Ingestion of Carbohydrate Prior to and during Maximal Sprint Interval Cycling Has No Ergogenic Effect: A Randomized, Double-Blind, Placebo Controlled, Crossover Study

Carbohydrate (CHO) ingestion may improve intermittent sprint performance in repeated sprint e orts 15 s. Yet, evidence for its e cacy on sprint interval durations ~30 s is lacking. The purpose of this study was to investigate the e ects of CHO ingestion on maximal sprint interval exercise. Fifteen (n=15) recreational athletes (13/2 males/females, age 22 2 years; height 176 11 cm; mass 76.8 11.3 kg) volunteered for this randomised, double-blind, placebo-controlled, crossover design. Participants completed two experimental trials (performed 10-days apart) involving the ingestion of an 8% CHO solution or a avour and appearance-matched placebo (PLA) solution (5 mL/kg/bw), immediately before exercise, and preceding the second interval of four 30 s bouts of repeated maximal sprint e orts (separated by 3.5 min of passive recovery). Peak and mean power (W) output progressively decreased during the repeated sprints (main e ect of time,p<0.0001), but there were no di erences between CHO and PLA during any of the sprints (p>0.05 for condition main e ect and condition time interaction). Physiological responses (blood lactate, heart rate, oxygen consumption, respiratory exchange ratio and RPE) were also unaltered by CHO ingestion. In conclusion, CHO ingestion does not enhance performance or modulate physiological responses during intermittent maximal, sprint cycling. Keywords:anaerobic; ergogenic aid; solution; substrate utilisation 1. Introduction It is well documented that acute carbohydrate (CHO) supplementation can enhance exercise performance across a range of exercise intensities and durations [1,2]. For example, CHO ingestion can help preserve blood glucose concentrations and augment rates of glucose oxidation in the later stages of prolonged exercise, when glycogen stores in skeletal muscle and liver are depleted [3]. It has also been shown that performance during shorter, higher intensity continuous exercise [2], and during high-intensity intermittent running

range of exercise intensities and durations [1,2]. For example, CHO ingestion can help preserve blood glucose concentrations and augment rates of glucose oxidation in the later stages of prolonged exercise, when glycogen stores in skeletal muscle and liver are depleted [3]. It has also been shown that performance during shorter, higher intensity continuous exercise [2], and during high-intensity intermittent running [4–6] can be enhanced with carbohydrate supplementation compared to a placebo. Yet, less is known about CHO supplementation during maximal sprint interval exercise (SIE). SIE is the performance of exercise at an `all-out' or `supramaximal' e ort, separated by periods of active or passive recovery [7], and has been shown to be a potent stimulus to promote whole-body and skeletal muscle oxidative adaptations in both recreationally active and highly trained populations [8–11]. There is evidence to suggest that both exercise intensity and exercise volume are the two primary components in modulating increases in aerobic adaptations, such as mitochondrial content, through high intensity interval training [7,12]. Therefore, and rstly from a training perspective, there is the potential Nutrients2020,12, 2223; doi:10.3390 /nu12082223 /journal/nutrients

Nutrients2020,12, 2223 2 of 12 that the addition of exogenous CHO prior to or during sprint interval exercise may: allow an individual to exercise to exercise more intensely (rate of work done), or similarly, complete more work within a speci ed timeframe (i.e., greater volume of work completed). If this greater exercise intensity/volume is repeated over a sustained period of training, this could potentially lead to superior physiological adaptations, such as skeletal muscle oxidative capacity, . VO2 max and endurance performance capacity [12–14]. Secondly, from a performance perspective, there are several sports/events, such as high performance cycling, where maximising the amount of work done (i.e., mean power output) can lead to improved performance outcomes [15,16]. Eight out of the 28 Union Cycliste Internationale (UCI) championship races are all-out sprint events, with four events decided upon by nal sprint e orts, and two events requiring repeated sprints. As such, sprint ability is a major performance determinant for many events [17]. To date, there are only a few studies that have investigated the e ects of CHO ingestion (prior to and during exercise) on repeated maximal SIE performance and associated physiological responses. These previous studies have reported a bene cial e ect of acute CHO ingestion on repeated sprint performance versus placebo [18], versus CHO and ca eine combined [19], and versus CHO mouth rinse [20] conditions. Previous recommendations have been made to suggest CHO ingestion may have an ergogenic e ect on exercise durations lasting a minimum 45–60 min [21], and that ergogenic e ects of CHO of exercise durations lasting 30–75 min can be mediated via the nervous system using CHO mouth-rinse strategies [2,21]. More recently, it has been demonstrated that the ingestion of 120 g/h of CHO can attenuate internal exercise load and also improve post-exercise recovery, by reducing exercise-induced muscle damage following a trail marathon [22,23]. However, such recommendations have been made in the context of continuous, time-trial or intermittent team sport type performance tests, and have not considered repeated, maximal e orts of a shorter total duration. Each of the three aforementioned SIE studies reporting an ergogenic

internal exercise load and also improve post-exercise recovery, by reducing exercise-induced muscle damage following a trail marathon [22,23]. However, such recommendations have been made in the context of continuous, time-trial or intermittent team sport type performance tests, and have not considered repeated, maximal e orts of a shorter total duration. Each of the three aforementioned SIE studies reporting an ergogenic e ect of CHO ingestion employed a variety of di erent maximal SIE protocols, including 5 15 s maximal sprints interspersed with 4 min of active recovery [20], 6 5 s maximal sprints interspersed with 25 secs passive recovery [18], and 10 sets of5 4 ssprints with 20 s active recovery between sprints, and 2 min between sets [19]. Therefore, the total session durations of these protocols were 17.25 min, 2.5 min and 34.66 min respectively, with extremely low actual exercise durations of 75 s, 30 s and 200 s, respectively. These studies therefore highlight the potential of CHO ingestion as an ergogenic aid in exercise durations of considerably less than 30 min. Moreover, there are a multitude of di erent protocol designs used during SIE, which are likely re ective of the intent to induce di erent (acute) physiological stresses, through altering the contribution of the ATP-PC, glycolytic and aerobic energy systems (and therefore accrual of di erent metabolites and enzymes involved from said systems [24–26]), ultimately, for either adaptive or performance replication outcomes. However, possibly the most frequently used SIE protocol for anaerobic/aerobic training involves several consecutive 30 s maximal e orts, separated by 3 min of passive recovery [8,10,11,14]. In terms of performance, 30 s all out e orts re ect speci c cycling sprint durations in the Team Sprint (M2 rider), Women's 500 m time trials, and the nal sprint in the Keirin. To date, no studies have investigated the role of CHO supplementation with interval durations of 30 s. The purpose of the present investigation was to assess the e ects of acute CHO supplementation during repeated, longer duration, maximal sprint interval exercise, on indices of cycling performance and associated physiological responses. 2. Materials and

and the nal sprint in the Keirin. To date, no studies have investigated the role of CHO supplementation with interval durations of 30 s. The purpose of the present investigation was to assess the e ects of acute CHO supplementation during repeated, longer duration, maximal sprint interval exercise, on indices of cycling performance and associated physiological responses. 2. Materials and Methods 2.1. Participants Fifteen physically active males (n=13) and females (n=2) (mean SD: age: 22 2 yrs; height: 176 11 cm; mass: 76.8 11.3 kg, BMI 24.7 2.4 kg/m 2 ) volunteered to participate in the study, and were recruited from the local university campus using posters, e-mails and word of mouth. To be

Nutrients2020,12, 2223 3 of 12 eligible for the study, individuals must have been aged between 18–39 years old, and had to participate in moderate intensity physical activity at least 2–3 times per week. All participants took part in recreational athletic endeavours, e.g., university or amateur club level sports. Self-reported activity levels of participants were 2–3 training sessions of moderate-high intensity activity lasting ~90 min each per week, in addition to 1–2 competitive matches per week. This varied slightly depending on each individual participant's sport and point in their relative competitive season. Exclusion criteria included not having any musculoskeletal or neurological disorders, free from injury and not currently supplementing with any ergogenic aids either 3 months prior to or during the study. Following a pre-screening physical activity questionnaire to ensure eligibility, participants were provided with information sheet, outlining the full experimental procedure and risks involved. All participants gave their written informed consent to participate. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ulster University School of Sport Ethics Committee (MSc321 2018–2019). 2.2. Study Design The study utilised a double-blind, placebo-controlled, randomised, cross-over design, with two experimental conditions: carbohydrate supplementation and placebo. Participants each visited the laboratory on two occasions to perform a bout of SIE (4 30 s maximal sprints). All participants self-reported as being familiar with SIE through routine training in their sports. Ten minutes prior to and during the bout of SIE, participants consumed either a carbohydrate solution or a placebo (described below). The order of conditions was randomised with ~10 days washout between the two trials. All participants were instructed to refrain from exercise 48 h prior to their lab visit and to abstain from alcohol and ca eine for 24 h before testing. All participants verbally con rmed on the morning of the trial that they avoided exercise for 48 h and consumption of alcohol and ca eine for 24 h. Participants were asked to maintain an identical nutritional intake 24 h before each visit to the lab, with participants' last food intake (breakfast) ~3 h prior

eine for 24 h before testing. All participants verbally con rmed on the morning of the trial that they avoided exercise for 48 h and consumption of alcohol and ca eine for 24 h. Participants were asked to maintain an identical nutritional intake 24 h before each visit to the lab, with participants' last food intake (breakfast) ~3 h prior to exercise. Participants con rmed that they had maintained nutritional intakes in the 24-h period prior to exercise between trials at their second laboratory visit. The timing of each trial was standardised within and between participants, and the lab conditions were similar (temperature between 19–21 C) during each visit. A member of the research team prepared each of the solutions and provided them to the participants, rea rming the ingestion instructions. Neither the researcher recording/analysing performance and physiological variables, nor the participant, knew the contents of the solution. The blinding continued to the stage of statistical analysis, where the trial conditions were revealed. 2.3. Experimental Protocol Participants reported to the laboratory where physical characteristics were assessed. Height and body mass were measured using a stadiometer with integrated scales (SECA, Birmingham, UK). Body mass was recorded on each of the two laboratory visits. Participants then performed a 5 min warm-up on a cycle ergometer (Wattbike Pro, Wattbike, Nottingham, UK) at a self-selected intensity, perceived to be 10 on the Borg scale (i.e., `light/fairly light'). Pre-exercise blood lactate and heart rate were taken at rest ~3–5 min, following completion of the warm-up and approximately 1 min prior to SIE. Participants then performed four bouts of SIE, consisting of repeated maximal e ort for 30 s at a standardised air resistance of level 6, followed by 3.5 min of passive recovery following each interval. During recovery, participants were allowed to disembark the ergometer, but remain stationary beside it, with no walking etc. permitted. Participants ingested a carbohydrate solution consisting of 8% carbohydrate (100% Maltodextrin, MyProtein, THG, Manchester, UK) and a single lemon- avoured sweetener tablet per litre water (Splenda, Heartland Food Products Group, PA, USA), or a placebo consisting of water and a

interval. During recovery, participants were allowed to disembark the ergometer, but remain stationary beside it, with no walking etc. permitted. Participants ingested a carbohydrate solution consisting of 8% carbohydrate (100% Maltodextrin, MyProtein, THG, Manchester, UK) and a single lemon- avoured sweetener tablet per litre water (Splenda, Heartland Food Products Group, PA, USA), or a placebo consisting of water and a single lemon sweetener tablet per litre. The volume of solution ingested was 5 mls/kg/body mass. Exactly 50% of the solution was consumed approximately ten minutes prior to the rst interval, with the remaining solution to be ingested during the rest periods of

Nutrients2020,12, 2223 4 of 12 the rst and second interval. To reduce the possibility of participants identifying the beverage they were consuming, both condition solutions were lemon- avoured, colourless and presented in opaque bottles. An exit question was posed upon completion of the study to ascertain whether participants detected any di erences in solutions between trials. All participants reported being unable to identify any di erences between the experimental solutions. Performance and physiological measures were recorded during each sprint interval. Verbal encouragement was provided during each experimental trial, to encourage the participants to maintain maximal e ort on the cycle ergometer. Each session lasted approximately 30 min in total. 2.4. Performance Outcomes The primary outcomes of interest in this study were peak and mean power output during each 30 s sprint. Power output was measured (100 Hz) continuously during each sprint (Wattbike Pro, Wattbike, Nottingham, UK), saved, and subsequently downloaded for analysis using the WattBike Expert Software. Relative peak power output (RPPO) and relative mean power output (RMPO) were calculated by dividing the absolute power outputs by body mass. 2.5. Physiological Outcomes Physiological responses, including oxygen uptake, respiratory exchange ratio (RER), blood lactate concentrations, heart rate, and ratings of perceived exertion (RPE) were secondary outcomes of this study. 2.6. Oxygen Uptake and Respiratory Exchange Ratio To measure oxygen uptake ( . VO2 ) and RER, participants were tted with a silicone face mask connected to a metabolic cart, with an online gas analysis system to enable breath by breath analysis of expired air (Cosmed, Quark CPET, Rome, Italy). The metabolic cart was calibrated prior to each participant trial. Breath by breath measurements of . VO2 and RER were recorded from 60 s before the rst 30 s sprint and terminated upon cessation of the nal 30 s sprint. Only the data from each of the 30 s exercise intervals were analysed. 2.7. Blood Lactate Quanti cation To obtain blood lactate, an alcohol wipe (Alcotip swab, Universal Hospital Supplies, London, UK) was used to cleanse the participant's nger, and a sterile lancet (Accu Chek, Roche, Mannheim, Germany) was used to pierce

upon cessation of the nal 30 s sprint. Only the data from each of the 30 s exercise intervals were analysed. 2.7. Blood Lactate Quanti cation To obtain blood lactate, an alcohol wipe (Alcotip swab, Universal Hospital Supplies, London, UK) was used to cleanse the participant's nger, and a sterile lancet (Accu Chek, Roche, Mannheim, Germany) was used to pierce the skin of the nger to produce blood. A Lactate Pro 2 lactate strip (Arkray, KDK Corp., Shiga, Japan) collected the blood, which was then inserted into a Lactate Pro 2 TM lactate analyser (Arkray, KDK Corp., Shiga, Japan), to determine the lactate content of the participant's blood. Lactate measures were taken during the rst 30 s, following the completion of the interval. 2.8. Heart Rate and RPE Heart rate was recorded using a Polar H7 heart rate monitor (Polar, Kempele, Finland) and a Polar RS400 watch, and as taken immediately, following the cessation of the interval. RPE (rate of perceived exertion) was provided by each participant via the Borg scale, and was taken immediately following cessation of the interval. 2.9. Statistical Analysis All data were analysed using SPSS software version 25 (IBM, Armonk, NY, USA). A Shapiro–Wilk test was used to check each variable for any deviation from a normal distribution. Data were revealed to be normally distributed and parametric. A two-way (condition time) repeated measures ANOVA, with sex (male/female) included as a covariate, was applied to determine the e ect of CHO supplementation compared to placebo on performance and physiological outcomes during

Nutrients2020,12, 2223 5 of 12 SIE. If appropriate, post-hoc comparisons were analysed via paired samplet-tests with a Bonferroni correction. In order to assess potential order e ects on performance variables, a two-way (condition time) repeated measures ANOVA was applied, with trial order as the between factor [27]. Statistical signi cance was set a priori atp<0.05. The e ect size for the main e ects and interactions was estimated by calculating partial eta squared values ( p 2), with 0.01, 0.06 and 0.14 used to denote small, moderate and large e ects sizes, respectively. All data are reported as mean SD. 3. Results Participant numbers for all results aren=15, except for . VO2 and RER variables (n=13). There were no signi cant condition time interactions assessing for order e ects (p>0.05) in either of the performance variables. A pairedt-test revealed body mass was not di erent between trials (Trial 1; 77.0 11.1 Kg, Trial 2; 76.7 11.3 Kg (p>0.05). 3.1. Performance For RPPO, during the sprints, there was a main e ect of time (p<0.0001, p 2=0.85), but no e ect of condition (p=0.79, p 2=0.03), and no condition time interaction (p=0.84, p 2=0.35). RPPO progressively decreased with each repeated sprint, and this e ect did not appear to be impacted by CHO supplementation (Figure). Similarly, in terms of RMPO, there was also a main e ect of time (p<0.0001, p 2=0.83), but no e ect of condition (p=0.79, p 2=0.03) or condition time interaction (p=0.77, p 2=0.41). There were marked reductions in RMPO with each interval, however, this e ect was not altered by CHO supplementation (Figure).Nutrients 2020, 12, × FOR PEER REVIEW 5 of 12 estimated by calculating partial eta squared values (η p 2), with 0.01, 0.06 and 0.14 used to denote small, moderate and large effects sizes, respectively. All data are reported as mean ± SD. 3. Results Participant numbers for all results are n = 15, except for V ̇O 2 and RER variables (n = 13). There were no significant condition × time interactions assessing for order effects (p>0.05) in either of the performance variables.

0.14 used to denote small, moderate and large effects sizes, respectively. All data are reported as mean ± SD. 3. Results Participant numbers for all results are n = 15, except for V ̇O 2 and RER variables (n = 13). There were no significant condition × time interactions assessing for order effects (p>0.05) in either of the performance variables. A paired t-test revealed body mass was not different between trials (Trial 1; 77.0 ± 11.1 Kg, Trial 2; 76.7 ± 1 1.3 Kg (p > 0.05). 3.1. Performance For RPPO, during the sprints, there was a main effect of time (p < 0.0001, η p 2 = 0.85), but no effect of condition (p = 0.79, η p 2 = 0.03), and no condition × time interaction (p = 0.84, η p 2 = 0.35). RPPO progressively decreased with each repeated sprint, and this effect did not appear to be impacted by CHO supplementation (Figure 1). Similarly, in terms of RMPO, there was also a main effect of time (p < 0.0001, η p 2 = 0.83), but no effect of condition (p = 0.79, η p 2 = 0.03) or condition × time interaction (p= 0.77, η p 2 = 0.41). There were marked reductions in RMPO with each interval, however, this effect was not altered by CHO supplementation (Figure 2). Figure 1. (A) Comparison of r elative peak power output ( RPPO) response between INT1–4 in acute carbohydrate (CHO) and flavour and appearance-matched placebo (PLA ) trials. Data are Mean ± SD.  Significantly different to INT1 (p < 0.05); ** Significantly different to INT2 (p < 0.05) # Significantly different to INT3 (p < 0.05). (B) Aggregated RPPO across intervals. R PPO; Relative Peak Power Output. Figure 1. (A) Comparison of relative peak power output (RPPO) response between INT1–4 in acute carbohydrate (CHO) and avour and appearance-matched placebo (PLA) trials. Data are Mean SD. ySigni cantly di erent to INT1 (p<0.05); ** Signi cantly di erent to INT2 (p<0.05) # Signi cantly di erent to INT3 (p<0.05). (B) Aggregated RPPO across intervals. RPPO; Relative Peak Power

This study investigates the effects of carbohydrate ingestion on sprint interval performance.