Combined Effects of Aerobic Interval Training and Nutrient- Fortified Fermented Rice Porridge on Endurance Performance, Cardiopulmonary Fitness, and Recovery Kinetics in Collegiate Distance Runners: A Four-Arm Randomised Controlled Trial

Abstract

To examine the combined effects of aerobic interval training (AIT) and nutrient-fortified fermented rice porridge (NFFRP) on endurance performance, cardiopulmonary fitness, and recovery kinetics in collegiate distance runners. A 12-week, single-centre, four-arm parallel-group randomised controlled trial enrolled 90 collegiate runners (18–25 years) allocated equally to: (1) AIT + NFFRP, (2) AIT + placebo, (3) conventional training (CT) + NFFRP, or (4) CT + placebo. AIT comprised three weekly sessions of 4×4-min intervals at 90–95% HRmax. NFFRP (300 mL twice daily on training days) provided carbohydrate, protein, iron, and probiotics; the placebo contained approximately 120 kcal versus 295 kcal in NFFRP. The primary outcome was half-marathon completion time. Secondary outcomes included VO₂max, peripheral oxygen satu- ration (SpO₂), one-minute recovery heart rate, blood lactate, heart rate variability (RMSSD), rating of perceived exertion, haemoglobin, and running economy. All 90 participants completed the trial. The AIT + NFFRP group showed the greatest improvement in half-marathon time (−14.6%; mean −16.8 min; 95% CI −19.3 to −14.3; p<0.001), VO₂max (+15.8%), blood lactate reduction (−31.7%), and RMSSD improvement (+34.9%). Significant group-by-time interactions were observed across all outcomes (p<0.001; η²p = 0.34–0.46). Combining AIT with NFFRP was associated with greater improvements in endurance performance and recovery than either intervention alone. However, NFFRP’s caloric and nutritional compo- sition differed substantially from the placebo, and the specific contributions of fermentation, probiotics, or iron cannot be isolated from the current design.