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Cynthia M. McKnight and Charles W. Armstrong

The purpose of this study was to determine if there were any differences in ankle range of motion, strength, or work between persons with normal ankles (Normal, n = 14), those with functional ankle instability (FAI, n = 15), and those with a history of FAI who have been through formal proprioceptive rehabilitation (Rehab, n = 14). A second puipose was to determine normative values for ankle strength and work measurements using the Biodex® isokinetic system. There were no significant differences between groups for ankle range of motion or for any strength or work measurements. The overall strength/work averages were 11.75/3.42 for plantar flexion, 339/1.48 for dorsiflexion, 3.30/2.40 for inversion, and 2.62/1.79 for eversion. Dorsiflexion torque overall was 31.43% of plantar flexion, and the evertors produced 75.42% of the torque produced by the invertors. It is recommended that clinicians continue to rehabilitate ankles with strength and proprioceptive exercises but do not rely on ankle strength/work testing as the only criteria for determining an athlete's readiness to return to full activity.

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W. Steven Tucker, Charles W. Armstrong, Erik E. Swartz, Brian M. Campbell and James M. Rankin

Context:

Closed kinetic chain exercises are reported to provide a more functional rehabilitation outcome.

Objective:

To determine the amount of muscle activity in 4 shoulder muscles during exercise on the Cuff Link.

Design:

Repeated measures.

Setting:

Laboratory.

Subjects:

10 men and 10 women, age 18–50.

Intervention:

Subjects performed 3 sets of 5 revolutions on the Cuff Link in non-weight-bearing, partial-weight-bearing, and full-weight-bearing positions.

Main Outcome Measures:

Electromyography data were collected from the upper trapezius, anterior deltoid, serratus anterior, and pectoralis major and were expressed as percentage of maximal isometric contractions.

Results:

Significant differences were found across the weight-bearing conditions for all 4 muscles. Exercise on the Cuff Link required minimal to significant amounts of muscle recruitment.

Conclusions:

Muscle recruitment increases as weight bearing increases during use of the Cuff Link, suggesting an increase in dynamic stabilization of the glenohumeral joint.

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Nicole M. Livecchi, Charles W. Armstrong, Mitchell L. Cordova, Mark A. Merrick and James M. Rankin

Objective:

To compare average electromyogram (EMG) activity of the vastus medialis obliquus (VMO) and vastus lateralis (VL) during straight-leg raise (SLR) and knee extension (KE) with the hip in neutral and lateral rotation.

Design:

1 × 4 factorial repeated-measures.

Setting:

Laboratory.

Participants:

13 male college students.

Intervention:

SLR with hip flexed at 40°, in neutral position, and maximally laterally rotated and KE with hip in neutral and maximally laterally rotated.

Main Outcome Measure:

Average EMG activity during each of the 4 conditions, normalized against peak muscle activity during that trial.

Results:

No differences were observed between exercises in VMO activity (F 3,36 = 0.646, P > .05), VL activity (F 3,36 = 1.08, P > .05), or VMO:VL ratio (F 3,36 = 0.598, P > .05).

Conclusions:

Electrical activity of the VMO or VL and VMO:VL ratio do not change with hip position or exercise.

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Tina L. Claiborne, Charles W. Armstrong, Varsha Gandhi and Danny M. Pincivero

The purpose of this study was to determine the relationship between hip and knee strength, and valgus knee motion during a single leg squat. Thirty healthy adults (15 men, 15 women) stood on their preferred foot, squatted to approximately 60 deg of knee flexion, and returned to the standing position. Frontal plane knee motion was evaluated using 3-D motion analysis. During Session 2, isokinetic (60 deg/sec) concentric and eccentric hip (abduction/adduction, flexion/extension, and internal/external rotation) and knee (flexion/extension) strength was evaluated. The results demonstrated that hip abduction (r 2 = 0.13), knee flexion (r 2 = 0.18), and knee extension (r 2 = 0.14) peak torque were significant predictors of frontal plane knee motion. Significant negative correlations showed that individuals with greater hip abduction (r = –0.37), knee flexion (r = –0.43), and knee extension (r = –0.37) peak torque exhibited less motion toward the valgus direction. Men exhibited significantly greater absolute peak torque for all motions, excluding eccentric internal rotation. When normalized to body mass, men demonstrated significantly greater strength than women for concentric hip adduction and flexion, knee flexion and extension, and eccentric hip extension. The major findings demonstrate a significant role of hip muscle strength in the control of frontal plane knee motion.