The purpose of this study was to examine whether β-alanine ingestion for 8 weeks can regulate isokinetic knee strength, and 3km record in middle-long distance woman cyclists. Fourteen middle-long woman cyclists participated in this study and were divided into two groups; training group with beta-alanine ingestion and training group with placebo ingestion. All subjects took in beta-alanine or placebo supplement three times per a day for 8 weeks. Physical activity was evaluated by measuring the isokinetic muscular strength and 3km record before and after intervention for 8 weeks. As a results, in isokinetic test, there were significant interrelationships in peak torque of the right and left flexors at 60°/sec, peak torque of the right and left extensors at 180°/sec, peak torque of the right flexors at 180°/sec. In 3km record, result showed a significant interrelationship by groups and time. The results of present study provide evidence that beta-alanine supplement may be effective to increase physical activity and competition record in middle-long woman cyclists.