Fatigue during a 5-km running time trial

This study investigated fatigue-induced changes in neuromuscular and stride characteristics during and immediately after the 5-km running time trial. Eighteen well-trained male distance runners performed a maximal 20-m sprint test and maximal voluntary contraction (MVC) in a leg press machine before and immediately after the 5-km running time trial. In all the tests the EMG of five lower limb muscles was measured. The results of the present study showed that muscle fatigue measured in maximal exercises like 20-m sprint and MVC are not related to the fatigue induced changes during the 5-km time trial. The fatigue in the 20-m sprint test was related to the maximal 20-m pretest velocity (r = 0.58, p < 0.05), but the velocity loss during the 5-km time trial was inversely related to 5-km performance (r = - 0.60, p < 0.05) and training volume (r = - 0.58, p < 0.05). It was concluded that the fatigue in 5-km running measured pre- and postexercise at maximal effort is more related to sprint performance rather than endurance performance, but the fatigue measured during the 5-km running is related to endurance performance and factors affecting pacing strategy.     

Placebo effects of caffeine on cycling performance

PURPOSE: The placebo effect-a change attributable only to an individual's belief in the efficacy of a treatment-might provide a worthwhile improvement in physical performance. Although sports scientists account for placebo effects by blinding subjects to treatments, little research has sought to quantify and explain the effect itself. The present study explored the placebo effect in laboratory cycling performance using quantitative and qualitative methods. METHOD: Six well-trained male cyclists undertook two baseline and three experimental 10-km time trials. Subjects were informed that in the experimental trials they would each receive a placebo, 4.5 mg.kg caffeine, and 9.0 mg.kg caffeine, randomly assigned. However, placebos were administered in all experimental conditions. Semistructured interviews were also conducted to explore subjects' experience of the effects of the capsules before and after revealing the deception. RESULTS: A likely trivial increase in mean power of 1.0% over baseline was associated with experimental trials (95% confidence limits, -1.4 to 3.6%), rising to a likely beneficial 2.2% increase in power associated with experimental trials in which subjects believed they had ingested caffeine (-0.8 to 5.4%). A dose-response relationship was evident in experimental trials, with subjects producing 1.4% less power than at baseline when they believed they had ingested a placebo (-4.6 to 1.9%), 1.3% more power than at baseline when they believed they had ingested 4.5 mg.kg caffeine (-1.4 to 4.1%), and 3.1% more power than at baseline when they believed they had ingested 9.0 mg.kg caffeine (-0.4 to 6.7%). All subjects reported caffeine-related symptoms. CONCLUSIONS: Quantitative and qualitative data suggest that placebo effects are associated with the administration of caffeine and that these effects may directly or indirectly enhance performance in well-trained cyclists.     

Effect of sucrose and caffeine ingestion on performance of prolonged strenuous running

To investigate the effect of sucrose or caffeine ingestion on the performance of prolonged running, five male distance runners attending senior high school (15.6 yrs) carried out running on a treadmill at an intensity corresponding to the individuals' 80% VO2 max until exhaustion. Before and 45 min after exercise, the subjects were given either a placebo (Con), sucrose (81 +/- 18 g) (Su), caffeine (384 +/- 13 mg) (Caf), or sucrose (72 +/- 22 g) plus caffeine (396 +/- 29 mg) (Su + Caf) solution. The duration of the exercise was significantly longer in Su, Caf, and Su + Caf than in Con. The duration in four of five subjects was longest in Su + Caf, although it was not significantly different from that in Su or Caf. Carbohydrate (CHO) utilization was highest in Su while fat utilization was highest in Caf. The energy supply from both sources was almost the same between Con and Su + Caf. The plasma glucose concentration was higher in Su than in Con. The plasma free fatty acid (FFA) level was higher in Caf than in Con. The plasma glucose and lactic acid concentrations were highest in Su + Caf while the plasma FFA level was the same as in Con. In conclusion, ingestion of sucrose, caffeine, or sucrose plus caffeine solution was equally effective in improving endurance during running carried out at an intensity of approximately 80% VO2 max.     

Effects of sucrose or caffeine ingestion on running performance and biochemical responses to endurance running

To elucidate the effects of sucrose or caffeine ingestion on metabolic responses to prolonged exercise and on performance of a finishing spurt after the prolonged exercise, seven male physical education students performed four sets of 30 min running (62%-67% VO2 max) followed by progressive exhaustive running on a treadmill. Before each set, they took 350 ml solution containing either sucrose 23.8 g (97.5 kcal), caffeine 200 mg, or a placebo. The duration of the exhaustive running after sucrose, caffeine, or placebo ingestion was not significantly different. Exhaustion would possibly be attained not by depletion of muscle glycogen but by a decrease in the capacity of muscle cells to produce high tension for anaerobic metabolism. Total energy and energy from carbohydrate combusted during four sets of running were estimated at 1255 kcal and 810 kcal in the sucrose trial, 1271 kcal and 624 kcal in the caffeine trial, and 1248 kcal and 649 kcal in the placebo trial. Judging from the figures above, glycogen sparing during prolonged running seemed to be attained by sucrose ingestion but not by caffeine ingestion. The latter finding would be caused by lower intensity and a larger amount of ingested caffeine. In conclusion, performance of progressive exhaustive running following endurance running for 2 h could not be improved either by sucrose or caffeine ingestion. Glycogen sparing in the muscle, however, was suggested by sucrose ingestion but not by caffeine ingestion.     

Combined caffeine and ephedrine ingestion improves run times of Canadian Forces Warrior Test

The ingestion of a combination of caffeine (C) and ephedrine (E) has been reported to prolong exercise time to exhaustion during cycle ergometry at 85% VO2max. The present study was undertaken to investigate whether this enhancement would occur in a field setting and if drug ingestion on 1 d would affect performance 1 d later. Two hours after ingesting either a combination of 375 mg of C and 75 mg E (C+E), or a placebo (P), 9 healthy male recreational runners completed six balanced and double-blind trials of the Canadian Forces Warrior Test (WT), a 3.2 km run wearing "fighting order" which weighed about 11 kg. The trials were performed in sets of two runs, i.e., two runs were done 24 h apart, and these sets were separated by a minimum of 7 d. The sets were: C+E trial on day 1 (D1), placebo on day 2 (P2); placebo first (P1), C+E second (D2); and placebo first (P3), placebo second (P4). In addition, 1 wk before the treatment trials the subjects performed a control trial WT. During the WT, heart rates (HR) were recorded every minute. Plasma C and E levels immediately before the WT were similar for both C+E trials, but were undetectable for all P trials. Run times (mean+/-SD) were 15.3+/-0.6, 15.4+/-0.9, 15.5+/-1.2, 15.4+/-0.9, 15.4+/-0.9, 14.8+/-0.7, and 14.6+/-0.8 min for control, P1, P2, P3, P4, D1, D2 trials, respectively. The two C+E trial run times were similar and both were significantly faster (p < 0.05) than control and all placebo trials. HR during the WT was significantly higher (p < 0.05) for the C+E trials compared with the other trials. WT performance was not impaired by C+E ingestion 24 h earlier. In conclusion, performance of the WT was improved by ingestion of C+E.     

The effect of two sports drinks and water on GI complaints and performance during an 18-km run

Gastrointestinal (GI) complaints are frequently experienced during running. Sports drinks to prevent dehydration and hypoglycemia during exercise are generally used. The aim was to investigate the effect of 3 different drinks on GI complaints and performance during competitive running in a controlled field study. Ninety-eight well-trained subjects (90 M, 8 F, age 41 +/- 8 y) performed a competitive 18-km run three times within 8 days. The study was a controlled, standardized field experiment following a randomized, crossover design. Three different drinks were compared: water, a sports drink (CES), and a sports drink with added 150 mg/l caffeine (CAF). The incidence of GI complaints and the effect of the drinks on performance was studied. Each subject consumed 4 times 150 ml as follows: at the start, after 4.5 km, 9 km, and 13.5 km. Fluid intake was controlled. Incidence and intensity of GI complaints during the run were determined using a 10 points scale questionnaire. There were no significant differences in performance between the 3 drinks. Run time (18 km, mean +/- SD): WAT 1 : 18 : 03 +/- 08 : 30, CES 1 : 18 : 23 +/- 08 : 47, CAF 1 : 18 : 03 +/- 08 : 42. The use of carbohydrate-containing sports drinks led to higher incidences of all types of GI complaints compared to water. Significant differences (p < 0.05) were reached for flatulence; incidence: WAT 17.9 %, CES 28.6 %, CAF 30.6 %, and reflux; incidence: WAT 55.7 %, CES 78.6 %, CAF 72.5 %. There were no significant differences in intensity of the GI complaints. Addition of caffeine to CES had no effect on GI complaints, compared to CES alone. We conclude that sports drinks used during an 18-km run in cool environmental conditions do not support the performance better than mineral water. The use of sports drinks during an 18-km run leads to a higher incidence of both upper and lower GI complaints compared to water. Addition of caffeine to the sports drink has no effect on either running performance or GI complaints.     

L-tryptophan supplementation does not improve running performance.

In 1988 Segura and Ventura (14) reported that 1.2 g of L-Tryptophan (L-TRY) supplementation increased total exercise time by 49.4% when the subjects were running at 80% of maximal oxygen uptake (VO2max). In human performance research, acute improvements of that category are rather uncommon. Both for this reason and because ingestion of purified L-TRY may have adverse effects, it seemed pertinent to repeat the investigation of Segura and Ventura. Forty-nine well-trained male runners, aged 18-44, with an average maximal aerobic power of 66 (57-78) ml.kg-1.min-1, participated in a randomized double blind placebo (P) study. Each subject underwent four trials on the treadmill. The first two served as learning experience, including measurement of VO2max and anaerobic threshold. During the last two trials the subjects ran until exhaustion at a speed corresponding to 100% of their VO2max-first an initial trial and then after receiving a total of 1.2 g L-TRY or P over a 24 hour period prior to the run. No significant difference between the improvements in the L-TRY and P group could be demonstrated. It is concluded that oral L-TRY supplementation does not enhance running performance.     

The influence of caffeine ingestion on incremental treadmill running.

The aim of this study was to determine the effects of caffeine ingestion on estimated substrate utilisation during treadmill running at an initial level of 70%-75% of maximal oxygen consumption after which subjects ran to exhaustion. Twelve subjects undertook either a control, placebo, a small (10 mg X kg-1) or a large (15 mg X kg-1) dose of caffeine in a double-blind design to determine whether caffeine affected the substrate usage during running. Venous blood was collected prior to and during the experimental runs and was later analysed for free fatty acids (FFA), glycerol, triglycerides, lactate and glucose concentrations. The results of this experiment suggest that maximal running performance can be increased by large doses of caffeine. Furthermore, the subjects' respiratory exchange ratios were lower and FFA concentrations were higher following the ingestion of large amounts of caffeine than during other trials, suggesting that a larger proportion of energy was derived from fat being used preferentially during the trial following ingestion of this large dose of caffeine. The subjects rating of perceived exertion (RPE) were lower following the ingestion of a large dose of caffeine than it was in any of the other trials. This study differs from others in this area in so much that caffeine has been found to have positive effects during maximal running when used in large doses.     

Reproducibility of endurance performance on a treadmill using a preloaded time trial

PURPOSE: The purpose of this study was to establish a highly reproducible test to measure endurance performance in runners. METHODS: We evaluated the reproducibility of endurance performance during a 10-km time trial performed on a treadmill after a 90-min preload run at 65% of maximal oxygen uptake VO2max). After screening and a practice test, eight endurance runners (4 men, 4 women, 33.4 +/- 10.1 yr, VO2max = 60.3 +/- 6.3 mL x kg(-1) x min(-1) in men and 51.8 +/- 2.2 mL x kg(-1) x min(-1) in women, mean +/- SD) completed two preloaded time trial tests spaced 3-4 wk apart in men and one menstrual cycle apart in women. A high-carbohydrate diet (15% protein, 10% fat, 75% carbohydrate) was provided the day before both tests. RESULTS: Runners completed time trial 1 and time trial 2 in 45:41 +/- 4:45 and 45:24 +/- 5:03 min:s, respectively (43:29 +/- 5:02 and 43:12 +/- 5:14 min:s for men and 47:53 +/- 3:47 and 47:35 +/- 4:23 min:s for women, trials 1 and 2, respectively). The within-subject coefficient of variation for 10-km time was 1.00% +/- 0.25% (point estimate +/- estimated standard error) (0.54% +/- 0.19% for men and 1.26% +/- 0.45% for women). CONCLUSION: These results suggest that performance measured as time to complete a 10-km time trial on a treadmill after a 90-min preload is extremely reliable and may be useful for future research assessing the effect of diet, ergogenic substances, or training methods on endurance running performance.     

The effect of caffeine ingestion on field hockey skill performance following physical fatigue

This study examined the impact of caffeine ingestion on field hockey skill performance following high-intensity fatigue. Thirteen male hockey players (mean age = 21.1 ± 1.2 years) performed hockey sprint dribble and ball handling tests at rest and after a bout of total body fatigue (90% maximal capacity) following caffeine (5 mg kg(-1)) or placebo ingestion. Sprint dribble times were slower postfatigue compared with rest but were significantly faster postfatigue with caffeine compared with postfatigue with placebo ingestion (P < 0.01). Ball handling scores were higher at rest compared with postfatigue, but scores postfatigue were higher following caffeine than placebo ingestion (P < 0.01). Rating of perceived exhaustion (RPE) was lower (P < 0.01) and readiness to invest physical (P < 0.01) and mental effort (P = 0.01) were significantly higher in the caffeine condition. Caffeine ingestion may therefore be effective in offsetting decrements in skilled performance associated with fatigue.     

Reliability of time-to-exhaustion versus time-trial running tests in runners

Both time-to-exhaustion (TTE) and time-trial (TT) exercise tests are commonly used to assess exercise performance, but no study has directly examined the reliability of comparable tests in the same subjects. PURPOSE: To evaluate the reliability of comparable TTE and TT treadmill running tests of high and moderately high exercise intensity in endurance-trained male distance runners, and to validate Hinckson and Hopkins TT prediction methods using log-log modeling from TTE results. METHODS: After familiarization tests, eight endurance-trained male distance runners performed, in a randomized, counterbalanced order, eight trials consisting of two 5-km TT and two 1500-m TT, and four TTE tests run at a speed equivalent to the average speed attained during both the 5-km and 1500-m TT distances. RESULTS: Typical error of the estimate (TEE) expressed as a coefficient of variation for the 5-km TT, 5-km TTE, 1500-m TT, and 1500-m TTE were 2.0, 15.1, 3.3, and 13.2%, respectively. The standard error of the estimate for predicted TT running speed using log-log modeling from TTE results was 0.67%, and the predicted versus criterion reliability of this method revealed TEE values of 1.6% and 2.5% for the prediction of 5-km and 1500-m TT, respectively. CONCLUSION: The variability of 5-km and 1500-m TT tests was significantly less than for similar TTE treadmill protocols. Despite the greater variability of the TTE tests, log-log modeling using the TTE test results reliably predicted actual TT performance.     

Blood lactate accumulation during exercise in older endurance runners

To delineate the possible age-related differences in blood lactate response during exercise and its relations to endurance performance, 34 male runners (aged 21 to 69 years) performed an incremental treadmill running test. There were no significant differences in training distance and relative body fat among younger runners (YR), middle-aged runners (MR), and older runners (OR). The 5-km run time slowed with age, but was ranked at relatively the same level in each age group. OR had a 23% (P less than 0.001) and 12% (P less than 0.01) lower maximal oxygen uptake (VO2max) and a 22% (P less than 0.001) and 11% (P less than 0.001) slower 5-km run time than YR and MR, respectively. However, mean VO2 corresponding to 4 mM of blood lactate (OBLA VO2) was the same among the groups when expressed as %VO2max (YR; 84.3%, MR; 85.9%, OR; 85.9%). Significant correlations were found between OBLA VO2 (ml.kg-1.min-1) and 5-km run time in each group (YR; r = -0.648, P less than 0.05; MR; r = -0.658, P less than 0.01; OR; r = -0.680, P less than 0.05). These results suggest that OR attain a given blood lactate level at almost similar %VO2max to YR and MR and that OBLA VO2 in OR is useful for evaluating an endurance performance as well as in YR and in MR.     

Training and bioenergetic characteristics in elite male and female Kenyan runners

PURPOSE: This study compares the training characteristics and the physical profiles of top-class male and female Kenyan long-distance runners. METHOD: The subjects were 20 elite Kenyan runners: 13 men (10-km performance time: 10-km performance time of 28 min, 36 s +/- 18 s) and 7 women (32 min, 32 s +/- 65 s). The male runners were separated into high-speed training runners (HST: N = 6) and low-speed training runners (LST: N = 7) depending on whether they train at speeds equal or higher than those associated with the maximal oxygen uptake (vVO2max ). All but one woman were high-speed training runners (female HST: N = 6). Subjects performed an incremental test on a 400-m track to determine VO2max, vVO2max, and the velocity at the lactate threshold (vLT). RESULTS: Within each gender among the HST group, 10-km performance time was inversely correlated with vVO2max (rho = -0.86, P = 0.05, and rho = -0.95, P = 0.03, for men and women, respectively). HST male runners had a higher VO2max, a lower (but not significantly) fraction of vVO2max (FVO2max ) at the lactate threshold, and a higher energy cost of running (ECR). Among men, the weekly training distance at vVO2max explained 59% of the variance of vVO2max, and vVO2max explained 52% of the variance of 10-km performance time. Kenyan women had a high VO2max and FVO2max at vLT that was lower than their male HST counterparts. ECR was not significantly different between genders. CONCLUSION: The velocity at the VO2max is the main factor predicting the variance of the 10-km performance both in men and women, and high-intensity training contributes to this higher VO2max among men.     

Caffeine is ergogenic after supplementation of oral creatine monohydrate

PURPOSE: The purpose of this investigation was to assess the acute effects of caffeine ingestion on short-term, high-intensity exercise (ST) after a period of oral creatine supplementation and caffeine abstinence. METHODS: Fourteen trained male subjects performed treadmill running to volitional exhaustion (T(lim)) at an exercise intensity equivalent to 125% VO(2max). Three trials were performed, one before 6 d of creatine loading (0.3 g x kg x d(-1) baseline), and two further trials after the loading period. One hour before the postloading trials, caffeine (5 mg x kg(-1)) or placebo was orally ingested in a cross-over, double-blind fashion. Four measurements of rating of perceived exertion were taken, one every 30 s, during the first 120 s of the exercise. Blood samples were assayed for lactate, glucose, potassium, and catecholamines, immediately before and after exercise. RESULTS: Body mass increased (P < 0.05) over the creatine supplementation period, and this increase was maintained for both caffeine and placebo trials. There was no increase in the maximal accumulated oxygen deficit between trials; however, total VO(2) was significantly increased in the caffeine trial in comparison with the placebo trial (13.35 +/- 3.89 L vs 11.67 +/- 3.61 L). In addition, caffeine T(lim) (222.1 +/- 48.9 s) was significantly greater (P < 0.05) than both baseline (200.8 +/- 33.4 s) and placebo (198.3 +/- 45.4 s) T(lim). RPE was also lower at 90 s in the caffeine treatment (13.8 +/- 1.8 RPE points) in comparison with baseline (14.6 +/- 1.9 RPE points). CONCLUSION: As indicated by a greater T(lim), acute caffeine ingestion was found to be ergogenic after 6-d of creatine supplementation and caffeine abstinence.     

Little effect of caffeine ingestion on repeated sprints in team-sport athletes

PURPOSE: The effect of caffeine ingestion on sprint performance is unclear. We have therefore investigated its effect on performance in a test that simulates the repeated sprints of team sports. METHODS: In a randomized double-blind crossover experiment, 16 male team-sport athletes ingested either caffeine (6 mg.kg-1 of body mass) or a placebo 60 min before performing a repeated 20-m sprint test. The test consisted of 10 sprints, each performed within 10 s and followed by rest for the remainder of each 10 s. The caffeine and placebo trials followed a familiarization trial, and the time between consecutive trials was 2-3 d. To allow estimation of variation in treatment effects between individuals, nine subjects performed three more trials without a supplement 7-14 d later. We estimated the smallest worthwhile effect on sprint time in a team sport to be approximately 0.8%. RESULTS: Mean time to complete 10 sprints increased by 0.1% (95% likely range -1.5 to 1.7%) with caffeine ingestion relative to placebo. Individual variation in this effect was a standard deviation of 0.7% (-2.7 to 2.9%). Time to complete the 10th sprint was 14.4% longer than the first; caffeine increased this time by 0.7% (-1.8 to 3.2%) relative to placebo, and individual variation in this effect was 2.4% (-3.4 to 4.9%). CONCLUSION: The observed effect of caffeine ingestion on mean sprint performance and fatigue over 10 sprints was negligible. The true effect on mean performance could be small at most, although the true effects on fatigue and on the performance of individuals could be somewhat larger. Pending confirmatory research, team-sport athletes should not expect caffeine to enhance sprint performance.     

Relationship of training and life-style to 16-km running time of 4000 joggers. The '84 Berne "Grand-Prix" Study

To investigate running activity, life-style, and endurance capacity of joggers, all competitors of a popular 16-km race were surveyed by questionnaire. The response rate was 83.6%, yielding a study population of 4358 male runners over age 16. In univariate analysis, there were significant associations between 16-km running time and weekly training distance (average of 1 year), weekly training frequency, body mass index (BMI), age, cigarette smoking, years of regular running, and frequency of alcohol cosumption. A multiple regression analysis provided six significant, independent predictors of 16-km time, explaining 47% of its variance: weekly training distance (standardized regression coefficient = -0.46), age (0.37), BMI (0.23), years of regular running (-0.19), weekly training frequency (-0.11), and cigarette smoking (0.10). Based on laboratory treadmill testing of a subsample of runners, 16-km running times were transformed into maximum aerobic capacities (VO2 max equivalents) for all competitors. In comparison with the general population, even the slowest 5% of the runners showed a higher endurance capacity than the age-specific population mean. Application of the multivariate regression model for an estimation of the overall impact of training and life-style on endurance capacity showed that the great difference in mean endurance levels between joggers and the general population could entirely be attributed to differences in running activity, BMI, and smoking. We conclude that the joggers investigated were, on average, not selected concerning biological predisposition and genetic endowment since their behavior alone explained their high average endurance capacity.     

Effects of sodium citrate ingestion before exercise on endurance performance in well trained college runners

OBJECTIVE: To test the hypothesis that sodium citrate administered two hours before exercise improves performance in a 5 km running time trial. METHODS: A total of 17 male well trained college runners (mean (SD) O(2)MAX 61.3 (4.9) ml/kg/min) performed a 5 km treadmill run with and without sodium citrate ingestion in a random, double blind, crossover design. In the citrate trial, subjects consumed 1 litre of solution containing 0.5 g of sodium citrate/kg body mass two hours before the run. In the placebo trial, the same amount of flavoured mineral water was consumed. RESULTS: The time required to complete the run was faster in the citrate trial than the placebo trial (1153.2 (74.1) and 1183.8 (91.4) seconds respectively; p = 0.01). Lower packed cell volume and haemoglobin levels were found in venous blood samples taken before and after the run in the citrate compared with the placebo trial. Lactate concentration in the blood sample taken after the run was higher in the citrate than the placebo trial (11.9 (3.0) v 9.8 (2.8) mmol/l; p<0.001), and glucose concentration was lower (8.3 (1.9) v 8.8 (1.7) mmol/l; p = 0.02). CONCLUSION: The ingestion of 0.5 g of sodium citrate/kg body mass shortly before a 5 km running time trial improves performance in well trained college runners.     

Enhancement of 2000-m rowing performance after caffeine ingestion

PURPOSE: To investigate the effect of caffeine ingestion on short-term endurance performance in competitive rowers. METHODS: In this randomized double-blind crossover study, eight competitive oarsmen (peak oxygen uptake [VO2peak] 4.7+/-0.4 L x min(-1), mean +/- SD) performed three familiarization trials of a 2000-m rowing test on an air-braked ergometer, followed by three experimental trials at 3- to 7-d intervals, each 1 h after ingesting caffeine (6 or 9 mg x kg(-1) body mass) or placebo. Trials were preceded by a standardized warm-up (6 min at 225+/-39 W; 75+/-7.7% VO2peak). RESULTS: Urinary caffeine concentration was similar before ingestion (approximately 1 mg x L(-1)) but rose to 6.2+/-3.6 and 14.5+/-7.0 mg x L(-1) for the low and high caffeine doses, respectively. Plasma free fatty acid concentration before exercise was higher after caffeine ingestion (0.29+/-0.17 and 0.39+/-0.20 mM for 6 and 9 mg x kg(-1), respectively) than after placebo (0.13+/-0.05 mM). Respiratory exchange ratio during the warm-up was also substantially lower with caffeine (0.94+/-0.09 and 0.93+/-0.06 for the low and high dose) than with placebo (0.98+/-0.12). Subjects could not distinguish between treatments before or after the exercise test. Both doses of caffeine had a similar ergogenic effect relative to placebo: performance time decreased by a mean of 1.2% (95% likely range 0.4-1.9%); the corresponding increase in mean power was 2.7% (0.4-5.0%). Performance time showed some evidence of individual differences in the effect of caffeine (SD 0.9%; 95% likely range 1.5 to -0.9%). CONCLUSIONS: Ingestion of 6 or 9 mg x kg(-1) of caffeine produces a worthwhile enhancement of short-term endurance performance in a controlled laboratory setting.     

Lactate and glucose minimum speeds and running performance

This study aimed to analyse the validity of glucose minimum speed (GMS) for lactate minimum speed (LMS) assessment during running and their relationship to endurance performance. Eight male trained runners (28.7 +/- 9.0 years) volunteered to take part in this study and underwent an official 10-km road race and a track lactate minimum test (LMT) (0.5-km sprint plus 6 x 800 m from 87 to 98% of maximal 3-km speed). Lactate and glucose minimum speeds were considered those related to the minimum blood lactate and glucose concentrations respectively attained during the graded phase of LMT. Significant correlations (p < 0.05) were found between LMS and GMS (r = 0.72) and LMS and 10-km performance (r = 0.83), but not between GMS and 10-km performance (r = 0.49). No significant differences (p > 0.05) were found between LMS (4.75 +/- 0.08 m/s), GMS (4.73 +/- 0.07 m/s) and 10-km mean speed (4.79 +/- 0.17 m/s). In conclusion, we found GMS to be a good predictor of LMS during track LMT, LMS being well related to endurance running performance.     

Caffeine maintains vigilance and improves run times during night operations for Special Forces

PURPOSE: This study examined the effects of caffeine (CAF) on vigilance, marksmanship, and run performance during 27 h of sustained wakefulness in Special Forces personnel. METHODS: There were 31 soldiers (29.8 +/- 5.4 yr, 86.4 +/- 8.6 kg) who were divided into placebo (PLAC, n = 15) and CAF (n = 16) groups. A 6.3-km control run was completed on the morning of Day 1. In the evening of Day 2, soldiers performed a control observation and reconnaissance vigilance task (ORVT) in the field. This 90-min task was repeated twice more between 02:00 and 06:00 on Day 3 during an overnight period of sleep deprivation. Marksmanship was assessed before and after the ORVT. PLAC or 200 mg of CAF gum was administered at 01:45, 03:45, and approximately 06:30 on Day 3. A final 6.3-km run commenced within 30 min of receiving the final dose. RESULTS: ORVT was maintained in CAF at control levels of 77 +/- 13% during the overnight testing. However, values decreased significantly for PLAC from 77 +/- 15% to 54 +/- 29% and 51 +/- 31% during the first and second overnight testing periods, respectively. CAF had no effect on marksmanship but improved 6.3-km run times by 1.2 +/- 1.8 min. Run times slowed for PLAC by 0.9 +/- 0.8 min from approximately 35 min during the control run; the changes in performance were significant between groups. CONCLUSIONS: It was concluded that CAF maintained vigilance and improved running performance during an overnight field operation for Special Forces personnel.