The Effects of an 8-Week Strength Development Program on Peak Torque of Shoulder, Elbow, Hip, and Knee Flexor Muscles in Karate Athletes

Background: The physical demands of Karate, particularly in disciplines like Kumite and Kata, emphasize the importance of explosive strength in executing offensive and defensive maneuvers. Muscle imbalances between flexor and extensor groups, particularly in major joints, pose significant risks to performance and injury prevention. Despite the growth of Karate in Vietnam, limited research has explored targeted strength training interventions for Vietnamese Karate athletes. Method: This study involved 20 male Karate athletes from Vietnam National University-Ho Chi Minh City (VNU-HCM), divided into an experimental group (EG, n=11) and a control group (CG, n=9). The EG participated in an 8-week strength training program, comprising an anatomical adaptation phase (weeks 1–4, 60–75% 1RM) and a maximum strength phase (weeks 5–8, 90–95% 1RM). The CG continued their standard training. Peak torque of flexor muscles at the shoulder, elbow, hip, and knee joints was assessed pre- and post-intervention using the Biodex System 4Pro-2012. Statistical analysis included paired and independent t-tests, growth rates (W%), and ANOVA. Result: The EG demonstrated significant improvements in flexor peak torque across all joints, with notable increases in the right thigh (31.3%, p=0.015) and left shoulder (28.94%, p=0.005). In contrast, the CG exhibited minimal, non-significant changes. Conclusion: The 8-week strength training program effectively enhanced peak torque and reduced muscle imbalances in Vietnamese Karate athletes. These findings support the implementation of structured, periodized strength interventions to optimize athletic performance and reduce injury risks.