Untrained subjects can display diverse strength gain following an identical period of resistance exercise. In this investigation, 28 untrained males completed 16-weeks of resistance exercise, comprising 4-weeks familiarisation, and 12-weeks of heavy-load (80–85%) activity. High and low responders were identified by the Δ1RM (Δ one repetition maximum) observed following familiarisation (25.1 ± 1.4%, 9.5 ± 1.4%, P < 0.0001) and differences in electromyographic root mean square amplitude (ΔEMGRMS 29.5 ± 8.3%, 2.4 ± 6.0%, P = 0.0140), and habitual and occupational activity patterns were observed between these respective groups. The strength gain (P < 0.0001) observed within high (29.6 ± 1.7%) and low (31.4 ± 2.7%) responding groups was similar during the heavy-load phase, yet ΔEMGRMS increased (P = 0.0048) only in low responders (31.5 ± 9.3%). Retrospectively, differences (P < 0.0001) in baseline 1RM strength of high- (19.7 ± 0.9 kg) and low-responding (15.6 ± 0.7 kg) groups were identified, and a strong negative correlation with Δ1RM after 16-weeks (r 2 = −0.85) was observed. As such, baseline 1RM strength provided a strong predicative measure of strength adaptation. The ΔEMGRMS suggests strength variability within high and low responders may be attributed to neural adaptation. However, differences in habitual endurance and occupational physical activity suggests one should consider screening not only recent resistance training, but also other modes of physical activity during participant recruitment.