Associations Among Smartphone Use, Activity Participation, and Hand Strength in University Students

This study examined associations among smartphone use, activity participation, and hand strength in university iPhone users. It was hypothesized that both smartphone use and activity participation would be associated with hand strength, and that activity participation would moderate the smartphone use-strength relationship.

Methods

A cross-sectional correlational study was conducted with 166 undergraduate/graduate students at one U.S. university (2026). Eligible participants owned an iPhone X+ with Screen Time enabled. Data (single session) include demographics (age, sex, hand dominance, academic level, injury history, iPhone ownership length), grip/lateral pinch strength per hand in pounds (Jamar dynamometer/pinch gauge, ASHT protocol, mean of 3 trials), weekly smartphone use in hours from Screen Time across 6 apps, and participation in 6 activity domains (sports, physical activity, arts/crafts, tabletop, video games, instrument), coded as binary and weekly-hours.

Smartphone use and strength variables were non-normally distributed (Shapiro-Wilk, p < .001); Spearman, point-biserial, and regression analyses were used accordingly. Results: Greater smartphone use was weakly, significantly associated with lower left-hand grip and pinch strength (rho = -.18, p < .03), concentrated among female and right-hand-dominant participants; no associations emerged for male or left-dominant participants.

Sports participation was positively associated with all four strength measures (r = .26-.31), arts/crafts was negatively associated (r = -.30 to -.35), instrument playing was positively associated with pinch strength. Activity participation showed more consistent associations with hand strength than smartphone use in regression models; smartphone use did not independently predict strength once activity was controlled. An exploratory smartphone use x sports interaction predicted lower right-hand pinch strength (p = .024), interpreted cautiously given modest model-fit improvement.

Conclusions: Activity participation, particularly sports and arts/crafts, was more consistently associated with hand strength than smartphone use, though associations were small-to-moderate and causality cannot be inferred. Reanalysis should use non-parametric methods given non-normal distributions; binary and hours-based measures diverged for some activities (e.g., tabletop), suggesting duration may matter beyond participation alone.

Data may interest researchers studying technology use, activity engagement, and upper-extremity function in young adults.