Impact of Nutritional Supplement Formulation on Knee Discomfort in Endurance-Trained Individuals

INTERVENTION: Group A (Undenatured Type II Collagen,Turmeric Extract, Enzymatically Hydrolyzed Bone Powder):Undenatured Type II Collagen,Turmeric Extract, Enzymatically Hydrolyzed Bone Powder;Group C (Placebo):Maltodextrin;Group B (glucosamine & chondroitin sulfate):Glucosamine Hydrochloride, Chondroitin Sulfate; CONDITION: Knee discomfort caused by exercise PRIMARY OUTCOME: Single‐Leg Step‐Down (SLSD) Test; SECONDARY OUTCOME: Oxidative Stress/Antioxidant indicators (superoxide dismutase (SOD), malondialdehyde(MDA));Muscle damage indicators (Creatine Kinase);Inflammation indicators (C‐reactive protein (CRP), Interleukin‐6 (IL‐6), Tumor Necrosis Factor‐alp (TNF‐a));Visual Analogue Scale (VAS);Western Ontario and McMaster Universities Osteoarthritis Inde X(WOMAC);Range of Motion;Cartilage metabolism indicators (Cartilage Oligomeric Matri XProtein (COMP) and C‐terminal telopeptide of type II collagen (CTX‐II)); INCLUSION CRITERIA: 1. Age: 18‐65 years old; 2. BMI: 18.5‐30 kg/m²; 3. Exercise habits: at least 3 endurance workouts per week (like running, swimming, cycling) for 3 months or more; 4. Reversible knee discomfort occurring during or after at least 3 months of physical activity; 5. Joint symptoms: Positive on the Single‐Leg‐Step‐Down (SLSD) test; 6. Participants are physically and mentally healthy, with no medical history, physical exam results, or vital signs that would affect the current study.