Joint Angle and Contraction Intensity Effects on Knee Extensor/Flexor Co-Activation During Isometric Knee Extension

2006 ◽  
Vol 38 (Supplement) ◽  
pp. S265
Author(s):  
Staci M. Stevens ◽  
Danny M. Pincivero
Keyword(s):  
Joint Angle ◽  
Knee Extensor ◽  
Knee Extension ◽  
Co Activation ◽  
Isometric Knee Extension

Neuromuscular Differences Between Men and Prepubescent Boys During a Peak Isometric Knee Extension Intermittent Fatigue Test

2010 ◽  
Vol 22 (2) ◽  
pp. 205-217 ◽  
Author(s):  
Vasilios Armatas ◽  
Eleni Bassa ◽  
Dimitrios Patikas ◽  
Ilias Kitsas ◽  
Georgios Zangelidis ◽  
...  
Keyword(s):  
Fatigue Test ◽  
Vastus Lateralis ◽  
Knee Extensor ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Initial Value ◽  
Antagonist Activity ◽  
Extensor Muscles ◽  
Isometric Knee Extension ◽  
Knee Extensor Muscles

The aim of this study was to examine the fatigue and recovery in boys and men during a maximal intermittent isometric fatigue test of the knee extensor muscles, by evaluating the electromyogram of vastus lateralis, vastus medialis and biceps femoris. Thirteen boys (10.0 ± 0.8yrs) and 13 men (26.1 ± 4.2yrs) were fatigued until torque reached 50% of its initial value. Three and 6 min after, a maximal isometric knee extension test was assessed. Men had faster torque decline during fatigue and slower torque recovery compared with boys. Agonist activity declined in both groups during fatigue but men had greater extent of reduction. After 6 min boys recovered fully in respect to agonist EMG, whereas this was not the case for the men. The lower level of fatigue and faster recovery in boys could be attributed to the limited inhibition that was observed in the boys’ agonist muscles, whereas the antagonist activity does not seem to play a role in the fatigue or recovery differences between the groups.

The Effects of Knee Joint Angle and Contractor Intensity on Perceived Exertion

2018 ◽  
Vol 125 (6) ◽  
pp. 1123-1139 ◽  
Author(s):  
Danny M. Pincivero ◽  
Staci M. Thomas
Keyword(s):  
Knee Joint ◽  
Perceived Exertion ◽  
Joint Angle ◽  
Muscle Length ◽  
Knee Extensor ◽  
Knee Extension ◽  
Opposite Pattern ◽  
Knee Flexor ◽  
Knee Joint Angle ◽  
Knee Muscle

This study examined knee joint angle and knee muscle contraction intensity effects on perceived exertion during isometric contractions. Fourteen healthy young adults participated in five experimental exercise sessions in which knee angles varied randomly (10°, 30°, 50°, 70°, and 90°), each separated by one week. During each session, subjects performed five isometric maximal voluntary contractions (MVCs) of knee extension, followed by nine, randomly ordered submaximal contractions (10%–90% MVC, 10% increments). The participants repeated the identical procedure for the knee flexor muscles. Immediately following each submaximal contraction, participants rated their perceived exertion using a modified Borg category-ratio scale. We found that the participants’ overall ratings of perceived exertion were significantly ( p < .05) greater at the 90° than at the 70° and 10° positions during the knee extensor contractions. There were also several significant angle by contraction intensity interactions in that perceived exertion was significantly greater across 60% to 70% MVC at 30° than at 50° ( p < .01), while the opposite pattern was observed across 70% to 80% MVC ( p < .01). During knee flexor contractions, perceived exertion was significantly greater ( p < .05) at 90°, when compared with all other knee angles. There were also significant ( p < .05) angle by contraction intensity interactions between the 50° and 70° knee positions across contraction intensities of 30–40%, 40–50%, 50–60%, and 60–70% MVC. We conclude that the higher perceived exertion rating at 90° during knee extension and flexion contractions suggests different peripheral and central contributors between both muscle groups, due to differences in muscle length.

scholarly journals Reliability of Concentric, Eccentric and Isometric Knee Extension and Flexion when using the REV9000 Isokinetic Dynamometer

2013 ◽  
Vol 37 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Alberto César Pereira de Carvalho Froufe Andrade ◽  
Paolo Caserotti ◽  
Carlos Manuel Pereira de Carvalho ◽  
Eduardo André de Azevedo Abade ◽  
António Jaime da Eira Sampaio
Keyword(s):  
Performance Studies ◽  
Sports Medicine ◽  
Dynamic Control ◽  
Knee Extensor ◽  
Knee Extension ◽  
Isokinetic Strength ◽  
Isokinetic Dynamometer ◽  
Flexor Muscle ◽  
Physically Active ◽  
Isometric Knee Extension

The aim of this study was to assess the reliability of isokinetic and ISO knee extensor and flexor muscle strength when using the REV9000 (Technogym) isokinetic dynamometer. Moreover, the reliability of several strength imbalance indices and bilateral ratios were also examined. Twenty-four physically active healthy subjects (age 23±3 years) underwent three testing sessions, two on the same day and a third, 7 days later. All sessions proceeded in the same order: five concentric contractions at 60ºs-1 followed by an isometric contraction (5 seconds) and five eccentric contractions (60ºs-1). The results of this study showed a high reproducibility in eccentric (0.95-0.97), concentric (0.95- 0.96) and isometric (0.93-0.96), isokinetic strength for knee extensor and flexor muscles, thus indicating that the REV9000 isokinetic dynamometer can be used in future sports performance studies. A low-to-moderate reliability was found in the isokinetic strength bilateral ratios while the Hamstring:Quadricep concentric ratio showed moderate reliability. The highest reliability (>0.90) was observed in the dynamic control ratio (Hamstring eccentric:Quadricep concentric) which consequently confirms that it is a more valid indicator for imbalanced reciprocal parameters and can be used in rehabilitation and sports medicine.

scholarly journals Characterizing rapid-onset vasodilation to single muscle contractions in the human leg

2015 ◽  
Vol 118 (4) ◽  
pp. 455-464 ◽  
Author(s):  
Daniel P. Credeur ◽  
Seth W. Holwerda ◽  
Robert M. Restaino ◽  
Phillip M. King ◽  
Kiera L. Crutcher ◽  
...  
Keyword(s):  
Maximum Voluntary Contraction ◽  
Knee Extensor ◽  
Rapid Onset ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Muscle Contractions ◽  
Isometric Contractions ◽  
Single Muscle ◽  
Isometric Knee Extension ◽  
Mechanical Factors

Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans.

scholarly journals 602 THE EFFECT OF BILATERAL ISOKINETIC KNEE EXTENSION/FLEXION ON JOINT ANGLE AT PEAK TORQUE

1993 ◽  
Vol 25 (Supplement) ◽  
pp. S108 ◽  
Author(s):  
J. R. Bryant ◽  
L. E. Brown ◽  
M. Whitehurst
Keyword(s):  
Joint Angle ◽  
Peak Torque ◽  
Knee Extension

scholarly journals EARLY STRENGTH TESTING AFTER ACL RECONSTRUCTION IMPACTS ISOKINETIC STRENGTH PERFORMANCE AT TIME OF RETURN TO SPORT

2021 ◽  
Vol 9 (7_suppl3) ◽  
pp. 2325967121S0011
Author(s):  
Adam Weaver ◽  
Dylan Roman ◽  
Maua Mosha ◽  
Nicholas Giampetruzzi
Keyword(s):  
Test Performance ◽  
Knee Extension ◽  
Strength Test ◽  
Strength Testing ◽  
Isokinetic Strength ◽  
Rehabilitation Process ◽  
Strength Performance ◽  
Knee Extension Strength ◽  
Isometric Knee Extension ◽  
Strength Tests

Background: The standard of care in ACL reconstruction (ACLR) typically involves standardized strength testing at 6 months or later to assess a patient’s readiness to return to play (RTP) using isokinetic and isometric testing, and functional strength testing. Recent literature suggests that isokinetic knee extension strength should demonstrate 89% limb symmetry index (LSI) or greater prior to returning to sport. However, there is little known on the effects of strength testing early in the rehabilitation process and the relationship to strength test performance at time of RTP. Purpose: The purpose of this study was to examine how early post-operative strength test performance impacts isokinetic strength outcomes at RTP testing in adolescents. Methods: The retrospective cohort study included patients undergoing primary ACLR between 12 and 18 years of age, early post-operative strength measures, and isokinetic dynamometer strength at RTP from July 2017 and April 2019. Data was dichotomized into desired outcomes at 3 months: >70% isometric knee extension LSI, > 20 repetitions on anterior stepdown test (AST), > 90% LSI Y Balance. At RTP testing, isokinetic knee extension strength data was categorized into >89% LSI at 3 speeds (300, 180, 60°/sec). Chi square testing and odds ratio statistics were used to examine association and its magnitude. Results: 63 patients met inclusion criteria (38 females; 15.37±1.66 years old). >70% LSI isometric knee extension strength at 3 months showed a significant association (Table 2) and demonstrated the strongest odds of having >89% LSI on isokinetic strength tests at all 3 speeds at RTP with 180°/sec being the highest (OR=14.5; 95% CI=4.25,49.43; p= <0.001). Performance on AST showed a significant association (χ2 (1, n=63) = 17.00, p <0.001), and highest odds at 180°/sec (OR=4.61; 95% CI = 1.59, 13.39, p=<0.001) and 60°/sec (OR= 3.07; 95% CI = 1.10, 8.63, p= 0.04). Combination of performance on isometric strength tests and AST showed a significant association to isokinetic strength at all three speeds, but less predictive then isometrics in isolation. (Table 2). There was no significant relationship between YBR LSI at 3 months and isokinetic strength at 6 months. Conclusion: Standardized strength testing early in rehabilitation can help identify patients that will successfully complete RTP testing. Our results suggest that isometric knee extension strength and timed anterior stepdown test provide meaningful clinical information early in the rehabilitation process. This data also suggests that the use of YBAL for predicting isokinetic strength performance is limited. [Table: see text][Table: see text]

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