Faculty Collaboration Database

Time to task failure and muscle activation vary with load type for a submaximal fatiguing contraction with the lower leg. J Appl Physiol (1985) 2008 Aug;105(2):463-72

Date

06/07/2008

Pubmed ID

18535136

DOI

10.1152/japplphysiol.90398.2008

Scopus ID

2-s2.0-53449096725 (requires institutional sign-in at Scopus site)   46 Citations

Abstract

The purpose was to compare the time to failure and muscle activation patterns for a sustained isometric submaximal contraction with the dorsiflexor muscles when the foot was restrained to a force transducer (force task) compared with supporting an equivalent inertial load and unrestrained (position task). Fifteen men and women (mean+/-SD; 21.1+/-1.4 yr) performed the force and position tasks at 20% maximal voluntary contraction force until task failure. Maximal voluntary contraction force performed before the force and position tasks was similar (333+/-71 vs. 334+/-65 N), but the time to task failure was briefer for the position task (10.0+/-6.2 vs. 21.3+/-17.8 min, P<0.05). The rate of increase in agonist root-mean-square electromyogram (EMG), EMG bursting activity, rating of perceived exertion, fluctuations in motor output, mean arterial pressure, and heart rate during the fatiguing contraction was greater for the position task. EMG activity of the vastus lateralis (lower leg stabilizer) and medial gastrocnemius (antagonist) increased more rapidly during the position task, but coactivation ratios (agonist vs. antagonist) were similar during the two tasks. Thus the difference in time to failure for the two tasks with the dorsiflexor muscles involved a greater level of neural activity and rate of motor unit recruitment during the position task, but did not involve a difference in coactivation. These findings have implications for rehabilitation and ergonomics in minimizing fatigue during prolonged activation of the dorsiflexor muscles.

Author List

Hunter SK, Yoon T, Farinella J, Griffith EE, Ng AV

Author

Alexander V. Ng PhD Associate Professor in the Exercise Science department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adult
Blood Pressure
Data Interpretation, Statistical
Electromyography
Electrophysiology
Female
Heart Rate
Humans
Isometric Contraction
Knee
Leg
Male
Muscle Contraction
Muscle Fatigue
Muscle, Skeletal
Physical Exertion
Regression Analysis