Background: Due to the important role of follistatin (FLST), myostatin (MSTN) and growth differentiation factor 11 (GDF11) in muscle mass regulation; alterations in the FLST to MSTN ratio (F:M) may result in muscle mass changes in response to different concurrent training (CT) order. This study investigated the influence of 8 weeks of CT order on body composition and serum concentrations of FLST, MSTN, their ratio (F:M) and GDF11 in sarcopenic elderly men. Methods: Thirty sarcopenic elderly men (age = 64.3 ± 3.5 years) were randomly assigned into one of three groups, endurance followed by resistance training (E + R; n = 10), resistance followed by endurance training (R + E; n = 10) or control (C; n = 10). Serum concentrations of muscle regulatory markers, body composition, maximum rate of oxygen consumption (VO2max), and upper and lower body strength were evaluated at baseline and after 8 weeks. The training protocol consisted of three training sessions per week for eight weeks. Results: There were significant group-by-time interactions (P < 0.05) for FLST, MSTN, GDF11 and F:M ratio. FLST (E + R = 187 pg/mL and R + E = 292 pg/mL) and F:M ratio (E + R = 0.20 and R + E = 0.27) significantly increased (P < 0.05) while MSTN (E + R = -308 pg/mL and R + E = -294 pg/mL) and GDF11 (E + R = -12 pg/mL and R + E = -10 pg/mL) significantly decreased (P < 0.05) following eight weeks in the E + R and R + E compared to no changes in the C group. In addition, there were significant group x time interactions (P < 0.01) for weight, BMI, body fat percentage (BFP), skeletal muscle mass (SMM), VO2max, upper body strength, and lower body strength. BFP (E + R = -1.5% and R + E = -2%) significantly decreased (P < 0.01) while weight (E + R = 2.4 kg and R + E = 1.1 kg), BMI (E + R = 0.8 kg/m2 and R + E = 0.3 kg/m2), SMM (E + R = 0.7 kg and R + E = 0.5 kg), VO2max (E + R = 2.0 mL/kg/min and R + E = 1.8 mL/kg/min), upper body strength (E + R = 6.9 kg and R + E = 2.3 kg), and lower body strength (E + R = 9.8 kg and R + E = 4.4 kg) significantly increased (P < 0.01) in the E + R and R + E compared to no changes in the C group. Conclusions: CT increases the F:M ratio and FLST as well as reducing MSTN and GDF11 in sarcopenic elderly men. Additionally, CT improved weight, body composition, muscle mass, function, and aerobic fitness. Notably, these results after CT were achieved irrespective of endurance and resistance exercise order in this population.

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