scholarly journals Diurnal Differences in Human Muscle Isometric Force In Vivo Are Associated with Differential Phosphorylation of Sarcomeric M-Band Proteins

Proteomes ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 22 ◽  
Author(s):  
Zulezwan Ab Malik ◽  
Kelly A. Bowden Davies ◽  
Elliott C. R. Hall ◽  
Jennifer Barrett ◽  
Samuel A. Pullinger ◽  
...  
Keyword(s):  
Isometric Force ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Human Muscle ◽  
Force Transmission ◽  
Force Output ◽  
Muscle Creatine Kinase ◽  
Maximal Voluntary Isometric Contraction ◽  
C Terminus

We investigated whether diurnal differences in muscle force output are associated with the post-translational state of muscle proteins. Ten physically active men (mean ± SD; age 26.7 ± 3.7 y) performed experimental sessions in the morning (08:00 h) and evening (17:00 h), which were counterbalanced in order of administration and separated by at least 72 h. Knee extensor maximal voluntary isometric contraction (MVIC) force and peak rate of force development (RFD) were measured, and samples of vastus lateralis were collected immediately after exercise. MVIC force was greater in the evening (mean difference of 67 N, 10.2%; p < 0.05). Two-dimensional (2D) gel analysis encompassed 122 proteoforms and discovered 6 significant (p < 0.05; false discovery rate [FDR] = 10%) diurnal differences. Phosphopeptide analysis identified 1693 phosphopeptides and detected 140 phosphopeptides from 104 proteins that were more (p < 0.05, FDR = 22%) phosphorylated in the morning. Myomesin 2, muscle creatine kinase, and the C-terminus of titin exhibited the most robust (FDR < 10%) diurnal differences. Exercise in the morning, compared to the evening, coincided with a greater phosphorylation of M-band-associated proteins in human muscle. These protein modifications may alter the M-band structure and disrupt force transmission, thus potentially explaining the lower force output in the morning.

scholarly journals Keratin 18 is an integral part of the intermediate filament network in murine skeletal muscle

2020 ◽  
Vol 318 (1) ◽  
pp. C215-C224 ◽  
Author(s):  
Joaquin M. Muriel ◽  
Andrea O’Neill ◽  
Jaclyn P. Kerr ◽  
Emily Kleinhans-Welte ◽  
Richard M. Lovering ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Isometric Force ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Type I ◽  
Mrna Levels ◽  
Force Transmission ◽  
Keratin 18 ◽  
Murine Skeletal Muscle

Intermediate filaments (IFs) contribute to force transmission, cellular integrity, and signaling in skeletal muscle. We previously identified keratin 19 (Krt19) as a muscle IF protein. We now report the presence of a second type I muscle keratin, Krt18. Krt18 mRNA levels are about half those for Krt19 and only 1:1,000th those for desmin; the protein was nevertheless detectable in immunoblots. Muscle function, measured by maximal isometric force in vivo, was moderately compromised in Krt18-knockout ( Krt18-KO) or dominant-negative mutant mice ( Krt18 DN), but structure was unaltered. Exogenous Krt18, introduced by electroporation, was localized in a reticulum around the contractile apparatus in wild-type muscle and to a lesser extent in muscle lacking Krt19 or desmin or both proteins. Exogenous Krt19, which was either reticular or aggregated in controls, became reticular more frequently in Krt19-null than in Krt18-null, desmin-null, or double-null muscles. Desmin was assembled into the reticulum normally in all genotypes. Notably, all three IF proteins appeared in overlapping reticular structures. We assessed the effect of Krt18 on susceptibility to injury in vivo by electroporating siRNA into tibialis anterior (TA) muscles of control and Krt19-KO mice and testing 2 wk later. Results showed a 33% strength deficit (reduction in maximal torque after injury) compared with siRNA-treated controls. Conversely, electroporation of siRNA to Krt19 into Krt18-null TA yielded a strength deficit of 18% after injury compared with controls. Our results suggest that Krt18 plays a complementary role to Krt19 in skeletal muscle in both assembling keratin-based filaments and transducing contractile force.

scholarly journals In vivo strain of the medial vs. lateral quadriceps tendon in patellofemoral pain syndrome

2009 ◽  
Vol 107 (2) ◽  
pp. 422-428 ◽  
Author(s):  
Nicole A. Wilson ◽  
Joel M. Press ◽  
Li-Qun Zhang
Keyword(s):  
Vastus Lateralis ◽  
Knee Extensor ◽  
Pain Syndrome ◽  
Quadriceps Tendon ◽  
Biomechanical Properties ◽  
Patellofemoral Pain ◽  
Control Subjects ◽  
Patellar Maltracking ◽  
Tendon Strain

Patellofemoral pain (PFP) is thought to be related to patellar maltracking due to imbalances in the knee extensor. However, no study has evaluated the in vivo biomechanical properties of the quadriceps tendon in PFP syndrome. Our purpose was to compare the biomechanical properties of the quadriceps tendons in vivo and noninvasively in patients with PFP syndrome to those of control subjects. The null hypothesis was that the quadriceps tendons of PFP subjects would have significantly decreased strain compared with control subjects. Fourteen subjects (7 control, 7 PFP) performed voluntary ramp isometric contractions to a range of torque levels, while quadriceps tendon elongation was measured using ultrasonography. Tendon strain was calculated for the vastus medialis obliquus (VMO) and vastus lateralis (VL) portion of the quadriceps tendon and compared between subjects (control vs. PFP) and within subjects (VMO vs. VL). PFP subjects showed significantly less VMO tendon strain than control subjects ( P < 0.001), but there was no difference in VL tendon strain between PFP and control subjects ( P = 0.100). Relative weakness of the VMO is the most likely cause of the decreased tendon strain seen in subjects with PFP. VMO weakness not only explains the decreased medial tendon strain but also explains the presence of increased lateral patellar translation and lateral patellar spin (distal pole rotates laterally) reported in the literature in this population. This technique can potentially be used in a clinical setting to evaluate quadriceps tendon properties and infer the presence of muscle weakness in PFP.

The Association of Obesity With Quadriceps Activation During Sit-to-Stand

2020 ◽  
Vol 100 (12) ◽  
pp. 2134-2143
Author(s):  
Lance M Bollinger ◽  
Amanda L Ransom
Keyword(s):  
Vastus Lateralis ◽  
Knee Extensor ◽  
Quadriceps Muscle ◽  
Knee Extensors ◽  
Emg Activity ◽  
Vastus Medialis ◽  
Trunk Flexion ◽  
Maximal Voluntary Isometric Contraction ◽  
Sit To Stand ◽  
The Mean

Abstract Objective Obesity reduces voluntary recruitment of quadriceps during single-joint exercises, but the effects of obesity on quadriceps femoris muscle activation during dynamic daily living tasks, such as sit-to-stand (STS), are largely unknown. The purpose of this study was to determine how obesity affects quadriceps muscle recruitment during STS. Methods In this cross-sectional study, 10 women who were lean and 17 women who were obese completed STS from a chair with arms crossed over the chest. Three-dimensional motion analysis was used to define 3 distinct phases (I–III) of the STS cycle. The electromyographic (EMG) activity of the vastus medialis, vastus lateralis, and semitendinosus was measured. Results STS duration was greater (3.02 [SD = 0.75] seconds vs 1.67 [SD = 0.28] seconds) and peak trunk flexion angle was lower (28.9 degrees [SD = 10.4 degrees] vs 35.8 degrees [SD = 10.1 degrees]) in the women who were obese than in the women who were lean. The mean EMG activity of the knee extensors increased from phase I to phase II in both groups; however, the mean EMG activities of both the vastus medialis (32.1% [SD = 16.6%] vs 47.3% [SD = 19.6%] maximal voluntary isometric contraction) and the vastus lateralis (31.8% [SD = 19.4%] vs 47.5% [SD = 19.6%] maximal voluntary isometric contraction) were significantly lower during phase II in the women who were obese. The mean EMG activity of the semitendinosus increased throughout STS but was not significantly different between the 2 groups. Coactivation of the semitendinosus and knee extensors tended to be greater in the women who were obese but failed to reach statistical significance. Conclusions Knee extensor EMG amplitude was reduced in women who were obese during STS, despite reduced trunk flexion. Impact Reduced knee extensor recruitment during STS in obesity may redistribute forces needed to complete this task to other joints. Functional movement training may help improve knee extensor recruitment during STS in people who are obese. Lay Summary People with obesity often have low quadriceps muscle strength and impaired mobility during daily activities. This study shows that women who are obese have lower voluntary recruitment of quadriceps when rising from a chair than women who are lean do, which could increase workload on hip or ankle muscles during this important daily task. Quadriceps strengthening exercises might improve the ability to rise from sitting to standing.

scholarly journals A new method to study in vivo protein synthesis in slow- and fast-twitch muscle fibers and initial measurements in humans

2010 ◽  
Vol 108 (5) ◽  
pp. 1410-1416 ◽  
Author(s):  
J. M. Dickinson ◽  
J. D. Lee ◽  
B. E. Sullivan ◽  
M. P. Harber ◽  
S. W. Trappe ◽  
...  
Keyword(s):  
Fiber Type ◽  
Vastus Lateralis ◽  
Muscle Fibers ◽  
Human Muscle ◽  
Synthesis Rate ◽  
Mhc I ◽  
Fast Twitch ◽  
Mixed Protein ◽  
Mhc Iia

The aim of this study was to develop an approach to directly assess protein fractional synthesis rate (FSR) in isolated human muscle fibers in a fiber type-specific fashion. Individual muscle fibers were isolated from biopsies of the vastus lateralis (VL) and soleus (SOL) obtained from eight young men during a primed, continuous infusion of [5,5,5-2H3]leucine performed under basal conditions. To determine mixed protein FSR, a portion of each fiber was used to identify fiber type, fibers of the same type were pooled, and the [5,5,5-2H3]leucine enrichment was determined via GC-MS. Processing isolated slow-twitch [myosin heavy chain (MHC) I] and fast-twitch (MHC IIa) fibers for mixed protein bound [5,5,5-2H3]leucine enrichment yielded mass ion chromatographic peaks that were similar in shape, abundance, and measurement reliability as tissue homogenates. In the VL, MHC I fibers exhibited a 33% faster ( P < 0.05) mixed protein FSR compared with MHC IIa fibers (0.068 ± 0.006 vs. 0.051 ± 0.003%/h). MHC I fibers from the SOL (0.060 ± 0.005%/h) and MHC I fibers from the VL displayed similar ( P > 0.05) mixed protein FSR. Feasibility of processing isolated human muscle fibers for analysis of myofibrillar protein [5,5,5-2H3]leucine enrichment was also confirmed in non-fiber-typed pooled fibers from the VL. These methods can be applied to the study of fiber type-specific responses in human skeletal muscle. The need for this level of investigation is underscored by the different contributions of each fiber type to whole muscle function and the numerous distinct adaptive functional and metabolic changes in MHC I and MHC II fibers originating from the same muscle.

Plantar flexor muscles of kangaroo rats (D. deserti) shorten at a velocity to produce optimal power during jumping

2021 ◽  
Author(s):  
M. Janneke Schwaner ◽  
David C. Lin ◽  
Craig P. McGowan
Keyword(s):  
Angular Velocity ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Extensor Muscle ◽  
Joint Work ◽  
Shortening Velocity ◽  
Kangaroo Rats ◽  
Optimal Velocity ◽  
Muscle Shortening

During jumping by kangaroo rats, the musculotendon work contributions across all joints are not well understood. Namely, measures of external joint work do not provide information on the contributions from individual muscles or in-series elastic structures. In this study, we examined the functional roles of a major ankle extensor muscle, lateral gastrocnemius (LG), and of a major knee extensor muscle, vastus lateralis (VL), through in vivo sonomicrometry and electromyography techniques, during vertical jumping by kangaroo rats. Our data showed that both muscles increased shortening and activity with higher jumps. We found that knee angular velocity and VL muscle shortening velocity were coupled in time. In contrast, the ankle angular velocity and LG muscle shortening velocity were decoupled, and rapid joint extension near the end of the jump produced high power outputs at the ankle joint. Further, the decoupling of muscle and joint kinematics allowed the LG muscle to prolong the period of shortening velocity near optimal velocity (Vopt), which likely enabled the muscle to sustain maximal power generation. These observations were consistent with a LG tendon that is much more compliant than that of the VL.

Calpain-3 is autolyzed and hence activated in human skeletal muscle 24 h following a single bout of eccentric exercise

2007 ◽  
Vol 103 (3) ◽  
pp. 926-931 ◽  
Author(s):  
Robyn M. Murphy ◽  
Craig A. Goodman ◽  
Michael J. McKenna ◽  
Jason Bennie ◽  
Murray Leikis ◽  
...  
Keyword(s):  
Eccentric Exercise ◽  
Human Subjects ◽  
Vastus Lateralis ◽  
Venous Blood ◽  
Knee Extensor ◽  
Vastus Lateralis Muscle ◽  
Healthy Human ◽  
Calpain 3 ◽  
Torque Measurements

The function and normal regulation of calpain-3, a muscle-specific Ca2+-dependent protease, is uncertain, although its absence leads to limb-girdle muscular dystrophy type 2A. This study examined the effect of eccentric exercise on calpain-3 autolytic activation, because such exercise is known to damage sarcomeric structures and to trigger adaptive changes that help prevent such damage on subsequent exercise. Six healthy human subjects performed a 30-min bout of one-legged, eccentric, knee extensor exercise. Torque measurements, vastus lateralis muscle biopsies, and venous blood samples were taken before and up to 7 days following the exercise. Peak isometric muscle torque was depressed immediately and at 3 h postexercise and recovered by 24 h, and serum creatine kinase concentration peaked at 24 h postexercise. The amount of autolyzed calpain-3 was unchanged immediately and 3 h after exercise, but increased markedly (from ∼16% to ∼35% of total) 24 h after the exercise, and returned to preexercise levels within 7 days. In contrast, the eccentric exercise produced little autolytic activation of the ubiquitous Ca2+-activated protease, μ-calpain. Eccentric exercise is the first physiological circumstance shown to result in calpain-3 activation in vivo.

scholarly journals In vivo oxidative capacity varies with muscle and training status in young adults

2009 ◽  
Vol 107 (3) ◽  
pp. 873-879 ◽  
Author(s):  
Ryan G. Larsen ◽  
Damien M. Callahan ◽  
Stephen A. Foulis ◽  
Jane A. Kent-Braun
Keyword(s):  
Physical Activity ◽  
Vastus Lateralis ◽  
Vigorous Physical Activity ◽  
Oxidative Capacity ◽  
Resonance Spectroscopy ◽  
Activity Levels ◽  
Training Status ◽  
Maximal Voluntary Isometric Contraction ◽  
Usage Patterns

It is well established that exercise training results in increased muscle oxidative capacity. Less is known about how oxidative capacities in distinct muscles, in the same individual, are affected by different levels of physical activity. We hypothesized that 1) trained individuals would have higher oxidative capacity than untrained individuals in both tibialis anterior (TA) and vastus lateralis (VL) and 2) oxidative capacity would be higher in TA than VL in untrained, but not in trained, individuals. Phosphorus magnetic resonance spectroscopy was used to measure the rate of phosphocreatine recovery ( kPCr), which reflects the rate of oxidative phosphorylation, following a maximal voluntary isometric contraction of the TA and VL in healthy untrained (7 women, 7 men, 25.7 ± 3.6 yr; mean ± SD) and trained (5 women, 7 men, 27.5 ± 3.4 yr) adults. Daily physical activity levels were measured using accelerometry. The trained group spent threefold more time (∼90 vs. ∼30 min/day; P < 0.001) in moderate to vigorous physical activity (MVPA). Overall, kPCr was higher in VL than in TA ( P = 0.01) and higher in trained than in untrained participants ( P < 0.001). The relationship between kPCr and MVPA was more robust in VL ( r = 0.64, P = 0.001, n = 25) than in TA ( r = 0.38, P = 0.06, n = 25). These results indicate greater oxidative capacity in vivo in trained compared with untrained individuals in two distinct muscles of the lower limb and provide novel evidence of higher oxidative capacity in VL compared with TA in young humans, irrespective of training status. The basis for this difference is not known at this time but likely reflects a difference in usage patterns between the muscles.

scholarly journals Neural adaptations in isometric contractions with EMG and force biofeedback

2015 ◽  
Vol 21 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Francisco Locks ◽  
Heleodório Honorato dos Santos ◽  
Luis Carlos Carvalho ◽  
Lígia Raquel Ortiz Gomes Stolt ◽  
José Jamacy de Almeida Ferreira
Keyword(s):  
Vastus Lateralis ◽  
Knee Extensor ◽  
Control Group ◽  
Isometric Contractions ◽  
Maximal Voluntary Isometric Contraction ◽  
Neural Adaptations ◽  
Emg Amplitude ◽  
Visual Biofeedback ◽  
Post Test ◽  
And Control

This study aimed to evaluate the quadriceps femoris neural adaptations during isometric contractions using force and electromyogram (EMG) signals as visual biofeedback. Forty-two participants were randomly assigned to three groups: EMG group, tested with EMG biofeedback; Force group, tested with force biofeedback; and Control group, tested without biofeedback. Evaluations were performed pre (baseline) and post-tests to determine the maximum force and EMG amplitude during maximal voluntary isometric contraction (MVIC). The tests consisted of series of MVICs in which the participants were encouraged to surpass the force or EMG thresholds determined at baseline. The vastus lateralis EMG amplitude and knee extensor force increased significantly in all groups when compared the baseline and post-test evaluations values (p < .05). EMG percentage gain was significantly different between Force and Control groups (p < .01), while force percentage gain was not different between groups. Force biofeedback was more effective in producing neural adaptations.

Localization and function of ATP-sensitive potassium channels in human skeletal muscle

2003 ◽  
Vol 284 (2) ◽  
pp. R558-R563 ◽  
Author(s):  
Jens Jung Nielsen ◽  
Michael Kristensen ◽  
Ylva Hellsten ◽  
Jens Bangsbo ◽  
Carsten Juel
Keyword(s):  
Skeletal Muscle ◽  
Muscle Activity ◽  
Human Skeletal Muscle ◽  
Knee Extensor ◽  
Human Muscle ◽  
Functional Importance ◽  
Gradient Technique ◽  
And Function

The present study investigated the localization of ATP-sensitive K+ (KATP) channels in human skeletal muscle and the functional importance of these channels for human muscle K+ distribution at rest and during muscle activity. Membrane fractionation based on the giant vesicle technique or the sucrose-gradient technique in combination with Western blotting demonstrated that the KATP channels are mainly located in the sarcolemma. This localization was confirmed by immunohistochemical measurements. With the microdialysis technique, it was demonstrated that local application of the KATP channel inhibitor glibenclamide reduced ( P < 0.05) interstitial K+ at rest from ∼4.5 to 4.0 mM, whereas the concentration in the control leg remained constant. Glibenclamide had no effect on the interstitial K+ accumulation during knee-extensor exercise at a power output of 60 W. In contrast to in vitro conditions, the present study demonstrated that under in vivo conditions the KATP channels are active at rest and contribute to the accumulation of interstitial K+.

Influences of repetitive muscle contractions with different modes on tendon elasticity in vivo

2001 ◽  
Vol 91 (1) ◽  
pp. 277-282 ◽  
Author(s):  
Keitaro Kubo ◽  
Hiroaki Kanehisa ◽  
Yasuo Kawakami ◽  
Tetsuo Fukunaga
Keyword(s):  
Vastus Lateralis ◽  
Force Production ◽  
Knee Extension ◽  
Muscle Contractions ◽  
Vastus Lateralis Muscle ◽  
Maximal Voluntary Isometric Contraction ◽  
Duration Of Action ◽  
Before And After ◽  
Endurance Tests

The present study aimed to investigate the effects of repetitive muscle contractions on the elasticity of human tendon structures in vivo. Before and after each endurance test, the elongation of the tendon and aponeurosis of vastus lateralis muscle ( L) was directly measured by ultrasonography while the subjects performed ramp isometric knee extension up to maximal voluntary isometric contraction (MVC). Six male subjects performed muscle endurance tests that consisted of knee extension tasks with four different contraction modes: 1) 50 repetitions of maximal voluntary eccentric action for 3 s with 3 s of relaxation (ET1), 2) three sets of 50 repetitions of MVC for 1 s with 3 s of relaxation (ET2), 3) 50 repetitions of MVC for 3 s with 3 s of relaxation (ET3), and 4) 50 repetitions of 50% MVC for 6 s with 6 s of relaxation (ET4). In ET1 and ET2, there were no significant differences in L values at any force production levels between before and after endurance tests. In the cases of ET3 and ET4, however, the extent of elongation after the completion of the tests tended to be greater. The L values above 330 N in ET3 and 440 N in ET4, respectively, were significantly greater after endurance tests than before. These results suggested that the repeated longer duration contractions would make the tendon structures more compliant and that the changes in the elasticity might be not be affected by either muscle action mode or force production level but by the duration of action.

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