TY - JOUR
T1 - Muscle fatigue does not lead to increased instability of upper extremity repetitive movements
AU - Gates, Deanna H.
AU - Dingwell, Jonathan B.
N1 - Funding Information:
Partial funding for this study was provided by NIH Grants 1-R21-EB003425-01A1 and 1-R03-HD058942-01 (to JBD), and by an American Society of Biomechanics Grant-in-Aid and a University of Texas Continuing Fellowship (to DHG).
PY - 2010/3/22
Y1 - 2010/3/22
N2 - Muscle fatigue alters neuromuscular responses. This may lead to increased sensitivity to perturbations and possibly to subsequent injury risk. We studied the effects of muscle fatigue on movement stability during a repetitive upper extremity task. Twenty healthy young subjects performed a repetitive work task, similar to sawing, synchronized with a metronome before and after performing each of two fatiguing tasks. The first fatigue task (LIFT) primarily fatigued the shoulder flexor muscles, while the second fatigue task (SAW) fatigued all of the muscles of the arm. Subjects performed each task in random order on two different days at least seven days apart. Instantaneous mean EMG frequencies (IMNF) decreased over both fatiguing tasks indicating that subjects did experience significant muscle fatigue. The slopes of the IMNF over time and the decreases in maximum force measurements demonstrated that the LIFT fatigue task successfully fatigued the shoulder flexors to a greater extent than any other muscle. On average, subjects exhibited more locally stable shoulder movements after the LIFT fatigue task (p=0.035). They also exhibited more orbitally stable shoulder (p=0.021) and elbow (p=0.013) movements after the SAW fatigue task. Subjects also had decreased cocontraction at the wrist post-fatigue for both tasks (p=0.001) and at the shoulder (p<0.001) for the LIFT fatigue task. Therefore, increased dynamic stability of these repeated movements cannot be explained by increased muscle cocontraction. Possible alternative mechanisms are discussed.
AB - Muscle fatigue alters neuromuscular responses. This may lead to increased sensitivity to perturbations and possibly to subsequent injury risk. We studied the effects of muscle fatigue on movement stability during a repetitive upper extremity task. Twenty healthy young subjects performed a repetitive work task, similar to sawing, synchronized with a metronome before and after performing each of two fatiguing tasks. The first fatigue task (LIFT) primarily fatigued the shoulder flexor muscles, while the second fatigue task (SAW) fatigued all of the muscles of the arm. Subjects performed each task in random order on two different days at least seven days apart. Instantaneous mean EMG frequencies (IMNF) decreased over both fatiguing tasks indicating that subjects did experience significant muscle fatigue. The slopes of the IMNF over time and the decreases in maximum force measurements demonstrated that the LIFT fatigue task successfully fatigued the shoulder flexors to a greater extent than any other muscle. On average, subjects exhibited more locally stable shoulder movements after the LIFT fatigue task (p=0.035). They also exhibited more orbitally stable shoulder (p=0.021) and elbow (p=0.013) movements after the SAW fatigue task. Subjects also had decreased cocontraction at the wrist post-fatigue for both tasks (p=0.001) and at the shoulder (p<0.001) for the LIFT fatigue task. Therefore, increased dynamic stability of these repeated movements cannot be explained by increased muscle cocontraction. Possible alternative mechanisms are discussed.
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U2 - 10.1016/j.jbiomech.2009.11.001
DO - 10.1016/j.jbiomech.2009.11.001
M3 - Article
C2 - 19942220
AN - SCOPUS:77549087728
SN - 0021-9290
VL - 43
SP - 913
EP - 919
JO - Journal of Biomechanics
JF - Journal of Biomechanics
IS - 5
ER -