Our previous work has demonstrated that professional athletes show protocol-dependent variability in salivary testosterone (T) responses to resistance exercise (RE). The current study examines the consistency and functional outcomes of prescribing a RE regimen based on T response. We hypothesized that prescribing an individual-specific RE protocol based on T response would enhance weight training gains. Sixteen amateur rugby players [(mean ± SD) age: 20 ± 2 years; height: 181.5 ± 8.2 cm; weight: 94.2 ± 11.1 kg] were characterized by their maximal (Tmax) and minimal (Tmin) T response to four RE protocols: four sets of 10 repetitions (reps) at 70% of one repetition maximum (1RM) with 2 minutes' rest between sets (4 ×10-70%); three sets of five reps at 85% 1RM with 3 minutes' rest (3 × 5-85%); five sets of 15 reps at 55% of 1RM with 1 minute's rest (5 × 15-55%); and three sets of 5 reps at 40% 1RM with 3 minutes' rest (3 × 5-40%). Eight athletes then performed a 3-week training block performing only their Tmax protocol. The remaining eight only performed Tmin. After 3 weeks, the athletes were retested on the RE protocols and then crossed over and performed the alternate 3-week training block. All 16 athletes showed significant increases in estimated bench and leg press 1RM strength and bodyweight while performing Tmax. When Tmin was performed, 75% of athletes showed either no change or a significant decline in 1RM performance. Consistent protocol-responses over the experimental period were seen for both the Tmax and Tmin protocols in 12 of 16 athletes. Thus, a relationship between an individual's biologically available T response to RE and enhanced functional gains is reported.