In several recent studies, athletes experienced substantial gains in sprint and endurance performance when explosive training or high-intensity interval training was added in the noncompetitive phase of a season. Here we report the effect of combining these 2 types of training on performance in the competitive phase. We randomized 18 road cyclists to an experimental (n = 9) or control (n = 9) group for 4-5 weeks of training. The experimental group replaced part of their usual training with twelve 30-minute sessions consisting of 3 sets of explosive single-leg jumps (20 for each leg) alternating with 3 sets of high-resistance cycling sprints (5 x 30 seconds at 60-70 min(-1) with 30-second recoveries between repetitions). Performance measures, obtained over 2-3 days on a cycle ergometer before and after the intervention, were mean power in a 1- and 4-km time trial, peak power in an incremental test, and lactate-profile power and oxygen cost determined from 2 fixed submaximal workloads. The control group showed little mean change in performance. Power output sampled in the training sprints of the experimental group indicated a plateau in the training effect after 8-12 sessions. Relative to the control group, the mean changes (+/-90% confidence limits) in the experimental group were: 1-km power, 8.7% (+/-2.5%); 4-km power, 8.1% (+/-4.1%); peak power, 6.8% (+/-3.6); lactate-profile power, 3.7% (+/-4.8%); and oxygen cost, -3.0% (+/-2.6%). Individual responses to the training were apparent only for 4-km and lactate-profile power (standard deviations of 2.5% and 2.8%, respectively). The addition of explosive training and high-resistance interval training to the programs of already well-trained cyclists produces major gains in sprint and endurance performance, partly through improvements in exercise efficiency and anaerobic threshold.