The Association Between Isometric Shoulder Strength and Sports Performances in University Soccer Players: A Cross-Sectional Study

Background Soccer, a globally popular sport, demands a complex interplay between physical attributes, including speed, agility, power, and endurance. Although lower-body strength and power are often emphasized, the role of upper-body strength, particularly shoulder strength, remains less explored. Given the importance of upper-body movements in activities such as heading, shooting, and defending, understanding the relationship between shoulder strength and soccer performance is crucial. Aims This study aimed to explore any possible correlation between isometric shoulder muscle strength (flexors and extensors) and sports performance (sprint and agility) and to evaluate whether isometric shoulder strength is associated with sports performance in university-level soccer players. Methods A total of 35 male amateur soccer players were recruited, who underwent demographic measurements such as age, height, weight, and body mass index (BMI), and were then subjected to isometric strength assessment of the shoulder flexors and extensors using a handheld dynamometer (HHD). Subsequently, the players' sprint and agility performances were recorded. Appropriate statistical tests were performed on the obtained data. Results The findings revealed a significant negative correlation between shoulder flexor strength and sprinting (r=-0.707, p<0.01) and between shoulder extensor strength and sprinting (r=-0.611, p<0.01). There was no significant correlation between shoulder flexor strength and agility (r=-0.121, p=0.48) or between shoulder extensor strength and agility (r=-0.212, p=0.22). Multiple linear regression analysis revealed that only shoulder flexor strength (β=-0.688, t=-2.651, p=0.01) was found to have statistically significant relationships with sprint performance, explaining 50% of the variance in sprint performance. Conclusions The present study found a negative bidirectional relationship between shoulder muscle strength and sprint performance. Shoulder flexor strength explained 50% of the variance in sprinting performance. This information is useful for physiotherapists, coaches, and trainers to focus on strengthening the shoulder musculature to improve performance.