Electromyography of 3 scapular muscles: a comparative analysis of the cuff link device and a standard push-up.
BACKGROUND
The Cuff Link is a closed kinetic chain rehabilitation apparatus for the upper extremity. Limited research has established its effectiveness to elicit muscle activation of the scapular muscles.


OBJECTIVE
To determine if scapular muscle activation differs in response to 2 upper extremity closed kinetic chain exercises: Cuff Link and standard push-up.


METHODS
A single-group, repeated-measures design.


METHODS
Controlled laboratory.


METHODS
Twenty-eight healthy individuals (13 women: age = 19.69 +/- 1.55 years, height = 167.44 +/- 9.52 cm, mass = 61.00 +/- 8.79 kg; 15 men: age = 22.00 +/- 3.91 years, height = 181.44 +/- 6.60 cm, mass = 82.36 +/- 13.23 kg) with no history of shoulder or low back injury volunteered to participate in this study.


METHODS
Participants performed 10 trials of complete revolutions on the Cuff Link and 10 full-weight-bearing push-ups. We controlled trial velocity and randomized order. Trunk and shoulder positions were normalized to the participant's height. Using surface electromyography, we recorded muscle activity of the serratus anterior, middle trapezius, and lower trapezius. Rectified and smoothed electromyography data for the serratus anterior, middle trapezius, and lower trapezius were normalized as a percentage of the maximal voluntary isometric contractions (%MVIC).


METHODS
Mean muscle activity of the serratus anterior, middle trapezius, and lower trapezius. We used paired-samples t tests to analyze the mean data for each condition. The alpha level was adjusted to .016 to avoid a type I error.


RESULTS
Middle trapezius %MVIC was greater during push-ups (27.01 +/- 20.40%) than during use of the Cuff Link (11.49 +/- 9.46%) (P = .001). Lower trapezius %MVIC was greater during push-ups (36.07 +/- 18.99%) than during use of the Cuff Link (16.29 +/- 8.64%) (P = .001). There was no difference in %MVIC for the serratus anterior between conditions.


CONCLUSIONS
The push-up demonstrated greater middle trapezius and lower trapezius activation levels compared with the Cuff Link. However, the push-up had a high participant failure rate. Because serratus anterior activation levels were similar, the Cuff Link may be an appropriate alternative for individuals lacking the upper body strength to perform a push-up.
Tucker
W Steven
WS
University of Toledo, Toledo, OH, USA. stucker@uca.edu
Campbell
Brian M
BM
Swartz
Erik E
EE
Armstrong
Charles W
CW
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D004576:Electromyography / Q000295:instrumentation*; D005080:Exercise Test; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D012016:Reference Values; D012540:Scapula / Q000294:innervation / Q000502:physiology; D000070599:Shoulder Injuries; D016474:Weight-Bearing / Q000502:physiology*; D055815:Young Adult