10-km Time Trial Research Articles

Protein supplementation elicits greater gains in maximal oxygen uptake capacity and stimulates lean mass accretion during prolonged endurance training: a double-blind randomized controlled trial

Endurance training induces numerous cardiovascular and skeletal muscle adaptations, thereby increasing maximal oxygen uptake capacity (VO2max). Whether protein supplementation enhances these adaptations remains unclear. The present study was designed to determine the impact of protein supplementation on changes in VO2max during prolonged endurance training. We used a double-blind randomized controlled trial with repeated measures among 44 recreationally active, young males. Subjects performed 3 endurance training sessions per week for 10 wk. Supplements were provided immediately after each exercise session and daily before sleep, providing either protein (PRO group; n=19; 21.5±0.4 y) or an isocaloric amount of carbohydrate as control (CON group; n=21; 22.5±0.5 y). The VO2max, simulated 10-km time trial performance, and body composition (dual-energy X-ray absorptiometry) were measured before and after 5 and 10 wk of endurance training. Fasting skeletal muscle tissue samples were taken before and after 5 and 10 wk to measure skeletal muscle oxidative capacity, and fasting blood samples were taken every 2 wk to measure hematological factors. VO2max increased to a greater extent in the PRO group than in the CON group after 5 wk (from 49.9±0.8 to 54.9±1.1 vs 50.8±0.9 to 53.0±1.1 mL · kg-1 · min-1; P<0.05) and 10 wk (from 49.9±0.8 to 55.4±0.9 vs 50.8±0.9 to 53.9±1.2 mL · kg-1 · min-1; P<0.05). Lean body mass increased in the PRO group whereas lean body mass in the CON group remained stable during the first 5 wk (1.5±0.2 vs 0.1±0.3 kg; P<0.05) and after 10 wk (1.5±0.3 vs 0.4±0.3 kg; P<0.05). Throughout the intervention, fat mass reduced significantly in the PRO group and there were no changes in the CON group after 5 wk (-0.6±0.2 vs -0.1±0.2 kg; P>0.05) and 10 wk (-1.2±0.4 vs -0.2±0.2 kg; P<0.05). Protein supplementation elicited greater gains in VO2max and stimulated lean mass accretion but did not improve skeletal muscle oxidative capacity and endurance performance during 10 wk of endurance training in healthy, young males. This trial was registered at clinicaltrials.gov as NCT03462381.

Analysis of a Submaximal Cycle Test to Monitor Adaptations to Training: Implications for Optimizing Training Prescription.

Capostagno, B, Lambert, MI, and Lamberts, RP. Analysis of a submaximal cycle test to monitor adaptations to training: Implications for optimizing training prescription. J Strength Cond Res 35(4): 924-930, 2021-The Lamberts and Lambert Submaximal Cycle Test (LSCT) was developed to monitor training adaptation to optimize the training prescription of cyclists. However, it is not known which of the variables within the LSCT are most closely associated with changes in training status. The aim of this study was to retrospectively analyze the LSCT data of cyclists (n = 15) who completed a 2-week high-intensity interval training intervention. The cyclists were retrospectively allocated to 1 of 2 groups based on the change in their 40-km time trial (40-km TT) performance. The "adapters" (n = 7) improved their 40-km TT performance, while the "nonadapters" (n = 8) failed to improve their 40-km TT performance. The variables measured in the LSCT were analyzed to determine which measures tracked the improvements in 40-km TT performance the best. Heart rate recovery increased significantly during the training period in the "adapters" group, but decreased in the "nonadapters" group. Mean power output in stage 2 of the LSCT tended to increase during the high-intensity interval training period in the "adapters" group and was unchanged in the "nonadapters" group. The findings of this study suggest that heart rate recovery and mean power output during stage 2 are the most sensitive markers to track changes in training status within the LSCT.

Acute Soy Supplementation Improves 20-km Time Trial Performance, Power, and Speed.

Isoflavones, a chemical class of phytoestrogens found in soybeans and soy products, may have biological functions similar to estradiol. After binding with ERβ or perhaps independently of estrogen receptors, isoflavones may augment vascular endothelial relaxation, contributing to improved limb blood flow. To determine if acute fermented soy extract supplementation influences 20-km time trial cycling performance and cardiac hemodynamics compared with a placebo. Subjects included 25 cyclists and triathletes (31 ± 8 yr, V˙O2peak: 55.1 ± 8.4 mL·kg·min). Each subject completed a V˙O2peak assessment, familiarization, and two 20-km time trials in randomized order after ingestion of a fermented soy extract supplement or placebo. The fermented soy extract consisted of 30 g powdered supplement in 16 fl. ounces of water. The placebo contained the same quantities of organic cocoa powder and water. Each trial consisted of 60 min of rest, 30 min at 55% Wpeak, and a self-paced 20-km time trial. Soy supplementation elicited a faster time to 20-km completion (-0.22 ± 0.51 min; -13 s), lower average HR (-5 ± 7 bpm), and significantly greater power (7 ± 3 W) and speed (0.42 ± 0.16 km·h) during the last 5 km of the time trial compared with placebo. Analysis of the results by relative fitness level (<57 vs ≥ 57 mL⋅kg⋅min) indicated that those with a higher level of fitness reaped the largest performance improvement alongside a reduced HR (-5 ± 7 bpm). Ingestion of a fermented soy extract supplement improved sprint-distance performance through improvements in both power and speed. For those with great aerobic fitness, soy supplementation may help to decrease cardiac demand alongside performance improvement.

GLUTAMINE SUPPLEMENTATION: EFFECTS ON GROWTH HORMONE AND TIME-TRIAL PERFORMANCE AFTER PROLONGED EXERCISE

Dietary glutamine supplementation has been proposed as a potential aid to athletic performance. The purpose of the investigation was to determine if glutamine supplementation might improve cycling performance, perhaps by stimulating growth hormone release, in athletes consuming a high-carbohydrate diet. Six trained young adult men participated in two four-day supplementation trials. In both trials, the subjects underwent an identical carbohydrate-loading regimen of controlled diet (75% carbohydrate) and exercise. The only difference in the trials was whether the subjects ingested dietary supplements of glutamine or glucose placebo. During the first three days of each trial, the diets were supplemented with either glutamine or glucose placebo at a dosage of 150 mg/kg body weight (~10.4 g/d). On the fourth day, the supplements were dissolved in a sports drink (4 g/L). The sports drink initially contained a 6% solution of carbohydrate. On the fourth day the subjects ingested 7 ml/kg of the supplemented sports drink 2 h before exercise, 5 ml/kg 1 h before exercise, and 3 ml/kg after 15, 30, 45, 60, and 90 min of exercise. The total amount of glutamine supplement or placebo consumed on the fourth day was 108 mg/kg or about 7.4 g, of which 3.3 g were consumed before and 4.1 g during exercise. On the fourth day, subjects completed 90 min of cycle ergometry, divided into six 15-min periods, each of which included in sequence 12 min @75% VO2max, 1 min @ 120% VO2max, and 2 min @ 50% VO2max. The 90 min exercise session was immediately followed by 15 min of rest and then a final 20-km time trial at ~85% VO2max. Plasma concentrations of glycerol and free fatty acids and serum growth hormone concentrations were measured before and during exercise, and time-trial performance was recorded. Times (± SEM) to complete the 20-km performance rides were 31.03 ± 0.58 min for the placebo trial and 30.93 ± 0.60 min for the glutamine trial and were not significantly different (P&gt;0.05). There were also no significant effects on serum growth hormone or on plasma glycerol or free fatty acids attributable to glutamine supplementation at any sampling time. In summary, we found no evidence that glutamine supplementation in moderate dosages has any effect on circulating growth hormone, glycerol, or free fatty acids or on time-trial performance in athletes who consume a high-carbohydrate diet

No Benefit of Ingestion of a Ketone Monoester Supplement on 10-km Running Performance.

Preexercise ingestion of exogenous ketones alters the metabolic response to exercise, but effects on exercise performance have been equivocal. On two occasions in a double-blind, randomized crossover design, eight endurance-trained runners performed 1 h of submaximal exercise at approximately 65% V˙O2max immediately followed by a 10-km self-paced time trial (TT) on a motorized treadmill. An 8% carbohydrate-electrolyte solution was consumed before and during exercise, either alone (CHO + PLA), or with 573 mg·kg of a ketone monoester supplement (CHO + KME). Expired air, HR, and RPE were monitored during submaximal exercise. Serial venous blood samples were assayed for plasma glucose, lactate, and β-hydroxybutyrate concentrations. CHO + KME produced plasma β-hydroxybutyrate concentrations of approximately 1.0 to 1.3 mM during exercise (P < 0.001), but plasma glucose and lactate concentrations were similar during exercise in both trials. V˙O2, running economy, respiratory exchange ratio, HR, and RPE were also similar between trials. Performance in the 10-km TT was not different (P = 0.483) between CHO + KME (mean, 2402 s; 95% confidence interval, 2204-2600 s) and CHO + PLA (mean, 2422 s; 95% confidence interval, 2217-2628 s). Cognitive performance, measured by reaction time and a multitasking test, did not differ between trials. Compared with carbohydrate alone, coingestion of KME by endurance-trained athletes elevated plasma β-hydroxybutyrate concentrations, but did not improve 10-km running TT or cognitive performance.

Muscle Oxygenation Patterns during a 20-km Time Trial with Intermediate Sprints and Recoveries.

PURPOSE: Pacing strategies are necessary during endurance events in which the goal is to finish in as little time as possible. Both anaerobic and aerobic attributable sources of ATP are used during such efforts. Rating of Perceived Exertion (RPE) increases linearly as heart rate (HR) and power output (PO) increases, however these markers of intensity are not instantaneous. Near infrared spectroscopy (NIRS) allows for the measurement of local muscle oxygen saturation (SmO2) which may respond to short-term fluctuations in PO. Previously, SmO2 has shown a moderate correlation with oxygen consumption (VO2) and HR during an incremental exercise. The purpose of this study was to determine how SmO2 changes with increases in PO during a non-incremental cycling time trial (20-km) with various interspersed sprints and if decrements in PO due to shorter rest times were associated with lower SmO2. METHODS: Well-trained cyclists (n=9) (VO2max=55.4±10.4 ml∙kg-1∙min-1; POmax=305±45 W), habituated to 20-km trial, performed a self-paced 20-km time trial and two time trials with 1-km sprints imposed, separated by 2- or 4-km of self-paced cycling. SmO2 saturation, PO, and HR were measured. RPE was recorded each kilometer. Pearson’s partial correlations were used to analyze relationship between SmO2 and PO. A one-way analysis of variance was used to determine if there were differences in finishing times between trials. RESULTS: There was a significant inverse relationship between SmO2 and PO during all time trials (r = -0.263, P < 0.0001). There was no significant difference (p = .572) between the finishing times amongst 20-km protocols. CONCLUSIONS: This study revealed that the imposed sprints caused reciprocal changes in the extent of SmO2 and PO that are larger than the changes in a self-paced time trial. In other words, as the subjects were instructed to significantly increase their PO to simulate a break-away, the SmO2 decreased in a reciprocal manner.

Nitrate Supplementation Combined with a Running Training Program Improved Time-Trial Performance in Recreationally Trained Runners.

Our purpose was to verify the effects of inorganic nitrate combined to a short training program on 10-km running time-trial (TT) performance, maximum and average power on a Wingate test, and lactate concentration ([La−]) in recreational runners. Sixteen healthy participants were divided randomly into two groups: Nitrate (n = 8) and placebo (n = 8). The experimental group ingested 750 mg/day (~12 mmol) of nitrate plus 5 g of resistant starch, and the control group ingested 6 g of resistant starch, for 30 days. All variables were assessed at baseline and weekly over 30 days. Training took place 3x/week. The time on a 10-km TT decreased significantly (p < 0.001) in all timepoints compared to baseline in both groups, but only the nitrate group was faster in week 2 compared to 1. There was a significant group × time interaction (p < 0.001) with lower [La] in the nitrate group at week 2 (p = 0.032), week 3 (p = 0.002), and week 4 (p = 0.003). There was a significant group time interaction (p = 0.028) for Wingate average power and a main effect of time for maximum power (p < 0.001) and [La−] for the 60-s Wingate test. In conclusion, nitrate ingestion during a four-week running program improved 10-km TT performance and kept blood [La−] steady when compared to placebo in recreational runners.

Protein Supplementation Does Not Augment Adaptations to Endurance Exercise Training.

Recently, it has been speculated that protein supplementation may further augment the adaptations to chronic endurance exercise training. We assessed the effect of protein supplementation during chronic endurance exercise training on whole-body oxidative capacity (V˙O2max) and endurance exercise performance. In this double-blind, randomized, parallel placebo-controlled trial, 60 recreationally active males (age, 27 ± 6 yr; body mass index, 23.8 ± 2.6 kg·m; V˙O2max, 47 ± 6 mL·min·kg) were subjected to 12 wk of triweekly endurance exercise training. After each session and each night before sleep, participants ingested either a protein supplement (PRO; 28.7 g casein protein) or an isoenergetic carbohydrate placebo (PLA). Before and after the 12 wk of training, V˙O2max and endurance exercise performance (~10-km time trial) were assessed on a cycle ergometer. Muscular endurance (total workload achieved during 30 reciprocal isokinetic contractions) was assessed by isokinetic dynamometry and body composition by dual-energy x-ray absorptiometry. Mixed-model ANOVA was applied to assess whether training adaptations differed between groups. Endurance exercise training induced an 11% ± 6% increase in V˙O2max (time effect, P < 0.0001), with no differences between groups (PRO, 48 ± 6 to 53 ± 7 mL·min·kg; PLA, 46 ± 5 to 51 ± 6 mL·min·kg; time-treatment interaction, P = 0.50). Time to complete the time trial was reduced by 14% ± 7% (time effect, P < 0.0001), with no differences between groups (time-treatment interaction, P = 0.15). Muscular endurance increased by 6% ± 7% (time effect, P < 0.0001), with no differences between groups (time-treatment interaction, P = 0.84). Leg lean mass showed an increase after training (P < 0.0001), which tended to be greater in PRO compared with PLA (0.5 ± 0.7 vs 0.2 ± 0.6 kg, respectively; time-treatment interaction, P = 0.073). Protein supplementation after exercise and before sleep does not further augment the gains in whole-body oxidative capacity and endurance exercise performance after chronic endurance exercise training in recreationally active, healthy young males.

Cycling time trial performance is improved by carbohydrate ingestion during exercise regardless of a fed or fasted state.

We tested the hypothesis that carbohydrate ingestion during exercise improves time trial (TT) performance and that this carbohydrate-induced improvement is greater when carbohydrates are ingested during exercise in a fasted rather than a fed state. Nine males performed 105minutes of constant-load exercise (50% of the difference between the first and second lactate thresholds), followed by a 10-km cycling TT. Exercise started at 9 am, 3hours after either breakfast (FED, 824kcal, 67% carbohydrate) or a 15-hour overnight fast (FAST). Before exercise, after every 15minutes of exercise and at 5km of the TT, participants ingested 2mLkg-1 body mass of a non-caloric sweetened solution containing either carbohydrate (8% of maltodextrin, CHO) or placebo (0% carbohydrate, PLA). Irrespective of the fasting state, when carbohydrate was ingested during exercise, the rating of perceived exertion (RPE) was lower throughout the constant-load exercise, while the plasma glucose concentration and carbohydrate oxidation were higher during the last stages of the constant-load exercise (P<0.05). Consequently, TT performance was faster when carbohydrate was ingested during exercise (18.5±0.3 and 18.7±0.4minutes for the FEDCHO and FASTCHO conditions, respectively) than when the placebo was ingested during exercise (20.2±0.8 and 21.7±1.4minutes for the FEDPLA and FASTPLA conditions, respectively), regardless of fasting. These findings indicate that even when breakfast is provided before exercise, carbohydrate ingestion during exercise is still beneficial for exercise performance. However, ingesting carbohydrate during exercise can overcome a lack of breakfast.

Histamine-Receptor Antagonists Slow 10-km Cycling Performance in Competitive Cyclists.

Determine the effects of histamine-receptor antagonism on cycling time trial performance in humans, with and without a preceding bout of sustained steady-state exercise. Eleven (3F) competitive cyclists performed six 10-km time trials on separate days. The first two time trials served as familiarization. The next four time trials were performed in randomized-block order, where two were preceded by 120 min of seated rest (rest) and two by 120 min of cycling exercise (Exercise) at 50% V˙O2peak. Within each block, subjects consumed either combined histamine H1 and H2 receptor antagonists (Blockade) or Placebo, before the start of the 120-min Rest/Exercise. Blockade had no discernible effects on hemodynamic or metabolic variables during Rest or Exercise. However, Blockade increased time-to-completion of the 10-km time trial compared with Placebo (+10.5 ± 3.7 s, P < 0.05). Slowing from placebo to blockade was not different between rest (+8.7 ± 5.2 s) and Exercise (+12.3 ± 5.8 s, P = 0.716). Exercise-related histaminergic signaling appears inherent to endurance exercise and may play a role in facilitating optimal function during high-intensity endurance exercise.

Chronic high-dose beetroot juice supplementation improves time trial performance of well-trained cyclists in normoxia and hypoxia

Dietary nitrate (NO3−) supplementation via beetroot juice (BR) is known to improve endurance performance in untrained and moderately trained individuals. However, conflicting results exist in well-trained individuals. Evidence suggests that the effects of NO3− are augmented during conditions of reduced oxygen availability (e.g., hypoxia), thereby increasing the probability of performance improvements for well-trained athletes in hypoxia vs. normoxia. This randomized, double-blinded, counterbalanced-crossover study examined the effects of 7 days of BR supplementation with 12.4 mmol NO3− per day on 10-km cycling time trial (TT) performance in 12 well-trained cyclists in normoxia (N) and normobaric hypoxia (H). Linear mixed models for repeated measures revealed increases in plasma NO3− and NO2− after supplementation with BR (both p < 0.001). Further, TT performance increased with BR supplementation (∼1.6%, p < 0.05), with no difference between normoxia and hypoxia (p = 0.92). For respiratory variables there were significant effects of supplementation on VO2 (p < 0.05) and VE (p < 0.05) such that average VO2 and VE during the TT increased with BR, with no difference between normoxia and hypoxia (p ≥ 0.86). We found no effect of supplementation on heart rate, oxygen saturation or muscle oxygenation during the TT. Our results provide new evidence that chronic high-dose NO3− supplementation improves cycling performance of well-trained cyclists in both normoxia and hypoxia.

Montmorency cherry supplementation improves 15-km cycling time-trial performance

AimMontmorency cherries are rich in polyphenols that possess antioxidant, anti-inflammatory and vasoactive properties. We investigated whether 7-day Montmorency cherry powder supplementation improved cycling time-trial (TT) performance.Methods8 trained male cyclists (dot {V}{{text{O}}_{2{text{peak}}}}: 62.3 ± 10.1 ml kg−1 min−1) completed 10-min steady-state (SS) cycling at ~ 65% dot {V}{{text{O}}_{2{text{peak}}}} followed by a 15-km TT on two occasions. Participants consumed 6 pills per day (Montmorency cherry powder, MC; anthocyanin 257 mg day−1 or dextrose powder, PL) for a 7-day period, 3 pills in the morning and evening. Capillary blood [lactate] was measured at baseline, post SS and post TT. Pulmonary gas exchange and tissue oxygenation index (TOI) of m. vastus lateralis via near-infrared spectroscopy, were measured throughout.ResultsTT completion time was 4.6 ± 2.9% faster following MC (1506 ± 86 s) supplementation compared to PL (1580 ± 102 s; P = 0.004). Blood [lactate] was significantly higher in MC after SS (PL: 4.4 ± 2.1 vs. MC: 6.7 ± 3.3 mM, P = 0.017) alongside an elevated baseline TOI (PL: 68.7 ± 2.1 vs. MC: 70.4 ± 2.3%, P = 0.018).DiscussionMontmorency cherry supplementation improved 15-km cycling TT performance. This improvement in exercise performance was accompanied by enhanced muscle oxygenation suggesting that the vasoactive properties of the Montmorency cherry polyphenols may underpin the ergogenic effects.

Acute Post-Exercise Recovery Strategies in Cycling: A Review

Cycling events often include multiple races a day or racing over consecutive days. Congested competition schedules and increased training load have led to the implementation of recovery strategies; with the goal of alleviating post-exercise fatigue and enhancing subsequent performance. This review aims to review the efficacy of recovery strategies used following different cycling events. Compression garments have been shown to improve subsequent 30s – 30min mean cycling power and 5-min max cycling power, while cold water immersion may improve 5-15s sprint cycling power output, 1-15min time trial (TT) total work performed and mean power output in hot and humid conditions. Cold water immersion was also more beneficial than active recovery at improving total work performed. Contrast water therapy could increase 15s – 15min TT work performed and sprint mean and peak power output. Similarly, active recovery has been shown to improve power measures and time to completion. Conversely, hot water immersion appears to be detrimental to sprint power output and TT power output over consecutive days. Thermoneutral water immersion appears beneficial for improving average cycling speed and time to completion during a 20-km TT, where humidification therapy and sports massage are beneficial at improving sprint and middle duration time trial performance. A combination of recovery strategies appear more beneficial than stand-alone strategies and various combinations should be explored further.

Beta-Alanine Supplementation Improved 10-km Running Time Trial in Physically Active Adults.

The purpose of this study was to investigate the effects of β-alanine supplementation on a 10 km running time trial and lactate concentration in physically active adults. Sixteen healthy subjects were divided randomly into two groups: β-alanine (n = 8) and placebo group (n = 8). The experimental group ingested 5 g/day of β-alanine plus 1 g of resistant starch, and control group ingested 6 g of resistant starch, both for 23 days. Time to complete a 10-km running time trial and lactate concentration following the test were assessed at baseline and post 23 days. The running training program was performed three times per week on non-consecutive days (day 1: running 7 km; day 2: six sprints of 500 m at maximum speed with 2 min of recovery; day 3: running 12 km). The time to complete a 10-km running time trial decreased significantly only for the β-alanine group (Pre = 3441 ± 326.7, Post = 3209 ± 270.5 s, p < 0.05). When analyzing the delta (Time post minus Time at baseline value) there was a statistically significant difference between the β-alanine vs placebo group (-168.8 ± 156.6 vs. -53.60 ± 78.81 s, p = 0.007), respectively. In addition, the β-alanine group presented lower blood lactate concentration after the 10-km test (β-alanine: Pre = 8.45 ± 1.94 vs. Post = 6.95 ± 2.44 mmol/L; Placebo: Pre = 8.7 ± 3.0 vs. Post = 10.8 ± 2.5 mmol/L, p = 0.03). In conclusion, β-alanine supplementation improved the 10-km running time trial and reduced lactate concentration in physically active adults.

The Psychophysiological Regulation of Pacing Behaviour and Performance Fatigability During Long-Distance Running with Locomotor Muscle Fatigue and Exercise-Induced Muscle Damage in Highly Trained Runners

BackgroundLocomotor muscle fatigue (LMMF) and exercise-induced muscle damage (EIMD) are common conditions experienced during long-distance running due to the pooled effect of mechanical and metabolic strain on the locomotor muscles. However, little is known about the instant effects of combined LMMF and EIMD on pacing behaviour and performance during the decisive final stages of ‘real-world’ long-distance running events.MethodsTwenty-two highly trained runners (11 females) completed two maximal self-paced 20-km treadmill time trials in a counterbalanced crossover design: (A) in a tapered condition and (B) with LMMF and EIMD. Indicators of muscle damage, muscle metabolic strain, and endocrinological stress were assessed to investigate the physiological effects, and a three-dimensional framework of perceived fatigability was applied to investigate the perceptual effects of running with LMMF and EIMD on performance fatigability.ResultsLMMF and EIMD caused restrictions in work capacity and medium increases in blood leucocyte and neutrophil count, interleukin-6, and cortisol concentrations, collectively constituting a physiological milieu likely not conducive to high performance. LMMF and EIMD further caused large increases in perceived physical strain and large decreases in valence as well as large increases and decreases in action crisis and flow state, respectively.ConclusionsUnder the constraint of amplified physical duress, findings are suggestive of heuristic and rational antecedents in the goal disengagement process. Dynamic changes in physiological and perceptual effects of LMMF and EIMD are hypothesised to underpin the observed alterations in pacing behaviour and performance fatigability during long-distance running. The applied three-dimensional framework provides a more comprehensive understanding of strain-perception-thinking-action coupling in centrally regulated and goal-directed exercise behaviour.

Modelling perception-action coupling in the phenomenological experience of \u201chitting the wall\u201d during long-distance running with exercise-induced muscle damage in highly trained runners

Background“Hitting the wall” (HTW) can be understood as a psychophysiological stress process characterised by (A) discrete and poignant onset, (B) dynamic interplay between physiological, affective, motivational, cognitive, and behavioural systems, and (C) unintended alteration of pace and performance. A preceding companion article investigated the psychophysiological responses to 20-km self-paced treadmill time trials after producing exercise-induced muscle damage (EIMD) via a standardised muscle-lengthening contraction protocol.MethodsA 5-step procedure was applied determining the extent to which the observed data fit the hypothesised cause-effect relationships. Running with EIMD negatively impacts performance fatigability via (A) amplified physiological responses and a non-adaptive distress response and (B) deterioration in perceived fatigability: increase in perceived physical strain precedes decrease in valence, which in turn precedes increase in action crisis, eventually dissolving the initially aspired performance goal.ResultsFirst, haematological indicators of EIMD predicted increased blood cortisol concentration, which in turn predicted increased performance fatigability. Second, perceived physical strain explained 44% of the relationship between haematological indicators of EIMD and valence, which in turn predicted increased action crisis, which in turn predicted increased performance fatigability. The observed data fitted the hypothesised dual-pathway model well with good model-fit indices throughout.ConclusionsThe hypothesised interrelationships between physiological strain, perception, and heuristic and deliberative decision-making processes in self-regulated and goal-directed exercise behaviour were applied, tested, and confirmed: amplified physiological strain and non-adaptive distress response as well as strain-perception-thinking-action coupling impact performance fatigability. The findings provide novel insights into the psychophysiological processes that underpin the phenomenological experience of HTW and alteration in pacing behaviour and performance.

Acute modulation in dietary behavior following glycogen depletion and postexercise supplementation in trained cyclists.

We investigated the influence of immediate postexercise dietary supplementation on the subsequent food consumption pattern and endurance exercise performance in physically trained individuals. On 2 occasions, trained male cyclists performed a glycogen-depleting exercise bout followed by a 2-h nutritional supplementation period, 28 h of free-living recovery, and a subsequent 40-km cycling time trial. During the 2-h postexercise supplementation, the subjects consumed equal volumes of reduced-fat chocolate milk (CM) or a sports beverage (SB) in a single-blind, randomized design. Thereafter, the cyclists maintained a food log during the free-living recovery period. Dietary and exercise performance parameters were compared between the treatment beverage visits. No differences in total caloric and macronutrient intakes were detected between the CM and SB trials over the course of the free-living recovery. However, a significant interaction (treatment × time) was detected for caloric and macronutrient intakes during the early phase of free-living recovery, such that significantly larger proportions were consumed shortly after SB as compared with CM. No difference was observed in completion time of the 40-km cycling time trial (CM: 66.9 ± 4.1 vs SB: 66.9 ± 3.7 min). Hence, the cyclists achieved similar levels of recovery during the prolonged, free-living period despite the different acute, postexercise nutrient intake rates. We suggest that given adequate time, athletes appear to subconsciously modify their food consumption in response to varied postexercise supplementation such that subsequent-day exercise performance is equivalent.

Case Study: Dose Response of Caffeine on 20-km Handcycling Time Trial Performance in a Paratriathlete

Caffeine's (CAF) ability to influence upper-body exercise endurance performance may be related to an individual's training status. This case study therefore aimed to investigate the ergogenic effects of CAF dose on 20-km time trial (TT) performance of an elite male paratriathlete (wheelchair user; age = 46 years, body mass = 76.9kg, body fat = 25.4%, and handcycling [Formula: see text]). The athlete completed four 20-km handcycling TTs on a Cyclus II ergometer under controlled laboratory conditions following the ingestion of 2, 4, and 6mg/kg CAF or placebo (PLA). Blood lactate concentration, power output, arousal, and ratings of perceived exertion were recorded. Ingestion of 2, 4, and 6mg/kg CAF resulted in a 2%, 1.5%, and 2.7% faster TT compared with PLA (37:40 min:s). The participant's blood lactate concentration increased throughout all trials and was greater during CAF compared with PLA. There were no obvious differences in ratings of perceived exertion between trials despite different performance times. Baseline arousal scores differed between PLA and 4mg/kg CAF (1 = low), and 2 and 6mg/kg CAF (3 = moderate). Arousal increased at each time point following the ingestion of 4 and 6mg/kg CAF. The largest CAF dose resulted in a positive pacing strategy, which, when combined with an end spurt, resulted in the fastest TT. CAF improved 20-km TT performance of an elite male paratriathlete, which may be related to greater arousal and an increased power output for a given rating of perceived exertion.

Effects of mild whole body hypothermia on self-paced exercise performance.

This study examined self-paced, high-intensity exercise during mild hypothermia and whether hyperoxia might offset any potential impairment. Twelve trained males each completed 15-km time trials in three environmental conditions: Neutral (23°C, [Formula: see text] 0.21), Cold (0°C, [Formula: see text] 0.21), and Cold+Hyper (0°C, [Formula: see text] 0.40). Cold and Cold+Hyper trials occurred after a 0.5°C drop in rectal temperature. Rectal temperature was higher ( P ≤ 0.016) throughout Neutral compared with Cold and Cold+Hyper; Cold had a higher ( P ≤ 0.035) rectal temperature than Cold+Hyper from 2.5 to 7.5 km, and hyperoxia did not alter thermal sensation or comfort. Oxyhemoglobin saturation decreased from ~98% to ~94% with Neutral and Cold, but was maintained at ~99% in Cold+Hyper ( P < 0.01). Cerebral tissue oxygenation index (TOI) was higher in Neutral than in Cold throughout the time trial (TT) ( P ≤ 0.001), whereas Cold+Hyper were unchanged ( P ≥ 0.567) from Neutral by 2.5 km. Muscle TOI was maintained in Cold+Hyper compared with Neutral and was higher ( P ≤ 0.046) than Cold throughout the entire TT. Power output during Cold (246 ± 41 W) was lower than Neutral (260 ± 38 W) at all 2.5-km intervals ( P ≤ 0.012) except at 12.5 km. Power output during Cold+Hyper (256 ± 42 W) was unchanged ( P ≥ 0.161) from Neutral throughout the TT, and was higher than Cold from 7.5 km onward. Average cadence was higher in Neutral (93 ± 8 rpm) than in either Cold or Cold+Hyper (Cold: 89 ± 7 and Cold+Hyper: 90 ± 8 rpm, P = 0.031). In conclusion, mild hypothermia reduced self-paced exercise performance; hyperoxia during mild hypothermia restored performance to thermoneutral levels, likely due to maintenance of oxygen availability rather than any thermogenic benefit. NEW & NOTEWORTHY We examined self-paced, high-intensity exercise with 0.5°C rectal temperature decreases in a 0°C ambient environment, along with whether hyperoxia could offset any potential impairment. During a 15-km time trial, power output was lower with hypothermia than with thermoneutral. However, with hypothermia, hyperoxia of [Formula: see text] = 0.40 restored power output despite there being no thermophysiological improvement. Hypothermia impairs exercise performance, whereas hyperoxia likely restored performance due to maintenance of oxygen availability rather than any thermogenic benefit.

Impact of sodium citrate ingestion during recovery after dehydrating exercise on rehydration and subsequent 40-km cycling time-trial performance in the heat.

The purpose of this study was to assess the impact of sodium citrate (CIT) ingestion (600 mg·kg-1) during recovery from dehydrating cycling exercise (DE) on subsequent 40-km cycling performance in a warm environment (32 °C). Twenty male nonheat-acclimated endurance athletes exercised in the heat until 4% body mass (BM) loss occurred. After 16 h recovery with consumption of water ad libitum and prescribed diet (evening meal 20 kcal·kg-1, breakfast 12 kcal·kg-1) supplemented in a double-blind, randomized, crossover manner with CIT or placebo (PLC), they performed 40-km time-trial (TT) on a cycle ergometer in a warm environment. During recovery greater increases in BM and plasma volume (PV) concomitant with greater water intake and retention occurred in the CIT trial compared with the PLC trial (p < 0.0001). During TT there was greater water intake and smaller BM loss in the CIT trial than in the PLC trial (p < 0.05) with no between-trial differences (p > 0.05) in sweat loss, PV decrement, ratings of perceived exertion, or TT time (CIT 68.10 ± 3.28 min, PLC 68.11 ± 2.87 min). At the end of TT blood lactate concentration was higher (7.58 ± 2.44 mmol·L-1 vs 5.58 ± 1.32 mmol·L-1; p = 0.0002) and rectal temperature lower (39.54 ± 0.50 °C vs 39.65 ± 0.52 °C; p = 0.033) in the CIT trial than in the PLC trial. Compared with pre-DE time point, PV had decreased to a lower level in the PLC trial than in the CIT trial (p = 0.0001). In conclusion, CIT enhances rehydration after exercise-induced dehydration but has no impact on subsequent 40-km cycling TT performance in a warm uncompensable environment.