The Association Between Internal and External Shoulder Load, Pre-season Strength and Power, with Shoulder Problems in Female Handball Players

Abstract

Background Injuries often result from an interaction between load and intrinsic risk factors, with female handball players demonstrating higher prevalence of shoulder problems compared to males. While shoulder rotation strength deficits are recognized as risk factors, the influence of lower body strength (LBS), trunk rotation power (TRP), and the relative importance of internal versus external load on shoulder problems in female handball players remains unknown. Purpose To assess whether pre-season LBS, TRP, and shoulder strength were associated with shoulder problems in female handball players, and whether pre-season strength and power influenced the association between load and shoulder problems. Study design Prospective observational cohort study. Methods Pre-season LBS (Isometric Mid-thigh Pull), TRP (measured while seated) and isometric external (ER) and internal rotation (IR) shoulder strength were measured (31 female handball players). Prevalence, substantial prevalence, and severity of shoulder problems were documented weekly through one season (29 weeks) via the Oslo Sports Trauma Research Center Overuse Questionnaire. Participation-related (internal) shoulder load (PSL) was documented weekly with the modified Borg rate of perceived exertion and the number of shots taken during the season documented to reflect external load. Data was analyzed using the Spearman´s correlation coefficient and a mixed model ANOVA (separate mixed model ANOVAs were constructed for each pre-season variable). Results Thirty-one players (mean age 23.5 +/-4.6 years) participated. For all mixed model ANOVAs, higher PSL was associated with higher severity score (F range: 31.1-39.9, p<0.001). Significant positive interactions were found between PSL and pre-season TRP (p=0.001), LBS (p<0.001), and ER strength (p=0.01) in terms of their influence on the severity score. High pre-season LBS and ER strength were correlated with prevalence of substantial shoulder problems (rs=0.40, rs=0.38, respectively). Conclusions The positive association between pre-season strength and power, and shoulder problems, highlights the complexity of shoulder problems in female handball players. Level of evidence 3.