Effects of a standardised Amaranthus tricolor-Spinacia oleracea extract on exercise performance, muscle strength, endurance and recovery in active adults: a randomised, double-blind, placebo-controlled trial

Dietary supplements are increasingly being adopted by physically active individuals to support exercise performance and recovery. This randomised, double-blind, placebo-controlled trial evaluated the ergogenic potential of SpinoleRG, an HPLC-PDA-standardised combination of Amaranthus tricolor L. and Spinacia oleracea L. in healthy, recreationally active adults over 12 weeks. Participants received a total of 1,600 mg of the extract or a placebo daily before exercise. Primary endpoints included cardiopulmonary exercise testing, muscle strength, and endurance. Secondary endpoints included treadmill-based time to exhaustion (TTE), body composition, repetitions to failure, biochemical markers, delayed onset muscle soreness (DOMS), and vitals. Routine investigations and safety monitoring were also conducted. Four participants per group were withdrawn due to non-compliance and 64 participants completed the study. Compared to the placebo, the test group showed a significant increase in the ventilatory threshold, but not in VO2 max or maximal ventilation. They also showed significantly improved one-repetition maximum strength, fatigue indices, TTE, repetitions to failure, plasma nitrite, blood lactate, creatine kinase, lactate dehydrogenase, and DOMS outcomes. Vital signs or routine parameters were not impacted meaningfully. Three minor adverse events across both groups were observed, considered unrelated to the interventions and fully resolved. Overall, the findings support the tolerability and ergogenic potential of the extract.