Effects of prolonged warm-up exercise above and below anaerobic threshold on maximal performance

Summary The purpose of the present study was to determine the effects of prolonged warm-up exercise above and below anaerobic threshold (AT) on maximal performance. Warm-up exercise consisted of pedalling the Monark cycle ergometer at either 40% (Below AT) or 68% (Above AT) of VO₂ max for 60 min. Each maximal performance consisted of two 40 s bouts of all out pedalling on the Monark cycle ergometer against 5.5 kg resistance separated by a 5 min rest period. These tests were administered on two occasions without warm-up exercise and were found to be reproducible for work output and peak blood lactate concentration. Below AT warm-up exercise significantly increased core temperature with no increase in steady state blood lactate concentration and was thus representative of a desired warmed-up status. This condition did not contribute to an improved maximal performance. Above AT warm-up exercise resulted in significant increases in core temperature and steady state blood lactate concentration. Work output and peak blood lactate concentration for maximal exercise were significantly decreased. It was concluded that task specific prolonged warm-up exercise below AT does not contribute to an improved maximal performance of the type employed in the present study. Following warm-up exercise above AT, maximal performance was impaired. This was attributed to probable glycogen depletion in fast twitch muscle fibers which in turn may have contributed to a decreased lactate production.This research was supported by the Graduate Research Council of the University of Louisville     

Effects of chronic bicarbonate ingestion on the performance of high-intensity work

We have evaluated whether sodium bicarbonate, taken chronically (0.5?g?·?kg^?1 body mass) for a period of 5 days would improve the performance of eight subjects during 60?s of high-intensity exercise on an electrically braked cycle ergometer. The first test was performed prior to chronic supplementation (pre-ingestion) while the post-ingestion test took place 6 days later. A control test took place approximately 1 month after the cessation of all testing. Acid-base and metabolite data (n?=?7) were measured from arterialised blood both pre- and post-exercise, as well as daily throughout the exercise period. The work completed by the subjects in the control and pre-ingestion test [21.1 (0.9) and 21.1 (0.9) MJ, respectively] was less than (P?F _(2,21)?=?3.4, P?P?F _(5,36)?=?12.5, P?P??1 after 24?h of ingestion. In conclusion, the addition of sodium bicarbonate to a normal diet proved to be of ergogenic benefit in the performance of short-term, high-intensity work.     

Cerebral oxygenation declines at exercise intensities above the respiratory compensation threshold

During incremental exercise PaCO2 and PETCO2 begin to decline at the respiratory compensation threshold (RCT-GEX). Since PaCO2 alters cerebral blood flow it was hypothesized that there would be a systematic decline in cerebral oxygenation (Cox) measured by near infrared spectroscopy above the RCT (RCT-NIRS). Cardiorespiratory and NIRS responses were simultaneously monitored from the left frontal lobe during incremental exercise in 17 men. All subjects showed a decline in Cox above the RCT-GEX with a 20-40 s delay. Significant differences (P<0.01) were observed between the RCT-GEX and RCT-NIRS for time (9.83 versus 10.39 min), power (198 versus 212 W) and oxygen uptake (2.31 versus 2.43 L min-1). Intra-class correlations for power and absolute VO2 were 0.97 and 0.98, respectively. Bland-Altman analysis revealed no outliers for any of the variables. The results suggested that the decrease in Cox observed above the RCT was most likely due to a reduction in cerebral blood flow mediated by a decline in PaCO2. This decline in Cox could reduce neuronal activation thereby limiting maximal exercise capacity in healthy subjects.     

Effect of L-ornithine hydrochloride ingestion on intermittent maximal anaerobic cycle ergometer performance and fatigue recovery after exercise

l-Ornithine plays an important role in ammonia metabolism via the urea cycle. This study aimed to examine the effect of l-ornithine hydrochloride ingestion on ammonia metabolism and performance after intermittent maximal anaerobic cycle ergometer exercise. Ten healthy young adults (age, 23.8 ± 3.9 year; height, 172.3 ± 5.5 cm; body mass, 67.7 ± 6.1 kg) with regular training experience ingested l-ornithine hydrochloride (0.1 g/kg, body mass) or placebo after 30 s of maximal cycling exercise. Five sets of the same maximal cycling exercise were conducted 60 min after ingestion, and maximal cycling exercise was conducted after a 15 min rest. The intensity of cycling exercise was based on each subject’s body mass (0.74 N kg⁻¹). Work volume (watt), peak rpm (rpm) before and after intermittent maximal ergometer exercise and the following serum parameters were measured before ingestion, immediately after exercise and 15 min after exercise: ornithine, ammonia, urea, lactic acid and glutamate. Peak rpm was significantly greater with l-ornithine hydrochloride ingestion than with placebo ingestion. Serum ornithine level was significantly greater with l-ornithine hydrochloride ingestion than with placebo ingestion immediately and 15 min after intermittent maximal cycle ergometer exercise. In conclusion, although maximal anaerobic performance may be improved by l-ornithine hydrochloride ingestion before intermittent maximal anaerobic cycle ergometer exercise, the above may not depend on increase of ammonia metabolism with l-ornithine hydrochloride.     

Sodium bicarbonate ingestion improves performance in interval swimming

Summary In an effort to determine the effects of bicarbonate (NaHCO₃) ingestion on exercise performance, ten male college swimmers were studied during five different trials. Each trial consisted of five 91.4m (100-yd) front crawl swims with a two-minute rest interval between each bout. The trials consisted of two NaHCO₃ treatments, two placebo trials and one test with no-drink. One hour before the onset of swimming, the subjects were given 300 ml of citric acid flavored solution containing either 17 mmol of NaCl (placebo) or 2.9 mmol of NaHCO₃ · kg^–1 body weight (experimental), or received no drink (no-drink). Performance times for each 91.4 m swim were recorded. Blood samples were obtained before and one hr after treatment, two min after warmup, and two min after the final 91.4 m sprint. Blood pH, lactate, standard bicarbonate (SBC) and base excess (BE) were measured. No differences were found for performance or the blood measurements between the placebo and no-drink trials. Bicarbonate feedings, on the other hand, produced a significant (P<0.05) improvement in performance on the fourth and fifth swimming sprints. Blood lactate, pH, SBC and BE were significantly higher (P<0.05) at post-exercise in NaHCO₃ treatments. These data are in agreement with previous findings that during repeated bouts of exercise pre-exercise administration of NaHCO₃ improves performance, possibly by facilitating the efflux of hydrogen ions from working muscles and thereby delaying the onset of fatigue.     

Effects of CO2 inhalation prior to maximal exercise on physical performance

In the untrained subjects, inhalation of 4.5-6.0% CO2 prior to maximal treadmill exercise does not affect physical performance and maximum oxygen uptake, while blood lactate levels during recovery have a tendency to greater decrease in CO2 breathing than that in the room-air breathing. It was suggested that CO2 inhalation immediately prior to maximal exercise as applied here is not a useful tool in increasing physical performance.     

Effects of bicarbonate ingestion and high intensity exercise on lactate and H(+)-ion distribution in different blood compartments

Lactate (La) and H⁺-ions are unequally distributed in the blood between plasma and red blood cells (RBCs). To our knowledge there is no data concerning the effects of an oral ingestion of bicarbonate (HCO₃ ⁻) on repeated high intensity sprint exercise and La and H⁺ distribution between plasma and RBCs. Since an oral ingestion of HCO₃ ⁻ leads to a higher efflux of La from the working skeletal muscle to the plasma, as it was shown by previous studies, this would lead to a higher gradient of La between plasma and RBCs. Although a higher gradient leads to a higher uptake, it is even more difficult for the RBCs to take up La fast enough, due to the more stressed transport system. Since RBCs function to transport La from the working muscle and help to maintain a concentration difference between plasma and muscle, this potentially increases performance during repeated sprint exercise (e.g. 4 × 30 s). The major goal of the present investigation was to test this hypothesis. 11 male participants ingested either a solution of sodium bicarbonate (NaHCO₃) or placebo (CaCO₃). Thereafter all performed four maximal 30 s sprints with 5 min of passive rest. During the resting periods concentrations of HCO₃ ⁻, La and H⁺ where measured in both blood compartments (plasma and RBCs). There were no significant differences in the La-ratios between plasma and RBCs between both interventions. These results indicate that the La/H⁺ co-transport is not affected by an oral ingestion on NaHCO₃.     

Sodium citrate ingestion and its effects on maximal anaerobic exercise of different durations

Summary The effects of an alkalising agent were studied in ten subjects who participated in anaerobic testing on a cycle ergometer to determine the effectiveness of sodium citrate (0.5 g·kg^–1 body mass) as an ergogenic aid during exercise of 10-s, 30-s, 120-s and 240-s duration. Blood was collected prior to, after ingestion of sodium citrate (NaHCO₃), and postexercise, from a heated (43–46°C) fingertip and analysed immediately postcollection for pH, partial pressure of oxygen and carbon dioxide, base excess and blood bicarbonate. Total work undertaken (kJ) and peak power (W) achieved during the tests was also obtained via a work monitor unit. The results indicated that a dose of 0.5 g sdkg^–1 body mass sodium citrate had no ergogenic benefit for exercise of either 10-s or 30-s duration. Blood bicarbonate concentrations, however, were significantly increased (P<0.05) following ingestion of the citrate during these trials. Exercise periods of 120 s and 240 s were significantly increased (P<0.05) above the control and placebo conditions following sodium citrate ingestion. Blood bicarbonate concentrations were again increased above control and placebo conditions and blood lactate concentrations were also increased following the citrate trials. The pH decreased significantly (P<0.05) in all trials below the control and placebo conditions. On the basis of the exercise undertaken in this study we would suggest that a dose of 0.5 g·kg^–1 body mass of sodium citrate could improve anaerobic exercise performance of 120-s and 240-s duration.     

The effect of ammonium chloride and sodium bicarbonate ingestion on the physical working capacity at the fatigue threshold

Summary The purpose of this investigation was to examine the effect of ammonium chloride (NH₄Cl) and sodium bicarbonate (NaHCO₃) ingestion on the physical working capacity at the fatigue threshold (PWC_FT). Eighteen adult males (mean age, SD=23, 2 years) volunteered for two experiments (experiment 1,n=9 ; experiment 2,n=9). In both experiments, the subjects orally ingested 0.3 g · kg^–1 body weight of NH₄Cl and NaHCO₃ over a 3-h period in random order on days separated by 72 h or more. In experiment 1, following ingestion of the substance, the subjects performed a discontinuous incremental cycle ergometer test to the onset of PWC_FT which was estimated from integrated electromyography voltages at the vastus lateralis muscle. In experiment 2, the subjects performed a continuous PWC_FT test. The results of these experiments indicated that NH₄Cl and NaHCO₃ ingestion had no significant (P>0.05) effect on PWC_FT (experiment 1: NH₄Cl=257, SD 26 W; NaHCO₃=256, SD 22 W;t=0.06;r=0.866; experiment 2: NH₄Cl=231, 14 W; NaHCO₃=216, 16 W;t=1.78;r=0.857).     

Effects of sodium bicarbonate ingestion on EMG,effort sense and ventilatory response during intense exercise and subsequent active recovery

To determine whether post-exercise ventilation is related to decrease in blood pH and also whether post-exercise ventilation, associated or not with decreased blood pH, involves an increase in central motor command during exercise, we examined the effects of NaHCO₃ ingestion on the ventilatory response ( [(\textV)\dot] {\dot{\text{V}}} E), integrated electromyogram (iEMG) and effort sense of legs (ESL) during intense exercise (IE) and subsequent active recovery. Subjects performed two IE tests (105–110% of maximal work rate, 2 min) after ingestion of NaHCO₃ or CaCO₃. Subjects performed light load exercise (20 W) before and after IE for 6 min and 30 min, respectively. Although there was a significant difference in blood pH between the two conditions during and after IE, [(\textV)\dot] {\dot{\text{V}}} E, iEMG and ESL were similar. iEMG returned to the pre-IE level immediately after the end of IE, while ESL showed slow recovery. [(\textV)\dot] {\dot{\text{V}}} E decreased rapidly until about 50 s after the end of IE (fast phase) and then showed a slow recovery kinetics (slow phase). The ventilatory responses during the fast phase and during the slow phase were correlated with ESL at the end of IE and from 3 min after the end of IE, respectively. Moreover, there was no significant difference in the slopes and intercepts of regression lines between [(\textV)\dot] {\dot{\text{V}}} E and ESL under the two conditions in both phases. These results suggest that the ventilatory response after IE is associated with effort sense indirectly-elicited by central motor command, but the effort sense-mediated response is not affected by blood pH.     

The effect of sodium bicarbonate and sodium citrate ingestion on anaerobic power during intermittent exercise

Summary The effect of sodium bicarbonate and sodium citrate ingestion on cycling performance in three 30 s Wingate Anaerobic Tests separated by 6 min recovery periods has been studied using 6 male subjects. Subjects ingested either sodium bicarbonate (B), sodium bicarbonate plus sodium citrate (BC), sodium citrate (C) or sodium chloride (P) 2.5 h prior to exercise in a dose of 0.3 g kg⁻¹ body weight. Pre-exercise blood pH was 7.44±0.06, 7.42±0.05, 7.41±0.05 and 7.38±0.04 in the C, BC, B and P conditions respectively. Mean and peak power output were significantly reduced by successive Wingate tests but not significantly affected by the treatments. Performance in the second and third tests was highest following C, BC and B ingestion. The total work done in the 3 tests was 103%, 102% and 101% of that achieved in the P condition after C, BC and B ingestion respectively. The increased alkali reserve recorded subsequent to bicarbonate and citrate treatment reduced mean post-exercise acidosis, although pH was significantly higher only in the C condition (p<0.05) compared to P after each exercise bout. No significant differences in plasma lactate concentration were recorded at any time. Citrate ingestion appears to be most effective in elevating blood pH and [HCO₃ ⁻], and in enhancing performance in short-term intermittent exercise. This study demonstrates that alkali ingestion results in significant shifts in the acid-base balance of the blood and has a small, but non-significant, effect on anaerobic power and capacity as measured in a series of 3 Wingate Anaerobic Tests.     

Effect of acute sodium bicarbonate ingestion on excess C02 output during incremental exercise

Summary The effect of bicarbonate ingestion on total excess volume of CO₂ Output (CO₂ excess), due to bicaronate buffering of lactic acid in exercise, was studied in eight healthy male volunteers during incremental exercise on a cycle ergometer performed after ingestion (0.3 g · kg^–1 body mass) of CaCO₃ (control) and NaHCO₃ (alkalosis). The resting arterialized venous blood pH (P<0.05) and bicarbonate concentration ([HCO₃ ^–]_b;P<0.01) were significantly higher in acute metabolic alkalosis [AMA; pH, 7.44 (SD 0.03); [HCO₃ ^–]_b; 29.4 (SD 1.5) mmol·1^-1] than in the control [pH, 7.39 (SD 0.03); [HCO₃ ^–]_b, 25.5 (SD 1.0) mmol·1^–1]. The blood lactate concentrations ([la^–]_b) during exercise below the anaerobic threshold (AT) were not affected by AMA, while significantly higher [la^–]_b at exhaustion [12.29 (SD 1.87) vs 9.57 (SD 2.14) mmol·1^–1,P < 0.05] and at 3 min after exercise [14.41 (SD 1.75) vs 12.26 (SD 1.40) mmol · l^–1,P < 0.05] were found in AMA compared with the control. The CO₂ excess increased significantly from the control [3177 (SD 506) ml] to AMA [3897 (SD 381) ml;P < 0.05]. The CO₂ excess per body mass was found to be significantly correlated with both the increase of [la^–]_b from rest to 3 min after exercise ( [la^–]_b;r=0.926,P < 0.001) and with the decrease of [HCO₃ ^–]_b from rest to 3 min after exercise ( [HCO₃ ^–]_b;_r=0.872,P<0.001), indicating that CO₂ excess per body mass increased linearly with both [la^– _b and [HCO₃ ^–]_b. As a consequence, CO₂ excess per body mass per unit increase of [la^–]_b (CO₂ excess·mass^–1· [la^–]_b) was similar for the two conditions. The present results would suggest that the relationship between CO₂ excess and blood lactate accumulation was unaffected by acute metabolic alkalosis, because the relative contribution of bicarbonate buffering of lactic acid was the same as in the control.     

Effect of muscle glycogen availability on maximal exercise performance

This investigation determined the influence of pre-exercise muscle glycogen availability on performance during high intensity exercise. Nine trained male cyclists were studied during 75 s of all-out exercise on an air-braked cycle ergometer following muscle glycogen-lowering exercise and consumption of diets (energy content approximately 14 MJ) that were either high (HCHO – 80% CHO) or low (LCHO – 25% CHO) in carbohydrate content. The exercise-diet regimen was successful in producing differences in pre-exercise muscle glycogen contents [HCHO: 578(SEM?55) mmol?·?kg^?1 dry mass; LCHO: 364 (SEM 58) P??1 dry mass]. Despite this difference in muscle glycogen availability, there were no between trial differences for peak power [HCHO 1185 (SEM 50)W, LCHO 1179 (SEM?48)W], mean power [HCHO 547 (SEM?5)W, LCHO 554 (SEM ?8)W] and maximal accumulated oxygen deficit [HCHO 54.4 (SEM?2.3)?ml?·?kg^?1, LCHO 54.6 (SEM?2.0) ml?·?kg^?1]. Postexercise muscle lactate contents (HCHO 95.9 (SEM?4.6)?mmol?·?kg^?1 dry mass, LCHO 82.7 (SEM?12.3) mmol?·?kg^?1 dry mass, n?=?8] were no different between the two trials, nor were venous blood lactate concentrations immediately after and during recovery from exercise. These results would indicate that increased muscle glycogen availability has no direct effect on performance during all-out high intensity exercise.     

Influence of sodium bicarbonate ingestion on plasma ammonia accumulation during incremental exercise in man

Summary This investigation evaluated the influence of metabolic alkalosis on plasma ammonia (NH₃) accumulation during incremental exercise. On two occasions separated by at least 6 days, six healthy men cycled at 70, 80, and 90%g of maximum oxygen consumption ( ) for 5 min; each exercise period was followed by 5 min of seated recovery. Exercise was then performed at 100% until exhaustion. Beginning 3 h prior to exercise, subjects ingested 3.6 mmol · kg body mass^– NaHCO₃ (test, T) or 3.0 mmol · kg body mass^–1 CaCO₃ (placebo, P) (both equivalent to 0.3 g · kg^–1) over a 2-h period. Trials were performed after an overnight fast and the order of treatments was randomized. Arterialized venous blood samples for the determination of acid-base status, blood lactate and plasma NH₃ concentrations were obtained at rest before treatment, 15 s prior to each exercise bout (Pre 70%, Pre 80%, Pre 90%, and Pre 100%), and at 0, 5 (5Post), and 10 (10'Post) min after exhaustion. Additional samples for blood lactate and plasma NH₃ determination were obtained immediately after each exercise bout (Post 70%, Post 80%, Post 90%) and at 15 min after exercise (15Post). Time to exhaustion at 100% of was not significantly different between treatments [mean (SE): 173 (42) s and 184 (44) s for T and P respectively]. A significant treatment effect was observed for plasma pH with values being significantly higher on T than on P Pre 70% [7.461 (0.007) vs 7.398 (0.008)], Pre 90% [7.410 (0.010) vs 7.340 (0.016)], and 10'Post [7.317 (0.032) vs 7.242 (0.036)]. The change in plasma pH was significantly greater following the 90%g bout (Pre 100% Pre 90%) for T [–0.09 (0.02)] than for P [–0.06 (0.01)]. Blood base excess and plasma bicarbonate concentrations were significantly higher for T than P before each exercise bout but not at the point of exhaustion. During recovery, base excess was higher for T than P at 5Post and 10Post while the bicarbonate concentration was higher for T than P at 10Post. A significant treatment effect was observed for the blood lactate concentration with T on the average being higher than P [7.0 (1.0) and 6.3 (1.1) mmol · l^–1 for T and P averaged across the 12 sampling times]. Plasma NH₃ accumulation was not different between treatments at any point in time. In addition, no differences were observed between treatments in blood alanine accumulation. The results suggest that under the conditions of the present investigation metabolic alkalosis does not influence plasma NH₃ accumulation or endurance capacity during intense incremental exercise.     

Effects of training at and above the lactate threshold on the lactate threshold and maximal oxygen uptake

Summary Thirty-three college women (mean age=21.8 years) participated in a 5 d·wk^–1, 12 week training program. Subjects were randomly assigned to 3 groups, above lactate threshold (> LT) (N=11; trained at 69 watts above the workload associated with LT), =LT (N=12; trained at the work load associated with LT) and control (C) (N=10). Subjects were assessed for , LT, LT/ , before and after training, using a discontinuous 3 min incremental (starting at 0 watts increasing 34 watts each work load) protocol on a cycle ergometer (Monark). Respiratory gas exchange measures were determined using standard open circuit spirometry while LT was determined from blood samples taken immediately following each work load from an indwelling venous catheter located in the back of a heated hand. Body composition parameters were determined before and after training via hydrostatic weighing. Training work loads were equated so that each subject expended approximately 1465 kJ per training session (Monark cycle ergometer) regardless of training intensity. Pretraining, no significant differences existed between groups for any variable. Post training the > LT group had significantly higher (13%), (47%) and LT/ (33%) values as compared to C (p<.05). Within group comparisons revealed that none of the groups significantly changed as a result of training, only the > LT group showed a significant increase in (48%) (p<.05), while both the = LT and > LT group showed significant increases in LT/ (= LT 16%, > LT 42% (p<.05)). No differences were found between or within groups post training for body composition parameters. It was concluded that training above the LT results in an improvement in LT and that large improvements in may not be required for large improvements in .Data were collected at the Human Performance Laboratory, University of Colorado     

The physiological stress response to high-intensity sprint exercise following the ingestion of sodium bicarbonate

The purpose of this study was to investigate the effects of pre-exercise alkalosis on the physiological stress response to high-intensity exercise. Seven physically active males (age 22 ± 3 years, height 1.82 ± 0.06 m, mass 81.3 ± 8.4 kg and peak power output 300 ± 22 W) performed a repeated sprint cycle exercise following a dose of 0.3 g kg^?1 body mass of sodium bicarbonate (NaHCO₃) (BICARB), or a placebo of 0.045 g kg^?1 body mass of sodium chloride (PLAC). Monocyte-expressed heat shock protein 72 (HSP72) and plasma thiobarbituric acid reactive substances (TBARS) were significantly attenuated in BICARB compared to PLAC (p = 0.04 and p = 0.039, respectively), however total anti-oxidant capacity, the ratio of oxidised to total glutathione, cortisol, interleukin 6 and interleukin 8 were not significantly induced by the exercise. In conclusion, monocyte-expressed HSP72 is significantly increased following high-intensity anaerobic exercise, and its attenuation following such exercise with the ingestion of NaHCO₃ is unlikely to be due to a decreased oxidative stress.     

Sodium bicarbonate supplementation improves hypertrophy-type resistance exercise performance

The aim of the present study was to examine the effects of sodium bicarbonate (NaHCO₃) administration on lower-body, hypertrophy-type resistance exercise (HRE). Using a double-blind randomized counterbalanced design, 12 resistance-trained male participants (mean ± SD; age = 20.3 ± 2 years, mass = 88.3 ± 13.2 kg, height = 1.80 ± 0.07 m) ingested 0.3 g kg^?1 of NaHCO₃ or placebo 60 min before initiation of an HRE regimen. The protocol employed multiple exercises: squat, leg press, and knee extension, utilizing four sets each, with 10–12 repetition-maximum loads and short rest periods between sets. Exercise performance was determined by total repetitions generated during each exercise, total accumulated repetitions, and a performance test involving a fifth set of knee extensions to failure. Arterialized capillary blood was collected via fingertip puncture at four time points and analyzed for pH, [HCO₃ ^?], base excess (BE), and lactate [Lac^?]. NaHCO₃ supplementation induced a significant alkaline state (pH: NaHCO₃: 7.49 ± 0.02, placebo: 7.42 ± 0.02, P < 0.05; [HCO₃ ^?]: NaHCO₃: 31.50 ± 2.59, placebo: 25.38 ± 1.78 mEq L^?1, P < 0.05; BE: NaHCO₃: 7.92 ± 2.57, placebo: 1.08 ± 2.11 mEq L^?1, P < 0.05). NaHCO₃ administration resulted in significantly more total repetitions than placebo (NaHCO₃: 139.8 ± 13.2, placebo: 134.4 ± 13.5), as well as significantly greater blood [Lac^?] after the exercise protocol (NaHCO₃: 17.92 ± 2.08, placebo: 15.55 ± 2.50 mM, P < 0.05). These findings demonstrate ergogenic efficacy for NaHCO₃ during HRE and warrant further investigation into chronic training applications.     

Effect of creatine feeding on maximal exercise performance in vegetarians

The effect of creatine supplementation on exercise performance in vegetarians was examined. Creatine was ingested for 1 week by a group of vegetarians (VC) and meat-eaters (MC); a control group of meat-eaters was fed only glucose (MG). Exercise performance during three, 20-s maximal cycling tests (modified Wingate anaerobic test, WAnT) was determined before and after creatine supplementation. Blood samples were also drawn before and after exercise prior to and after supplementation. Basal plasma creatine (after an overnight fast) averaged (SE) 11 (2) μM in VC, and 24 (2) and 23 (7) μM in MG and MC, respectively (P < 0.05 for VC vs meat-eaters). These findings were expected, since most of the body's exogenous creatine source is meat. There was no significant difference in any other parameter between groups prior to supplementation. Creatine feedings significantly increased body mass (≅1 kg) and mean power output during the WAnTs (≅5%) to a similar extent in the VC and MC groups (P < 0.05–0.001). These parameters were not affected by supplementation in the MG group. Peak power output was also significantly increased by supplementation in MC (≅5%, P < 0.05), but not in VC. It is concluded that vegetarians and meat-eaters respond to creatine feedings with similar increases in mean power output during short-term, maximal exercise. Accepted: 24 March 2000     

Maximal lactate steady state,respiratory compensation threshold and critical power

Critical power (CP) and the second ventilatory threshold (VT₂) are presumed to indicate the power corresponding to maximal lactate steady state (MLSS). The aim of this study was to investigate the use of CP and VT₂ as indicators of MLSS. Eleven male trained subjects [mean (SD) age 23 (2.9) years] performed an incremental test (25 W·min⁻¹) to determine maximal oxygen uptake (V˙O_2max), maximal aerobic power (MAP) and the first and second ventilatory thresholds (VT₁ and VT₂) associated with break points in minute ventilation (V˙_E), carbon dioxide production (V˙CO₂), V˙_E/V˙CO₂ and V˙_E/V˙O₂ relationships. Exhaustion tests at 90%, 95%, 100% and 110% of V˙O_2max and several 30-min constant work rates were performed in order to determine CP and MLSS, respectively. MAP and V˙O_2max values were 344 (29) W and 53.4 (3.7) ml·min⁻¹·kg⁻¹, respectively. CP [278 (22) W; 85.4 (4.8)% V˙O_2max] and VT₂ power output [286 (28) W; 85.3 (5.6)% V˙O_2max] were not significantly different (p=0.96) but were higher (p<0.05) than the MLSS work rate [239 (21) W; 74.3 (4.0)% V˙O_2max] and VT₁ power output [159 (23) W; 52.9 (6.9)% V˙O_2max]. MLSS work rate was significantly correlated (p<0.05) with those noted at VT₁ and VT₂ (r=0.74 and r=0.93, respectively). VT₂ overestimated MLSS by 10.9 (6.3)% V˙O_2max which was significantly higher than VT₁ [+21.4 (5.6)% V˙O_2max; p<0.01]. CP calculated from a given range of exhaustion times does not correspond to MLSS. Electronic Publication