['Nicotinamide adenine dinucleotide (NAD(+)) and its phosphorylated form (NADP(+)) are key molecules in ubiquitous bioenergetic and cellular signaling pathways, regulating cellular metabolism and homeostasis. Thus, supplementation with NAD(+) and NADP(+) precursors emerged as a promising strategy to gain many and multifaceted health benefits. In this proof-of-concept study, we sought to investigate whether chronic nicotinamide riboside administration (an NAD(+) precursor) affects exercise performance.', 'Eighteen Wistar rats were equally divided in two groups that received either saline vehicle or nicotinamide riboside at a dose of 300\xa0mg/kg body weight/day for 21\xa0days via gavage. At the end of the 21-day administration protocol, both groups performed an incremental swimming performance test.', 'The nicotinamide riboside group showed a tendency towards worse physical performance by 35\xa0% compared to the control group at the final 10\xa0% load (94\u2009±\u200953\xa0s for the nicotinamide riboside group and 145\u2009±\u200959\xa0s for the control group; P\u2009=\u20090.071).'] Does the NAD ( + ) precursor nicotinamide riboside decrease exercise performance in rats?