Carbohydrate (CHO) supplementation during endurance exercise can improve performance. However, it is unclear whether low glycemic index (GI) CHO leads to differential ergogenic and metabolic effects compared with a standard high GI CHO. This study investigated the ergogenic and metabolic effects of CHO supplementation with distinct GIs, namely, (a) trehalose (30 g/hr), (b) isomaltulose (30 g/hr), (c) maltodextrin (60 g/hr), and (d) placebo (water). In this double-blind, crossover, counterbalanced, placebo-controlled study, 13 male cyclists cycled a total of 100 min at varied exercise intensity (i.e., 10-min stages at 1.5, 2.0, and 2.5 W/kg; repeated three times plus two 5-min stages at 1.0 W/kg before and after the protocol), followed by a 20-min time trial on four separated occasions. Blood glucose and lactate (every 20 min), heart rate, and ratings of perceived exertion were collected throughout, and muscle biopsies were taken before and immediately after exercise. The results showed that trehalose improved time-trial performance compared with placebo (total work done 302 ± 39 vs. 287 ± 48 kJ; p = .01), with no other differences between sessions (all p ≥ .07). Throughout the 100-min protocol, blood glucose was higher with maltodextrin compared with the other supplements at all time points (all p < .05). Heart rate, ratings of perceived exertion, muscle glycogen content, blood glucose, and lactate were not different between conditions when considering the 20-min time trial (all p > .05). Trehalose supplementation throughout endurance exercise improved cycling performance and appears to be an appropriate CHO source for exercise tasks up to 2 hr. No ergogenic superiority between the different types of CHO was established.

Objectives: This study investigated the effects of the menstrual cycle phases on cortisol levels before and after a maximal incremental exercise test in women with and without premenstrual syndrome (PMS). Methods: Nineteen healthy, active and eumenorrheic women completed five maximal incremental exercise tests; three of those were performed at specific phases of the menstrual cycle (i.e., menses, follicular, and luteal). The participants were allocated into two groups according to the presence of PMS (n = 11) or absence of PMS (NO-PMS, n = 8). Samples of blood were collected before and after each experimental test. A three-way ANOVA was conducted to compare the differences between menstrual cycle phases (i.e., menses, follicular, and luteal), time (before and after) and groups (PMS and NO-PMS). Results: The results demonstrated an alteration of cortisol across the menstrual cycle, with cortisol levels significantly (p < 0.05) higher during the follicular phase (mean = 11.0 µg/dL, CI95% = 9.1, 12.9) compared to the luteal phase (mean = 8.6 µg/dL, CI95% = 7.2, 10.4) in the PMS and NO-PMS groups. There was no difference (p > 0.05) in cortisol levels for groups or time. Conclusions: This study observed significant cortisol fluctuations across the menstrual cycle phases in women with and without PMS. Future studies should consider alternative maximal incremental test protocols and incorporate a more comprehensive hormonal profile to provide a deeper physiological understanding of this population.

The primary role of creatine is to facilitate rapid ATP regeneration during moments of intense metabolic demand (i.e., high-intensity exercise). Since creatine supplementation can increase intramuscular and brain creatine content, this has important implications for exercise and cognitive performance. Creatine appears particularly effective to improve strength training and short bursts of single- or repeated-bout high metabolic demand exercise (e.g., sprints), while there is also performance-enhancing potential during endurance exercise performance. These characteristics make it a supplement of interest for cyclists. Since creatine is a safe supplement, cyclists may wish to implement specific supplementation strategies based upon their needs to benefit from this nutritional supplement. This chapter discusses the evidence in respect of dosing regimen (dose and timing), side effects, and the effects on exercise performance. <!----> <!----> <!----> <!---->

Objectives: To investigate whether wearing a cloth facemask could affect physiological and perceptual responses to exercise at distinct exercise intensities in non-trained men and women. Methods: In a crossover design, participants (17 men and 18 women) underwent a progressive square-wave test at four intensities (i. at 80% of the ventilatory anerobic threshold [80%VAT]; ii. at VAT; iii. at the respiratory compensation point [RCP]; iv. at exercise peak [Peak] to exhaustion), with or without a triple-layered cloth mask (Mask or No-Mask). Several physiological, metabolic and perceptual measures were analyzed. Results: Mask reduced inspiratory capacity at all exercise intensities vs. No-Mask (p<0.0001), irrespective of sex. Mask reduced respiratory frequency vs. No-Mask (p=0.001) at Peak (−8.3 breaths·min ^-1 ; CI: -5.8, -10.8), RCP (−6.9 breaths·min ^-1 ; CI: -4.6, -9.2) and VAT (−6.5 breaths·min ^-1 ; CI: -4.1, -8.8), but not at Baseline or at 80%VAT. Mask also reduced tidal volume (p<0.0001) at both RCP (−0.5L; CI: -0.3, -0.6) and Peak (−0.8L; CI: -0.6, -0.9), but not at Baseline, 80%VAT or VAT. Shallow breathing index was increased with Mask at Peak compared to No-Mask (11.3; CI: 7.5, 15.1), but not at any other intensities. Mask did not change heart rate, lactate, ratings of perceived exertion, blood pressure or oxygen saturation. Conclusions: Wearing a cloth facemask during exercise at moderate to heavy intensities is unlikely to incur significant respiratory or cardiovascular changes, irrespective of sex. These data can inform new exercise recommendations for health during the COVID-19 pandemic and debunk unfounded allegations of harmful effects of masks during exercise. ClinicalTrials.gov : NCT04887714 What are the new findings?: ✓ Using a progressive square-wave test, we showed that wearing a cloth facemask during exercise increased breathing difficulty, but this was dependent upon the exercise intensity. ✓ Respiratory variables (e.g., inspiratory capacity, respiratory frequency, shallow breathing index) were affected at higher rather than lower intensities. ✓ Mask wearing did not change heart rate, lactate, ratings of perceived exertion, blood pressure or oxygen saturation at any exercise intensity. ✓ There were no substantial sex differences on the effects of mask wearing during exercise. How might it impact on clinical practice in the future?: ✓ These data can debunk unfounded allegations on harmful effects of masks during exercise, and help inform new exercise recommendations for health during the COVID-19 pandemic, particularly where facemasks remain necessary.

Introduction: The CYP1A2 -164 A>C single nucleotide polymorphism (SNP) has been identified as a possible factor influencing the exercise responses to caffeine. Methods: Six databases were searched for studies determining the effect of caffeine (except mouth rinsing) on exercise between CYP1A2 genotypes. Three-level meta-analyses were performed using standardized mean differences (SMD; Hedge’s g) to determine the effect of caffeine on exercise outcomes within and between CYP1A2 genotypes (AA, AC, CC). Meta-regressions were performed for dose, timing, and for the presence of conflict of interests (COI). Results: Thirteen studies, totalling 119 outcomes and 440 participants were included (233 AA, 175 AC, 34 CC). Caffeine improved performance for AAs (SMD=0.30, 95%CI: 0.21; 0.39, p<.0001) and ACs (SMD=0.16, 95%CI: 0.06; 0.25, p=0.022), but was ergolytic for CCs (SMD=-0.22, 95%CI: -0.44; -0.01, p<.0001). Dose affected only CCs, with greater doses generating larger responses (CC*dose: +0.19/1 mg/kg BM, 95%CI: 0.04; 0.33, p = 0.01). Timing influenced only CCs, with larger SMDs with later onset of exercise after supplementation (CC*timing: +0.01/minute, 95%CI: 0.00; 0.02, p = 0.02). COI only affected CCs (CC*COI: -0.57, 95%CI: -1.02; -0.12, p=0.01), and after excluding studies with COI, no influence of CYP1A2 genotype was seen (all p≥0.19). Conclusion: Caffeine improved performance for AAs and ACs, worsening performance for CCs. Dose and timing moderated the efficacy of caffeine for CCs alone. Caution is advised since studies with COI appear to heavily influence these results.

Sports supplements composed of carbohydrate and protein are widely used by endurance athletes and recreational practitioners, mostly aimed at improving performance. This study investigated the effect of a novel carbohydrate + protein honey powder (HP) product on endurance cycling performance and physiological and perceptual responses using a double-blind, crossover, counterbalanced, placebo-controlled (PLA) design. Twelve male cyclists exercised for 100 min (i.e., 5 min at 1 W/kg of body mass, followed by three sets of 10-min stages at 1.5, 2.0, and 2.5 W/kg, followed by 5 min at 1 W/kg), followed by a 20-min self-paced time trial (20-min TT). Blood glucose, lactate, pH, bicarbonate, heart rate, ratings of perceived exertion, and side effects were analyzed throughout the 100-min cycling protocol and the 20-min TT. The 20-min TT performance was similar between HP and PLA (total work done: 294 ± 40 vs. 292 ± 44 kJ, p = .72; mean power output: 245 ± 33 vs. 243 ± 37 W, p = .61), as was blood glucose, lactate, pH, and ratings of perceived exertion either during the 100 or 20-min TT protocols (all p > .05). Blood bicarbonate was lower in HP compared with PLA throughout the 100-min protocol ( p = .01), and heart rate was higher in HP compared with PLA during the 20-min TT ( p = .01). Finally, HP supplementation did not elicit greater side effects compared with PLA, either during the 100 or the 20-min TT protocols (all p > .05). This novel HP supplement did not improve endurance performance in this study, though future research with higher doses is encouraged.