Introduction. People with reduced physical fitness (PF) are at greater risks of reduced health-related outcomes [1]. In response to COVID-19 global pandemic, French government has imposed lockdown on March 2020 for 8 weeks. A decreased physical activity (PA) levels in several countries and different populations were observed [2-3], which could in turn reduce both PF and health-related outcomes. Increases in the body mass index (BMI) and decreases in several PF outcomes were observed in adolescents after COVID-19 lockdown, compared to the pre-pandemic period [4]. However, less data are available in the adult population. The aim of this study was to assess PF in adults during the first French lockdown. Methods.Adults (age >18 years) never been tested positive for COVID-19 took part in an online survey including sociodemographic outcomes (sex, age, BMI, socio-professional categories (SPC), education status, daily physical activity, sedentary behaviors, familial environment and four self-administered PF tests (one-minute sit-to stand test: STS; unipodal tests: UP left & right; chair test: CT). Measures were carried out at three weeks in lockdown (P1), at the end of lockdown (P2) and one-month after lockdown (P3). Participants were grouped based on their previous (before lockdown) lifestyles (four profiles regarding sedentary behaviour (SB) and PA levels : sedentary is ≥ 7h/d of sedentary behaviors and active is ≥ 150 min/d of at least moderate physical activity [5]). Linear mixed effects models were fitted to analyze the differences in PF tests at the three lockdown times periods and the influence of the sociodemographic parameters. Results. A total of 104 participants (32 men and 72 women) completed tests of PF (age, 44.3±15.8 years; BMI, 22.8±3.3 kg/m²; 12% lived alone, 34% had children; 28% were active and 56% were sedentary; 17% were retired). Sixty percent had a professional activity during lockdown, 80% of them working as executives, employees or retired, and 56% had at least a master's degree. No differences were observed at P1 between the SB and PA subgroups for the four tests. However, the non-sedentary sub-groups present higher PF performances. PF performances for the non-sedentary subgroups increased from P1 to P2 and from P1 to P3 (p<0.05). The sedentary – non active subgroup increased UP test performance (p<0.02). PF did not change throughout the time periods for the sedentary – active subgroup. SPC (STS, CT, UP), BMI (CT), age (STS, CT, UP) and SB (STS) were the variables exerting the greater influence on PF outcomes. Discussion. The great lockdown did not negatively affected PF outcomes in our population. However, the participants presented high levels of education that also contributed to explain the results of sedentary – active subgroup. Age, SB, high SPC and obesity are the parameters explaining most of the variance in PF outcomes. Lockdown and reduction of practicable activities may have led participants to train for and with the tests. The older participants were more affected and should receive more specifics recommendations. Conclusion. Lockdown did not lead to a decrease in PF but rather tended to increase some of its components.