New Zealand blackcurrant extract augments muscle glycogen storage at rest and enhances intramuscular triglyceride degradation during prolonged exercise
摘要
New Zealand blackcurrant (NZBC) extract increases fat oxidation during prolonged exercise. We investigated if increased fat oxidation following NZBC extract supplementation is linked to greater utilisation of intramuscular triglyceride (IMTG), and if this improves exercise capacity via muscle glycogen sparing. In a randomised, crossover, double-blind design, ten moderately trained males ingested 600 mg·day−1 NZBC extract (CurraNZ™) or placebo (600 mg·day−1 microcrystalline cellulose) for 7 days. On day 7, participants performed 120 min cycling at 65% VO2max followed by an exercise capacity test. Muscle biopsies were obtained immediately before, after 30 and 120 min of submaximal cycling. Exercise decreased IMTG content in type I fibres (~ 44%), with net IMTG degradation by 120 min being greater following NZBC extract compared to placebo (P < 0.05). No differences in plasma NEFA or glycerol concentrations were observed between conditions despite whole-body rates of fat oxidation being ~ 24% greater following NZBC extract (P = 0.025). Pre-exercise muscle glycogen concentrations were greater following NZBC extract (NZBC: 493 ± 85, PLA: 355 ± 65 mmol∙kg−1 dw; P < 0.01), but post-exercise muscle glycogen concentrations were similar between conditions (NZBC: 112 ± 113, PLA: 132 ± 87 mmol∙kg−1 dw; P > 0.05). Exercise capacity was not improved following NZBC extract supplementation (P = 0.081). Greater rates of fat oxidation during prolonged exercise following NZBC extract supplementation are linked to increased IMTG utilisation in type I fibres. NZBC extract did not improve exercise capacity or spare muscle glycogen. Interestingly, pre-exercise muscle glycogen concentrations were elevated with NZBC extract supplementation, the physiological benefits of which now require investigation.