Clinical Measures Predicting Knee Extensor Muscle Activation During a Maximal Voluntary Isometric Contraction

Hikers and soldiers usually walk up and down slopes with a load carriage, causing injuries of the musculoskeletal system, especially during a prolonged load journey. The slope walking has been reported to lead to higher leg extensor muscle activities and joint moments. However, most of the studies investigated muscle activities or joint moments during slope walking without load carriage or only investigated the joint moment changes and muscle activities with load carriages during level walking. Whether the muscle activation such as the signal amplitude is influenced by the mixed factor of loads and grades and whether the influence of the degrees of loads and grades on different muscles are equal have not yet been investigated. To explore the effects of backpack loads on leg muscle activation during slope walking, ten young male participants walked at 1.11 m/s on a treadmill with different backpack loads (load masses: 0, 10, 20, and 30 kg) during slope walking (grade: 0, 3, 5, and 10°). Leg muscles, including the gluteus maximus (GM), rectus femoris (RF), hamstrings (HA), anterior tibialis (AT), and medial gastrocnemius (GA), were recorded during walking. The hip, knee, and ankle extensor muscle activations increased during the slope walking, and the hip muscles increased most among hip, knee, and ankle muscles (GM and HA increased by 46% to 207% and 110% to 226%, respectively, during walking steeper than 10° across all load masses (GM: p = 1.32 × 10−8 and HA: p = 2.33 × 10−16)). Muscle activation increased pronouncedly with loads, and the knee extensor muscles increased greater than the hip and ankle muscles (RF increased by 104% to 172% with a load mass greater than 30 kg across all grades (RF: p = 8.86 × 10−7)). The results in our study imply that the hip and knee muscles play an important role during slope walking with loads. The hip and knee extension movements during slope walking should be considerably assisted to lower the muscle activations, which will be useful for designing assistant devices, such as exoskeleton robots, to enhance hikers’ and soldiers’ walking abilities.

Download Full-text

Knee Extensor Torque Complexity During A Maximal Voluntary Isometric Contraction Differs Between Acl-reconstructed And Healthy Individuals

Medicine & Science in Sports & Exercise ◽

10.1249/01.mss.0000676220.78820.43 ◽

2020 ◽

Vol 52 (7S) ◽

pp. 243-243

Author(s):

Stephan G. Bodkin ◽

Emily A. Dooley ◽

Shawn D. Russel ◽

Joseph M. Hart

Keyword(s):

Isometric Contraction ◽

Knee Extensor ◽

Healthy Individuals ◽

Maximal Voluntary Isometric Contraction ◽

Extensor Torque

Download Full-text

Maximal oxygen uptake, maximal voluntary isometric contraction and physical activity in young Danish adults

European Journal of Applied Physiology and Occupational Physiology ◽

10.1007/bf00357629 ◽

1993 ◽

Vol 67 (4) ◽

pp. 315-320 ◽

Cited By ~ 8

Author(s):

Lars Bo Andersen ◽

J�hanna Haraldsd�ttir

Keyword(s):

Physical Activity ◽

Oxygen Uptake ◽

Isometric Contraction ◽

Maximal Oxygen Uptake ◽

Maximal Voluntary Isometric Contraction

Download Full-text

Initial phase of maximal voluntary and electrically stimulated knee extension torque development at different knee angles

Journal of Applied Physiology ◽

10.1152/japplphysiol.00230.2004 ◽

2004 ◽

Vol 97 (5) ◽

pp. 1693-1701 ◽

Cited By ~ 118

Author(s):

C. J. de Ruiter ◽

R. D. Kooistra ◽

M. I. Paalman ◽

A. de Haan

Keyword(s):

Muscle Activation ◽

Knee Extensor ◽

Surface Emg ◽

Knee Extension ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Knee Angle ◽

Time Integral ◽

Voluntary Contractions ◽

Torque Development

We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60, and 90° knee angle. Experiments were performed in subjects ( n = 7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions. During maximal electrical nerve stimulation (8 pulses at 300 Hz), the maximal rate of torque development (MRTD) and torque time integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60°). At each knee angle, voluntary MRTD and stimulated MRTD were similar ( P < 0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent ( P > 0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects, the averaged (across knee angles) values ranged from 10.3 ± 3.1 to 83.3 ± 3.2% and were positively related ( r2 = 0.75, P < 0.05) to the knee-extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of maximal voluntary contraction, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects, torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.

Download Full-text

Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production

PLoS ONE ◽

10.1371/journal.pone.0242324 ◽

2020 ◽

Vol 15 (11) ◽

pp. e0242324

Author(s):

Jonathan Harnie ◽

Thomas Cattagni ◽

Christophe Cornu ◽

Peter McNair ◽

Marc Jubeau

Keyword(s):

Isometric Contraction ◽

Vastus Lateralis ◽

Force Production ◽

Knee Extensor ◽

Acute Effect ◽

Knee Extension ◽

Voluntary Contraction ◽

Voluntary Activation ◽

Tendon Vibration ◽

Knee Angle

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

Download Full-text