1 Auto-regulated exercise selection training regimen ABSTRACT: The purpose of this investigation was to compare the effects of auto-regulatory exercise selection (AES) vs. fixed exercise selection (FES) on muscular adaptations in strength-trained individuals. Seventeen males (Mean ± SD; age = 24 ± 5.45 years; height = 180.3 ± 7.54cm, lean body mass [LBM] 66.44 ± 6.59kg; squat and bench press 1RM: body mass ratio 1.87, 1.38 respectively) were randomly assigned into either AES or FES. Both groups trained three times a week for 9 weeks. AES self-selected the exercises for each session, whereas FES was required to perform exercises in a fixed order. LBM was assessed via DEXA and maximum strength via 1RM testing, pre and post training intervention. Total volume load was significantly higher for AES than for FES (AES: 573,288kg ± 67,505, FES: 464,600 ± 95,595, p=0.0240). For LBM, there was a significant main time effect (p=0.009). However, confidence interval analysis (95%CI diff) suggested that only AES significantly increased LBM (AES: 2.47%, ES: 0.35, 95% CI diff [0.030kg: 3.197kg], FES: 1.37 %, ES: 0.21, 95% CI diff [-0.500kg: 2.475kg]). There was a significant main time effect for maximum strength (p≤0.0001). However, 95% CI diff suggested that only AES significantly improved Bench-press 1RM (AES: 6.48%, ES: 0.50, 95% CIdiff [0.312kg: 11.42kg; FES: 5.14%, ES: 0.43 95%CIdiff [-0.311kg: 11.42kg]. On the other hand for back squat 1RM similar responses were observed between groups, (AES: 9.55%, ES: 0.76 95% CIdiff [0.04kg: 28.37kg], FES: 11.54%, ES: 0.80, 95%CIdiff [1.8kg: 28.5kg]. Our findings, suggest AES may provide a small advantage in LBM and upper body maximal strength in strength-trained individuals.