This study aimed to evaluate the effects of an 8-week concurrent training (CT) program that combined short sprint interval training (sSIT) and resistance training (RT) in alternating sequences (i.e., sSIT + RT or RT + sSIT) on the physical fitness, aerobic capacity, and anaerobic performance of male karate athletes, in comparison to each training intervention conducted independently. Forty national-level young male athletes volunteered to participate in this study and were divided into sSIT, RT, sSIT + RT, RT + sSIT, and active control (CG) groups, each group consisted of eight athletes and performed 3 days of weekly training intervention including 4 sets of 5 repetitions of 5 seconds of all-out running for sSIT program and also back squats, leg presses, seated knee flexions, and calf raises for 3 sets of 6 - 12 repetition maximum for the RT intervention. After the intervention, the sSIT, RT, sSIT + RT and RT + sSIT groups demonstrated improvements in the countermovement vertical jump (CMVJ) (effect size [ES] = 0.64, 0.88, 1.58, 1.55), 20-m sprint (ES = -0.82, -0.62, -1.10, -1.16), 4 9-m shuttle run (ES = -0.62, -0.35, -1.15, -0.89), strength (ES = 0.19, 0.44, 0.34, 0.43), peak (ES = 1.27, 0.73, 1.80, 1.53), and mean power output (ES = 0.87, 0.54, 1.37, 1.11), as well as in comparison to the CG (p < 0.05), respectively. Additionally, improvements in aerobic performance were observed in the sSIT, sSIT + RT, and RT + sSIT groups (ES = 0.75, 0.92, 0.62) after the training intervention, and in comparison to CG (p < 0.05), while the RT group did not show significant changes post-training. By comparing the CT groups, no sequencing effects were observed in the adaptations of variables between the sSIT + RT vs. RT + sSIT groups. In conclusion, this study’s findings demonstrate that sSIT, RT, and CT with different orders have a positive impact on inducing adaptations in physical fitness, aerobic and anaerobic performance. Additionally, combining sSIT and RT resulted in further adaptations in karate athletes without any differences between CT groups.
