Isokinetic shoulder strength adaptations to weighted jump rope training in CrossFit athletes: A pre–post study

Abstract

Background

The isokinetic shoulder profile is commonly used to assess injury risk in overhead sports. CrossFit athletes are vulnerable to shoulder injuries due to high-load, high-repetition demands. This exploratory study aimed to evaluate the effects of a 6-week weighted jump rope (WJR) program on isokinetic shoulder performance.

Methods

CrossFit athletes performed WJR sessions three times per week, integrated into their usual training. The program involved a progressive increase in total jumps per week. Isokinetic assessments of internal and external rotational peak torque and external rotation/internal rotation (ER/IR) ratios were conducted bilaterally at 60°/s, 180°/s, and 300°/s. Paired t-tests and two-way analysis of variance (ANOVA) were used, with significance set at p < 0.05 and Cohen's d effect sizes calculated.

Results

No significant changes were observed in rotational peak torque or ER/IR ratios across conditions. An exploratory sex-based difference was observed, with females showing a higher ER/IR ratio at 60°/s.

Discussion

No detectable changes were observed across isokinetic variables; however, the absence of a control group limits the interpretation of these preliminary findings. The sex-related difference observed at 60°/s should be interpreted as an exploratory finding.

The study protocol and procedures are publicly registered in ClinicalTrials.gov Protocol Registration and Results System (PRS) under the ID NCT06924775.