S1 Data -

Background
Satisfaction of fundamental needs is an important concept in sport, but currently there is no tool in Arabic to measure this construct. Basic needs are often linked to high rates of motivation and performance. It is necessary to develop tools to assess psychological needs in the sport context.
Aim
This study aimed to validate the Basic Needs Satisfaction in Sport Scale (BNSSS) in Arabic language across Tunisian athletes, and to test its psychometric properties (factorial structure, internal reliability, construct validity, and sensitivity).
Methods
Athletes in various sports participated in this study (370 men, 146 women; mean age 18.35) and voluntarily completed the Arabic version of the BNSSS-20. Both exploratory (EFA, N = 294; males: 68%; females: 32%; [14–18] = 182; [19–28] = 112) and confirmatory (CFA; N = 222; males: 76.6%; females: 23.4%; [14–18] = 103; [19–28] = 119) factor analyses were examined.
Results
Results from the EFA suggest that the BNSSS scale reflects the theoretical model well, with good internal consistency for all factors. All 20 items of BNSSS revealed excellent reliability (McDonald’s omega = 0.773, Cronbach’s α = 0.886, Gutmann’s λ6 = 0.970) and good temporal stability (ICC = 0.84, 95% CI = 0.55–0.93) over a 4-week period. Likewise, the CFA fit indices were excellent.
Conclusion
The BNSSS presented excellent fit to the theoretical model for all indices, confirming the factorial structure and providing validity of the instrument for Tunisian athletes.