Determining the Force-Length-Velocity Relations of the Quadriceps Muscles: II. Maximum Muscle Stress

1999 ◽  
Vol 15 (2) ◽  
pp. 191-199 ◽  
Author(s):  
John W. Chow ◽  
Warren G. Darling ◽  
James C. Ehrhardt
Keyword(s):  
Knee Flexion ◽  
Isometric Force ◽  
Muscle Length ◽  
Gravitational Effect ◽  
Knee Extension ◽  
Cross Sectional ◽  
Average Value ◽  
Isometric Knee Extension ◽  
Maximum Effort ◽  
Muscle Stress

The purpose of this study was to determine the maximum muscle stress (σ), defined as the maximum isometric force divided by the physiological cross-sectional area, of the quadriceps muscles for a pilot study involving musculoskeletal modeling. One female subject performed maximum effort isometric knee extension exercises on an isokinetic dynamometer at different attachment arm angles. The gravitational effect was taken into consideration when determining the isometric resultant knee torques at different knee flexion angles. The anatomical and geometric parameters of the quadriceps muscles were obtained from radiography and magnetic resonance imaging taken from the subject. The σ value was computed using me measured knee torques, musculoskeletal parameters data, and information reported in the literature. The computation procedures used in this study represented the first attempt to incorporate the concept of optimal muscle length in the determination of maximum muscle stress. The σ values obtained from the data for nine different knee flexion angles ranged from 21.4 to 30.5 N/cm2. The average value of 25.6 ± 2.6 N/cm2 is notably smaller than the human σ values reported in the literature, but is comparable to the σ values obtained from isolated muscles.

Lower-Extremity Isokinetic Strength Profiling in Professional Rugby League and Rugby Union

2014 ◽  
Vol 9 (2) ◽  
pp. 358-361 ◽  
Author(s):  
Scott R. Brown ◽  
Matt Brughelli ◽  
Peter C. Griffiths ◽  
John B. Cronin
Keyword(s):  
Lower Extremity ◽  
Knee Flexion ◽  
Peak Torque ◽  
Rugby League ◽  
Knee Extension ◽  
Rugby Union ◽  
Joint Torque ◽  
Cross Sectional ◽  
Hip Strength ◽  
Hip Extension

Purpose:While several studies have documented isokinetic knee strength in junior and senior rugby league players, investigations of isokinetic knee and hip strength in professional rugby union players are limited. The purpose of this study was to provide lower-extremity strength profiles and compare isokinetic knee and hip strength of professional rugby league and rugby union players.Participants:32 professional rugby league and 25 professional rugby union players.Methods:Cross-sectional analysis. Isokinetic dynamometry was used to evaluate peak torque and strength ratios of the dominant and nondominant legs during seated knee-extension/flexion and supine hip-extension/flexion actions at 60°/s.Results:Forwards from both codes were taller and heavier and had a higher body-mass index than the backs of each code. Rugby union forwards produced significantly (P < .05) greater peak torque during knee flexion in the dominant and nondominant legs (ES = 1.81 and 2.02) compared with rugby league forwards. Rugby league backs produced significantly greater hip-extension peak torque in the dominant and nondominant legs (ES = 0.83 and 0.77) compared with rugby union backs. There were no significant differences in hamstring-to-quadriceps ratios between code, position, or leg. Rugby union forwards and backs produced significantly greater knee-flexion-to-hip-extension ratios in the dominant and nondominant legs (ES = 1.49–2.26) than rugby union players.Conclusions:It seems that the joint torque profiles of players from rugby league and union codes differ, which may be attributed to the different demands of each code.

Maximum Power During Vertical Jump and Isometric Knee Extension Torque Alter Mobility Performance: A Cross-Sectional Study of Healthy Individuals

PM&R ◽  
2015 ◽  
Vol 8 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Atsuhiro Tsubaki ◽  
Masayoshi Kubo ◽  
Ryosaku Kobayashi ◽  
Hirofumi Jigami ◽  
Kazuhiro Sugawara ◽  
...  
Keyword(s):  
Vertical Jump ◽  
Knee Extension ◽  
Cross Sectional Study ◽  
Maximum Power ◽  
Healthy Individuals ◽  
Sectional Study ◽  
Cross Sectional ◽  
Mobility Performance ◽  
Isometric Knee Extension

scholarly journals Differences in the Flexion and Extension Phases during Kneeling Investigated by Kinematic and Contact Point Analyses: A Cross-sectional Study

2021 ◽  
Author(s):  
Yusuke Nakazoe ◽  
Akihiko Yonekura ◽  
Hiroyuki Takita ◽  
Takeshi Miyaji ◽  
Narihiro Okazaki ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Contact Point ◽  
Knee Extension ◽  
Cross Sectional Study ◽  
Extension Phase ◽  
3D Registration ◽  
Cross Sectional ◽  
Registration Method ◽  
Computed Tomography Images ◽  
Flexion And Extension

Abstract Background: Kneeling is necessary for certain religious and ceremonial occasions, crouching work, and gardening, which many people take part in worldwide. However, there have been few reports regarding kneeling activities. The purpose of this study was to clarify the kinematics of kneeling.Methods: The subjects were 15 healthy young males. Kneeling activity was analysed within a knee flexion angle from 100° to maximum flexion (maxflex, mean ± SD = 161.3 ± 3.2°). The kinematic and contact point (CP) analyses were performed using a 2D/3D registration method, in which a 3D bone model created from computed tomography images was matched to knee lateral fluoroscopic images and analysed on a personal computer.Results: In the kinematic analysis, the femur translated 37.5 mm posteriorly and rotated 19.8° externally relative to the tibia during the knee flexion phase. During the knee extension phase, the femur translated 36.4 mm anteriorly, which was almost the same amount as in the knee flexion phase. However, the femur rotated only 7.4° internally during the knee extension phase. In the CP analysis, the amount of anterior translation of the CP in the knee extension phase was greater in the medial CP and smaller in the lateral CP than that of posterior translation in the knee flexion phase.Conclusions: In kneeling, there was a difference in the rotational kinematics between the flexion phase and the extension phase. The kinematic difference between the flexion and extension phases may have some effect on the meniscus and articular cartilage.

Depression of force by phosphate in skinned skeletal muscle fibers of the frog

1990 ◽  
Vol 259 (2) ◽  
pp. C349-C357 ◽  
Author(s):  
G. J. Stienen ◽  
M. C. Roosemalen ◽  
M. G. Wilson ◽  
G. Elzinga
Keyword(s):  
Skeletal Muscle ◽  
Atp Hydrolysis ◽  
Isometric Force ◽  
Muscle Fibers ◽  
Diffusion Constant ◽  
Phosphate Concentration ◽  
Cross Sectional ◽  
Average Value ◽  
A Value ◽  
Skeletal Muscle Fibers

The relation between isometric force and phosphate concentration in skinned skeletal muscle fibers of the frog is found to depend on fiber size. Force decreased with increasing phosphate concentration, but depression of force in thick fibers was smaller than in thin segments. When the external phosphate concentration was abruptly altered during a sustained contracture, force changed. The half-time of the force change was proportional to the cross-sectional area of the preparation. From this relation, a value for the diffusion constant of phosphate in skinned fibers of 0.9 x 10(-10) m2/s was derived. The rate of phosphate production was determined photometrically via the enzymatic coupling of the resynthesis of ATP to the oxidation of nicotinamide adenine dinucleotide. The average value (+/- SE) of the rate of ATP hydrolysis (at 4 degrees C) was 2.7 +/- 0.3 mumol.s-1.g dry wt-1, which corresponds to 0.34 mmol.l-1.s-1. From a calculation based on the diffusion constant and the rate of phosphate production determined, it follows that the dependency of the force-phosphate relation on fiber diameter is due to phosphate accumulation inside the fiber.

scholarly journals Rate of Muscle Activation in Power-and Endurance-Trained Boys

2011 ◽  
Vol 6 (1) ◽  
pp. 94-105 ◽  
Author(s):  
Cameron Mitchell ◽  
Rotem Cohen ◽  
Raffy Dotan ◽  
David Gabriel ◽  
Panagiota Klentrou ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Peak Torque ◽  
Surface Emg ◽  
Knee Extension ◽  
Endurance Athletes ◽  
Group Differences ◽  
Electromechanical Delay ◽  
Cross Sectional ◽  
Isometric Knee Extension ◽  
Muscle Cross Sectional Area

Previous studies in adults have demonstrated power athletes as having greater muscle force and muscle activation than nonathletes. Findings on endurance athletes are scarce and inconsistent. No comparable data on child athletes exist.Purpose:This study compared peak torque (Tq), peak rate of torque development (RTD), and rate of muscle activation (EMG rise, Q30), in isometric knee extension (KE) and fexion (KF), in pre- and early-pubertal power- and endurance-trained boys vs minimally active nonathletes.Methods:Nine gymnasts, 12 swimmers, and 18 nonathletes (7–12 y), performed fast, maximal isometric KE and KF. Values for Tq, RTD, electromechanical delay (EMD), and Q30 were calculated from averaged torque and surface EMG traces.Results:No group differences were observed in Tq, normalized for muscle cross-sectional area. The Tq-normalized KE RTD was highest in power athletes (6.2 ± 1.9, 4.7 ± 1.2, 5.0 ± 1.5 N·m·s–1, for power, endurance, and nonathletes, respectively), whereas no group differences were observed for KF. The KE Q30 was significantly greater in power athletes, both in absolute terms and relative to peak EMG amplitude (9.8 ± 7.0, 5.9 ± 4.2, 4.4 ± 2.2 mV·ms and 1.7 ± 0.8, 1.1 ± 0.6, 0.9 ± 0.5 (mV·ms)/(mV) for power, endurance, and nonathletes, respectively), with no group differences in KF. The KE EMD tended to be shorter (P = .07) in power athletes during KE (71.0 ± 24.1, 87.8 ± 18.0, 88.4 ± 27.8 ms, for power, endurance, and nonathletes), with no group differences in KF.Conclusions:Pre- and early-pubertal power athletes have enhanced rate of muscle activation in specifically trained muscles compared with controls or endurance athletes, suggesting that specific training can result in muscle activation-pattern changes before the onset of puberty.

ELECTROMYOGRAPHIC ANALYSIS OF LEG EXTENSION EXERCISE DURING DIFFERENT ANKLE AND KNEE POSITIONS

2015 ◽  
Vol 15 (02) ◽  
pp. 1540037 ◽  
Author(s):  
GUIDO BELLI ◽  
LUCA VITALI ◽  
MATTEO BOTTEGHI ◽  
LEYDI NATALIA VITTORI ◽  
ELISABETTA PETRACCI ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Vastus Lateralis ◽  
Pain Syndrome ◽  
Knee Extension ◽  
Maximal Voluntary Isometric Contraction ◽  
Leg Extension ◽  
Isometric Knee Extension ◽  
Medial Rotation ◽  
Electromyographic Analysis ◽  
Main Factor

The imbalance between vastus medialis oblique (VMO) and vastus lateralis (VL) strength is one of the main factor for patellofemoral pain syndrome (PFPS) onset, related to improper alignment of the patella. The aim of this paper is to investigate the effects of knee flexion, knee rotation and ankle flexion attitudes on the activity of the VMO and VL muscles during unilateral maximal voluntary isometric contraction (MIVC) of the quadriceps femoris. Eighteen healthy subjects volunteered for the study. Five conditions for two different knee flexion angles (90°; 30°) were tested using leg extension machine: Neutral (N) condition, maximal knee medial rotation (MR), maximal knee lateral rotation (LR), maximal ankle plantarflexion (PF) and maximal ankle dorsiflexion (DF). Data were normalized in order to calculate the normalized VMO/VL ratio. The normalized VMO/VL ratio for all the conditions occurred at 90° of knee flexion was higher than the same conditions at 30° of knee flexion (p = 0.02). No statistical differences between conditions at the same knee angle and for angle x condition interaction were observed (p > 0.05). These findings suggest that knee flexion should be the first variable to be managed during isometric knee extension movement performed by leg extension machine, in order to increase VMO/VL ratio.

Longer Integration Intervals Reduce Variability and Improve Reliability of EMG Derived from Maximal Isometric Exertions

1999 ◽  
Vol 15 (2) ◽  
pp. 210-220 ◽  
Author(s):  
Peter F. Vint ◽  
Richard N. Hinrichs
Keyword(s):  
Vastus Lateralis ◽  
Knee Extension ◽  
Vastus Lateralis Muscle ◽  
Electromechanical Delay ◽  
Integration Interval ◽  
Isometric Knee Extension ◽  
Extension Force ◽  
Maximum Effort ◽  
Integrated Emg ◽  
Force Relationship

Isometric knee extension force and average integrated EMG of the vastus lateralis muscle were obtained from 27 healthy subjects using a maximum effort, ramp and hold protocol. In each of the 125 total trials mat were included in the analysis, a 2-s plateau region was extracted and divided into two adjacent 1000-ms bins. Variability and reliability of bin-to-bin measurements of force and EMG were then evaluated across 14 different integration intervals ranging from 10 to 1000 ms. Statistical analyses of bin-to-bin variability measures demonstrated that integration intervals of 250 ms and longer significantly reduced variability and improved reliability of average integrated EMG values during maximum effort isometric exertions. Bin-to-bin EMG reliability increased from .728 at 10 ms to .991 at 1000 ms. Force parameters appeared less sensitive to changes in length of the integration interval. It was suggested that longer intervals might also improve the validity of the EMG-force relationship during maximum effort isometric exertions by reducing problems associated with electromechanical delay.

scholarly journals Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m

Sports ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 43
Author(s):  
Gordon E. Barkwell ◽  
James P. Dickey
Keyword(s):  
Lower Limb ◽  
Knee Flexion ◽  
High Speed ◽  
Sagittal Plane ◽  
Body Position ◽  
Knee Extension ◽  
Knee Extensors ◽  
Start Time ◽  
Performance Impact ◽  
Maximum Effort

Backstroke starts involve the athlete starting from a flexed position with their feet against the pool wall and then extending their ankles, knees, hips and back to push off; however, swimmers can start in different positions. The purpose of this study was to evaluate the performance impact of different knee extension angles in the setup position for a backstroke start. Ten backstroke swimmers completed maximum-effort starts in each of two setup positions: one with the knees maximally flexed, and one with the knees less flexed. The start handles and touchpad were instrumented with multi-axial force sensors. Activity of major hip and knee extensors was measured using surface electromyography. Body position in the sagittal plane was recorded using high-speed cameras. There was no overall difference in time to 10 m between the two conditions (p = 0.36, dz = 0.12), but some participants showed differences as large as 0.12 s in time to 10 m between start conditions. We observed that starts performed from a setup position with less knee flexion had an average 0.07 m greater head entry distance (p = 0.07, dz = 0.53), while starts from a setup position with maximal knee flexion had an average 0.2 m/s greater takeoff velocity (p = 0.02, dz = 0.78). Both head entry distance and takeoff velocity are related to start performance, suggesting each position may optimize different aspects of the backstroke start. Coaches should assess athletes individually to determine which position is optimal.

Structure-function correlation in airway smooth muscle adapted to different lengths

2003 ◽  
Vol 285 (2) ◽  
pp. C384-C390 ◽  
Author(s):  
Kuo-Hsing Kuo ◽  
Ana M. Herrera ◽  
Lu Wang ◽  
Peter D. Paré ◽  
Lincoln E. Ford ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Airway Smooth Muscle ◽  
Muscle Power ◽  
Isometric Force ◽  
Muscle Length ◽  
Length Change ◽  
Cell Length ◽  
Myosin Filament ◽  
Shortening Velocity ◽  
Cross Sectional

Airway smooth muscle is able to adapt and maintain a nearly constant maximal force generation over a large length range. This implies that a fixed filament lattice such as that found in striated muscle may not exist in this tissue and that plastic remodeling of its contractile and cytoskeletal filaments may be involved in the process of length adaptation that optimizes contractile filament overlap. Here, we show that isometric force produced by airway smooth muscle is independent of muscle length over a twofold length change; cell cross-sectional area was inversely proportional to cell length, implying that the cell volume was conserved at different lengths; shortening velocity and myosin filament density varied similarly to length change: increased by 69.4% ± 5.7 (SE) and 76.0% ± 9.8, respectively, for a 100% increase in cell length. Muscle power output, ATPase rate, and myosin filament density also have the same dependence on muscle cell length: increased by 35.4% ± 6.7, 34.6% ± 3.4, and 35.6% ± 10.6, respectively, for a 50% increase in cell length. The data can be explained by a model in which additional contractile units containing myosin filaments are formed and placed in series with existing contractile units when the muscle is adapted at a longer length.

Influence of muscle length and force on endurance and pressor responses to isometric exercise

1994 ◽  
Vol 76 (6) ◽  
pp. 2561-2569 ◽  
Author(s):  
A. V. Ng ◽  
J. C. Agre ◽  
P. Hanson ◽  
M. S. Harrington ◽  
F. J. Nagle
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Muscle Length ◽  
Cardiovascular Responses ◽  
Knee Extension ◽  
Endurance Time ◽  
External Torque ◽  
Significant Difference ◽  
Isometric Knee Extension

Experiments were performed to determine whether endurance time, mean arterial pressure, or heart rate was related to either muscle length or external torque production in humans during isometric knee extension. Eight men and nine women performed isometric knee extension to the endurance limit at each of three muscle lengths, determined by knee angles of 40 degrees (0.698 rad, shortest), 60 degrees (1.047 rad, intermediate), and 90 degrees (1.571 rad, longest), and at intensities of 30 and 50% maximal voluntary contraction (MVC). Knee extension forms an ascending-descending length-torque curve, and lengths were chosen to result in different external torques. MVC was greatest at a knee angle of 60 degrees (P < 0.05 vs. 40 degrees, 90 degrees), with no significant difference between 90 degrees and 40 degrees. Endurance time was inversely related to muscle length, independent of torque production, at 30% MVC [40 degrees, 395 +/- 139 (SE); 60 degrees, 237 +/- 60; 90 degrees, 165 +/- 51 s; P < 0.05 vs. each other] and 50% MVC (40 degrees, 176 +/- 64; 60 degrees, 137 +/- 40; 90 degrees, 85 +/- 23 s; P < 0.05 vs. each other). Evidence is presented that endurance is a function of internal muscle force and not resultant external torque. The experimental design allowed the relationship of external torque and cardiovascular responses to be examined independent of exercise intensity. Muscle mass was also controlled in that the same muscle group was involved in all contractions. There were no differences in mean arterial pressure, heart rate, or rating of perceived exertion at any percentage of endurance time under any condition.(ABSTRACT TRUNCATED AT 250 WORDS)

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