New Zealand blackcurrant extract enhances muscle oxygenation during repeated intermittent forearm muscle contractions in advanced and elite rock climbers.

Anthocyanin-rich New Zealand blackcurrant (NZBC) may improve forearm muscle oxygenation and enhance performance in high-level rock climbers. As such, using a double-blind, randomised, cross-over design study, twelve participants performed an oxidative capacity assessment, and two successive exhaustive exercise trials (submaximal forearm muscle contractions at 60% of their maximal volitional contraction). Each visit was conducted following 7-days intake of 600 mg·day-1 NZBC extract or placebo. Oxidative capacity was estimated by calculating the oxygen half time recovery using near infrared spectroscopy. Time to exhaustion (s), impulse (kg·s), and minimum tissue saturation index (min-TSI %) were assessed during both the exercise trials. Muscle oxidative capacity was greater with NZBC (mean difference [MD] = 5.3 s, 95% confidence intervals [95% CI] = 0.4-10.2 s; p = 0.036; Cohen's d = 0.94). During the exercise trials, there was an interaction for min-TSI % (time x condition, p = 0.046; ηp2 = 0.372), which indicated a greater level of oxygen extraction during trial two with NZBC extract (MD = 9%, 95% CI = 2-15%) compared to the placebo (MD = 2%, 95% CI = 1-7%). There was a decrease in time to exhaustion (p <0.001, ηp2 = 0.693) and impulse (p = 0.001, ηp2 = 0.672) in exercise trial two, with no effect of NZBC extract. In high-level rock climbers 7-days NZBC extract improves forearm muscle oxygenation with no effect on isolated forearm muscle performance.

Effect of New Zealand Blackcurrant Extract on Isometric Contraction-Induced Fatigue and Recovery: Potential Muscle-Fiber Specific Effects.

New Zealand blackcurrant (NZBC) extract has shown performance-enhancing effects during cycling, running and sport climbing. We examined effects of NZBC extract on (1) voluntary and twitch force of the quadriceps femoris muscles during repeated isometric contraction-induced fatigue, (2) twitch force during recovery and (3) muscle fiber-specific effects. Familiarized recreationally active males (n = 12, age: 24 ± 5 yrs; height: 180 ± 5 cm; body mass: 89 ± 11 kg) performed sixteen, 5-s voluntary maximal isometric contractions (iMVC) separated by 3-s rest. Twitch force was recorded before, during the 3-s rests and 5-min recovery. Supplementation consisted of 7-days intake of NZBC extract (600 mg∙day-1 containing 210 mg anthocyanin) in a double-blind, randomized, placebo-controlled crossover design with a 14-days washout. NZBC extract allowed for greater force in the first quartile of the iMVCs. Twitch force at baseline was 12% higher with NZBC extract (p = 0.05). However, there was no effect of NZBC for twitch force during the 16-iMVCs and recovery. Based on the maximum post-activation potentiation during the placebo 16-iMVCs, four subjects were classified of having a predominant type I or II muscle fiber typology. In type II, NZBC extract provided a trend for increased MVC force (~14%) in the first quartile and for type I in the fourth quartile (~10%). In type I, NZBC extract seemed to have higher twitch forces during the fatiguing exercise protocol and recovery, indicating increased fatigue resistance. New Zealand blackcurrant extract affects force during repeated maximal isometric contractions. Future work on mechanisms by NZBC extract for muscle fiber-specific fatigue-induced force responses is warranted.

New Zealand Blackcurrant Extract Enhances Muscle Oxygenation During Forearm Exercise in Intermediate-Level Rock Climbers.

The delivery to and utilization of oxygenated hemoglobin to the forearm muscles are key determinants of rock-climbing performance. Anthocyanin-rich New Zealand blackcurrant (NZBC) has been suggested to improve blood flow and may enhance forearm endurance performance. As such, a double-blind, randomized crossover design study with 12 participants performed submaximal intermittent contractions (at 40% maximal voluntary contraction) to failure after a 7-day intake of 600 mg/day NZBC extract or placebo. Minimum tissue saturation index (TSI%) was assessed during the contractions. During recovery, time to half recovery of TSI% and brachial artery blood flow were assessed. There was no difference in time to exhaustion between NZBC and placebo. Minimum TSI% was lower with NZBC extract (43 ± 8 vs. 50 ± 11 TSI%; p = .007; Cohen's d = 1.01). During recovery, there was no effect on brachial artery blood flow. However, time to half recovery was faster with NZBC (26 ± 17 vs. 42 ± 26 s; p = .001; Cohen's d = 1.3) following exhaustive contractions. Seven days of NZBC extract appears to improve muscle oxygenation during and following contractions with no change in either arterial blood flow or forearm endurance performance.