Significantly Increased Odds of Reporting Previous Shoulder Injuries in Female Marines Based on Larger Magnitude Shoulder Rotator Bilateral Strength Differences

Abstract

Background:Musculoskeletal injuries to the extremities are a primary concern for the United States (US) military. One possible injury risk factor in this population is side-to-side strength imbalance.Purpose:To examine the odds of reporting a previous shoulder injury in US Marine Corps Ground Combat Element Integrated Task Force volunteers based on side-to-side strength differences in isokinetic shoulder strength.Study Design:Cohort study; Level of evidence, 3.Methods:Male (n = 219) and female (n = 91) Marines were included in this analysis. Peak torque values from 5 shoulder internal/external rotation repetitions were averaged and normalized to body weight. The difference in side-to-side strength measurements was calculated as the absolute value of the limb difference divided by the mean peak torque of the dominant limb. Participants were placed into groups based on the magnitude of these differences: <10%, 10% to 20%, and >20%. Odds ratios (ORs) and 95% CIs were calculated.Results:When separated by sex, 13.2% of men reported an injury, while 5.5% of women reported an injury. Female Marines with >20% internal rotation side-to-side strength differences demonstrated increased odds of reporting a previous shoulder injury compared with female Marines with <10% strength differences (OR, 15.4; 95% CI, 1.4-167.2; P = .03 ) and female Marines with 10% to 20% strength differences (OR, 13.9; 95% CI, 1.3-151.2; P = .04). No significant ORs were demonstrated in male Marines.Conclusion:Marines with larger magnitude internal rotation strength differences demonstrated increased odds of reporting a previous shoulder injury compared with those with lesser magnitude differences. Additionally, female sex appears to drastically affect the increased odds of reporting shoulder injuries (OR, 13.9-15.4) with larger magnitude differences (ie, >20%) compared with those with lesser magnitude differences (ie, <10% and 10%-20%). The retrospective cohort design of this study cannot delineate cause and effect but establishes a relationship between female Marines and greater odds of larger magnitude strength differences after returning from an injury.

Comparison between the isokinetics parameters of shoulder joint and independence functional level in manual wheelchair users

“…In addition, the means described in the results of this work show that the external / internal rotator ratios at speeds 75°/s and 150°/s on the right and left sides are above the range of normality described in the literature ranging from 0.67 to 0.85. 19 These results may suggest an impairment of the internal rotator muscles in the studied population, and approaches of Berckmans et al 25 studies that propose this muscular group as more prone to overload injuries.…”

“…Pvalue calculated by Student's t test for independent samples (p= 0.110). Considering the values of normality on the peak torque ratio of the external / internal rotators between 0.67 and 0.85, 19 it is possible to observe a significant difference between values above this interval with the age of the individual studied for the right limb and with the total MIF on the left limb. These data suggest that values above the normal interval were significantly higher in older individuals when considered the right side (p= 0.033) and with the lower MIF when considered the left side (p= 0.006) (Table 4).…”

“…All tests were performed with visual and verbal feedback. 17,19 Qualitative variables were described by Absolute Frequency Distribution (f) and Relative Frequency Distribution (%). Quantitative variables were described by mean standard deviation (SD).…”