Effect of New Zealand Blackcurrant Extract on Cycling Performance and Substrate Oxidation in Normobaric Hypoxia in Trained Cyclists

sports Article Effect of New Zealand Blackcurrant Extract on Cycling Performance and Substrate Oxidation in Normobaric Hypoxia in Trained Cyclists Mark Elisabeth Theodorus Willems 1, * , Mehmet Akif Şahin 1,2 , Tim Berendsen 1,3 and Matthew David Cook 1,4 1 2 3 4 * Institute of Sport, University of Chichester, College Lane, Chichester PO19 6PE, UK; (M.A.Ş.); (T.B.); (M.D.C.) Department of Nutrition and Dietetics, Faculty of Health Sciences, Hacettepe University, Sihhiye, 06100 Ankara, Turkey Human Movement Sciences, Faculty of Health, Medicine and Life Sciences, Maastricht University, 6229 ET Maastricht, The Netherlands School of Sport and Exercise Science, University of Worcester, Henwick Grove, Worcester WR2 6AJ, UK Correspondence: Received: 20 February 2019; Accepted: 13 March 2019; Published: 16 March 2019



 Abstract: New Zealand blackcurrant (NZBC) extract enhanced exercise-induced fat oxidation and 16.1 km cycling time trial (TT) in normobaric normoxia. The effect of NZBC extract on physiological and metabolic responses was examined during steady state cycling and a 16.1 km TT in normobaric hypoxia. This study used a randomized, double-blind, crossover design. Eleven healthy male cyclists (age: 38 ± 11 y, height: 179 ± 4 cm, body mass: 76 ± 8 kg, V̇O2max : 47 ± 5 mL·kg−1 ·min−1 , mean ± SD) ingested NZBC extract (600 mg·day−1 CurraNZ®containing 210 mg anthocyanins) or a placebo (600 mg microcrystalline cellulose M102) for seven days (washout 14 days) and performed a steady state cycling test (3 × 10 min at 45%, 55% and 65% V̇O2max ) followed by a 16.1 km TT at a simulated altitude of ~2500 meters (~15% of O2 ). Indirect calorimetry was used to measure substrate oxidation during steady state cycling. Intake of NZBC extract had no effect on blood glucose and lactate, heart rate, substrate oxidation, and respiratory exchange ratio during steady state cycling at 45%, 55% and 65% V̇O2max , and on 16.1 km TT performance (placebo: 1685 ± 92 s, NZBC extract: 1685 ± 99 s, P = 0.97). Seven days intake of New Zealand blackcurrant extract does not change exercise-induced metabolic responses and 16.1 km cycling time trial performance for moderately endurance-trained men in normobaric hypoxia. Keywords: time trial; substrate oxidation; hypoxia; anthocyanins; indirect calorimetry; New Zealand blackcurrant; sports nutrition 1. Introduction Blackcurrant is a berry with high nutritional value and many health benefits [1]. The nutritional value and health benefits are obtained from the polyphenol content of the blackcurrant, consisting primarily of the anthocyanins delphinidin-3-O-rutinoside, delphinidin-3-O-glucoside, cyanidin-3-O-rutinoside and cyanidin-3-O-glucoside [2]. Anthocyanins provide the blackcurrant with antioxidant and anti-inflammatory effects. Other nutritional ergogenic aids with polyphenol content, such as Montmorency tart cherry, chokeberry and pomegranate have recently provided observations with applications for sport and exercise [3–5]. In the case of blackcurrants, a seven-day intake of New Zealand blackcurrant extract improved 16.1 km cycling time trial performance by 2.6% in endurance-trained male cyclists [6]. In addition, Sports 2019, 7, 67; doi:10.3390/sports7030067 www.mdpi.com/journal/sports Sports 2019, 7, 67 2 of 9 the intake of blackcurrant increased blood flow in the forearm after venous occlusion at rest by 22% (i.e., relative to pre-values) during typing [7] and a larger femoral artery diameter by about 6–8% was observed during a 2-min 30% isometric contraction of knee extensors [8]. An increased blood flow may provide better oxygenation of skeletal muscles, as well as improved clearance of muscle metabolites associated with exercise-induced fatigue [9]. In general, vasodilation is associated with a release of nitric oxide (NO) from the endothelium. Blackcurrant juice concentrate activated endothelial NO synthase via the Akt/PI3 kinase pathway in human umbilical vein endothelial cells [10]. In support, Nakamura et al. [11] observed endothelium-dependent relaxation of contracted rat aortic rings with exposure to blackcurrant concentrate. Caution is required to generalize results from in vitro studies, however the high anthocyanin intake in women was associated with lower arterial stiffness and central blood pressure [12], which suggests beneficial cardiovascular effects from regular the intake of anthocyanins. Many studies have metabolic, physiological and cardiovascular observations with a seven-day intake of New Zealand blackcurrant during exercise and at rest in normobaric normoxic conditions [6,8,13–17]. For example, New Zealand blackcurrant extract enhanced whole-body fat oxidation during cycling in males and females [6,13,16] and increased 16.1 km time-trial performance [6]. However, exercise at altitude affects energy metabolism and fatigue of skeletal . muscles [18], for example maximum oxygen uptake (VO2max ) and power output decrease with altitude. The physiological mechanism behind the decrease in exercise performance at altitude depends mainly on the lower partial pressure of oxygen. A larger role for metabolic processes that lead to the accumulation of fatigue related metabolites (i.e., ADP, Pi and H+ ) may contribute to reduced exercise performance in hypoxic environments [18]. In addition, exercise in a hypoxic environment may provide higher levels of oxidative stress [19] and affect exercise-induced fatigue, with blackcurrant having the ability to reduce exercise-induced oxidative stress [20]. The hypoxia-induced fatigue mechanisms may be attenuated by the intake of blackcurrant. The effects of an anthocyanin-rich berry supplement on metabolic, physiological and performance responses during cycling at altitude is not known. Therefore, the primary aim of the present study was to examine the effect of New Zealand blackcurrant extract on the 16.1 km cycling time-trial performance in normobaric hypoxia. This study also examined whether there was an effect of New Zealand blackcurrant extract on the physiological and metabolic responses during low and moderate intensity cycling in normobaric hypoxia. 2. Materials and Methods 2.1. Participants and Study Design Eleven healthy male cyclists and triathletes between the ages of 18 and 55 years provided written informed consent for voluntary participation in the study. Participants were recruited from local triathlon and cycling clubs and their characteristics are presented in Table 1. Participants were required to have at least three years membership, were not involved in a training program, cycled for 8–10 h per week and were able to complete the 16.1 km cycling time trial in less than 40 min. None of the participants were required to have a washout period because of taking other supplements. The University of Chichester Research Ethics Committee approved the study (approval number: 1819_06). All procedures were conducted in accordance with the 2013 Declarat (...truncated)