FST and rheumatoid arthritis: The RA + functional disability group, as compared to the RA + preserved physical function group, had higher serum follistatin levels (218 ± 159 vs. 141 ± 59; p = 0.030), lower grip strength (7.9 ± 4.6 vs. 14.5 ± 5.1; p < 0.001), reduced gait speed (0.77 ± 0.20 vs. 0.92 ± 0.20; p = 0.010), as well as higher proportions of tender joints ≥4 (48% vs. 16%; p = 0.008), and higher disease activity scores (3.8 ± 1.5 vs. 2.8 ± 1.2; p = 0.008).