Effects of Sodium Bicarbonate on High-Intensity Endurance Performance in Cyclists: A Double-Blind,Randomized Cross-Over Trial

Background

While the ergogenic effect of sodium bicarbonate (BICA) on short-term, sprint-type performance has been repeatedly demonstrated, little is known about its effectiveness during prolonged high-intensity exercise in well-trained athletes. Therefore, this study aims to examine the influence of BICA on performance during exhaustive, high-intensity endurance cycling.

Methods

This was a single-center, double-blind, randomized, placebo-controlled cross-over study. Twenty-one well-trained cyclists (mean ± SD: age 24±8 y, BMI 21.3±1.7, VO_2peak 67.3±9.8 ml·kg⁻¹·min⁻¹) were randomly allocated to sequences of following interventions: oral ingestion of 0.3 g·kg⁻¹ BICA or 4 g of sodium chloride (placebo), respectively. One h after ingestion subjects exercised for 30 min at 95% of the individual anaerobic threshold (IAT) followed by 110% IAT until exhaustion. Prior to these constant load tests stepwise incremental exercise tests were conducted under both conditions to determine IAT and VO_2peak. Analysis of blood gas parameters, blood lactate (BLa) and gas exchange measurements were conducted before, during and after the tests. The main outcome measure was the time to exhaustion in the constant load test.

Results

Cycling time to exhaustion was improved (p<0.05) under BICA (49.5±11.5 min) compared with placebo (45.0±9.5 min). No differences in maximal or sub-maximal measures of performance were observed during stepwise incremental tests. BICA ingestion resulted in an increased pH, bicarbonate concentration and BLa before, throughout and after both exercise testing modes.

Conclusion

The results suggest that ingestion of BICA may improve prolonged, high-intensity cycling performance.

Trial Registration

German Clinical Trials Register (DRKS) DRKS00006198.     

PRE-EXERCISE ARGININE SUPPLEMENTATION INCREASES TIME TO EXHAUSTION IN ELITE MALE WRESTLERS

Dietary supplements containing arginine are among the most popular ergogenics intended to enhance strength, power and muscle recovery associated with both anaerobic and aerobic exercise. The aim of the present study was to evaluate the possible effect of pre-exercise acute intake of arginine on performance and exercise metabolism during incremental exhaustive exercise in elite male wrestlers. Nine volunteer elite male wrestlers (24.7±3.8 years) participated in this study. The test-retest protocol was used on the same subjects. The study was conducted using a cross-over design. A single dose of arginine (1.5 g · 10 kg^-1 body weight) or placebo was given to the subjects after 12 hours fasting (during the night) for both test and retest. Subjects were allowed to drink water but not allowed to eat anything between arginine or placebo ingestion and the exercise protocol. An incremental exercise protocol was applied and oxygen consumption was measured during the exercise. Heart rate and plasma lactate levels were measured during the exercise and recovery. Results showed that in the same working loads there was no significant difference for the mean lactate levels and no difference in maximum oxygen consumption (arginine 52.47±4.01 mL · kg^-1 · min^-1, placebo 52.07±5.21 mL · kg^-1 · min^-1) or in maximum heart rates (arginine 181.09±13.57 bpm, placebo 185.89±7.38 bpm) between arginine and placebo trials. Time to exhaustion was longer with arginine supplementation (1386.8±69.8 s) compared to placebo (1313±90.8 s) (p < 0.05). These results suggest that L-arginine supplementation can have beneficial effects on exercise performance in elite male wrestlers but cannot explain the metabolic pathways which are responsible from these effects.     

Local Pain Dynamics during Constant Exhaustive Exercise

The purpose of this study was to delineate the topological dynamics of pain and discomfort during constant exercise performed until volitional exhaustion. Eleven physical education students were tested while cycling and running at a “hard” intensity level (e.g., corresponding to Borg’s RPE (6–20) = 15). During the tests, participants reported their discomfort and pain on a body map every 15s. “Time on task” for each participant was divided into five equal non-overlapping temporal windows within which their ratings were considered for analysis. The analyses revealed that the number of body locations with perceived pain and discomfort increased throughout the five temporal windows until reaching the mean (± SE) values of 4.2 ± 0.7 and 4.1 ± 0.6 in cycling and running, respectively. The dominant locations included the quadriceps and hamstrings during cycling and quadriceps and chest during running. In conclusion, pain seemed to spread throughout the body during constant cycling and running performed up to volitional exhaustion with differences between cycling and running in the upper body but not in the lower body dynamics.     

Disturbances in Pro-Oxidant-Antioxidant Balance after Passive Body Overheating and after Exercise in Elevated Ambient Temperatures in Athletes and Untrained Men

The aim of the study was to investigate pro-oxidant-antioxidant balance in two series of examinations with two types of stressors (exogenous heat and the combined exogenous and endogenous heat) in trained and untrained men. The exogenous stressor was provided by Finnish sauna session, whereas the combined stressor was represented by the exercise in elevated ambient temperature. The men from the two groups performed the physical exercise on a cycle ergometer with the load of 53±2% maximal oxygen uptake at the temperature of 33±1°C and relative humidity of 70% until their rectal temperature rose by 1.2°C. After a month from completion of the exercise test the subjects participated in a sauna bathing session with the temperature of 96±2°C, and relative humidity of 16±5%. 15-minutes heating and 2-minute cool-down in a shower with the temperature of 20°C was repeated until rectal temperature rose by 1.2°C compared to the initial value. During both series of tests rectal temperature was measured at 5-minute intervals. Before both series of tests and after them body mass was measured and blood samples were taken for biochemical tests. Serum total protein, serum concentration of lipid peroxidation products and serum antioxidants were determined. The athletes were characterized by higher level of antioxidant status and lower concentration of lipid peroxidation products. Physical exercise at elevated ambient temperature caused lower changes in oxidative stress indices compared to sauna bathing. Sauna induced a shift in pro-oxidant-antioxidant balance towards oxidation, which was observed less intensively in the athletes compared to the untrained men. This leads to the conclusion that physical exercise increases tolerance to elevated ambient temperature and oxidative stress.     

Caffeine Ingestion Increases Estimated Glycolytic Metabolism during Taekwondo Combat Simulation but Does Not Improve Performance or Parasympathetic Reactivation

ObjectivesThe aim of this study was to evaluate the effect of caffeine ingestion on performance and estimated energy system contribution during simulated taekwondo combat and on post-exercise parasympathetic reactivation.MethodsTen taekwondo athletes completed two experimental sessions separated by at least 48 hours. Athletes consumed a capsule containing either caffeine (5 mg∙kg^-1) or placebo (cellulose) one hour before the combat simulation (3 rounds of 2 min separated by 1 min passive recovery), in a double-blind, randomized, repeated-measures crossover design. All simulated combat was filmed to quantify the time spent fighting in each round. Lactate concentration and rating of perceived exertion were measured before and after each round, while heart rate (HR) and the estimated contribution of the oxidative (W_AER), ATP-PCr (W_PCR), and glycolytic (W_[La-]) systems were calculated during the combat simulation. Furthermore, parasympathetic reactivation after the combat simulation was evaluated through 1) taking absolute difference between the final HR observed at the end of third round and the HR recorded 60-s after (HRR_60s), 2) taking the time constant of HR decay obtained by fitting the 6-min post-exercise HRR into a first-order exponential decay curve (HRR_τ), or by 3) analyzing the first 30-s via logarithmic regression analysis (T30).ResultsCaffeine ingestion increased estimated glycolytic energy contribution in relation to placebo (12.5 ± 1.7 kJ and 8.9 ± 1.2 kJ, P = 0.04). However, caffeine did not improve performance as measured by attack number (CAF: 26. 7 ± 1.9; PLA: 27.3 ± 2.1, P = 0.48) or attack time (CAF: 33.8 ± 1.9 s; PLA: 36.6 ± 4.5 s, P = 0.58). Similarly, RPE (CAF: 11.7 ± 0.4 a.u.; PLA: 11.5 ± 0.3 a.u., P = 0.62), HR (CAF: 170 ± 3.5 bpm; PLA: 174.2 bpm, P = 0.12), oxidative (CAF: 109.3 ± 4.5 kJ; PLA: 107.9 kJ, P = 0.61) and ATP-PCr energy contributions (CAF: 45.3 ± 3.4 kJ; PLA: 46.8 ± 3.6 kJ, P = 0.72) during the combat simulation were unaffected. Furthermore, T30 (CAF: 869.1 ± 323.2 s; PLA: 735.5 ± 232.2 s, P = 0.58), HRR_60s (CAF: 34 ± 8 bpm; PLA: 38 ± 9 bpm, P = 0.44), HRRτ (CAF: 182.9 ± 40.5 s, PLA: 160.3 ± 62.2 s, P = 0.23) and HRR_amp (CAF: 70.2 ± 17.4 bpm; PLA: 79.2 ± 17.4 bpm, P = 0.16) were not affected by caffeine ingestion.ConclusionsCaffeine ingestion increased the estimated glycolytic contribution during taekwondo combat simulation, but this did not result in any changes in performance, perceived exertion or parasympathetic reactivation.     

Hypothalamic Temperature of Rats Subjected to Treadmill Running in a Cold Environment

Different strategies for cooling the body prior to or during physical exercise have been shown to improve prolonged performance. Because of ethical and methodological issues, no studies conducted in humans have evaluated the changes in brain temperature promoted by cooling strategies. Therefore, our first aim sought to measure the hypothalamic temperature (T_hyp) of rats subjected to treadmill running in a cold environment. Moreover, evidence suggests that T_hyp and abdominal temperature (T_abd) are regulated by different physiological mechanisms. Thus, this study also investigated the dynamics of exercise-induced changes in T_hyp and T_abd at two ambient temperatures: 25°C (temperate environment) and 12°C (cold). Adult male Wistar rats were used in these experiments. The rats were implanted with a guide cannula in the hypothalamus and a temperature sensor in the abdominal cavity. After recovery from this surgery, the rats were familiarized with running on a treadmill and were then subjected to the two experimental trials: constant-speed running (20 m/min) at 12°C and 25°C. Both T_hyp and T_abd increased during exercise at 25°C. In contrast, T_hyp and T_abd remained unchanged during fatiguing exercise at 12°C. The temperature differential (i.e., T_hyp - T_abd) increased during the initial min of running at 25°C and thereafter decreased toward pre-exercise values. Interestingly, external cooling prevented this early increase in the temperature differential from the 2^nd to the 8^th min of running. In addition, the time until volitional fatigue was higher during the constant exercise at 12°C compared with 25°C. Together, our results indicate that T_hyp and T_abd are regulated by different mechanisms in running rats and that external cooling affected the relationship between both temperature indexes observed during exercise without environmental thermal stress. Our data also suggest that attenuated hypothalamic hyperthermia may contribute to improved performance in cold environments.     

Branched-Chain Amino Acids and Arginine Improve Performance in Two Consecutive Days of Simulated Handball Games in Male and Female Athletes: A Randomized Trial

The central nervous system plays a crucial role in the development of physical fatigue. The purpose of this study is to investigate the effect of combined supplementation of branched-chain amino acids (BCAA) and arginine on intermittent sprint performance in simulated handball games on 2 consecutive days. Methods: Fifteen male and seven female handball players consumed 0.17 g/kg BCAA and 0.04 g/kg arginine together (AA trial), or placebo (PB trial) before exercise. Each trial contained two 60-min simulated handball games on consecutive days. The game was consisted of 30 identical 2-min blocks and a 20 m all-out sprint was performed at the end of each block. The performance, measured by percentage changes of sprint time between day 1 and 2, was significantly better in the AA trial (first half: AA trial: -1.34±0.60%, PB trial: -0.21±0.69%; second half: AA trial: -1.68±0.58%, PB trial: 0.49±0.42%). The average ratings of perceive exertion throughout the 2-day trial was significantly lower in the AA trial (14.2±0.3) than the PB trial (15.1±0.4). Concurrently, post-exercise tryptophan/BCAA ratio on both days in the AA trial was significantly lower than the baseline. This study showed that BCAA and arginine supplementation could improve performance in intermittent sprints on the second consecutive day of simulated handball games in well-trained athletes by potentially alleviating central fatigue.     

Melatonin ingestion after exhaustive late-evening exercise attenuate muscle damage,oxidative stress,and inflammation during intense short term effort in the following day in teenage athletes

ABSTRACT

The present study aimed to investigate whether nocturnal melatonin (MEL) ingestion has beneficial effects against exercise-induced oxidative stress and muscle damage in young athletes. Fourteen healthy-trained teenagers performed two-test sessions separated by at least, 1 week. During each session, participants completed the Running-Based Anaerobic Sprint Test (RAST) at 20:00 h. Then, they ingested a single 10-mg tablet of MEL or Placebo (PLA) in a double-blind randomized order at 22:00 h. The following morning (i.e., 07:30 h), participants performed the same test as the previous night. Blood samples were taken before and after exercise. MEL intake increased the peak power (P_peak) (p < .01), mean power (P_mean) (p < .001) and decreased the total time (TT) (p < .001) and the fatigue index (FI) (p < .05). Furthermore, MEL ingestion attenuated the hematologic parameters before and after exercise (White Blood Cells (WBC: p < .001 and p < .001, respectively); Neutrophiles (NE: p < .001 and p < .001, respectively); Lymphocytes (LY: p < .001 and p < .001, respectively)) and the ultra-sensitive C-reactive protein (us-CRP: p < .001 and p < .001; respectively) compared to PLA. Also, MEL reduced muscle and hepatic damage enzymes before and after exercise (creatine kinase (CK: p < .001 and p < .001; respectively), lactate dehydrogenase (LDH: p < .05 and p < .01; respectively), aspartate aminotransferase (ASAT: p < .01 and p < .001; respectively)), Malondialdehyde (MDA: p < .001 and p < .001; respectively) and Homocysteine (Hcy: p < .001 and p < .001; respectively)) from placebo. Plasma lactate [La] and glucose (GL) remained unchangeable during the two conditions. In summary, acute MEL ingestion after strenuous late-evening exercise attenuated transient leucocytosis and protected against lipid peroxidation and muscle damage induced by strenuous exercise the following morning in healthy male teenage athletes.     

A Fast-Start Pacing Strategy Speeds Pulmonary Oxygen Uptake Kinetics and Improves Supramaximal Running Performance

The focus of the present study was to investigate the effects of a fast-start pacing strategy on running performance and pulmonary oxygen uptake () kinetics at the upper boundary of the severe-intensity domain. Eleven active male participants (28±10 years, 70±5 kg, 176±6 cm, 57±4 mL/kg/min) visited the laboratory for a series of tests that were performed until exhaustion: 1) an incremental test; 2) three laboratory test sessions performed at 95, 100 and 110% of the maximal aerobic speed; 3) two to four constant speed tests for the determination of the highest constant speed (HS) that still allowed achieving maximal oxygen uptake; and 4) an exercise based on the HS using a higher initial speed followed by a subsequent decrease. To predict equalized performance values for the constant pace, the relationship between time and distance/speed through log-log modelling was used. When a fast-start was utilized, subjects were able to cover a greater distance in a performance of similar duration in comparison with a constant-pace performance (constant pace: 670 m±22%; fast-start: 683 m±22%; P = 0.029); subjects also demonstrated a higher exercise tolerance at a similar average speed when compared with constant-pace performance (constant pace: 114 s±30%; fast-start: 125 s±26%; P = 0.037). Moreover, the mean response time was reduced after a fast start (constant pace: 22.2 s±28%; fast-start: 19.3 s±29%; P = 0.025). In conclusion, middle-distance running performances with a duration of 2–3 min are improved and response time is faster when a fast-start is adopted.     

Physical and Perceptual Cooling with Beverages to Increase Cycle Performance in a Tropical Climate

Purpose

This study compares the effects of neutral temperature, cold and ice-slush beverages, with and without 0.5% menthol on cycling performance, core temperature (T_co) and stress responses in a tropical climate (hot and humid conditions).

Methods

Twelve trained male cyclists/triathletes completed six 20-km exercise trials against the clock in 30.7°C±0.8°C and 78%±0.03% relative humidity. Before and after warm-up, and before exercise and every 5 km during exercise, athletes drank 190 mL of either aromatized (i.e., with 0.5 mL of menthol (5 gr/L)) or a non-aromatized beverage (neutral temperature: 23°C±0.1°C, cold: 3°C±0.1°C, or ice-slush: −1°C±0.7°C). During the trials, heart rate (HR) was continuously monitored, whereas core temperature (T_co), thermal comfort (TC), thermal sensation (TS) and rate of perceived exertion (RPE) were measured before and after warm-up, every 5 km of exercise, and at the end of exercise and after recovery.

Results

Both the beverage aroma (P<0.02) and beverage temperature (P<0.02) had significant and positive effects on performance, which was considerably better with ice-slush than with a neutral temperature beverage, whatever the aroma (P<0.002), and with menthol vs non-menthol (P<0.02). The best performances were obtained with ice-slush/menthol and cold/menthol, as opposed to neutral/menthol. No differences were noted in HR and T_co between trials.

Conclusion

Cold water or ice-slush with menthol aroma seems to be the most effective beverage for endurance exercise in a tropical climate. Further studies are needed to explore its effects in field competition.     

The Positive Effects of Priming Exercise on Oxygen Uptake Kinetics and High-Intensity Exercise Performance Are Not Magnified by a Fast-Start Pacing Strategy in Trained Cyclists

The purpose of this study was to determine both the independent and additive effects of prior heavy-intensity exercise and pacing strategies on the VO2 kinetics and performance during high-intensity exercise. Fourteen endurance cyclists (VO₂max  = 62.8±8.5 mL.kg⁻¹.min⁻¹) volunteered to participate in the present study with the following protocols: 1) incremental test to determine lactate threshold and VO₂max; 2) four maximal constant-load tests to estimate critical power; 3) six bouts of exercise, using a fast-start (FS), even-start (ES) or slow-start (SS) pacing strategy, with and without a preceding heavy-intensity exercise session (i.e., 90% critical power). In all conditions, the subjects completed an all-out sprint during the final 60 s of the test as a measure of the performance. For the control condition, the mean response time was significantly shorter (p<0.001) for FS (27±4 s) than for ES (32±5 s) and SS (32±6 s). After the prior exercise, the mean response time was not significantly different among the paced conditions (FS = 24±5 s; ES = 25±5 s; SS = 26±5 s). The end-sprint performance (i.e., mean power output) was only improved (∼3.2%, p<0.01) by prior exercise. Thus, in trained endurance cyclists, an FS pacing strategy does not magnify the positive effects of priming exercise on the overall VO2 kinetics and short-term high-intensity performance.     

Time-Course Changes of Oxidative Stress Response to High-Intensity Discontinuous Training versus Moderate-Intensity Continuous Training in Masters Runners

Beneficial systemic effects of regular physical exercise have been demonstrated to reduce risks of a number of age-related disorders. Antioxidant capacity adaptations are amongst these fundamental changes in response to exercise training. However, it has been claimed that acute physical exercise performed at high intensity (>60% of maximal oxygen uptake) may result in oxidative stress, due to reactive oxygen species being generated excessively by enhanced oxygen consumption. The aim of this study was to evaluate the effect of high-intensity discontinuous training (HIDT), characterized by repeated variations of intensity and changes of redox potential, on oxidative damage. Twenty long-distance masters runners (age 47.8±7.8 yr) on the basis of the individual values of gas exchange threshold were assigned to a different 8-weeks training program: continuous moderate-intensity training (MOD, n = 10) or HIDT (n = 10). In both groups before (PRE) and after (POST) training we examined the following oxidative damage markers: thiobarbituric acid reactive substances (TBARS) as marker of lipid peroxidation; protein carbonyls (PC) as marker of protein oxidation; 8-hydroxy-2-deoxy-guanosine (8-OH-dG) as a biomarker of DNA base modifications; and total antioxidant capacity (TAC) as indicator of the overall antioxidant system. Training induced a significant (p<0.05) decrease in resting plasma TBARS concentration in both MOD (7.53±0.30 and 6.46±0.27 µM, PRE and POST respectively) and HIDT (7.21±0.32 and 5.85±0.46 µM, PRE and POST respectively). Resting urinary 8-OH-dG levels were significantly decreased in both MOD (5.50±0.66 and 4.16±0.40 ng mg⁻¹creatinine, PRE and POST respectively) and HIDT (4.52±0.50 and 3.18±0.34 ng mg⁻¹creatinine, PRE and POST respectively). Training both in MOD and HIDT did not significantly modify plasma levels of PC. Resting plasma TAC was reduced in MOD while no significant changes were observed in HIDT. In conclusion, these results suggest that in masters runners high-intensity discontinuous does not cause higher level of exercise-induced oxidative stress than continuous moderate-intensity training, inducing similar beneficial effects on redox homeostasis.     

Deletion of CD73 increases exercise power in mice

Ecto-5′-nucleotidase or CD73 is the main source of extracellular adenosine involved in the activation of adenosine A_2A receptors, responsible for the ergogenic effects of caffeine. We now investigated the role of CD73 in exercise by comparing female wild-type (WT) and CD73 knockout (KO) mice in a treadmill-graded test to evaluate running power, oxygen uptake (V̇O₂), and respiratory exchange ratio (RER) — the gold standards characterizing physical performance. Spontaneous locomotion in the open field and submaximal running power and V̇O₂ in the treadmill were similar between CD73-KO and WT mice; V̇O₂max also demonstrated equivalent aerobic power, but CD73-KO mice displayed a 43.7 ± 4.2% larger critical power (large effect size, P < 0.05) and 3.8 ± 0.4% increase of maximum RER (small effect size, P < 0.05). Thus, KO of CD73 was ergogenic; i.e., it increased physical performance.     

Effects of Mountain Ultra-Marathon Running on ROS Production and Oxidative Damage by Micro-Invasive Analytic Techniques

Purpose

Aiming to gain a detailed insight into the physiological mechanisms involved under extreme conditions, a group of experienced ultra-marathon runners, performing the mountain Tor des Géants® ultra-marathon: 330 km trail-run in Valle d’Aosta, 24000 m of positive and negative elevation changes, was monitored. ROS production rate, antioxidant capacity, oxidative damage and inflammation markers were assessed, adopting micro-invasive analytic techniques.

Methods

Forty-six male athletes (45.04±8.75 yr, 72.6±8.4 kg, 1.76±0.05 m) were tested. Capillary blood and urine were collected before (Pre-), in the middle (Middle-) and immediately after (Post-) Race. Samples were analyzed for: Reactive Oxygen Species (ROS) production by Electron Paramagnetic Resonance; Antioxidant Capacity by Electrochemistry; oxidative damage (8-hydroxy-2-deoxy Guanosine: 8-OH-dG; 8-isoprostane: 8-isoPGF2α) and nitric oxide metabolites by enzymatic assays; inflammatory biomarkers (plasma and urine interleukin-6: IL-6-P and IL-6-U) by enzyme-linked immunosorbent assays (ELISA); Creatinine and Neopterin by HPLC, hematologic (lactate, glucose and hematocrit) and urine parameters by standard analyses.

Results

Twenty-five athletes finished the race, while twenty-one dropped out of it. A significant increase (Post-Race vs Pre) of the ROS production rate (2.20±0.27 vs 1.65±0.22 μmol^.min^-1), oxidative damage biomarkers (8-OH-dG: 6.32±2.38 vs 4.16±1.25 ng^.mg^-1 Creatinine and 8-isoPGF2α: 1404.0±518.30 vs 822.51±448.91 pg^.mg^-1Creatinine), inflammatory state (IL-6-P: 66.42±36.92 vs 1.29±0.54 pg^.mL^-1 and IL-6-U: 1.33±0.56 vs 0.71±0.17 pg^.mL¹) and lactate production (+190%), associated with a decrease of both antioxidant capacity (-7%) and renal function (i.e. Creatinine level +76%) was found.

Conclusions

The used micro-invasive analytic methods allowed us to perform most of them before, during and immediately after the race directly in the field, by passing the need of storing and transporting samples for further analysis. Considered altogether the investigated variables showed up that exhaustive and prolonged exercise not only promotes the generation of ROS but also induces oxidative stress, transient renal impairment and inflammation.     

Ingestion of a Cold Temperature/Menthol Beverage Increases Outdoor Exercise Performance in a Hot,Humid Environment

Purpose

A recent laboratory study demonstrated that the ingestion of a cold/menthol beverage improved exercise performance in a hot and humid environment during 20 km of all-out cycling. Therefore, the aim of this study was to determine whether the ingestion of cold water/ice-slurry with menthol would improve performance in hot and humid outdoor conditions.

Methods

Ten trained males completed three trials of five blocks consisting of 4-km cycling and 1.5-km running. During warm-up, every block and recovery, the athletes drank 190 ml of aromatized (i.e., with 0.05 mL of menthol) beverage at three temperatures: Neutral (ambient temperature) (28.7°C±0. 5°C), Cold (3.1°C±0.6°C) or Ice-slurry (0.17°C±0.07°C). Trial time, core temperature (T_co), heart rate (HR), rate of perceived exertion (RPE), thermal sensation (TS) and thermal comfort (TC) were assessed.

Results

Ice-slurry/menthol increased performance by 6.2% and 3.3% compared with neutral water/menthol and cold water/menthol, respectively. No between-trial differences were noted for T_co, HR, RPE, TC and TS was lower with ice-slurry/menthol and cold water/menthol compared with neutral water/menthol.

Conclusion

A low drink temperature combined with menthol lessens the performance decline in hot/humid outdoor conditions (i.e., compared with cold water alone). Performances were better with no difference in psycho-physiological stress (T_co, HR and RPE) between trials. The changes in perceptual parameters caused by absorbing a cold/menthol beverage reflect the psychological impact. The mechanism leading to these results seems to involve brain integration of signals from physiological and psychological sources.     

Caffeine Increases Anaerobic Work and Restores Cycling Performance following a Protocol Designed to Lower Endogenous Carbohydrate Availability

The purpose this study was to examine the effects of caffeine ingestion on performance and energy expenditure (anaerobic and aerobic contribution) during a 4-km cycling time trial (TT) performed after a carbohydrate (CHO) availability-lowering exercise protocol. After preliminary and familiarization trials, seven amateur cyclists performed three 4-km cycling TT in a double-blind, randomized and crossover design. The trials were performed either after no previous exercise (CON), or after a CHO availability-lowering exercise protocol (DEP) performed in the previous evening, followed by either placebo (DEP-PLA) or 5 mg.kg⁻¹ of caffeine intake (DEP-CAF) 1 hour before the trial. Performance was reduced (−2.1%) in DEP-PLA vs CON (421.0±12.3 vs 412.4±9.7 s). However, performance was restored in DEP-CAF (404.6±17.1 s) compared with DEP-PLA, while no differences were found between DEP-CAF and CON. The anaerobic contribution was increased in DEP-CAF compared with both DEP-PLA and CON (67.4±14.91, 47. 3±14.6 and 55.3±14.0 W, respectively), and this was more pronounced in the first 3 km of the trial. Similarly, total anaerobic work was higher in DEP-CAF than in the other conditions. The integrated electromyographic activity, plasma lactate concentration, oxygen uptake, aerobic contribution and total aerobic work were not different between the conditions. The reduction in performance associated with low CHO availability is reversed with caffeine ingestion due to a higher anaerobic contribution, suggesting that caffeine could access an anaerobic “reserve” that is not used under normal conditions.     

The Metabolic and Performance Effects of Caffeine Compared to Coffee during Endurance Exercise

There is consistent evidence supporting the ergogenic effects of caffeine for endurance based exercise. However, whether caffeine ingested through coffee has the same effects is still subject to debate. The primary aim of the study was to investigate the performance enhancing effects of caffeine and coffee using a time trial performance test, while also investigating the metabolic effects of caffeine and coffee. In a single-blind, crossover, randomised counter-balanced study design, eight trained male cyclists/triathletes (Mean±SD: Age 41±7y, Height 1.80±0.04 m, Weight 78.9±4.1 kg, VO₂ max 58±3 ml•kg⁻¹•min⁻¹) completed 30 min of steady-state (SS) cycling at approximately 55% VO₂max followed by a 45 min energy based target time trial (TT). One hour prior to exercise each athlete consumed drinks consisting of caffeine (5 mg CAF/kg BW), instant coffee (5 mg CAF/kg BW), instant decaffeinated coffee or placebo. The set workloads produced similar relative exercise intensities during the SS for all drinks, with no observed difference in carbohydrate or fat oxidation. Performance times during the TT were significantly faster (∼5.0%) for both caffeine and coffee when compared to placebo and decaf (38.35±1.53, 38.27±1.80, 40.23±1.98, 40.31±1.22 min respectively, p<0.05). The significantly faster performance times were similar for both caffeine and coffee. Average power for caffeine and coffee during the TT was significantly greater when compared to placebo and decaf (294±21 W, 291±22 W, 277±14 W, 276±23 W respectively, p<0.05). No significant differences were observed between placebo and decaf during the TT. The present study illustrates that both caffeine (5 mg/kg/BW) and coffee (5 mg/kg/BW) consumed 1 h prior to exercise can improve endurance exercise performance.     

THE COMBINATION OF α-LIPOIC ACID INTAKE WITH ECCENTRIC EXERCISE MODULATES ERYTHROPOIETIN RELEASE

The generation of reactive nitrogen/oxygen species (RN/OS) represents an important mechanism in erythropoietin (EPO) expression and skeletal muscle adaptation to physical and metabolic stress. RN/OS generation can be modulated by intense exercise and nutrition supplements such as α-lipoic acid, which demonstrates both anti- and pro-oxidative action. The study was designed to show the changes in the haematological response through the combination of α-lipoic acid intake with running eccentric exercise. Sixteen healthy young males participated in the randomised and placebo-controlled study. The exercise trial involved a 90-min run followed by a 15-min eccentric phase at 65% VO₂max (-10% gradient). It significantly increased serum concentrations of nitric oxide (NO), hydrogen peroxide (H₂O₂) and pro-oxidative products such as 8-isoprostanes (8-iso), lipid peroxides (LPO) and protein carbonyls (PC). α-Lipoic acid intake (Thiogamma: 1200 mg daily for 10 days prior to exercise) resulted in a 2-fold elevation of serum H₂O₂ concentration before exercise, but it prevented the generation of NO, 8-iso, LPO and PC at 20 min, 24 h, and 48 h after exercise. α-Lipoic acid also elevated serum EPO level, which highly correlated with NO/H₂O₂ ratio (r = 0.718, P < 0.01). Serum total creatine kinase (CK) activity, as a marker of muscle damage, reached a peak at 24 h after exercise (placebo 732 ± 207 IU · L^-1, α-lipoic acid 481 ± 103 IU · L^-1), and correlated with EPO (r = 0.478, P < 0.01) in the α-lipoic acid group. In conclusion, the intake of high α-lipoic acid modulates RN/OS generation, enhances EPO release and reduces muscle damage after running eccentric exercise.     

Effect of ambient temperature on female endurance performance

Ambient temperature can affect physical performance, and an ambient temperature range of −4 °C to 11 °C is optimal for endurance performance in male athletes. The few similar studies of female athletes appear to have found differences in response to cold between the genders. This study investigated whether ambient temperature affects female endurance performance. Nine athletes performed six tests while running on a treadmill in a climatic chamber at different ambient temperatures: 20, 10, 1, −4, −9 and −14 °C and a wind speed of 5 m s⁻¹. The exercise protocol consisted of a 10-min warm-up, followed by four 5-min intervals at increasing intensities at 76%, 81%, 85%, and 89% of maximal oxygen consumption. This was followed by an incremental test to exhaustion. Although peak heart rate, body mass loss, and blood lactate concentration after the incremental test to exhaustion increased as the ambient temperature rose, no changes in time to exhaustion, running economy, running speed at lactate threshold or maximal oxygen consumption were found between the different ambient temperature conditions. Endurance performance during one hour of incremental exercise was not affected by ambient temperature in female endurance athletes.     

Thermal,Metabolic, Blood,and Circulatory Adjustments in Prolonged Outdoor Exercise

Thermal, metabolic, and circulatory responses were studied in six hill-walkers taking part in a 28-mile (45-km.) walk in rough country in autumn and winter, air temperatures being 6 to 12° C. and –2 to 2° C., respectively.Though they were an apparently well-matched party, the walkers had to split into three pairs to avoid exhaustion. They adjusted their clothing so that mean skin temperatures were similar in both warm and cold conditions, the average value being 30·5° C. compared with the resting comfort range of 33 to 34·5° C. When, on the winter trial, skin temperatures were lowered by reduction of clothing, mean skin temperatures fell to 26·5 to 27·8° C., one subject showing a value of 21·3° C. These temperatures were associated with moderate discomfort from cold.Gut temperatures during exercise, measured with a radio pill, averaged 38·7 to 37·9° C. on the autumn exercise. Slightly lower values were observed in winter, but this was associated with slower walking rather than cold stress. A fat and a thin subject walking together with minimal clothing showed widely different temperature responses, the fatter subject having a lower skin temperature and higher gut temperature than his companion. These results were compared with other results on extreme cold stress and discussed in relation to hypothermia. Heart rate and blood pressure findings were unremarkable, except for increased post-exercise heart rates and standing/lying heart rate differences, and a tendency to postural hypotension associated with exhaustion. Blood volume was not reduced in exhaustion and there were no significant changes in blood electrolytes or other constituents apart from a small rise in potassium. Ketonuria developed in all subjects.