Individual and additive effects of New Zealand blackcurrant powder and caffeine intake on high-intensity intermittent exercise performance : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Sport and Exercise Science, Massey University, Auckland, New Zealand
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2025-04-15
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Massey University
Appendix 6.1 is reproduced under a Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/
Appendix 6.1 is reproduced under a Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/
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Abstract
Background: Intake of New Zealand blackcurrant in various forms such as powdered extracted anthocyanins, juice concentrate, powdered juice concentrate, and powdered whole fruit (NZBC; containing 105-315 mg of anthocyanins) for 7 days has been shown to improve running and cycling performance and increase fat oxidation during exercise in trained athletes and recreationally active individuals. However, most studies provide the last dose during the 7-day intervention period 1-3 h before exercise, thus raising the question if the improvement in fat oxidation and performance was due to the 7-day loading phase or the acute intake. Caffeine, on the other hand, when consumed acutely, has been shown to improve repeated-sprint performance during a high-intensity intermittent running protocol. Thus, combining NZBC with caffeine may provide an additive or a synergistic effect to athletes to improve exercise performance. Similarly, evaluating the effect of a single dose of NZBC on fat oxidation may provide valuable insights on its potential to delay fatigue during exercise.
Aims: 1) To examine the acute effect of NZBC drink consumption (120 mg anthocyanins) on substrate oxidation and plasma free fatty acids (FFA) levels during mixed-intensity cycling in recreationally active males. 2) To examine the acute individual and additive effects of consumption of a NZBC drink (240 mg anthocyanins) with and without caffeine (240 mg) on sprint performance during high-intensity intermittent running in previously fatigued recreationally active males.
Methods: Fourteen recreationally active male participants were recruited for this double-blind, randomised controlled crossover trial and each participant took part in four main trials (>7-day washout between trials): placebo (PLA), placebo + caffeine (CAFF), NZBC drink, and NZBC + caffeine drink (NZBC-CAFF). Each main trial was divided into two visits across two days. On the afternoon of Day 1, participants consumed PLA or NZBC and after a 1-h wait period, completed a ~90-min cycling protocol at ~60% maximal power output. Breath-by-breath gas analysis was conducted during exercise (to measure substrate utilisation) and blood samples were taken before, during and immediately after the exercise (to measure FFA). Following cessation of exercise and post-exercise measures, participants were provided with a standardised dinner and reported to the laboratory the next morning after completing >8-h fast. On the morning of Day 2, participants consumed a standardised breakfast and one of the four experimental beverages. Following a 1-h wait period, participants undertook a 10-min standardised warm-up and then completed the modified Loughborough Intermittent Shuttle-Test (m-LIST) – a validated test designed to replicate the demands of intermittent team sports like football (soccer) and rugby. The m-LIST included 4 x 15-min “paced” intermittent exercise blocks (movement dictated by pre-determined audible “beeps”), followed by 2 x 15-min “prescribed” intermittent exercise blocks (movement at their own pace). Various performance metrics including sprint speed, maximum speed, and distance covered were measured during exercise using sprint timing gates and insole-embedded inertial measurement units. Blood samples were taken before, during, and after the m-LIST to evaluate serum FFA concentration and blood lactate was measured every 15 min before, during and following the m-LIST.
Results: Consumption of the NZBC drink had no effect on substrate oxidation during the mixed-intensity cycling protocol. There were no differences in oxygen consumption, fat oxidation, carbohydrate oxidation, and serum FFA concentration with the intake of PLA and NZBC during the trial. There was an effect of treatment on average sprint speed (p = 0.049, η² = 0.259), with NZBC-CAFF and CAFF sustaining higher average sprint speeds from blocks 1 to 6 compared to other treatments during the m-LIST protocol. However, the sprint speed reduced significantly for all four treatments as the trial progressed from blocks 1 to 6 (p = 0.032, η² = 0.341). We also observed a higher peak deceleration with CAFF treatment compared to NZBC (p = 0.038) during the m-LIST protocol. Blood lactate concentrations were higher with NZBC-CAFF treatment compared to PLA (p = 0.038) and NZBC-CAFF was the only treatment in which serum FFA concentration kept increasing 1-h post exercise (p = 0.042 and η² = 0.214).
Conclusion: Ingestion of a single drink of reconstituted NZBC powder containing 120 mg anthocyanins had no effect on substrate oxidation and serum FFA concentration during mixed-intensity cycling in recreationally active males. Intake of caffeine with and without NZBC improved sprint performance when consumed, whereas consumption of the NZBC drink alone did not offer similar benefits. Previous studies indicated that the intake of NZBC for 7 days may enhance sprint and time to exhaustion performance, however, the current study's focus on acute effects did not show ergogenic properties on sprint and exercise performance during high-intensity exercise. The increase in serum FFA concentrations with the intake of NZBC-CAFF drink after high-intensity intermittent exercise highlights the need for investigating different markers such as glycerol and β-hydroxybutyrate before, during, and after exercise to provide further insights on fat metabolism. More research is needed to understand the mechanism of action and metabolic consequences of NZBC intake during moderate and high-intensity intermittent exercise.
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New Zealand blackcurrant, caffeine, sprint performance, exercise metabolism, sports nutrition, anthocyanins