Effects of Daily Dark Chocolate Supplementation on Arterial Stiffness Induced by High-Intensity Resistance Training in Women

Intervention 1: High-Intensity Resistance Training (HIRT) + 85% Dark Chocolate Supplementation Physical or informational materials used: Participants received 25 g of 85% dark chocolate (DiRaja Chocolate, Pingtung County, Taiwan) daily for four weeks. Each serving contained approximately 1092.5 mg total cocoa flavanols (including catechin = 164.9 mg; epicatechin = 94.2 mg). Nutrition facts were confirmed by an accredited lab (OHC Lab, Taiwan). Exercise sessions were performed in a controlled laboratory gym at National Chung Cheng University. Training equipment included standard Olympic barbells and weight plates. Procedures, activities, and processes: Participants completed a 4-week high-intensity resistance training (HIRT) program, three sessions per week. Each session included: deadlift, bench press, and squat, performed at 75% 1RM, 5 sets × 6 repetitions, 3 min rest between sets, and 5 min rest between exercises. Warm-up and stretching were completed before each session. Participants consumed the chocolate daily after lunch and before dinner, avoiding other flavanol-rich foods. Pre- and post-tests (vascular and cardiovascular assessments) were scheduled during the early follicular phase (cycle days 2–5) to control for hormonal variation. Who delivered the intervention and their expertise: Exercise sessions were supervised one-on-one by trained research staff with qualifications in exercise physiology and resistance training (NSCA guidelines). Dietary control and supplement distribution were managed by research assistants trained in nutrition monitoring. Mode of delivery: HIRT sessions were delivered face-to-face, individually, in the university gym. Chocolate supplementation was self-administered at home with daily adherence monitoring. Frequency, duration, and schedule: Exercise: 3 sessions per week × 4 weeks (total = 12 sessions). Each session lasted approximately 60 minutes. Supplementation: 25 g dark chocolate daily for 28 days. Location: Laboratory gym, Department of Athletic Sports, National Chung Cheng University, Chiayi, Taiwan. Personalisation or adaptation: 1RM strength values were reassessed after 4 weeks and increased by 10% to adjust for expected strength gains (maintaining 75% intensity). Adherence and fidelity: Exercise attendance recorded by research staff. Supplement adherence verified by return of empty chocolate wrappers and daily intake logs. Participants received daily reminders and weekly check-ins to maintain compliance.