Running economy and maximal oxygen consumption after 4 weeks of oral Echinacea supplementation

The purpose of this investigation was to determine the effects of 4 weeks of oral Echinacea (ECH) supplementation on erythropoietin (EPO), red blood cell (RBC) count, running economy (RE), and VO2max. Twenty-four men aged 24.9 ± 4.2 years, height 178.9 ± 7.9 cm, weight 87.9 ± 14.6 kg, body fat 19.3 ± 6.5% were grouped using a double-blind design and self-administered an 8,000-mg·d(-1) dosage of either ECH or placebo (PLA) in 5 × 400 mg × 4 times per day for 28 days. Blood samples were collected and analyzed for RBCs and EPO using automated flow cytometery and enzyme-linked immunosorbent assay. Maximal graded exercise tests (GXTs) were administered to measure VO2max, RE, and heart-rate responses. Analysis of variance was used to determine statistically significant differences (P ≤ 0.05). The EPO increased significantly in ECH at 7 days (ECH: 15.75 ± 0.64, PLA: 10.01 ± 0.73 mU·ml(-1)), 14 days (ECH: 18.88 ± 0.71, PLA: 11.02 ± 0.69 mU·ml(-1)), and 21 days (ECH: 16.06 ± 0.55, PLA: 9.20 ± 0.55 mU·ml(-1)). VO2max increased significantly in ECH (ECH: 1.47 ± 1.28, PLA: -0.13 ± 0.52%). Running economy improved significantly in ECH as indicated by a decrease in submaximal VO2max during the first 2 stages of the GXT (stage 1: ECH -1.50 ± 1.21, PLA 0.60 ± 1.95%; stage 2: ECH -1.67 ± 1.43, PLA 0.01 ± 1.03%). These data suggest that ECH supplementation results in significant increases in EPO, VO2max, and running economy.     

Physiological parameters related to running performance in college trackmen.

Submaximal and maximal oxygen consumption (VO2) and heart rate (HR) were correlated with running performance in events ranging from 100 yards to 2 miles, using as subjects 20 members of a college track team. In the first of two studies (n=11) a multi-stage walking test was used to determine VO2 and HR. Max VO2 expressed in ml/kg/min, was significantly related to 1 mile run performance but not to any of the other runs. Submaximal HR was significantly related to performance in both the 1 mile and 2 mile runs. Correlations between these physiological parameters and performance in the 220, 440, and 880 yard runs were nonsignificant. Multiple R's using max VO2 (ml/kg/min) and submaximal H were .758 and 9671, respectively, for the 1 and 2 mile runs. In study two (n=9) a running test for VO2 and HR was used, which resulted in a mean max VO2 about 7 ml higher than than elicited in the walking test, implying that for trained runners a running test was a more valid test of aerobic power. Marked relationships were found between body weight and performance, positive for the 100 yard dash and negative for the 2 mile run. Submaximal HR was again significantly related to performance in the 1 and 2 mile runs. Max VO2 was positively related to 2 mile performance and negatively related to 100 yard dash performance. Multiple R's using max VO2 and submaximal HR were .799 and .925 for the 1 and 2 mile runs, respectively. Using submaximal HR and weight the multiple R's were .777 and .945, showing that these two can account for a large amount of the variance in distance running performance. In neither study was submaximal VO2 significantly related to running performance.     

Development of a submaximal test to predict elliptical cross-trainer VO2max

The purpose of this study was to develop an equation to predict VO2max from a submaximal elliptical cross-trainer test. Fifty-four apparently healthy subjects (25 men and 29 women, mean +/- SD age: 29.5 +/- 7.1 years, height: 173.3 +/- 12.6 cm, weight: 72.3 +/- 7.9 kg, percent body fat: 17.3 +/- 5.0%, and elliptical cross-trainer VO2max: 43.9 +/- 7.2 ml x kg(-1) x min(-1)) participated in the study and were randomly assigned to an original sample group (n = 40) and a cross-validation group (n = 14). Each subject completed an elliptical cross-trainer submaximal (3 5-minute submaximal stages) and a VO2max test on the same day, with a 15-minute rest period in between. Stepwise multiple regression analyses were used to develop an equation for estimating elliptical cross-trainer VO2max from the data of the original sample group. The accuracy of the equation was tested by using data from the cross-validation group. Because there was no shrinkage in R2 between the original sample group and the cross-validation group, data were combined in the final prediction equation (R2 = 0.732, standard error of the estimate = 3.91 ml x kg(-1) x min(-1), p < 0.05): VO2max = 73.676 + 7.383(gender) - 0.317(weight) + 0.003957(age x cadence) - 0.006452(age x heart rate at stage 2). The correlation coefficient between the predicted and measured VO2max values was r = 0.86. Dependent t-tests resulted in no significant differences (p > 0.05) between predicted (43.8 ml x kg(-1) x min(-1)) and measured (43.9 ml x kg(-1) x min(-1)) VO2max measurements. Results indicate that the protocol and equation developed in the current study can be used by exercise professionals to provide acceptably accurate estimates of VO2max in non-laboratory-based settings.     

The physiological effects of caffeine in women during treadmill walking

Although the effects of caffeine ingestion on athletic performance in men have been studied extensively, there is limited previous research examining caffeine's effects on women of average fitness levels participating in common modes of physical activity. The purpose of this study was to determine the effect of 2 levels of caffeine dosage on the metabolic and cardiorespiratory responses to treadmill walking in women. Subjects were 20 women (19-28 years of age) of average fitness, not habituated to caffeine. Each subject was assigned randomly a 3-mg x kg(-1) dose of caffeine, 6-mg x kg(-1) dose of caffeine, and placebo for 3 trials of moderate steady-state treadmill walking at 94 m x min(-1) (3.5 mph). Steady-state rating of perceived exertion (RPE), heart rate (HR), respiratory exchange ratio (RER), weight-relative VO2, %VO2max reserve (%VO2R), and rate of energy expenditure (REE) were measured during each trial. Repeated measures analysis of variance revealed that a 6-mg x kg(-1), but not a 3-mg x kg(-1) dose of caffeine increased VO2 (p = 0.04), REE (p = 0.03), and %VO2R (p = 0.03), when compared to the placebo. Caffeine had no effect on RPE, HR, or RER. No significant differences were observed between the placebo trials and the 3-mg x kg(-1) dose trials. Although a 6-mg x kg(-1) dose of caffeine significantly increased REE during exercise, the observed increase (approximately 0.23 kcal x min(-1)) would not noticeably affect weight loss. Because caffeine had no effect on RPE, it would not be prudent for a trainer to recommend caffeine in order to increase a woman's energy expenditure or to decrease perception of effort during mild exercise. These data also demonstrate that caffeine intake should not interfere with monitoring walking intensity by tracking exercise heart rate in women.     

Propranolol does not impair exercise oxygen uptake in normal men at high altitude

Decreased maximal O2 uptake (VO2max) and stimulation of the sympathetic nervous system have been previously shown to occur at high altitude. We hypothesized that tachycardia mediated by beta-adrenergic stimulation acted to defend VO2max at high altitude. Propranolol treatment beginning before high-altitude (4,300 m) ascent reduced heart rate during maximal and submaximal exercise in six healthy men treated with propranolol (80 mg three times daily) compared with five healthy subjects receiving placebo (lactose). Compared with sea-level values, the VO2max fell on day 2 at high altitude, but the magnitude of fall was similar in the placebo and propranolol treatment groups (26 +/- 6 vs. 32 +/- 5%, P = NS) and VO2max remained similar at high altitude in both groups once treatment was discontinued. During 30 min of submaximal (80% of VO2max) exercise, propranolol-treated subjects maintained O2 uptake levels that were as large as those in placebo subjects. The maintenance of maximal or submaximal levels of O2 uptake in propranolol-treated subjects at 4,300 m could not be attributed to increased minute ventilation, arterial O2 saturation, or hemoglobin concentration. Rather, it appeared that propranolol-treated subjects maintained O2 uptake by transporting a greater proportion of the O2 uptake with each heartbeat. Thus, contrary to our hypothesis, beta-adrenergic blockade did not impair maximal or submaximal O2 uptake at high altitude due perhaps to compensatory mechanisms acting to maintain stroke volume and cardiac output.     

Evaluation of the American College of Sports Medicine submaximal treadmill running test for predicting VO2max

The purpose of this study was to assess the validity of the American College of Sports Medicine's (ACSM's) submaximal treadmill running test in predicting VO2max. Twenty-one moderately well-trained men aged 18-34 years performed 1 maximal treadmill test to determine maximal oxygen uptake (M VO2max) and 2 submaximal treadmill tests using 4 stages of continuous submaximal exercise. Estimated VO2max was predicted by extrapolation to age-predicted maximal heart rate (HRmax) and calculated in 2 ways: using data from all submaximal stages between 110 b·min(-1) and 85% HRmax (P VO2max-All), and using data from the last 2 stages only (P VO2max-2). The measured VO2max was overestimated by 3% on average for the group but was not significantly different to predicted VO2max (1-way analysis of variance [ANOVA] p = 0.695; M VO2max = 53.01 ± 5.38; P VO2max-All = 54.27 ± 7.16; P VO2max-2 = 54.99 ± 7.69 ml·kg(-1)·min(-1)), although M VO2max was not overestimated in all the participants--it was underestimated in 30% of observations. Pearson's correlation, standard error of estimate (SEE), and total error (E) between measured and predicted VO2max were r = 0.646, 4.35, 4.08 ml·kg(-1)·min(-1) (P VO2max-All) and r = 0.642, 4.21, 3.98 ml·kg(-1)·min(-1) (P VO2max-2) indicating that the accuracy in prediction (error) was very similar whether using P VO2max-All or P VO2max-2, with up to 70% of the participants predicted scores within 1 SEE (～4 ml·kg(-1)·min(-1)) of M VO2max. In conclusion, the ACSM equation provides a reasonably good estimation of VO2max with no difference in predictive accuracy between P VO2max-2 and P VO2max-All, and hence, either approach may be equally useful in tracking an individual's aerobic fitness over time. However, if a precise knowledge of VO2max is required, then it is recommended that this be measured directly.     

Growth hormone treatment in growth hormone-deficient adults. II. Effects on exercise performance

Growth hormone (GH) treatment in adults with GH deficiency increases lean body mass and thigh muscle cross-sectional area. The functional significance of this was examined by incremental cycle ergometry in 24 GH-deficient adults treated in a double-blind placebo-controlled trial with recombinant DNA human GH (rhGH) for 6 mo (0.07 U/kg body wt daily). Compared with placebo, the rhGH group increased mean maximal O2 uptake (VO2max) (+406 +/- 71 vs. +133 +/- 84 ml/min; P = 0.016) and maximal power output (+24.6 +/- 4.3 vs. +9.7 +/- 4.8 W; P = 0.047), without differences in maximal heart rate or ventilation. Forced expiratory volume in 1 s, vital capacity, and corrected CO gas transfer were within normal limits and did not change with treatment. Mean predicted VO2max, based on height and age, increased from 78.9 to 96.0% in the rhGH group (compared with 78.5 and 85.0% for placebo; P = 0.036). The anaerobic ventilatory threshold increased in the rhGH group (+159 +/- 39 vs. +1 +/- 51 ml/min; P = 0.02). The improvement in VO2max was noted when expressed per kilogram body weight but not lean body mass or thigh muscle area. We conclude that rhGH treatment in adults with GH deficiency improves and normalizes maximal exercise performance and improves submaximal exercise performance and that these changes are related to increases in lean body mass and muscle mass. Improved cardiac output may also contribute to the effect of rhGH on exercise performance.     

Physiological profiles and performance predictors of a women's NCAA rowing team

We described the physiological profiles of rowers (N = 16; age = 20.1 +/- 1.4 years, weight = 78.6 +/- 9.5 kg, height = 177.5 +/- 3.1 cm) of the top 2 varsity boats on an NCAA women's crew and determined whether physiological measures predict boat assignment as determined by the head coach. Eight participants were members of the top varsity boat (1V) and 8 competed at a lower level (2V). Expired gases were collected while subjects completed the U.S. National Team VO(2)max (3-minute stages) and 2 kilometer (2K) time trial rowing ergometer protocols. Heart rates (HR) and blood lactates were measured before, during, and after each test. The VO(2)max and blood lactate at stage 2 of the VO(2)max test were used to predict boat assignment. Average (+/-SD) VO(2)max was 3.86 +/- 0.40 L.min(-1). The 2K times averaged 453.0 +/- 10.5 seconds. Subjects used approximately 96% of VO(2)max and 98% of HR(max) during the 2K time trials. Neither VO(2)max nor submaximal lactate were related to boat assignment. The VO(2) values during the 2K trial indicated that rowing economy differed among athletes. Results of physiological measures should help the coach individualize workouts of top performers.     

Relationships between body dimensions and resting and working oxygen consumption in boys aged 11 to 18 years

The relationships between VO2 at rest, VO2max and VO2 during submaximal work on a treadmill with body weight, height and lean body mass assessed by densitometry were analyzed annually in 39 boys aged 11 to 18 years. Interindividual differences in VO2 at rest and VO2max during growth depended in the first place on interindividual differences in lean body mass, to a lesser extent on differences in body weight and least on differences in height. Intersubject differences in VO2 during submaximal work were primarily conditioned by differences in body weight, due to the fact that, at a given running speed, energy output depends on body weight. The differences in submaximal VO2 depended to a lesser extent on differences in lean body mass and least on differences in height. The relationships between VO2 increments and increases in body dimensions were somewhat different in 90 boys between the ages of 11 and 15 years: VO2max increments were determined primarily by changes in body weight and height, changes in lean body mass being of secondary importance. Increases in submaximal VO2 were influenced decisively by increments in body weight, followed by increments in lean body mass and least by increments in height. In the equation y = a.xb expressing the relationship of VO2max to body weight and height, the values of b at the ages of 14 and 15 years were 0.87 and 0.88 in relation to body weight, 2.63 and 2.72 in relation to height. These values are significantly higher than the theoretical values of 0.67 for body weight and 2.00 for height. Similar significant differences from these theoretical values were found for all values between the ages of 11 and 15 years.     

Cardiopulmonary responses to exercise in obese girls and young women.

A study of exercise performance was carried out in 17 obese girls and young adults. During submaximal steady-state bicycle exercise oxygen intake (Vo2) for a given work output (W) was raised in obese subjects but minute ventilation at a fixed carbon dioxide output, gas exchange, blood gases, and cardiac output at a given VO2 were similar to the values previously found for normals. In obese subjects high levels of VO2 for fixed W were also obtained on the treadmill but when these were standardized for body weight (unlike the bicycle test) it was shown that the obese girls and women exercised within the normal (expected) range of aerobic energy expenditure. During maximal performance the absolute VO2 max was the same in obese and nonobese subjects but for a given body weight, lean body mass, and leg muscle (plus) bone volume, VO2max was reduced by 23.8, 16.3, and 24.5% respectively, in the former group. It was concluded that obesity though having minimal affect on responses to submaximal exercise is nevertheless associated with a marked reduction in physiological performance at or near maximal effort.     

Validation of the Cosmed Fitmate for prediction of maximal oxygen consumption

The main purpose of this study was to assess the validity of the Cosmed Fitmate (FM) for the prediction of maximal oxygen consumption (VO(2)max). In addition, this study examined whether measuring submaximal VO(2), rather than predicting it, can improve upon the prediction of VO(2)max. Participants for the study were 48 young to middle-age adults (32 men, 16 women), with a mean age of 31 yr. Each participant completed a submaximal and maximal treadmill test on 2 separate occasions. During the submaximal test, VO(2)max was predicted using the FM. This device extrapolates the linear regression relating heart rate (HR) and measured VO(2) at submaximal work rates to age-predicted maximum HR (HR = 220 - age). The criterion measure was obtained using a graded, maximal treadmill test, with VO(2) measured by the Douglas bag (DB) method. There was no significant difference between VO(2)max predicted by the FM and VO(2)max measured by the DB method. The results of this study showed that a strong positive correlation (r = 0.897) existed between VO(2)max predicted by the FM and VO(2)max measured by the DB method, with a standard error of the estimate (SEE) = 3.97 ml·kg(-1)·min(-1). There was a significant difference in VO(2)max predicted by the American College of Sports Medicine (ACSM) metabolic equations and VO(2)max measured by the DB method (p = 0.01). The correlation between these variables was r = 0.758 (SEE = 5.26 ml·kg(-1)·min(-1)). These findings indicate that a small, portable, and easy-to-use metabolic system provides valid estimates of VO(2)max, and improves upon predictive accuracy, compared to using generalized ACSM metabolic equations.     

Standards and predicted values of anaerobic threshold

Mean values for body size, body composition and endurance indices have been obtained from a homogeneous group of 125 physically active men to find predicted values of AT (age 23.4 +/- 4.3 years; height 175.9 +/- 6.5 cm; weight 72.2 +/- 8.9 kg; body fat 17.9 +/- 4.7% body weight, muscularity index 19.0 +/- 1.5 kg fat-free mass/cm2 X 10(-4) height; forced vital lung capacity 5667 +/- 815 cm3; VO2max 48.5 +/- 6.0 cm3 X kg-1 X min-1; anaerobic threshold 61.0 +/- 7.8% VO2max). Endurance performance and fitness indices were a little higher than average, but about 10% lower than in endurance-trained athletes. The authors suggest that standards of anaerobic threshold (AT) for ergonomics and endurance training should be about 55-65% VO2max, but not lower than 1800 cm3 O2 X min-1. The coefficients of correlation of AT relating to VO2max, PFO2 and submaximal load were significant at the 0.01 level. Using regression analysis, predicted values of AT were developed. A predicted value of AT can be obtained from the regression line of AT on Lsubmax used as a nomogram, during a simple PWC170 exercise test without blood or gas analysis.     

Effects of eight weeks of caffeine supplementation and endurance training on aerobic fitness and body composition

The purpose of this study was to examine the effects of daily administration of a supplement that contained caffeine in conjunction with 8 weeks of aerobic training on VO(2)peak, time to running exhaustion at 90% VO(2)peak, body weight, and body composition. Thirty-six college students (14 men and 22 women; mean +/- SD, age 22.4 +/- 2.9 years) volunteered for this investigation and were randomized into either a placebo (n = 18) or supplement group (n = 18). The subjects ingested 1 dose (3 pills = 201 mg of caffeine) of the placebo or supplement per day during the study period. In addition, the subjects performed treadmill running for 45 minutes at 75% of the heart rate at VO(2)peak, three times per week for 8 weeks. All subjects were tested pretraining and posttraining for VO(2)peak, time to running exhaustion (TRE) at 90% VO(2)peak, body weight (BW), percentage body fat (%FAT), fat weight (FW), and fat-free weight (FFW). The results indicated that there were equivalent training-induced increases (p < 0.05) in VO(2)peak and TRE for the supplement and placebo groups, but no changes (p > 0.05) in BW, %FAT, FW, or FFW for either group. These findings indicated that chronic use of the caffeine-containing supplement in the present study, in conjunction with aerobic training, provided no ergogenic effects as measured by VO(2)peak and TRE, and the supplement was of no benefit for altering body weight or body composition.     

Effect of beta-blockade on the drift in O2 consumption during prolonged exercise

The effect of beta-adrenergic blockade on the drift in O2 consumption (VO2 drift) typically observed during prolonged constant-rate exercise was studied in 14 healthy males in moderate heat at 40% of maximal O2 consumption (VO2max). After an initial maximum cycle ergometer test to determine the subjects' control VO2max, subjects were administered each of three medications: placebo, atenolol (100 mg once daily), and propranolol (80 mg twice daily), in a randomized double-blind fashion. Each medication period was 5 days in length and was followed by a 4-day washout period. On the 3rd day of each medication period, subjects performed a maximal cycle ergometer test. On the final day of each medication period, subjects exercised at 40% of their control VO2max for 90 min on a cycle ergometer in a warm (31.7 +/- 0.3 degrees C) moderately humid (44.7 +/- 4.7%) environment. beta-Blockade caused significant (P less than 0.05) reductions in VO2max, maximal minute ventilation (VEmax), maximal heart rate (HRmax), and maximal exercise time. Significantly greater decreases in VO2max, VEmax, and HRmax were associated with the propranolol compared with the atenolol treatment. During the 90-min submaximal rides, beta-blockade significantly reduced heart rate. Substantially lower values for O2 consumption (VO2) and minute ventilation (VE) were observed with propranolol compared with atenolol or placebo. Furthermore, VO2 drift and HR drift were observed under atenolol and placebo conditions but not with propranolol. Respiratory exchange ratio decreased significantly over time during the placebo and atenolol trials but did not change during the propranolol trial.(ABSTRACT TRUNCATED AT 250 WORDS)     

Caffeine and sprinting performance: dose responses and efficacy

The aims of this study were to evaluate the effects of caffeine supplementation on sprint cycling performance and to determine if there was a dose-response effect. Using a randomized, double-blind, placebo-controlled design, 17 well-trained men (age: 24 ± 6 years, height: 1.82 ± 0.06 m, and body mass(bm): 82.2 ± 6.9 kg) completed 7 maximal 10-second sprint trials on an electromagnetically braked cycle ergometer. Apart from trial 1 (familiarization), all the trials involved subjects ingesting a gelatine capsule containing either caffeine or placebo (maltodextrin) 1 hour before each sprint. To examine dose-response effects, caffeine doses of 2, 4, 6, 8, and 10 mg·kg bm(-1) were used. There were no significant (p ≥ 0.05) differences in baseline measures of plasma caffeine concentration before each trial (grand mean: 0.14 ± 0.28 μg·ml(-1)). There was, however, a significant supplement × time interaction (p < 0.001), with larger caffeine doses producing higher postsupplementation plasma caffeine levels. In comparison with placebo, caffeine had no significant effect on peak power (p = 0.11), mean power (p = 0.55), or time to peak power (p = 0.17). There was also no significant effect of supplementation on pretrial blood lactate (p = 0.58), but there was a significant time effect (p = 0.001), with blood lactate reducing over the 50 minute postsupplementation rest period from 1.29 ± 0.36 to 1.06 ± 0.33 mmol·L(-1). The results of this study show that caffeine supplementation has no effect on short-duration sprint cycling performance, irrespective of the dosage used.     

Aerobic fitness and body fat of young British males entering the army.

Aerobic fitness and percent body fat were measured in a sample of 438 male Army recruits between the ages of 17 and 30 prior to the commencement of training. The sample came from all areas of England and Wales. Aerobic fitness, as represented by maximal oxygen uptake (VO2 max), was predicted from the Astrand submaximal bicycle heart rate test. Body fat was predicted from four skinfold measurements. Total group means +/- SD were: age, 19.5 +/- 2.5 years; VO2 max 41.7 +/- 8.3 ml/kg . min; and body fat, 14.5 +/- 4.8% of body weight. VO2 max varied with age, athletic participation and aptitude score. No relationship was found with occupation of parent, prior civilian occupation or smoking severity. When adjusted for methodological differences, VO2 max was slightly below similar Army entrants in Norway and the United States.     

Effect of maternal weight gain during pregnancy on exercise performance

We examined the effect of maternal weight gain during pregnancy on exercise performance. Ten women performed submaximal cycle (up to 60 W) and treadmill (4 km/h, up to 10% grade) exercise tests at 34 +/- 1.5 (SD) wk gestation and 7.6 +/- 1.7 wk postpartum. Postpartum subjects wearing weighted belts designed to equal their body weight during the antepartum tests performed two additional treadmill tests. Absolute O2 uptake (VO2) at the same work load was higher during pregnancy than postpartum during cycle (1.04 +/- 0.08 vs. 0.95 +/- 0.09 l/min, P = 0.014), treadmill (1.45 +/- 0.19 vs. 1.27 +/- 0.20 l/min, P = 0.0002), and weighted treadmill (1.45 +/ 0.19 vs. 1.36 +/- 0.20 l/min, P = 0.04) exercise. None of these differences remained, however, when VO2 was expressed per kilogram of body weight. Maximal VO2 (VO2max) estimated from the individual heart rate-VO2 curves was the same during and after pregnancy during cycling (1.96 +/- 0.37 to 1.98 +/- 0.39 l/min), whereas estimated VO2max increased postpartum during treadmill (2.04 +/- 0.38 to 2.21 +/- 0.36 l/min, P = 0.03) and weighted treadmill (2.04 +/- 0.38 to 2.19 +/- 0.38 l/min, P = 0.03) exercise. We conclude that increased body weight during pregnancy compared with the postpartum period accounts for 75% of the increased VO2 during submaximal weight-bearing exertion in pregnancy and contributes to reduced exercise capacity. The postpartum increase in estimated VO2max during weight-bearing exercise is the result of consistently higher antepartum heart rates during all submaximal work loads.     

Influence of altitude and caffeine during rest and exercise on plasma levels of proenkephalin peptide F

The purpose of this study was to examine the resting and exercise response patterns of plasma Peptide F immunoreactivity (ir) to altitude exposure (4300 m) and caffeine ingestion (4 mg.kg b.w.-1). Nine healthy male subjects performed exercise tests to exhaustion (80-85% VO2max) at sea level (50 m), during an acute altitude exposure (1 hr, hypobaric chamber, 4300 m) and after a chronic (17-day sojourn, 4300 m) altitude exposure. Using a randomized, double-blind/placebo experimental design, a placebo or caffeine drink was ingested 1 hour prior to exercise. Exercise (without caffeine) significantly (p less than 0.05) increased plasma Peptide F ir values during exercise at chronic altitude only. Caffeine ingestion significantly increased plasma Peptide F ir concentrations during exercise and in the postexercise period at sea level. Conversely caffeine ingestion at altitude resulted in significant reductions in the postexercise plasma Peptide F ir values. The results of this study demonstrate that the exercise and recovery response patterns of plasma Peptide F ir may be significantly altered by altitude exposure and caffeine ingestion. These data support further study examining relationships between Peptide F (and other enkephalin-containing polypeptides) and epinephrine release in response to these types of physiological stresses.     

Endurance training of older men: responses to submaximal exercise.

The purpose of this study was to quantify the exercise response of older subjects on a time-to-fatigue (TTF) submaximal performance test before and after a training program. Eight older men (67.4 +/- 4.8 yr) performed two maximal treadmill tests to determine maximum oxygen uptake (VO2max) and ventilation threshold (TVE) and a constant-load submaximal exercise treadmill test that required an oxygen uptake (VO2) between TVE and VO2max. The submaximal test, performed at the same absolute work rate before and after the training program, was performed to volitional fatigue to measure endurance time. The men trained under supervision at an individualized pace representing approximately 70% of VO2max (80% maximum heart rate) for 1 h, four times per week for 9 wk. Significant increases were demonstrated for VO2max (ml.kg-1.min-1; 10.6%); maximal ventilation (VE, l/min; 11.6%), and TVE (l/min; 9.8%). Weight decreased 2.1%. Performance time on the TTF test increased by 180% (7.3 +/- 3.0 to 20.4 +/- 13.5 min). The similar end points for VO2, VE, and heart rate during the TTF and maximal treadmill tests established that the TTF test was stopped because of physiological limitations. The increase in performance time among the subjects was significantly correlated with improvements in VO2max and TVE, with the submaximal work rate representing a VO2 above TVE by 88% of the difference between TVE and VO2max pretraining and 73% of this difference on posttraining values.     

Effects of short-term training using powercranks on cardiovascular fitness and cycling efficiency

Powercranks use a specially designed clutch to promote independent pedal work by each leg during cycling. We examined the effects of 6 wk of training on cyclists using Powercranks (n=6) or normal cranks (n=6) on maximal oxygen consumption (VO2max) and anaerobic threshold (AT) during a graded exercise test (GXT), and heart rate (HR), oxygen consumption (VO2), respiratory exchange ration (RER), and gross efficiency (GE) during a 1-hour submaximal ride at a constant load. Subjects trained at 70% of VO2max for 1 h.d(-1), 3 d.wk(-1), for 6 weeks. The GXT and 1-hour submaximal ride were performed using normal cranks pretraining and posttraining. The 1-hour submaximal ride was performed at an intensity equal to approximately 69% of pretraining VO2max with VO2, RER, GE, and HR determined at 15-minute intervals during the ride. No differences were observed between or within groups for VO2max or AT during the GXT. The Powercranks group had significantly higher GE values than the normal cranks group (23.6 +/- 1.3% versus 21.3 +/- 1.7%, and 23.9 +/- 1.4% versus 21.0 +/- 1.9% at 45 and 60 min, respectively), and significantly lower HR at 30, 45, and 60 minutes and VO2 at 45 and 60 minutes during the 1-hour submaximal ride posttraining. It appears that 6 weeks of training with Powercranks induced physiological adaptations that reduced energy expenditure during a 1-hour submaximal ride.