Abstract：This study aimed to investigate the effects of Chlorella supplementation for 7-12 days on muscle damage and maximal muscle strength during the recovery period after exercise. Twenty-four badminton players from Taipei Medical University were recruited as subjects and divided into the placebo or Chlorella group in a randomized, double-blind, placebo-controlled designed study. All subjects were orally given high-dose Chlorella (9 g/day) or placebo for 12 days, and performed three different resistance exercises to induce muscle damage after 7-day oral administration. Muscle damage, muscle soreness and liver function markers were determined 24 and 48 hours after resistance exercise., Three tests of muscle strength were also measured on the 3rd, 4th and 5th day during the recovery period (the 10th, 11th, 12th day after oral administration). The results showed that the blood creatine kinase activity was relatively lower at 24 hours after resistance exercise in Chlorella group than that of placebo group. The muscle strength of leg press and leg curl on 3rd day and chest press on 4th day during the recovery period in the Chlorella group were significantly higher compared to the placebo group, and the muscle soreness were significantly greater compared to pre-teat for both groups. However, the activities of lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase, and muscle soreness index were not significantly different between the two groups. In conclusion, short-term with high-dose Chlorella supplementation for 7-12 days inhibited resistance exercise-induced muscle damage, and improved the muscle strength performance of upper and lower body during recovery. In addition, no damage to liver function markers was found in this study. (Full text)