximum voluntary isometric contraction force (MVC)], pain intensity [visual analogue scale (VAS)], biological markers of muscle injury (serum myoglobin and creatine kinase levels), and MMG-derived muscle contractile properties were measured at seven different time points. Pre-exercise 'control' measures were taken prior to a strenuous eccentric exercise task, followed by an immediate post-exercise measurement and further four consecutive daily measurements. A final post-exercise measurement was completed on day12 post-exercise. Compared to pre-exercise control, MVC was lower immediately post-exercise (day1) and on days2-3. VAS scores were higher post-exercise (day1) and from days2-5. Myoglobin was significantly higher on day4, whilst creatine kinase was significantly higher on days4-5. MMG-derived maximum muscle displacement (Dmax) was significantly diminished post-exercise (day1) at all vertebral segments (L1-MT), while contraction velocity (Vc) was significantly slower at all segments except sacral multifidus. Vc recovered rapidly (by day2), while mid-lumbar Dmax resolved on day12. Dmax had moderate correlations with MVC (R = 0.61) and VAS (R = - 0.50), and low correlations with myoglobin (R = - 0.36). MMG appears capable of detecting changes in muscle contractile properties associated with an acute bout of low back pain.

Exercise-induced hyperemia is associated with knee extensor fatigability in adults with type 2 diabetes.

The aim of this study was to compare fatigability, contractile function, and blood flow to the knee extensor muscles after dynamic exercise in patients with type 2 diabetes mellitus (T2DM) and controls. The hypotheses were that patients with T2DM would demonstrate greater fatigability than controls, and greater fatigability would be associated with a lower exercise-induced increase in blood flow and greater impairments in contractile function. Patients with T2DM ( n = 15; 8 men; 62.4 ± 9.0 yr; 30.4 ± 7.7 kg/m2; 7,144 ± 3,294 steps/day) and 15 healthy control subjects (8 men, 58.4 ± 6.9 yr; 28.4 ± 4.6 kg/m2; 7,893 ± 2,323 steps/day) were matched for age, sex, body mass index, and physical activity. Fatigability was quantified as the reduction in knee extensor power during a 6-min dynamic exercise. Before and after exercise, vascular ultrasonography and electrical stimulation were used to assess skeletal muscle blood flow and contractile properties, respectively. Patients with T2DM had greater fatigability (30.0 ± 20.1% vs. 14.6 ± 19.0%, P < 0.001) and lower exercise-induced hyperemia (177 ± 90% vs. 194 ± 79%, P = 0.04) than controls but similar reductions in the electrically evoked twitch amplitude (37.6 ± 24.8% vs. 31.6 ± 30.1%, P = 0.98). Greater fatigability of the knee extensor muscles was associated with postexercise reductions in twitch amplitude ( r = 0.64, P = 0.001) and lesser exercise-induced hyperemia ( r = -0.56, P = 0.009). Patients with T2DM had greater lower-limb fatigability during dynamic exercise, which was associated with reduced contractile function and lower skeletal muscle blood flow. Thus, treatments focused on enhancing perfusion and reversing impairments in contractile function in patients with T2DM may offset lower-limb fatigability and aid in increasing exercise capacity. NEW & NOTEWORTHY Although prior studies compare patients with type 2 diabetes mellitus (T2DM) with lean controls, our study includes controls matched for age, body mass, and physical activity to more closely assess the effects of T2DM. Patients with T2DM demonstrated no impairment in macrovascular endothelial function, evidenced by similar flow-mediated dilation to controls. However, patients with T2DM had greater fatigability and reduced exercise-induced increase in blood flow (hyperemia) after a lower-limb dynamic fatiguing exercise compared with controls.

20대 성인의 하지 근수축 특성이 보행에 미치는 영향

The purpose of this study was to investigate the relationship between lower limb muscle contractile properties and walking ability. We measured muscle contractile properties and the walking ability using a Tensiomyography (TMG) and a 6-axis IMU sensor accelerometer (GaitUp PhysiologySUP®/SUP 5) of young 25 adults. The measured data were subjected to stepwise multiple regression analysis with the muscle contractile parameters as the independent variable and the gait variables as the dependent variable. The results showed that the maximal displacement (Dm) which quantified muscle stiffness, and contraction time (Tc) which magnified the muscle contraction of each muscle were significantly correlated with the general, temporal, spatial gait parameters and foot kinematics. Also the muscle contractile parameters were identified as potential factors affecting walking performance. The results of this study suggest that improving muscle strength and muscle condition through proper strength training or rest may help improve walking ability. In addition, TMG could be considered to be effective as a methodology for predicting gait performance.