Muscle activity of the upper extremity during oscillation exercise using the Thera-Band® FlexBar
Page P1, Ross O2, Rogers M3, Rogers N4.
1
Benchmark Physical Therapy; 2Slippery Rock University; 3Wichita State University; 4University of
Kansas Medical School
Oscillatory exercise of the upper extremity requires reflexive stabilization to control the acceleration and
deceleration of the device. The purpose of this study was to investigate the muscle activation (with surface
electromyography) of the upper extremity during oscillatory exercise in different shoulder positions and
planes of oscillation. Number of Subjects. 11. Methods. Surface EMG was recorded on 11 healthy
subjects (6 females and 5 males) aged 26-49 from the dominant shoulder muscles. MVIC was determined
for each muscle. Subjects held a green FlexBar in 2 positions that were randomly determined: shoulder
flexion at 90° and shoulder abduction in the scapular plane at 90°. Subjects then oscillated the FlexBar in
either the frontal plane or sagittal plane (randomized order) for 10 seconds. Results. Raw surface EMG was
normalized to MVIC for each muscle and condition. Normalized mean activation ranged from 42.4%
(Wrist Extensors in Scaption/Frontal condition) to 6.5% (Upper Trapezius in Flexion/Sagittal condition).
Conditions with the highest activation were noted for each muscle:
Muscle
Wrist Extensors
Serratus Anterior
Wrist Flexors
Triceps
Biceps
Middle Deltoid
Lower Trapezius
Upper Trapezius
Position/Plane
Scaption/Frontal
Scaption/Sagittal
Flexion/Frontal
Flexion/Sagittal
Flexion/Frontal
Flexion/Frontal
Scaption/Sagittal
Scaption/Sagittal
% MVIC
42.4
24.2
22.3
21.1
19.1
18.9
17.9
9.5
Repeated Measures Analysis of Variance noted a significant difference between muscle conditions
indicating variation in EMG activation. However, this significance was not dependent on the plane in
which the oscillation was performed. Conclusions: This study is the first to describe the muscle activation
of different conditions of FlexBar oscillatory exercise in the upper extremity. Future research should
involve more subjects, different muscle groups (including the trunk), and should compare oscillatory
exercise to traditional resistance exercise for muscle activation. Clinical Relevance: By describing the
oscillatory conditions that may preferentially activate certain upper extremity muscles, clinicians should be
able to make better decisions on specific exercise prescription. Several other observations were made: The
scapular muscles (Upper & Lower Trapezius and Serratus Anterior) exhibited the highest activation in the
Scaption/Sagittal condition; suggesting that this condition be used in the rehabilitation of scapular
stabilizers. The ratio of lower trap:upper trap activation demonstrated values of 1.6 to 2.3, indicating the
flexion position may be optimal for improving this ratio. Muscles classified as “phasic” by Janda (wrist
extensors, triceps, and lower trapezius) exhibited higher activation than their antagonistic “tonic” muscles
(wrist flexors, biceps, upper trapezius) in each condition. Therefore, oscillation exercise of the upper
extremity may be clinically useful in preferentially activating phasic muscles and restoring normal muscle
balance.
Published in 2004. Hand Prints 21(5):7. Presented at APTA Combined Sections Meeting, February 2005 in
New Orleans, LA.