The aim of this study was to investigate the effects of six weeks of PQQ supplementation in non-endurance-trained individuals on:

1. physiological and metabolic response during a FATmax-VO₂peak exercise test
2. resting energy expenditure, body composition and blood biomarkers (fasting glucose, lactate dehydrogenase (LDH), creatine phosphokinase (CPK) and C-reactive protein (CRP) levels)
3. blood and urine omics markers of oxidative metabolism 24 basketball players will be randomized to consume a supplement containing 20 mg/day of PQQ or placebo (PLA) during a six-week intervention. Subjects will be encouraged to maintain their usual diet and training schedule. Body composition will be assessed by dual-energy-x-ray-absorptiometry and bioimpedance analysis. Aerobic exercise performance will be evaluated through a graded exercise protocol (six 5-minutes steps followed by n 2-minutes steps until exhaustion; the initial workload was 60 watts and increased by 35 watts at the end of each step) performed on a cycle ergometer. Capillary blood lactate samples were collected at the end of each step. Blood and urine samples were also collected, and metabolomics analysis will be performed.

Inclusion Criteria:

• 1) Age: Participants aged between 18 and 40 years.
• 2) Body mass index (BMI): BMI within the range of 18-30 kg/m².
• 4) Physical activity: Regular engagement in non-endurance physical activities (3-4 times a week), with no participation in structured endurance training programs.

Exclusion Criteria:

• 1) chronic disease;
• 2) acute illness; and
• 3) use of dietary supplements, pharmacological agents, or adherence to a hypocaloric diet.