Abstract
Impaired torque production is a major physical impairment following stroke, and has been studied extensively in isometric conditions. However, functional use of a limb requires torque production during movement, and the effects of velocity on maximal torque production may be abnormally enhanced in the paretic limb. The purpose of this study was to quantify the effects of movement velocity on maximal torque production during isokinetic, concentric flexion and extension of the elbow in poststroke subjects. Three speeds were tested (30, 75, 120 deg/s) over a 100-deg range of motion. To control for strength variations between subjects and limbs, isokinetic torques were normalized by peak isometric torque. As flexion velocity increased, paretic limb torque decreased at a greater rate than in the unaffected limb. During extension, paretic limb torque was much lower than torque in the unaffected limb at all speeds. In both flexion and extension, the disparity between limbs in the constant-velocity torque-angle curves became more pronounced as velocity increased. Torque decreased 44% ± 7% in flexion and 63% ± 9% in extension as velocity increased from 30 to 120 deg/s, whereas the corresponding decreases in the unaffected limb were only 9% ± 5% in flexion and 16% ± 4% in extension. No electromyographic (EMG) abnormalities were observed during flexion. During extension, EMG data provided evidence for abnormally increased antagonist coactivation in brachioradialis and markedly reduced activation in triceps as potential contributors to the decreased extension torques. The finding that movement velocity produces large deficits in maximal torque might explain why functional use of the paretic limb is often impaired even though isometric strength appears adequate.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 732-742 |
| Number of pages | 11 |
| Journal | Muscle and Nerve |
| Volume | 30 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 1 2004 |
| Externally published | Yes |
Fingerprint
Keywords
- Elbow
- Hemiparesis
- Isokinetic
- Stroke
- Weakness
ASJC Scopus subject areas
- Clinical Neurology
- Neuroscience(all)
Cite this
Effects of velocity on maximal torque production in poststroke hemiparesis. / Lum, Peter S.; Patten, Carolynn; Kothari, Dhara; Yap, Ruth.
In: Muscle and Nerve, Vol. 30, No. 6, 01.12.2004, p. 732-742.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Effects of velocity on maximal torque production in poststroke hemiparesis
AU - Lum, Peter S.
AU - Patten, Carolynn
AU - Kothari, Dhara
AU - Yap, Ruth
PY - 2004/12/1
Y1 - 2004/12/1
N2 - Impaired torque production is a major physical impairment following stroke, and has been studied extensively in isometric conditions. However, functional use of a limb requires torque production during movement, and the effects of velocity on maximal torque production may be abnormally enhanced in the paretic limb. The purpose of this study was to quantify the effects of movement velocity on maximal torque production during isokinetic, concentric flexion and extension of the elbow in poststroke subjects. Three speeds were tested (30, 75, 120 deg/s) over a 100-deg range of motion. To control for strength variations between subjects and limbs, isokinetic torques were normalized by peak isometric torque. As flexion velocity increased, paretic limb torque decreased at a greater rate than in the unaffected limb. During extension, paretic limb torque was much lower than torque in the unaffected limb at all speeds. In both flexion and extension, the disparity between limbs in the constant-velocity torque-angle curves became more pronounced as velocity increased. Torque decreased 44% ± 7% in flexion and 63% ± 9% in extension as velocity increased from 30 to 120 deg/s, whereas the corresponding decreases in the unaffected limb were only 9% ± 5% in flexion and 16% ± 4% in extension. No electromyographic (EMG) abnormalities were observed during flexion. During extension, EMG data provided evidence for abnormally increased antagonist coactivation in brachioradialis and markedly reduced activation in triceps as potential contributors to the decreased extension torques. The finding that movement velocity produces large deficits in maximal torque might explain why functional use of the paretic limb is often impaired even though isometric strength appears adequate.
AB - Impaired torque production is a major physical impairment following stroke, and has been studied extensively in isometric conditions. However, functional use of a limb requires torque production during movement, and the effects of velocity on maximal torque production may be abnormally enhanced in the paretic limb. The purpose of this study was to quantify the effects of movement velocity on maximal torque production during isokinetic, concentric flexion and extension of the elbow in poststroke subjects. Three speeds were tested (30, 75, 120 deg/s) over a 100-deg range of motion. To control for strength variations between subjects and limbs, isokinetic torques were normalized by peak isometric torque. As flexion velocity increased, paretic limb torque decreased at a greater rate than in the unaffected limb. During extension, paretic limb torque was much lower than torque in the unaffected limb at all speeds. In both flexion and extension, the disparity between limbs in the constant-velocity torque-angle curves became more pronounced as velocity increased. Torque decreased 44% ± 7% in flexion and 63% ± 9% in extension as velocity increased from 30 to 120 deg/s, whereas the corresponding decreases in the unaffected limb were only 9% ± 5% in flexion and 16% ± 4% in extension. No electromyographic (EMG) abnormalities were observed during flexion. During extension, EMG data provided evidence for abnormally increased antagonist coactivation in brachioradialis and markedly reduced activation in triceps as potential contributors to the decreased extension torques. The finding that movement velocity produces large deficits in maximal torque might explain why functional use of the paretic limb is often impaired even though isometric strength appears adequate.
KW - Elbow
KW - Hemiparesis
KW - Isokinetic
KW - Stroke
KW - Weakness
UR - http://www.scopus.com/inward/record.url?scp=10044284158&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=10044284158&partnerID=8YFLogxK
U2 - 10.1002/mus.20157
DO - 10.1002/mus.20157
M3 - Article
C2 - 15468340
AN - SCOPUS:10044284158
VL - 30
SP - 732
EP - 742
JO - Muscle and Nerve
JF - Muscle and Nerve
SN - 0148-639X
IS - 6
ER -