Min Of Constant-load Cycling Research Articles

Oxidative Stress in Endurance Cycling Is Reduced Dose-Dependently after One Month of Re-Esterified DHA Supplementation.

Docosahexaenoic acid (DHA) supplementation can reduce exercise-induced oxidative stress generated during long aerobic exercise, with the minimum dose yet to be elucidated for physically active subjects. In this study, we performed a dose finding with re-esterified DHA in triglyceride form in a randomized double-blind parallel trial at different doses (350, 1050, 1750, and 2450 mg a day) for 4 weeks in males engaged in regular cycling (n = 100, 7.6 ± 3.7 h/week). The endogenous antioxidant capacity of DHA was quantified as a reduction in the levels of the oxidative stress marker 8-hydroxy-2′-deoxyguanosine (8-OHdG) recollected in 24-h urine samples after 90 min of constant load cycling before and after intervention. To ascertain incorporation of DHA, erythrocyte polyunsaturated fatty acid (PUFA) composition was compared along groups. We found a dose-dependent antioxidant capacity of DHA from 1050 mg with a trend to neutralization for the highest dose of 2450 mg (placebo: n = 13, F = 0.041; 350 mg: n = 10, F = 0.268; 1050 mg: n = 11, F = 7.112; 1750 mg: n = 12, F = 9.681; 2450 mg: n = 10, F = 15.230). In the erythrocyte membrane, the re-esterified DHA increased DHA and omega-3 percentage and decreased omega 6 and the omega-6 to omega-3 ratio, while Eicosapentaenoic acid (EPA) and PUFA remained unchanged. Supplementation of re-esterified DHA exerts a dose-dependent endogenous antioxidant property against moderate-intensity long-duration aerobic exercise in physically active subjects when provided at least 1050 mg a day for 4 weeks.

Dyspnea on exertion provokes unpleasantness and negative emotions in women with obesity

PurposeWhile dyspnea on exertion (DOE) is a common complaint in otherwise healthy obese women, less is known about feelings of unpleasantness and/or negative emotions provoked by DOE. We examined whether ratings of perceived breathlessness (RPB) during exercise were associated with ratings of unpleasantness and negative emotions (depression, anxiety, frustration, anger, and fear) in obese women. MethodsSeventy-four women (34 ± 7 yrs, 36 ± 4 kg/m2, 46 ± 5% body fat) performed 6 min of constant-load cycling (60 W); RPB (0–10 scale), and unpleasantness and negative emotions (visual analog scales, 10 cm) were assessed at the end. ResultsRPB were significantly correlated with unpleasantness and negative emotions (p < 0.05). The strongest correlations were between RPB and unpleasantness (r = 0.61, p < 0.001), and RPB and anxiety (r = 0.50, p < 0.001). ConclusionsDOE can significantly provoke unpleasantness and negative emotions during exercise in obese women. This may affect their willingness to engage in regular physical activity.

Influence Of Carbohydrate Intake On Pacing Changes During Prolonged Cycling

PURPOSE: The effects of carbohydrate intake on temporal changes in power output during cycling were examined. METHODS: Eight male cyclists (VO2max: 62 ± 6 mL[BULLET OPERATOR]kg-1[BULLET OPERATOR]min-1) completed two trials consisting of 120 min of constant load cycling at 55% Wmax, followed by a simulated 30 km time trial (TT). Subjects consumed 150 ml of a glucose-fructose solution (CHO) or a non-caloric placebo (PL) every 15 minutes during the constant-load portion of the trial, and at 7.5 km intervals during the TT. Average power output during the TT was compared between treatments, and changes in power output within trials were examined across four segments of the TT (S1 = 0-7.5 km, S2 = 7.5-15 km, S3 = 15-22.5 km, and S4 = 22.5-30 km). Power output was also averaged for three minutes immediately before and after each feeding, to determine if changes in pacing between treatments were influenced by the proximity to CHO feedings. Magnitude-based qualitative inferences were used to evaluate differences between treatments and/or time-points. RESULTS: Average TT power output during the CHO trial (242 ± 30 W) was ‘likely’ greater than PL (217 ± 40 W). In the PL trial, cycling power ‘almost certainly’ decreased between S1 (235 ± 41 W) and S2 (223 ± 38 W), and ‘likely’ decreased further during S3 (201 ± 41 W). Subsequently, cycling power ‘very likely’ increased between S3 and S4 (219 ± 43 W), but remained lower than S1 levels. By contrast, power output during the CHO trial showed no clear changes from S1 (246 ± 41 W) to S2 (242 ± 28 W). Thereafter, power output ‘possibly’ decreased during S3 (232 ± 27 W), followed by a ‘likely’ increase in power during S4 (249 ± 32 W), resulting in power levels during S4 that were similar to S1. Power output during the period immediately following each PL ingestion (210 ± 40 W) was not clearly different from the period prior to PL ingestion (213 ± 39 W); whereas power output immediately following CHO ingestion (244 ± 27 W) was ‘possibly’ increased versus pre-ingestion (236 ± 31 W). CONCLUSIONS: CHO ingestion increased average power output during a cycling TT and attenuated declines in power output over the duration of the trial, compared to PL. In addition, improvements in power output with CHO were possibly greater in the periods immediately following each feeding, potentially due to effects of CHO on the central nervous system.

Sex, Lungs, And Forced Expiratory Flows

Women display lower maximal, forced expiratory flows (FEFs) across the vital capacity range compared with height- and age-matched men. This sex-difference on FEFs is believed to increase the prevalence of ventilatory constraint in women compared with men at a given ventilation during exercise. It remains unclear whether this sex-difference in FEFs is evident when absolute lung size is taken into account. Purpose: To investigate the influences of sex, TLC and residual volume on FEFs at rest, and during exercise in healthy adults. METHODS: Forty-seven untrained adults (24 women; 29 ± 6 yrs) with normal pulmonary function (>90% pred.) participated in this study. Subjects completed 9 min of constant-load cycling at 75% of the peak work rate achieved during an incremental cycling test. TLC and RV were obtained at rest and at the end of exercise using He-dilution, and inspiratory and forced vital capacity manoeuvres. FEFs were obtained at 25, 50 and 75% of vital capacity (FEF25%, FEF50% and FEF75%, respectively). Multivariate analyses of covariance (MANCOVA) were used to examine the effect of sex on FEFs after controlling for RV and TLC. RESULTS: Height, TLC and RV were larger for men than women (P < 0.05), as expected. The TLC to height ratio was greater in men than women (45 ± 9 ml·cm-1 v 35 ± 5 ml·cm-1, P < 0.05). FEFs increased during exercise for both sexes (P < 0.05), suggesting bronchodilation. The MANCOVA revealed a main-effect of sex on FEFs at rest and during exercise, where FEFs were systematically higher for men than women (P < 0.05). Importantly, however, the main-effect of sex on FEFs disappeared when TLC and RV were entered into the model as covariates. CONCLUSIONS: The differences in FEFs of our subjects could not be explained on the basis of sex alone. Instead, our analyses suggests that FEFs appear similar between young men and women if one controls for static lung volumes - a result that was also observed in the presence of exercise-induced bronchodilation. Thus, the higher prevalence of ventilatory constraint during exercise in women compared with height-matched men is likely the result of women having a smaller TLC relative to their height, as opposed to a sexual dimorphism in airway size/caliber for a given lung size (dysanapsis). Supported by NIH Grant HL71478

Effects of high-intensity intermittent priming on physiology and cycling performance

The pre-event warm-up or “priming” routine for optimising cycling performance is not well-defined or uniform to a specific event. We aimed to determine the effects of varying the intensity of priming on 3 km cycling performance. Ten endurance-trained male cyclists completed four 3 km time-trials (TT) on four separate occasions, each preceded by a different priming strategy including “self-selected” priming and three intermittent priming strategies incorporating 10 min of constant-load cycling followed by 5 × 10 s bouts of varying relative intensity (100% and 150% of peak aerobic power, Wpeak, and all-out priming). The self-selected priming trial (379 ± 44 W) resulted in similar mean power during the 3 km TT to intermittent priming at 100% (376 ± 45 W; −0.7%; unclear) and 150% (374 ± 48 W; −1.5%, unclear) of Wpeak, but significantly greater than all-out priming (357 ± 45 W; −5.8%, almost certainly harmful). Differences between intermittent and self-selected priming existed with regards to heart rate (6.2% to 11.5%), blood lactate (−22.9% to 125%) and VO2 kinetics (−22.9% to 8.2%), but these were not related to performance outcomes. In conclusion, prescribed intermittent priming strategies varying in intensity did not substantially improve 3 km TT performance compared to self-selected priming.

Cycling time trial performance may be impaired by whey protein and L-alanine intake during prolonged exercise.

Previous studies reported that adding protein (PRO) to carbohydrate (CHO) solutions enhances endurance performance. The ergogenic effect may be a function of additional protein/amino acid calories, but this has not been examined. In addition, although supplemental L-alanine (ALA) is readily oxidized during exercise, the subsequent impact on metabolism and prolonged endurance performance is unknown. The purpose of this investigation was to independently gauge the impact of whey PRO hydrolysate and ALA supplementation on performance and various physiological parameters. Eight cyclists (age: 22.3 ± 5.6 yr, weight: 70.0 ± 8.0 kg, VO2max: 59.4 ± 4.9 ml · kg(-1) · min(-1)) performed 120 min of constant-load cycling (55% of peak power) followed by a 30-km time trial (TT) under placebo (PLA), PRO, and ALA conditions. Magnitude-based qualitative inferences were applied to evaluate treatment differences and data are presented as percent difference between treatments ± 90% confidence limit. Both ALA (2.1 ± 2.7%) and PRO intake (-2.1 ± 2.2%) possibly harmed performance compared with PLA. Of interest, heart rate was possibly lower with ALA than PLA at 20- (-2.7 ± 3.4%) and 120-min (-1.7 ± 2.9%) of constant-load cycling and the serum interleukin-6 (IL-6) response to 120 min of cycling was likely attenuated with PRO compared with PLA (PLA, 6.6 ± 3.7 fold vs. PRO, 2.9 ± 1.8 fold). In addition, blood glucose levels were lower with PRO than PLA at 20- (-8.8 ± 2.3%; very likely) and 120-min (-4.9 ± 4.6%; likely) of constant-load cycling. Although ALA intake appears to lower HR and PRO ingestion dampens the IL-6 response to exercise, the ingestion of PRO (without CHO) or ALA does not enhance, and may actually impair, performance following prolonged cycling.

The incidence of plateau at 2max is affected by a bout of prior‐priming exercise

The purpose of this study was to determine the effect of 6 min of prior-priming exercise on the incidence of plateau at VO(2max). Twelve trained cyclists (age, 21 ± 3 years; height, 175·0 ± 8·0 cm; weight, 69·0 ± 10·4 kg; maximal oxygen uptake (VO(2max)), 56·3 ± 6·9 ml kg(-1) min(-1)) completed three incremental tests to volitional exhaustion, which were classified as unprimed (UP), heavy-primed (HP) and severe-primed (SP), at a work rate of 1 W 2 s(-1), from an initial workload of 100 W, for the determination of VO(2max). VO(2max) trial in the HP and SP conditions was preceded by a period of 4-min unloaded cycling followed by a further 6 min of constant load cycling at Δ50% VO(2) gas exchange threshold (GET)-VO(2max) (HP) and Δ75% VO(2) GET-VO(2max) (SP). Expired air was recorded on a breath-by-breath basis during all trials. The criteria adopted for a plateau in VO(2max) was a ΔVO(2) over the final two consecutive 30-s sampling periods ≤ 2·1 ml kg(-1) min(-1). There was a significant increase in plateau responses between the UP (50%) and HP (100%) conditions (P = 0·001) coupled with a significant change in the slope of the regression line during the final 60 s of the VO(2max) test, UP and HP (P = 0·0299) and UP and SP (P = 0·0296). These data suggest that a bout of prior-priming exercise promotes an increased incidence of plateau responses at VO(2max) . It is suggested that future studies address how such an approach can be adopted without prior knowledge of GET.

1 - Classification and Aetiology of the Aplastic Anaemias

While dyspnea on exertion (DOE) is a common complaint in otherwise healthy obese women, less is known about feelings of unpleasantness and/or negative emotions provoked by DOE. We examined whether ratings of perceived breathlessness (RPB) during exercise were associated with ratings of unpleasantness and negative emotions (depression, anxiety, frustration, anger, and fear) in obese women.Seventy-four women (34 ± 7 yrs, 36 ± 4 kg/m2, 46 ± 5% body fat) performed 6 min of constant-load cycling (60 W); RPB (0–10 scale), and unpleasantness and negative emotions (visual analog scales, 10 cm) were assessed at the end.RPB were significantly correlated with unpleasantness and negative emotions (p < 0.05). The strongest correlations were between RPB and unpleasantness (r = 0.61, p < 0.001), and RPB and anxiety (r = 0.50, p < 0.001).DOE can significantly provoke unpleasantness and negative emotions during exercise in obese women. This may affect their willingness to engage in regular physical activity.