Neuromuscular activation of vastus intermedius muscle during fatiguing exercise

Spatial EMG potential distribution pattern of vastus lateralis muscle during isometric knee extension in young and elderly men

“…It could be speculated that muscle fatigue might have occurred during the given task and induced task failure. However, previous studies reported that young men could keep the sustained isometric force for 30-70 s at moderate to high force level (50-80% of MVC) during knee extension (Ebenbichler et al, 1998;Smolander et al, 1998;Watanabe and Akima, 2010). Since duration was 10 s in our ramp contraction, we supposed that the main cause of task failure was not induced by muscle fatigue, but induced by difficulty to control force at high force level.…”

Muscle fatigue – from motor units to clinical symptoms

“…The net motor unit activity, therefore, is reflected in the magnitude of the activation signal discharged by the spinal cord and can be related to the force exerted by the muscle. Consequently, selected properties of EMG signals have been used as an index of the fatigue-associated adjustments in motor unit activity during sustained and repetitive contractions (Molinari et al, 2006;Rainoldi et al, 2008;Watanabe and Akima, 2010). Such an interpretation, however, assumes a stable association between the EMG signal and muscle force.…”

Validity of surface electromyography for vastus intermedius muscle assessed by needle electromyography

“…Surface EMG signals of the VI muscle were recorded using the same procedure as that used in our previous studies (Watanabe and Akima, 2009a, 2010, 2009b. The superficial region of the VI muscle at the distolateral portion of the thigh was identified by ultrasonography (Logiq 5; General Electrics, Duluth, USA) (Fig.…”

“…Therefore, recording of surface electromyography (EMG) from the VI muscle has been considered impossible. However, we have previously developed a novel technique to record surface EMG from the VI muscle (Watanabe and Akima, 2009a, 2010, 2009b). The contribution of the VI muscle to knee extension torque is estimated approximately 50% in the QF muscle group (Zhang et al, 2003); therefore, we believe that the findings of surface EMG of the VI muscle will offer valuable information that would enhance our understanding of the neuromuscular activation of the QF muscle group.…”