To do so, the international research team collected muscle biopsies before supplementation and pre-, immediately post-, and three-hours post-exercise (one-hour of cycling) performed following the supplementation period. The researchers postulated that NR supplementation would increase whole-body fat oxidation during exercise and augment SIRT1 and SIRT3 signaling in the post-exercise period compared to placebo. Contrary to their expectations, Stocks and colleagues found no such thing.
One week of twice-daily 500 mg NR supplementation in eight healthy human patients did not alter whole-body metabolism during and after exercise. Along these lines, there were no changes in the levels of key metabolic compounds — like glucose, lactate, and non-esterified fatty acids (NEFA) — during or after one hour of riding a stationary bike. Also, this acute NR treatment didn’t affect skeletal muscle mitochondrial function or production. So, it is not surprising that the researchers also did not observe the induction of signaling related to mitochondrial adaptation and production in resting or exercised human skeletal muscle of healthy human volunteers.