Effects of NR Supplementation on Metabolic Flexibility in Zone 2 Training

NCT07344636 — Not applicable, Recruiting, 16 participants, ZHANG Jiaqi

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Temporal and Dose-response Effects of Nicotinamide Riboside Supplementation on Metabolic Flexibility During Zone 2 Training in Adults: a Double-blinded, Randomized, Controlled, Crossover Trial

Registry	NCT07344636
Status	Recruiting
Phase	Not applicable
Study type	Interventional; randomized, crossover, masking: double, other
Enrollment	16 (Estimated)
Sponsor	ZHANG Jiaqi (Other)
Conditions	Health Adult Subjects
Interventions	Nicotinamide Riboside (NR) (Dietary supplement)
Dates	start 2026-01-06, primary completion 2027-07-01 (estimated), completion 2027-07-01 (estimated), first posted 2026-01-15, last updated 2026-03-18
Locations	1 site in China

-Summary

Zone 2 training, a low-intensity endurance exercise performed at approximately 66-80% of VO₂max or near the first ventilatory threshold, has gained popularity for improving aerobic capacity, fat metabolism, and mitochondrial efficiency. It preserves glycogen stores and delays fatigue, making it an essential training method for both athletes and recreational exercisers. Nicotinamide adenine dinucleotide (NAD) is a vital metabolite that regulates cellular energy metabolism and redox homeostasis. It participates in oxidative reactions within the tricarboxylic acid cycle and electron transport chain, sustaining ATP synthesis and mitochondrial efficiency. Exercise influences multiple pathways of NAD metabolism, altering the NAD⁺/NADH ratio and thereby affecting energy production and fatigue resistance. Studies have shown that both aerobic exercise and NAD precursor supplementation (e.g., nicotinamide riboside \[NR\]) can elevate body NAD levels and enhance mitochondrial function, though findings remain inconsistent due to variations in dosage and participants' characteristics. This study aims to investigate how acute NR supplementation interacts with Zone 2 cycling training in adults. Specifically, it examines the temporal and dose-dependent effects of NR supplementation on metabolic flexibility and exercise performance. The results may clarify the potential synergistic benefits of combining NAD supplementation with low-intensity endurance training to improve aerobic adaptability.

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+Arms and interventions

Arm	Type	Interventions
600 mg	Experimental	Dietary Supplement: Nicotinamide Riboside (NR)
300 mg	Experimental	Dietary Supplement: Nicotinamide Riboside (NR)
0 mg	No intervention

Nicotinamide Riboside (NR) (Dietary supplement): 600 mg NR
Nicotinamide Riboside (NR) (Dietary supplement): 300 mg NR

+Outcome measures

Primary outcomes

Substrate utilization (CHO and fat oxidation rate) [From enrollment to the end of treatment at 4 weeks]

Secondary outcomes

Oxygen consumption [From enrollment to the end of treatment at 4 weeks]
Heart rate [From enrollment to the end of treatment at 4 weeks]
Blood glucose concentration [From enrollment to the end of treatment at 4 weeks]
Blood lactate concentration [From enrollment to the end of treatment at 4 weeks]
Peak power output [From enrollment to the end of treatment at 4 weeks]
Mean power output [From enrollment to the end of treatment at 4 weeks]
Rating of perceived exertion [From enrollment to the end of treatment at 4 weeks]
Muscle pain scale [From enrollment to the end of treatment at 4 weeks]: Muscle pain scale is a 5-point likert scale ranging from "1- Not at all" to "5- Extreme", with higher value indicating muscle pain.
Muscle fatigue scale [From enrollment to the end of treatment at 4 weeks]: Muscle fatigue scale is a 5-point likert scale ranging from "1- Not at all" to "5- Extreme", with higher value indicating muscle fatigue.

Other outcomes

Height [From enrollment to the end of treatment at 4 weeks]
Weight [From enrollment to the end of treatment at 4 weeks]
Power output at VT1 [From enrollment to the end of treatment at 4 weeks]
Health history questionnaire [From enrollment to the end of treatment at 4 weeks]: This questionnaire includes questions regarding participant's present/past history of diseases and his/her family history of diseases.
International Physical Activity Questionnaire (IPAQ) [From enrollment to the end of treatment at 4 weeks]: IPAQ is a validated questionnaire to measure the physical activity of participants during the past 7 days. The score will be transformed to metabolic equivalents of tasks per week (METs/week), with higher value indicating greater participation in physical activity.

+Eligibility

Sex: All, ages: 18 Years to 80 Years, accepts healthy volunteers

Inclusion Criteria:

* Over 18 years old
* BMI <30 kg/m2

Exclusion Criteria:

* Present of health conditions that contraindicate participation in exercise training, such as a history of cardiovascular disease, cancer, or musculoskeletal disorders
* Currently taking vitamin B supplements and/or NAD precursors
* Taking medication that may affect the test results

+Locations (1)

Facility	City	Country	Status
G02, Kwok Sports Building, The Chinese University of Hong Kong	Hong Kong, Please Select	China	Recruiting