An 8-week, split-body, linear periodized resistance training program was completed by college-aged (CA: 18-22 years; n = 24) and middle-aged (MA: 35-50 years; n = 25) men to determine early-phase adaptations in body composition and upper- and lower-body strength. Participants completed 2 upper-body and 2 lower-body resistance training workouts each week. During weeks 1-4, subjects completed 3-6 sets at a 10-repetition maximum (RM) intensity and increased to 8RM for weeks 5-8. The 1RM strength levels were determined on the bench press and leg press, and 30-second Wingate tests were assessed at baseline and after 8 weeks of resistance training. Body composition was assessed using dual-energy X-ray absorptiometry (DXA). For selected data, delta values (post - pre values) were calculated and reported as mean +/- SEM. No changes (p > 0.05) were reported for peak and average Wingate power. Bench press (CA, 3.2 +/- 1.9 kg; MA, 6.2 +/- 3.3 kg; p < 0.001) and leg press (CA, 25.0 +/- 4.4 kg; MA, 18.2 +/- 13.3 kg; p < 0.001) 1RM significantly increased in both groups over time. Lean mass significantly increased over time in both groups (CA, 0.9 +/- 2.4 kg; MA, 1.1 +/- 1.9 kg; p < 0.001). Significant group x time effects were seen for fat mass changes (CA, 0.5 +/- 1.3 kg; MA, -0.5 +/- 1.1 kg; p = 0.01) and % body fat changes (CA, 0.4 +/- 1.4%; MA, -0.7 +/- 1.1%; p = 0.01). These results indicate that performing a split-body, linearly periodized resistance training program for 8 weeks significantly increases bench press 1RM, leg press 1RM, and DXA lean mass in CA and MA men. Furthermore, MA men lost significantly more fat mass and significantly decreased % body fat compared with CA men. A split-body, linearly periodized resistance training program may be used as an effective program to increase strength and lean mass in both young and MA populations.