Increases in aldosterone precede those of cortisol during graded exercise

The purpose of this study was to determine the intensity threshold needed to elicit increases in plasma aldosterone and cortisol during graded exercise in humans. Seven male volunteers performed a maximal oxygen uptake (VO2max) test on a cycle ergometer. Plasma levels of aldosterone, cortisol, angiotensin II, ACTH, and potassium were measured at rest and at each 50 W workload of the exercise test. The results showed that aldosterone significantly (p less than or equal to 0.05) increased from a mean (+/- SE) of 231 +/- 22 pmol/L at rest to 464 +/- 22 pmol/L at exhaustion. Cortisol significantly (p less than or equal to 0.05) increased from 284 +/- 38 nmol/L at rest to 311 +/- 39 nmol/L at exhaustion. More importantly, however, was the fact that aldosterone was significantly increased above the resting level at exercise intensities greater than or equal to 60% VO2max. Cortisol, on the other hand, was only significantly increased at exhaustion (i.e. 100% VO2max). These results clearly show that increases in aldosterone precede those of cortisol during graded exercise in humans. Interestingly, potassium (r = 0.79), ACTH (r = 0.55), and angiotensin II (r = 0.54) were all significantly correlated with aldosterone during exercise. Such a finding seems to suggest that all 3 variables may be important stimuli for aldosterone secretion during graded exercise.     

Acute moderate hypoxia affects the oxygen desaturation and the performance but not the oxygen uptake response

The purpose of this study was to examine the influence of hypoxia on the O2 uptake response, on the arterial and muscular desaturation and on the test duration and test duration at VO2max during exhaustive exercise performed in normoxia and hypoxia at the same relative workload. Nine well-trained males cyclists performed an incremental test and an exhaustive constant power test at 90 % of maximal aerobic power on a cycling ergometer, both in normoxia and hypoxia (inspired O2 fraction = 16 %). Hypoxic normobar conditions were obtained using an Alti Trainer200 and muscular desaturation was monitored by near-infrared spectroscopy instrument (Niro-300). The mean response time (66 +/- 4 s vs. 44 +/- 7 s) was significantly lower in hypoxia caused by the shorter time constant of the VO2 slow component. This result was due to the lower absolute work rate in hypoxia which decreased the amplitude of the VO2 slow component. The arterial (94.6 +/- 0.3 % vs. 84.2 +/- 0.7 %) and muscular desaturation (in the vastus lateralis and the lateral gastrocnemius) were reduced by hypoxia. The test duration (440 +/- 31 s vs. 362 +/- 36 s) and the test duration at VO2max (286 +/- 53 s vs. 89 +/- 33 s) were significantly shorter in hypoxia. Only in normoxia, the test duration was correlated with arterial and muscular saturation (r = 0.823 and r = 0.828; p < 0.05). At the same relative workload, hypoxia modified performance, arterial and muscular oxygen desaturation but not the oxygen uptake response. In normoxia, correlation showed that desaturation seems to be a limiting factor of performance.     

Plasma beta-endorphin immunoreactivity during graded cycle ergometry

The present study was undertaken to define the response of plasma beta-endorphin immunoreactivity (ir-BE) to exercise of increasing intensity. Nineteen healthy males performed continuous exercise for 32 min on a cycle ergometer, comprised of 8-min bouts at %VO2max approximating 25, 50, and 75% of maximal exercise. Venous blood samples were collected before exercise (T = -20 and 0 min), during exercise (T = 8, 16, 24, and 32 min), and in recovery (T = +15, +30 min). Ir-BE in plasma was measured by radioimmunoassay using Immuno Nuclear assay kits. Plasma ir-BE level (pg X ml-1) was not altered from pre-exercise (18.3 +/- 1.3) after 8 min of exercise at 25 and 50% VO2max intensity; however, ir-BE rose significantly after 8 min of 75% VO2max work intensity (27.1 +/- 2.4) and was further elevated at maximal exercise (74.1 +/- 8.6). Ir-BE level remained elevated 15 min (60.9 +/- 8.1) and 30 min (35.2 +/- 5.2) post-exercise. The response pattern was further characterized by a significant (P less than 0.05) inter-individual variation, both at rest and during exercise; also, regression analysis indicated the ir-Be levels attained at maximal exercise were inversely related to the relative VO2max (ml X kg-1 X min-1) of the subject (predicted ir-BE = 248.2 - 3.39 VO2max; r = -0.397, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Enkephalins, catecholamines, and psychological mood alterations: effects of prolonged exercise

Seven healthy trained men were studied to determine if running at various relative intensities [percent maximal oxygen consumption (VO2max)] alters peripheral venous levels of leucine enkephalin-like material. Enkephalins were measured using a radio-receptor assay (Leu-Enk RRA). Subjects ran for 80 min at 40 and 60% VO2max and for 40 min at 80% VO2max. Each session was separated by at least 1 wk. Heart rate, blood pressure, lactic acid, and rectal temperature responses increased in an intensity-dependent manner. Epinephrine increased from resting values of 38.2 +/- 6.8 pg X ml-1, mean +/- SE to 75.0 +/- 13.3 pg X ml-1 during the 40% VO2max run, from 60.2 +/- 15 to 186 +/- 45 pg X ml-1 during the 60% run, and from 33.4 +/- 7.6 to 311 +/- 52 pg X ml-1 at the 40th min of the highest workload (80% VO2max). These increases were significant (P less than 0.05). Plasma Leu-Enk RRA was between 3.8 and 6.2 pmol X ml-1 prior to each run and did not change significantly as a result of exercise. Levels of Leu-Enk RRA also did not change during 30 min of supine recovery. Perception of effort increased (P less than 0.05) with increases in exercise intensity, and effort sense was unrelated to plasma Leu-Enk RRA. Psychological tension decreased significantly (P less than 0.05) following exercise at 60 and 80% of VO2max, but the decrease following the 40% run was not significant (P greater than 0.05). Reduced tension following exercise was not related to Leu-Enk RRA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Whole‐body fat oxidation determined by graded exercise and indirect calorimetry: a role for muscle oxidative capacity?

During whole-body exercise, peak fat oxidation occurs at a moderate intensity. This study investigated whole-body peak fat oxidation in untrained and trained subjects, and the presence of a relation between skeletal muscle oxidative enzyme activity and whole-body peak fat oxidation. Healthy male subjects were recruited and categorized into an untrained (N=8, VO(2max) 3.5+/-0.1 L/min) and a trained (N=8, VO(2max) 4.6+/-0.2 L/min) group. Subjects performed a graded exercise test commencing at 60 W for 8 min followed by 35 W increments every 3 min. On a separate day, muscle biopsies were obtained from vastus lateralis and a 3 h bicycle exercise test was performed at 58% of VO(2max). Whole-body fat oxidation was calculated during prolonged and graded exercise from the respiratory exchange ratio using standard indirect calorimetry equations. Based on the graded exercise test, whole-body peak fat oxidation was determined. The body composition was determined by DEXA. Whole-body peak fat oxidation (250+/-25 and 462+/-33 mg/min) was higher (P<0.05) and occurred at a higher (P<0.05) relative workload (43.5+/-1.8% and 49.9+/-1.2% VO(2max)) in trained compared with untrained subjects, respectively. Muscle citrate synthase activity and beta-hydroxy-acyl-CoA-dehydrogenase activity were higher (49% and 35%, respectively, P<0.05) in trained compared with untrained subjects. Both lean body mass and maximal oxygen uptake were significantly correlated to whole-body peak fat oxidation (r(2)=0.57, P<0.001), but leg muscle oxidative capacity was not correlated to whole-body peak fat oxidation. In conclusion, whole-body peak fat oxidation occurred at a higher relative exercise load in trained compared with untrained subjects. Whole-body peak fat oxidation was not significantly related to leg muscle oxidative capacity, but was related to lean body mass and maximal oxygen uptake. This may suggest that leg muscle oxidative activity is not the main determinant of whole-body peak fat oxidation.     

Hemoglobin desaturation in highly trained athletes during heavy exercise

It has been generally accepted that during exercise at sea level, the pulmonary system of normal, healthy individuals is capable of maintaining arterial oxygen tension at near resting levels. However, recent evidence questions whether this generalization applies to the highly trained endurance athlete who is capable of achieving very high levels of metabolic demand. Hence, the purpose of these experiments was to examine the relationship between maximal oxygen consumption (VO2max) and arterial oxygen-hemoglobin saturation (%SaO2) during short-term heavy exercise in trained athletes and untrained individuals. Ten trained distance runners and 7 untrained males exercised at 95% of VO2max for 3 min. Minute-by-minute measurement of %SaO2 was obtained via ear oximetry. The correlation coefficients between %SaO2 and VO2max during exercise were r = -0.68, r = -0.74, and r = -0.72 (P less than 0.05) for minutes 1 through 3, respectively. In general those individuals with the highest VO2max showed the greatest decrease in %SaO2. By comparison there was no difference (P greater than 0.05) in resting %SaO2 between the trained (96.3 +/- 0.2% [SE]) and the untrained (96.3 +/- 0.4%) subjects. However, at minute 3 of exercise, %SaO2 was significantly lower (P less than 0.05) in the trained subjects (87.0 +/- 0.7%) than in the untrained subjects (92.6 +/- 0.7%). These data demonstrate that arterial desaturation occurs in healthy, highly trained endurance athletes during heavy exercise and that the level of the arterial desaturation is inversely related to VO2max.     

Respiratory muscle oxygenation kinetics: relationships with breathing pattern during exercise

This work aimed to investigate accessory respiratory muscle oxygenation (RMO(2)) during exercise, using near-infrared spectroscopy, and to study relationships between RMO(2) kinetics and breathing parameters. Nineteen young males (19.3 +/- 1.5 years) performed a maximal incremental test on a cycle ergometer. Changes in breathing pattern were characterized by accelerated rise in the breathing frequency (f (Racc)), plateau of tidal volume (V (Tplateau)) and inflection point in the V. (E)/V (T) relationship (V. (E)/V (T inflection)). First and second ventilatory thresholds (VT1 and VT2) were also determined. RMO (2) kinetics were monitored by NIRS on the serratus anterior. During exercise, all subjects showed reduced RMO (2) (deoxygenation) with a breakdown (B-RMO(2)) at submaximal workload (86 % .VO(2max)). .VO(2) corresponding to B-RMO (2) and to f (Racc), V (Tplateau), .V(E)/V(T inflection), or VT2 were not different. Relationships were found between the .VO(2) at B-RMO(2) and the .VO(2) at f (Racc) (r = 0.88, p < 0.001), V (Tplateau) (r = 0.84, p < 0.001), V. (E)/V (T inflection) (r = 0.58, p < 0.05) or VT2 (r = 0.79, p < 0.001). The amplitude of RMO(2) at maximal workload was weakly related to .VO(2max) (r = 0.58, p < 0.05). B-RMO (2) seems to be due to the change in breathing pattern and especially to the important rise in breathing frequency at the VT2 exercise level. Moreover, subjects who exhibit higher .VO(2max) also exhibit a higher decrease in respiratory muscle oxygenation during exercise.     

Clinical significance of I-123 MIBG myocardial scintigraphy for evaluating the severity of congestive heart failure

We studied the significance of I-123 MIBG (metaiodobenzylguanidine) myocardial scintigraphy for evaluating the severity of congestive heart failure. I-123 MIBG scintigraphy was performed in 7 patients with congestive heart failure (CHF) of NYHA class I-III (6 with dilated cardiomyopathy and 1 with Adriamycine cardiomyopathy) and in 2 normals. The SPECT and anterior planar myocardial images were obtained 15 minutes after (initial images) and 4 hours after (delayed images) an injection of I-123 MIBG (111 MBq). Compared with normals, patients with CHF demonstrated (1) low myocardial uptake and (2) rapid myocardial washout of I-123 MIBG, indicating myocardial sympathetic disarrangement. Then, quantitating these abnormalities with the heart to upper mediastinum uptake ratio (H/B) and the percent washout rate (%WR) during 4 hours, respectively, we compared these two indices with LV ejection fraction (EF) at rest measured by echocardiography and exercise capacity (max VO2 and VO2 at anaerobic threshold (AT] determined with respiratory gas exchange analysis during maximal bicycle exercise. H/B was lower and %WR was greater in patients with CHF than in normals. H/B correlated with EF (r = 0.77, p less than 0.05) and AT (r = 0.74, p less than 0.05). On the other hand, %WR significantly correlated with EF (r = 0.79, p less than 0.05), max VO2 (r = -0.74, p less than 0.05) and AT (r = -0.81, p less than 0.05). Thus, H/B and %WR were closely related to the severity of CHF. These results suggest that I-123 MIBG myocardial scintigraphy and the quantitative analysis of I-123 MIBG myocardial uptake provide useful information about the severity of CHF.     

Reliability of the rating of perceived exertion at ventilatory threshold in children.

The purpose of this study was to examine the reliability of the rating of perceived exertion (RPE), using the Borg 6-20 scale, at ventilatory threshold (VT) in children. Thirty children (19 male, 11 female) with a mean +/- SD age of 10.4 +/- 1.1 yrs performed two graded exercise tests for the assessment of VT and VO2max. RPE was recorded throughout each exercise test. There were no significant (p > 0.05) differences between the mean VO2max (50.9 +/- 6.0 vs 51.0 +/- 5.7 ml.kg-1.min-1; r = 0.95) or the mean VO2 at VT (36.2 +/- 4.4 vs 36.7 +/- 4.5 ml.kg-1.min-1; r = 0.87) between trials. The mean RPE at VT during trial 1 (12.4 +/- 2.7) was significantly higher than during trial 2 (11.4 +/- 3.3; p < 0.05). The test-retest reliability correlation for the RPE at VT was r = 0.78. The lower RPE in the second trial may have been due to a greater comfort and familiarity with the testing procedures. The reliability analysis indicates that the RPE at VT within a given child is fairly consistent from trial to trial. However, large inter-individual variability in the RPE at VT (range = 6 to 19) was noted and was not related to variations in the onset of VT. This raises some concern over the use of a given RPE value or range of RPE values in the regulation of exercise intensity for this age group. The test-retest reliability of VT and VO2max in this age group is similar to previous reports.     

Correlation between ventilatory threshold and endurance capability in marathon runners

The purpose of the study was to develop an index of endurance capability [i.e., "the ability to sustain a high fractional utilization of maximal oxygen uptake (VO2max) for a prolonged period of time"]. The index was based on the linear reduction of fractional utilization of VO2max with total running time greater than 7 min plotted on a log scale. The endurance index estimated from VO2max, running efficiency and the marathon performance of 18 male runners (30 +/- 7 yr old; VO2max = 66 +/- 5 ml.kg-1.min-1) ranged between -4.07 and -9.96% VO2max.1 nt-1 (mean +/- SD = -6.40 +/- 1.50) and was not related to VO2max (r = 0.107) or speed in the marathon race (r = 0.354). However, the endurance index was closely related (r = 0.853) to the fractional utilization of VO2max at ventilatory threshold (breakaway of the excess CO2 elimination curve) which occurred at 76.1 +/- 5.5% VO2max in response to a graded treadmill test. These results indicate that: (i) running time on long distance races is not, per se, an adequate measure of endurance capability because of the major contribution of VO2max to long distance running performance; (ii) the endurance index expressed as %VO2max.1n t-1 is an objective and independent index of endurance capability; and (iii) runners with a high endurance capability tend to hyperventilate at higher relative workload during a graded treadmill test.     

Short-arm (1.9 m) +2.2 Gz acceleration: isotonic exercise load-O2 uptake relationship

BACKGROUND: The deconditioning syndrome from prolonged bed rest (BR) or spaceflight includes decreases in maximal oxygen uptake (VO2max), muscular strength and endurance, and orthostatic tolerance. In addition to exercise training as a countermeasure, +Gz (head-to-foot) acceleration training on 1.8-2.0 m centrifuges can ameliorate the orthostatic and acceleration intolerances induced by BR and immersion deconditioning. PURPOSE: Study A was designed to determine the magnitude and linearity of the heart rate (HR) response to human-powered centrifuge (HPC) acceleration with supine exercise vs. passive (no exercise) acceleration. Study B was designed to test the hypothesis that moderate +Gz acceleration during exercise will not affect the respective normal linear relationships between exercise load and VO2max, HR, and pulmonary ventilation (VEBTPS). Study C: To determine if these physiological responses from the HPC runs (exercise + on-platform acceleration) will be similar to those from the exercise + off-platform acceleration responses. METHODS: In Study A, four men and two women (31-62 yr) were tested supine during exercise + acceleration and only passive acceleration at 100% [maximal acceleration (rpm) = Amax] and at 25%, 50%, and 75% of Amax. In Studies B and C, seven men (33+/-SD 7 yr) exercised supine on the HPC that has two opposing on-platform exercise stations. A VO2max test and submaximal exercise runs occurred under three conditions: (EX) exercise (on-platform cycle at 42%, 61%, 89% and 100% VO2max) with no acceleration; (HPC) exercise + acceleration via the chain drive at 25%,50%, and 100% Gzmax (35%, 72% and 100% VO2max); and (EXA) exercise (on-platform cycle at 42%, 61%, 89%, and 100% VO2max) with acceleration performed via the off-platform cycle operator at +2.2+/-0.2 Gz [50% of max (rpm) G]. RESULTS: Study A: Mean (+/-SE) Amax was 43.7+/-1.3 rpm (mean = +3.9+/-0.2, range = 3.3 to 4.9 Gz). Amax run time for exercise +acceleration was 50-70 s, and 40-70 s for passive acceleration. Regression of X HR on Gz levels indicated explained variances (r2) of 0.88 (exercise) and 0.96 (passive). The mean exercise HR of 107+/-4 (25%), to 189+/-13 (100%) bpm were 43-50 bpm higher (p < 0.05) than comparable passive HR of 64+/-2 to 142+/-22 bpm, respectively. Study B: There were no significant differences in VO2, HR or VEBTPS at the submaximal or maximal levels between the EX and EXA runs. Mean (+/-SE) VO2max for EX was 2.86+/-0.12 L x min(-1)(35+/-2 ml x min(-1) x kg(-1)) and for EXA was 3.09+/-0.14 L x min(-1) (37+/-2 ml-min(-1) x kg(-1)). Study C: There were no significant differences in the essentially linear relationships between the HPC and EXA data for VO2 (p = 0.45), HR (p < 0.08), VEBTPS (p = 0.28), or the RE (p = 0.15) when the exercise load was % VO2max. CONCLUSION: Addition of + 2.2 Gz acceleration does not significantly influence levels of oxygen uptake, heart rate, or pulmonary ventilation during submaximal or maximal cycle ergometer leg exercise on a short-arm centrifuge.     

Exercise intensities during a ballet lesson in female adolescents with different technical ability

To investigate the exercise intensity during a typical grade five ballet lesson, thirty-nine dancers (13 - 16 yrs) were divided into three different technical proficiency groups: low level (n = 13), intermediate level (n = 14), and high level (n = 12). A progressively incremented treadmill test was administered to determine VO(2max), individual ventilatory threshold (IVT), and the individual anaerobic threshold (IAT). Oxygen uptake (VO(2)), heart rate (HR) and blood lactate (La) were then evaluated during a grade five ballet lesson. Oxygen uptake at IVT, IAT and maximal oxygen uptake were greater (p < 0.05) in the high-level dancers indicating a higher level of fitness. HR and %VO(2max) obtained during the various exercises of the ballet lesson were similar among groups. During the ballet lesson, low technical level dancers had more V.O (2) and La values above (p < 0.05) the IAT than the other groups. Correlation analysis revealed that the number of exercises performed above IAT was positively related to anthropometric characteristics (BMI, %FM; r = 0.36, p < 0.05; r = 0.46, p < 0.01), negatively related to fitness parameters (VO(2IVT), VO(2IAT), VO(2max); r between - 0.43 and - 0.69; p < 0.001) and to technical level (r = - 0.70; p < 0.001). The subjects classified as having low technical abilities had lower fitness levels and performed more exercises above IAT than the more skilled dancers.     

Effects of controlled frequency breathing during exercise on blood gases and acid-base balance

The purpose of this study was to determine the effect of a reduced ventilatory frequency (Vf) on blood gases and acid-base changes during three intensities of cycling exercise. VO2max and lactate threshold workload (LaT) of six subjects were assessed on a Monark ergometer. Experimental rides were performed 1) with no restriction on Vf (NB) and 2) with a prescribed Vf of 10/min (CFB). Each exercise period consisted of 8 min at 10% of VO2max below the LaT (WI), followed immediately by 8 min at LaT (WII), followed immediately by 8 min at 10% of VO2max above LaT (WIII). Blood was taken from a heated fingertip at the end of each load and analyzed for lactate concentration, pH, PO2, and PCO2. Respiratory exchange was monitored continuously using open circuit indirect calorimetry. Minute ventilation (VE) was significantly reduced by CFB at all three workloads. The reduced VE resulted in lower (p less than 0.05) blood PO2 at each workload (p less than 0.05), however, neither blood lactate nor VO2 were significantly different between CFB and NB for the three loads. Blood [H+] was significantly higher in CFB than NB at all three loads with the greatest difference between trials at WIII (NB: 37.93 +/- 0.68 nM: CFB: 44.77 +/- 1.02 nM). This was accounted for by a significantly higher PCO2 during CFB in WII and WIII (WII, NB: 33.0 +/- 1.4 mmHg, CFB: 35.7 +/- 2.7 mmHg; WIII, NB: 31.2 +/- 1.7 mmHg, CFB: 38.9 +/- 2.4 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxygen uptake response to an 800-m running race

We tested the hypothesis that time course of O (2) uptake (VO (2)) measured during a supramaximal exercise performed in the field is driven to maximal oxygen uptake (VO (2max)). On an outdoor track, five middle-distance male runners first performed a test to determine VO (2max) and a supramaximal 800-m running test at least two days apart. VO (2) response was measured from the start to the end of exercise with the use of a miniaturised telemetric gas exchange system (Cosmed K4). VO (2max) was reached by all subjects 45 +/- 11 s (mean +/- SD) after the onset of the 800-m race (i.e., 316 +/- 75 m), and was maintained during the next 33 +/- 6 s (i.e., 219 +/- 41 m). The mean relative exercise intensity of the 800 m was 120 % VO (2max). An unexpected significant decrease in VO (2) (24.1 +/- 7.0 %; p < 0.05) was observed in all subjects during the final 38 +/- 17 s (i.e., the last 265 +/- 104 m). We concluded that, at onset of a simulated 800 m running event, VO (2) is quickly projected towards the VO (2max), and then becomes limited by the achievable VO (2max). This race profile shown by all athletes is in some contrast to what can be expected from earlier findings in a laboratory setting.     

Comparison of energy expenditure in men and women at rest and during exercise recovery.

The purpose of this study was to compare the energy expenditure (EE) of men and women at rest and during a 1 h recovery from 30 min of exercise at 40% of VO2max. Subjects were five physically active lean men (mean age, % fat, and VO2max = 34.8 +/- 8.1 years, 8.1 +/- 3.2% and 63.8 +/- 8 ml.kg-1.min-1, respectively) and five physically active lean women (mean age, % fat, and VO2max = 26.2 +/- 5.1 years, 17.6 +/- 4.5%, and 50.2 +/- 13.6 ml.kg-1.min-1, respectively). Energy expenditure (EE) was measured continuously by standard open circuit spirometry for 20 min at rest and for 1 h immediately after 30 min of exercise at 40% of VO2max. Independent t tests and ANCOVA were used to compare EE of men and women at rest and during exercise recovery. EE at rest in the men was significantly greater using a t test (p less than .05) than in the women but it was not when the data were adjusted with ANCOVA using body weight, VO2max in ml.kg-1.min-1, and percent body fat as covariates. The EE during 1 h of recovery was also significantly higher in the men using a t test (p less than .05) and after the data were adjusted for differences in VO2max (p less than .02). With body weight and percent fat as covariates. The EE during 1 h of recovery was also significantly higher in the men using a t test (p less than .05) and after the data were adjusted for differences in VO2max (p less than .02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlations between VO2max and performance times of recreational triathletes.

Twenty-three recreational triathletes, 16 male and 7 female (mean = 21.7 yrs), performed max tethered swim (TS), cycle ergometer (CE), and treadmill run (TR) tests prior to participation in a competitive triathlon (0.91 km swim, 40 km cycle, 10 km run). The VO2max values on the TS, CE and TR were similar to those reported for trained athletes in each sport. As a group, cycling times were significantly correlated to both absolute (p less than 0.01) and relative (p less than 0.001) cycling VO2max (r = -0.57 and r = -0.78, respectively); running times significantly correlated with relative (p less than 0.001, r = -0.84) but not absolute (p greater than 0.05) running VO2max; and swimming times significantly correlated with absolute (p less than 0.01, r = -0.49) but not relative (p greater than 0.05) swimming VO2max. With the exception of absolute swim VO2max, the total performance times were significantly correlated to all VO2max values when expressed in both absolute and relative values. This study indicates the important role a moderately trained individual's aerobic power has in determining performances in endurance events such as the triathlon.     

Peak power output, the lactate threshold, and time trial performance in cyclists.

PURPOSE: To determine the relationship between maximum workload (W(peak)), the workload at the onset of blood lactate accumulation (W(OBLA)), the lactate threshold (W(LTlog)) and the D(max) lactate threshold, and the average power output obtained during a 90-min (W(90-min)) and a 20-min (W(20-min)) time trial (TT) in a group of well-trained cyclists. METHODS: Nine male cyclists (.VO(2max) 62.7 +/- 0.8 mL.kg(-1).min(-1)) who were competing regularly in triathlon or cycle TT were recruited for the study. Each cyclist performed four tests on an SRM isokinetic cycle ergometer over a 2-wk period. The tests comprised 1) a continuous incremental ramp test for determination of maximal oxygen uptake (.VO(2max) (L.min(-1) and mL.kg(-1).min(-1)); 2) a continuous incremental lactate test to measure W(peak), W(OBLA), W(LTlog), and the D(max) lactate threshold; and 3) a 20-min TT and 4) a 90-min TT, both to determine the average power output (in watts). RESULTS: The average power output during the 90-min TT (W(90-min)) was significantly (P < 0.01) correlated with W(peak) (r = 0.91), W(LTlog) (r = 0.91), and the D(max) lactate threshold (r = 0.77, P < 0.05). In contrast, W(20-min) was significantly (P < 0.05) related to .VO(2max) (L.min(-1)) (r = 0.69) and W(LTlog) (r = 0.67). The D(max) lactate threshold was not significantly correlated to W(20-min) (r = 0.45). Furthermore, W(OBLA) was not correlated to W(90-min) (r = 0.54) or W(20-min) (r = 0.23). In addition, .VO(2max) (mL.kg(-1).min(-1)) was not significantly related to W(90-min) (r = 0.11) or W(20-min) (r = 0.47). CONCLUSION: The results of this study demonstrate that in subelite cyclists the relationship between maximum power output and the power output at the lactate threshold, obtained during an incremental exercise test, may change depending on the length of the TT that is completed.     

Is ventilatory anaerobic threshold a good index of endurance capacity?

This study was undertaken to assess whether ventilatory anaerobic threshold (T vent) reflected endurance capacity (EC) in sports medical control. Fifteen subjects performed two cycle ergometer tests. The first was a maximal exercise test, which consisted of increasing the load 20 W/min until exhaustion. During this test, the gas exchange anaerobic threshold was determined and VO2 max was measured. The second was an endurance exercise test, which consisted of asking the subject to work, as long as possible, a load representing 80% of his maximal aerobic power. During this test, we measured endurance time (ET). The statistical analysis showed the lack of relationship between VO2 max and ET and the linear correlations between VO2 T vent ml/min/kg and ET min (r = 0.521, P less than 0.05), VO2 T vent l/min and ET min (r = 0.524, P less than 0.05), and T vent % VO2 max and ET (r = 0.738, P less than 0.01). These results establish that ventilatory anaerobic threshold actually reflects endurance capacity. This relation can be explained referring to the muscle energetic metabolism during exercise. Therefore, T vent should be determined systematically in addition to VO2 max during maximal exercise tests to better evaluate physical fitness.     

The influence of training on endurance and blood lactate concentration during submaximal exercise.

The purpose of this study was to examine the effect of short-term training on maximum oxygen uptake (VO2 max) and two different measures of endurance performance. Endurance was determined for 15 female subjects (7 training, 8 control) as (1) exercise time to exhaustion at 80% VO2 max (T80%) and (2) the highest relative exercise intensity tolerable during a 30-minute test (T30 min), before and after a 6-week training period. In addition, VO2 max and the work rate equivalent to a blood lactate concentration of 4 mmol.l-1 (OBLA) were determined. Maximum oxygen uptake increased by 24% (p less than 0.01) for the training group (TG) and 7% (p less than 0.01) for the control group (CG). Cumulative average work rate (CAWR) during T30 min increased by 25% for the TG while there was no change for the CG. No significant difference was found pre- and post-training in the %VO2 max (estimated from CAWR) at which the TG and CG performed T30 min. Exercise time to exhaustion on T80% increased by 347% (p less than 0.01) and 16% (NS) for the TG and the CG respectively. Good correlations were found between VO2 max and CAWR (W) (pre-training r = 0.84; post-training r = 0.83), OBLA (W) and CAWR (W) (pre-training r = 0.89; post-training r = 0.88) and change in endurance time and the change in submaximal blood lactate concentration (r = 0.70, p less than 0.01). The results of this study suggest that the ability to sustain a high relative exercise intensity is not enhanced following short-term training.     

Bioenergetic characteristics of swimmers determined during an arm-ergometer test and during swimming.

The maximal oxygen uptake (VO2max) of 13 swimmers was determined by an arm-ergometer test (direct method) and estimated from a maximal multistage swimming test (indirect method) (23). A test-retest of the progressive swimming exercise showed that there were no significant differences from one test to the other and that there were significant correlations between the principal parameters: arm stroke index: 0.73, maximal aerobic swimming velocity: 0.94, VO2max: 0.95, p less than 0.01. Therefore, for swimmers of average ability, the reproducibility of this test has been proved. A significant difference (p less than 0.001) was observed between the two tests for VO2max: arm-ergometer test (VO2max arms): 2.4 +/- 0.5 l.min-1, swimming test (VO2max ST): 3.2 +/- 0.7 l.min-1, p less than 0.01. This difference appeared to be linked to the use of a greater muscle mass (arms and legs) during swimming. A significant correlation (r = 0.73, p less than 0.01) was obtained between VO2max (l.min-1) by using both the direct and indirect exercises as methods of measurement. However, the level of r did not permit the prediction of one parameter from the other. Significant correlations were obtained between VO2max and performances over 200 and 400 m free style regardless of the methodology used (VO2max arm, VO2max ST). Moreover, only VO2max (arm, ST) emerged as a variable accounting for swimming performance from a step-wise multiple regression analysis, in which biometric and bioenergetic parameters were taken into account.