at the same angles for the agonist and antagonist muscle groups, while 10° AST DCR allows an angle specific measure of IR and ER shoulder rotator strength ...
Specific Joint Angle Assessment of the Shoulder Rotators Rex W. Hafenstine Cassio V. Ruas Ronei S. Pinto Maria C. Pereira Lee E. Brown, FACSM
ABSTRACT
INTRODUCTION
RESULTS
Shoulder strength ratios based only on peak torque have failed in replicating the functionality of the muscles used during overhead activities. PURPOSE: To compare shoulder external rotation (ER) and internal rotation (IR) independent peak torque (IPT) ratios with ten degree angle specific torque (AST) ratios. METHODS: Twenty healthy adult males (24.65 ± 2.4 yrs) performed concentric (C) and eccentric (E) IR and ER of the right shoulder on an isokinetic dynamometer through 150° of ROM at -1 -1 -1 60°·s and 180°·s . RESULTS: At 60°·s , IPT dynamic control ratio (DCR) was significantly less than AST DCR at -40° and -30°, but significantly greater at -80°, -70°, -60° and 40°. At 180°·s-1 while IPT DCR was significantly less than ASPT DCR at 0°, but significantly greater than -80°, -70°, -60°, 40°, 50°. IPT conventional ratios (CR) were not significantly different than any AST CR at either speed. The last three 10° AST DCR were also compared, where the end of ROM occurred. At 60°·s-1, AST DCR at 30° was significantly greater than 40°. AST DCR at 40° was significantly less than 30°. At 180°·s-1, AST DCR at 30° was significantly greater than 40° and 50°. AST DCR at 40° was significantly less than 30°, but significantly greater than 50°. AST DCR at 50° was significantly less than 30° and 40°. CONCLUSION: Misinterpretation of shoulder rotator strength DCR may occur due to IPT DCR not occurring at the same angles for the agonist and antagonist muscle groups, while the 10° AST DCR allows an angle specific measure of IR and ER shoulder rotator strength ratios. Significant differences between the last three 10° segments of AST DCR, where the end of ROM occurred, could also lead to discrepancies where 30° AST DCR intervals are used to analyze end ROM ratios, considering that those are the angles where most imbalances occur. These results show that IPT could be used to calculate CR, but 10° AST should be used to calculate DCR.
Shoulder strength ratios based only on peak torque have failed in replicating the functionality of the muscles used during overhead activities.
At 60°·s-1, IPT dynamic control ratio (DCR) was significantly less than AST DCR at -40° and -30°, but significantly greater at -80°, -70°, -60° and 40° (Figure 2). At 180°·s-1 IPT DCR was significantly less than ASPT DCR at 0°, but significantly greater than -80°, -70°, -60°, 40°, 50° (Figure 3). IPT conventional ratios (CR) were not significantly different than any AST CR at either speed. The last three 10° AST DCR were also compared, where the end of ROM occurred. At 60°·s-1, AST DCR at 30° was significantly greater than 40°. AST DCR at 40° was significantly less than 30°. At 180°·s-1, AST DCR at 30° was significantly greater than 40° and 50°. AST DCR at 40° was significantly less than 30°, but significantly greater than 50°. AST DCR at 50° was significantly less than 30° and 40°.
To compare shoulder external rotation (ER) and internal rotation (IR) independent peak torque (IPT) ratios with ten degree angle specific torque (AST) ratios.
METHODS Twenty healthy adult males (24.65 ± 2.4 yrs) performed concentric (C) and eccentric (E) IR and ER of the right shoulder on an isokinetic dynamometer through 150° of ROM at 60°·s-1 and 180°·s-1 (Figure 1).
1.80 1.60
ER/IR Ratio 60°.s-1
PURPOSE
ER/IR Ratio 180°.s-1
Human Performance Laboratory Center for Sport Performance Department of Kinesiology California State University, Fullerton, CA 2.80 2.60 2.40 2.20 2.00 1.80 1.60 1.40 1.20 1.00 0.80 0.60 0.40 0.20
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PT -80 RATIO
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Angle AST CR
IPT DCR
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Figure 3. Means and SD of angle specific torque dynamic control ratios (AST DCR), angle specific torque conventional ratios (AST CR), independent peak torque dynamic control ratio (IPT DCR), and independent peak torque conventional ratio (IPT CR) at 180°·s-1.
1.20 1.00
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AST DCR
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× Significantly less than AST DCR, + significantly greater than AST DCR, (c) 30° AST DCR significantly greater than 40° and 50° AST DCR, (d) 40° AST DCR significantly less than 30° but significantly greater than 50° AST DCR, (e) 50° AST DCR significantly less than 30° and 40° AST DCR.
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PT -80 RATIO
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Angle AST DCR
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IPT DCR
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Figure 2. Means and SD of angle specific torque dynamic control ratios (AST DCR), angle specific torque conventional ratios (AST CR), independent peak torque dynamic control ratio (IPT DCR), and independent peak torque conventional ratio (IPT CR) at 60°·s-1. Figure 1: Test set up.
× Significantly less than AST DCR, + significantly greater than AST DCR, (a) 30° AST DCR significantly greater than 40° AST DCR, (b) 40° AST DCR significantly less than 30° AST DCR.
CONCLUSION Misinterpretation of shoulder rotator strength DCR may occur due to IPT DCR not occurring at the same angles for the agonist and antagonist muscle groups, while 10° AST DCR allows an angle specific measure of IR and ER shoulder rotator strength ratios. Significant differences between the last three 10° segments of AST DCR, where the end of ROM occurs, could also lead to discrepancies where 30° AST DCR intervals are used to analyze end ROM ratios, considering that those are the angles where most imbalances occur. These results show that IPT could be used to calculate CR, but 10° AST should be used to calculate DCR.
