Reliability and validity of measures taken during the Chester step test to predict aerobic power and to prescribe aerobic exercise

OBJECTIVES: To evaluate the reliability and validity of measures taken during the Chester step test (CST) used to predict VO(2)max and prescribe subsequent exercise. METHODS: The CST was performed twice on separate days by 7 males and 6 females aged 22.4 (SD 4.6) years. Heart rate (HR), ratings of perceived exertion (RPE), and oxygen uptake (VO(2)) were measured at each stage of the CST. RESULTS: RPE, HR, and actual VO(2) were the same at each stage for both trials but each of these measures was significantly different between CST stages (p<0.0005). Intertrial bias +/-95% limits of agreement (95% LoA) of HR reached acceptable limits at CST stage IV (-2+/-10 beats/min) and for RPE at stages III (0.2+/-1.4) and IV (0.5+/-1.9). Age estimated HRmax significantly overestimated actual HRmax of 5 beats/min (p = 0.016) and the 95% LoA showed that this error could range from an underestimation of 17 beats/min to an overestimation of 7 beats/min. Estimated versus actual VO(2) at each CST stage during both trials showed errors ranging between 11% and 19%. Trial 1 underestimated actual VO(2)max by 2.8 ml/kg/min (p = 0.006) and trial 2 by 1.6 ml/kg/min (not significant). The intertrial agreement in predicted VO(2)max was relatively narrow with a bias +/-95% LoA of -0.8+/-3.7 ml/kg/min. The RPE and %HRmax (actual) correlation improved with a second trial. At all CST stages in trial 2 RPE:%HRmax coefficients were significant with the highest correlations at CST stages III (r = 0.78) and IV (r = 0.84). CONCLUSION: CST VO(2)max prediction validity is questioned but the CST is reliable on a test-retest basis. VO(2)max prediction error is due more to VO(2) estimation error at each CST stage compared with error in age estimated HRmax. The HR/RPE relation at >50% VO(2)max reliably represents the recommended intensity for developing cardiorespiratory fitness, but only when a practice trial of the CST is first performed.     

Cardiovascular fitness and thermoregulation during prolonged exercise in man.

Nine healthy male subjects differing in their training status (VO2 max 54 +/- 7 ml.min-1.kg-1, mean +/- SD; 43-64 ml.min-1 kg-1, range) exercised on two occasions separated by one week. On each occasion, having fasted overnight, subjects exercised for 1 h on an electrically braked cycle ergometer at a workload equivalent to 70 per cent VO2 max (test A) or at a fixed workload of 140 W (test B). Each test was assigned in a randomized manner and was performed at an ambient temperature of 22.5 +/- 0.0 degrees C and a relative humidity of 85 +/- 0 per cent. Absolute exercise workload was the most successful predictor of sweat loss during test A (r = 0.82, p less than 0.01). Sweat loss was also related to VO2 max tests A (r = 0.67, p less than 0.05) and B (r = 0.67, p less than 0.05). There was no relationship between resting pre-exercise core temperature and VO2 max. However, core temperature recorded during the final min of exercise in test B was inversely related to VO2 max (r = -0.86, p less than 0.01). As a consequence, core temperature during the final minute of exercise was also related to the relative exercise intensity (% VO2 max) performed (r = 0.82, p less than 0.01). The heart rate response during test B was inversely related to VO2 max (r = -0.71, p less than 0.05) and was positively related to the relative exercise intensity performed (r = 0.68, p less than 0.05). No relationship was found between weighted mean skin temperature during the final minute of exercise and the relative (r = 0.26) or absolute (r = 0.03) workloads performed during exercise. The results of the present experiment suggest that cardiovascular fitness (as indicated by VO2 max) will have a significant influence upon the thermoregulatory responses of Man during exercise.     

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)     

Effect of high-intensity submaximal work, with or without rest, on subsequent VO2max

PURPOSE: In practice, tests of maximal oxygen uptake (.VO2max) are often preceded by a lactate profile, a highly intense but submaximal exercise bout. The .VO2max response to preceding high-intensity submaximal exercise, with or without a rest period, has not been determined. If .VO2max is limited after a lactate profile, exercise-induced hypoxemia (EIH) may explain the deficit. The purposes of this study were to: 1) examine the effects of high-intensity submaximal exercise, with or without rest, on subsequent .VO2max; and 2) evaluate the role of EIH in causing any observed changes. METHODS: Ten healthy, well-trained, male cross-country skiers (age = 20.5 +/- 4.7 yr, height = 181.6 +/- 6.0 cm, mass = 72.1 +/- 5.7 kg) completed three exercise trials: an incremental run to fatigue (MAX), MAX preceded by a high-intensity submaximal run (lactate profile) and a 20-min rest period (discontinuous protocol [DC]), and MAX preceded by a high-intensity submaximal exercise run with no rest (continuous protocol [C]). .VO2max, minute ventilation, and arterial oxygen saturation were measured throughout, and diffusion capacity was evaluated 2 min postexercise.RESULTS No significant between trial differences were observed, although the difference between .VO2max determined during the MAX trial (62.7 +/- 6.7 mL.kg-1.min-1) and during the DC trial (58.3 +/- 4.4 mL.kg-1.min-1) approached significance (P = 0.059). DC .VO2max responses could be separated into two groups: five responders whose .VO2max suffered during the DC trial (decreased >7.5% from MAX) and five nonresponders, whose .VO2max was unaffected by preceding submaximal exercise and a rest period. Responders showed greater aerobic capacity during the MAX trial. CONCLUSION: .VO2max is significantly reduced in approximately 50% of cross-country skiers when a maximal exercise test is preceded by high-intensity submaximal exercise and a 20 min rest period; the role of EIH in causing these reductions is unclear.     

Dissociation of the ventilatory and lactate thresholds following caffeine ingestion

Caffeine ingestion prior to the start of exercise has been shown to have an effect on ventilatory parameters and substrate utilization. Changes in either substrate utilization or ventilatory parameters may influence the determination of the lactate threshold (LT) and/or the ventilatory threshold (VT). Therefore, it was the purpose of this investigation to determine whether the VT and LT occur at similar metabolic rates and what effect caffeine ingestion will have on these two measures. Ten male subjects completed two maximal exercise bouts on the treadmill using a single blind procedure. One trial was performed 45 min after the ingestion of caffeine citrate (CC) in an amount equal to 7.0 mg of anhydrous caffeine.kg-1 body weight. The second trial was performed 45 min after the ingestion of a gelatin powdered placebo (P). Ventilatory parameters were monitored on a breath-by-breath basis, and blood for lactate determination was obtained from an antecubital vein every minute. Maximal oxygen consumption did not differ significantly between the CC (60.3 +/- 5.2 ml.kg-1.min-1) and P (59.7 +/- 5.6 ml.kg-1.min-1) trials. Oxygen consumption (VO2) values during the P trial at the VT (40.2 +/- 6.1 ml.kg-1.min-1) and the LT (38.6 +/- 3.3 ml.kg-1.min-1) were not significantly different (P less than 0.05). During the CC trial, VO2 values at the VT (44.4 +/- 6.6 ml.kg-1.min-1) and the LT (39.7 +/- 5.8 ml.kg-1.min-1) were significantly different. When comparing the VO2 at the LTs between the CC and P trials, there was no significant difference. There was, however, a significant difference in VO2 at the VTs when comparing the two trials. These data demonstrate a dissociation between the VT and LT following caffeine ingestion and suggest that the use of the VT as an indicator of the LT may be inappropriate following ingestion of moderate dosages of caffeine.     

An evaluation of the predictive validity and reliability of ventilatory threshold

PURPOSE: To identify a valid and reliable method to determine 40-km time trial (40K) performance in a laboratory setting. METHODS: Part 1: Ventilatory threshold (VT) and 40K performance were determined on two occasions (February/September) using two subsets of cyclists (N = 15 each; VO(2max) 67.6 +/- 4.2/71.5 +/- 3.0 mL x kg(-1) x min(-1)) to determine the predictive validity of VT assessments. Variables of interest were power output at VT, peak power output (MaxVT(w)), and average power output during 40K (40K(avgwatts)). For VT determination we used: breakpoint of VE/VO2; breakpoint of VE/VCO2; V-slope; RER = 1; and RER = 0.95. In part 2, test-retest reliability of VT and MaxVT(w) were examined in 20 subjects (VO(2max) 64.8 +/- 8.0 mL x kg(-1) x min(-1)) on two occasions, separated by 48 h. RESULTS: Regression analyses between power outputs at VTs and 40K(avgwatts) showed significant predictive validity for (February/September): V-slope (r = 0.79/0.84; SEE 155/13.3W), VE/VO2 (r = 0.80/0.81; SEE 15.2/14.2W), RER0.95 (r = 0.73/0.58; SEE 17.4/21.2W), RER1 (r = 0.75/0.74; SEE 16.8/16.7W), and MaxVT(w) (r = 0.81/0.73; SEE 15.0/17.1W). Paired t-tests between power outputs at VTs and the 40K(avgwatts) indicated that mean power outputs at VE/O2 (261 +/- 29W; P = 0.33) and RER0.95 (274 +/- 55W; P = 0.93) in February and VE/VO2 (274 +/- 37W; P = 0.79) in September were not significantly different from the respective 40K(avgwatts) (277 +/- 30W/281 +/- 30W). Test-retest reliability analysis yielded the following intraclass correlation and relative test-retest errors: V-slope: 0.98, 2.6%; VE/VO2: 0.95, 5.3%; RER0.95: 0.87, 9.8%; RER1: 0.94, 5.7%; VE/VCO2: 0.87, 12.1%; MaxVT(w): 0.98, 2.6%. CONCLUSION: The high test-retest reliability and consistent ability to accurately predict athletes' 40K(avgwatts) across a competitive season indicated that VE/VO2 was superior to the other evaluated methods.     

Exercise training below and above the lactate threshold in the elderly

In this study we report the effects of training at intensities below and above the lactate threshold on parameters of aerobic function in elderly subjects (age range 65-75 yr). The subjects were randomized into high-intensity (HI, N = 8; 75% of heart rate reserve = approximately 82% VO2max = approximately 121% of lactate threshold) and low-intensity (LI, N = 9; 35% of heart rate reserve = approximately 53% VO2max = approximately 72% of lactate threshold) training groups which trained 4 d.wk-1 for 30 min.session-1 for 8 wk. Before and after the training, subjects performed an incremental exercise test for determination of maximal aerobic power (VO2max) and lactate threshold (LT). In addition, the subjects performed a 6-min single-stage exercise test at greater than 75% of pre-training VO2max (SST-High) during which cardiorespiratory responses were evaluated each minute of the test. After training, the improvements in VO2max (7%) for LI and HI were not different from one another (delta VO2max for LI = 1.8 +/- 0.7 ml.kg-1.min-1; delta VO2max for HI = 1.8 +/- 1.0 ml.kg-1.min-1) but were significantly greater (P = 0.02) than the post-testing change observed in the control group (N = 8). Training improved the LT significantly (10-12%; P less than 0.01) and equally for both LI and HI (delta LT for for LI = 2.3 +/- 0.6 ml O2.kg-1.min-1; delta LT for HI = 1.8 +/- 0.8 ml O2.kg-1.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Circulating white blood cells affect red cell pulmonary transit times in endurance athletes during intense exercise

PURPOSE: The aim of this study was to determine the relationship between the right-to-left ventricular red cell pulmonary transit times (PTT) during intense exercise and circulating white blood cell (WBC) counts in highly trained endurance athletes. We postulated that high levels of WBCs preexercise would slow PTT. Eleven endurance-trained athletes (VO2max = 69.6 +/- 7.7 mL.kg-1.min-1; weight = 75.0 +/- 6.2 kg; height = 181.0 +/- 7.1 cm) performed 6.5 min constant-load, near-maximal cycling exercise (approximately 92% VO2max) on two different days. Preexercise WBC counts were measured in arterial blood drawn from the radial artery 30 min before exercise. PTT was measured during the 3rd min of exercise by first-pass radionuclide cardiography using centroid and deconvolution analysis, whereas cardiac output (Q) was measured during the last 2.5 min of exercise via a count-based ratio method from the MUGA technique. RESULTS: Combined mean PTT from both deconvolution and centroid analysis at minute three of exercise was 2.45 +/- 0.21 s, whereas the preexercise WBC count was 5.3 +/- 1.6 x 109.L-1. Cardiopulmonary blood volume at minute three of exercise was 1.22 +/- 0.13 L, VO2 was 4.58 +/- 0.44 L.min-1, and Q was 30.2 +/- 4.2 L.min-1. We found that PTT was negatively correlated with circulating WBC (r = -0.61; adjusted r2 = 0.30; P = 0.04; N = 11) but not with the dispersion (spread) of transit times around the mean (r = 0.19; P = 0.57). CONCLUSION: This suggests that athletes with higher circulating numbers of WBCs preexercise have faster (shorter) red cell transit times through the lung during intense exercise.     

High VO2max with no history of training is primarily due to high blood volume

PURPOSE: To investigate the high VO2max observed occasionally in young men who have no history of training. METHODS: VO2max, blood volume (BV), maximal stroke volume (SVmax), maximal cardiac output (Qmax), and related measurements (reported as mean +/- SEM) were studied in six men (mean age 20.0 +/- 0.5 yr) with no history of training, who all had a VO2max below 49 mL.kg-1.min-1 (LO group) and six age- and weight-matched men (mean age 19.5 +/- 0.5 yr) with no history of training, who all had a VO2max above 62.5 mL.kg-1.min-1 (HI group). RESULTS: Compared with the LO group, the HI group had a higher SVmax (149 +/- 5 vs 102 +/- 5 mL), higher Qmax (28.9 +/- 0.9 vs 20.0 +/- 1.0 L.min-1) and higher BV (88.1 +/- 3.8 vs 76.7 +/- 0.9 mL.kg-1). The BV of four participants in the HI group (mean = 92.3 +/- 4.3 mL.kg-1) was substantially higher than the BV of all participants in the LO group, but two participants in the HI group had a BV (mean = 79.7 +/- 0.8 mL.kg-1) that was similar to the mean BV of the LO group. CONCLUSION: The primary explanation for the high VO2max observed occasionally in young men who have no history of training is a naturally occurring (perhaps genetically determined) high BV that brings about a high SVmax and Qmax. However, some young men with no history of training have a high VO2max, SVmax, and Qmax possibly because a greater portion of their BV is hemodynamically active.     

Endurance training enhances critical power.

The present investigation was conducted to determine whether critical power (CP) assesses the ability to perform continuous aerobic exercise and to determine whether training-induced changes in aerobic endurance are reflected by changes in the slope, but not the y-intercept of the CP function. Twelve healthy, active, but untrained male students (mean age +/- SD = 19.1 +/- 0.8 yr) undertook 8 wk of cycle ergometer endurance training (30-40 min a day, three times a week) at an intensity corresponding to their CP. Six control subjects of similar age and initial training status refrained from regular exercise for the same period. Before and immediately following the training period, each of the 18 participants completed three cycle ergometer tests to determine their CP function, an incremental exercise task to establish their maximal oxygen uptake (VO2max), and 40 min of continuous cycle ergometry at or near their calculated CP. CP was significantly correlated with endurance time at 270 W (r = 0.65, P < 0.05) and with the mean power that could be maintained for 40 min (r = 0.87-0.95, P < 0.01), but overestimated the latter by less than 6%. In response to endurance training, CP increased from a mean of 196 +/- 40.9 W to 255 +/- 28.4 W (31%) (ANCOVA, P < 0.01), while the mean power output maintained for 40 min of exercise increased from 190 +/- 34.5 W to 242 +/- 34.9 W (28%). VO2max increased from 49.2 +/- 7.8 ml.kg-1.min-1 to 53.4 +/- 6.4 ml.kg-1.min-1 (8.5%) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

.VO2 is attenuated above the lactate threshold in endurance-trained runners

PURPOSE: To determine whether a deviation from linearity occurs in the .VO2-speed relationship, above the lactate threshold (LT) in running; and whether the length of the submaximal exercise bouts alters the magnitude of any deviation. METHODS: Ten endurance-trained runners (N = 3 state level, N = 4 club level, and N = 3 recreational) (mean +/- SE; age 24.4 +/- 2.8 yr, mass 76.1 +/- 2.2 kg, .VO2 59.3 +/- 10.6 mL.kg-1.min-1) completed a .VO2, LT test and 10 x 4-min submaximal constant load exercise bouts. Data were evenly spread above and below LT, which was fitted by a dual linear regression model. RESULTS: There was a significant decrease (51.4%) in slope of the .VO2-speed relationship above LT. The use of 3-min, in comparison with 4-min, submaximal data did not alter the slope of the .VO2-speed regression above LT. There was no significant difference in the .VO2max estimated from the .VO2-speed regression above LT (58.1 +/- 3.3 mL.kg-1.min-1) but a significant difference below LT (63.6 +/- 3.9 mL.kg-1.min-1) to that obtained during the .VO2max test. CONCLUSION: Data from the current study suggest that the use of the linear regression of .VO2-speed data below the LT may potentially overestimate the prediction of .VO2 values above LT.     

Estimation of VO2max from a one-mile track walk, gender, age, and body weight

The purpose of this investigation was to explore an alternative field test to estimate maximal oxygen consumption (VO2max) using a one-mile walk test. VO2max was determined in 343 healthy adult (males = 165, females = 178) subjects 30 to 69 yr using a treadmill protocol (mean +/- SD: VO2max = 37.0 +/- 10.7 ml X kg-1 X min-1). Each subject performed a minimum of two, one-mile track walks as fast as possible. The two fastest walks (T1, T2) with elapsed times within 30 s were used for subsequent analyses. Heart rates were monitored continuously and recorded every one-quarter mile. Multiple regression analysis (best sub-sets) to estimate VO2max (l X min-1) yielded the following predictor variables: track walk-1 time (T1); fourth quarter heart rate for track walk-1 (HR 1-4); age (yr); weight (lb); and sex (1 = male, 0 = female). The best equation (N = 174) was: VO2max = 6.9652 + (0.0091*WT) - (0.0257*AGE) + (0.5955*SEX) - (0.2240*T1) - (0.0115*HR1-4); r = 0.93, SEE = 0.325 l X min-1. Comparing observed and estimated VO2max values in a cross-validation group (N = 169) resulted in r = 0.92, SEE = 0.355 l X min-1. Generalized and sex-specific equations to estimate VO2max (ml X kg-1 X min-1) were also generated. The accuracy of estimation as expressed by SEE was similar among the equations. The results indicate that this one-mile walk test protocol provides a valid sub-maximum assessment for VO2max estimation.     

Reproducibility of ventilation of thresholds in trained cyclists during ramp cycle exercise

The reproducibility of peak cardiopulmonary exercise responses and the first (VT1) and second [VT2) ventilation thresholds was studied in sixteen endurance-trained male cyclists (mean +/- SD peak oxygen uptake [VO2 peak] = 63.3 +/- 7.1 ml x kg(-1) x min(-1)) during duplicate 30 W x min(-1) ramp cycling protocols. Expired gas sampled from a mixing chamber was analysed on-line and VT1 and VT2 were determined by computerised V-slope analysis and visually by two evaluators (test-retest reliability) and again by one of the evaluators 12 months later (intra-evaluator reliability) from 20-s-average respiratory data. The results demonstrated high intra-evaluator reliability (r = 0.91-0.97, P < 0.0001) for repeat determinations of VO2, work rate (WR) and heart rate (HR) at VT1 and VT2. No significant differences were observed between Tests 1 and 2 for any of the measured variables (P > 0.05). Test-retest intraclass reliability coefficients ranged from 0.86 to 0.98 (P < 0.0001) for VO2 peak, peak pulmonary ventilation (VE), carbon dioxide output (VCO2), HR and WR values, and measurements of VO2 and WR at VT2, and from 0.67 to 0.80 (P < 0.01) for measurements of VO2 and WR at VT1. The reliability of VT1 and VT2 was reduced when the thresholds were expressed as relative (%VO2 peak) (r = 0.67-0.70, P<0.01) rather than absolute (l x min(-1)) (r = 0.77-0.93, P<0.001) VO2 values. It was concluded that VO2 peak, peak VE, VCO2. HR and WR values, and VT2 are highly reproducible in trained cyclists using a 30 W x min(-1) ramp exercise function. However, determinations of VT1 are less reliable. Additionally, ventilation thresholds are more reliably described using absolute rather than relative VO2 values.     

Blood lactate during exercise: time course of training adaptation in humans

We determined the time course of adaptation in blood lactate concentration ([La]) during constant-load exercise in response to training. Thirteen healthy subjects (11 males, 2 females) exercised on a cycle ergometer for 30 min/day at a work rate calculated to elicit 70% of pre-training VO2max, 6 days/week for 3 weeks. VO2max and blood [La] during constant-load exercise (training work rate) were determined at the end of each week of training. Training increased VO2max 8.5% (from 48.2 +/- 1.5 ml.kg-1.min-1 pre-training to 52.3 +/- 1.4 ml.kg-1.min-1 post-training, P less than 0.01) and decreased constant-load blood [La] 53% (from 7.8 +/- 0.6 mM pre-training to 3.7 +/- 0.3 mM post-training, P less than 0.01). The training-induced reduction in exercise blood [La] was well fit to an exponential (5.5e (-t/2.2) + 2.3, r = 0.99) with a half-time of 10.7 days. However, this was not the case for the time course of VO2max adaptation. The absolute decrease in blood [La] was correlated with the initial blood [La] (r = 0.88, P less than 0.01), but changes in VO2max were not significantly correlated with initial blood [La] (r = -0.14) nor with changes in blood [La] (r = -0.02). We conclude that (1) blood [La] response to constant-load exercise decreases rapidly and exponentially with training, with a t1/2 of 10.7 days, (2) the magnitude of training adaptation is positively related to the initial blood [La], and (3) the time course and extent of the training-induced adaptations of blood [La] and VO2max appear to be independent of one another.     

Test-retest reliability of the aerobic power index component of the tri-level fitness profile in a sedentary population

Use of maximal aerobic power (VO2(max)) testing, which requires subjects to exercise to physiological limits, may deter eligible candidates from volunteering for trials and may also be contraindicated in patients suffering from various medical illnesses. An alternative to maximal testing is submaximal testing. The Aerobic Power Index, which represents the aerobic component of the Tri-level Fitness Profile, is a submaximal test that has been shown to be reliable in trained athletes. The purpose of this study was to establish reliability of the Aerobic Power Index, as well as associated variables of VO2 (ml x kg(-1) x min(-1) and rate of perceived exertion (RPE), in a group of sedentary subjects. Results for the 20 subjects who participated in a test-retest trial indicated high reliability (ICC r = 0.98, %TEM 3.87 W x kg(-1); SEM 0.04 W x kg(-1) for the main measurement outcome of Watts per kilogram (W x kg(-1)). Oxygen uptake (ml x kg(-1)min(-1)) also demonstrated high reliability (ICC r = 0.92; %TEM 4.63 ml x kg(-1) x min(-1); SEM 0.58 ml x kg(-1) min (-1), as did RPE (ICC r = 0.97,%TEM 7.78; SEM 0.63). Limits of agreement were -0.02+/-0.16 W x kg(-1). -0.41+/-2.31 ml x kg(-1) x min(-1) for VO2 and -0.05 < or = 2.10 for RPE. These results indicate that the Aerobic Power Index is a reliable submaximal exercise test for use in sedentary subjects.     

Increased training intensity effects on plasma lactate, ventilatory threshold, and endurance

The purpose of this study was to determine the effects of increased training intensity (ITI) on VO2max, plasma lactate accumulation, ventilatory threshold (VT), and performance in trained distance runners. Seven trained male distance runners increased their training intensity three d.wk-1 at 90-95% HRmax for eight wk. ITI did not alter VO2max (65.3 +/- 2.3 vs 65.8 +/- 2.4 ml.kg-1.min-1) but improved 10 km race time (means = 63 s decrease) and increased run time to exhaustion on the treadmill at the same speed and grade (means = 3.88 min). Significant decreases in plasma lactate concentration at 85 and 90% of VO2max were observed after ITI. No differences were found in plasma lactate at 65, 70, 75 or 80% of VO2max or VT following ITI. Significant correlations were obtained between 10 km race times and changes in plasma lactate at 85 and 90% of VO2max (r = 0.69 and 0.73, respectively). Lactate accumulation at both 2.5 and 4.0 mM were at a significantly greater percent of VO2max after ITI. Additionally, the changes in plasma lactate were dissociated from alterations in VT after ITI. These data indicate that previously trained runners can increase training intensity to improve endurance performance by lowering lactate at the intensity at which they trained despite no changes in VO2max and VT.     

Elite special forces: physiological description and ergogenic influence of blood reinfusion

We measured the physical exercise capabilities of U.S. Army Special Forces soldiers (male) and determined the subsequent ergogenic influence of autologous blood reinfusion. Twelve subjects (Ss) completed maximal exercise treadmill testing in a comfortable (Ta = 20 degrees C, Tdp = 9 degrees C) environment. Six Ss were later transfused with a 600 ml autologous red blood cell (50% Hct) NaCl glucose-phosphate solution and completed identical maximal exercise tests 3 and 10 d posttransfusion. Pretransfusion, the 12 Ss had a maximal oxygen uptake (VO2max) of 4.36 +/- 0.56 L . min-1 and 55 +/- 4 ml . kg-1 . min-1 with a heart rate of 188 +/- 10 b . min-1 and ventilatory equivalent for oxygen of 37 +/- 3. For the 6 reinfused Ss, hemoglobin and red cell volume (RCV) increased by 10% (p less than 0.05) and 11% (p less than 0.05), respectively, posttransfusion. Reinfusion increased (p less than 0.05) VO2max from 4.28 +/- 0.22 L . min-1 (54 +/- 5 ml . kg-1 . min-1) to 4.75 +/- 0.42 L . min-1 (60 +/- 6 ml . kg-1 . min-1) and 4.63 +/- 0.21 L . min-1 (59 +/- 6 ml . kg-1 . min-1) at 3 and 10 d posttransfusion, respectively. No significant relationship was found between the individual change in RCV and VO2max values pre- to posttransfusion. We conclude that Special Forces soldiers have high levels of aerobic fitness that can be further increased by blood reinfusion for at least 10 d.     

Rating of perceived exertion during high-intensity treadmill running.

PURPOSE: The purpose of this investigation was 1) to evaluate the time course of the rating of perceived exertion (RPE; 6-20 Borg scale) during short-term, high-intensity, constant-load running (ST); and 2) to determine the reproducibility of RPE during ST. METHODS: Fifteen well-trained males (VO2max = 58.0 +/- 4.6 mL x kg(-1) x min(-1), mean +/- SD) performed treadmill running (i.e., between 3 and 4 m.s-1 at 10.5% incline) to volitional exhaustion (Tlim) at an exercise intensity equivalent to 125% VO2max. A total of four RPE measurements were taken during each test, one every 30 s during the first 120 s of the exercise. The tests were repeated at the same time of day on three occasions within a 3-wk period. RESULTS: Tlim for the three tests was 197.6 +/- 34.8 s. RPE was linearly related with exercise time (mean +/- SD for the three tests: RPE at 30 s = 10.8 +/- 2.2; RPE at 60 s = 12.6 +/- 1.8; RPE at 90 s = 14.5 +/- 1.7; RPE at 120 s = 16.0 +/- 1.9; RPE = 9.06 + (0.06 x time (s)); r = 0.71, SEE = 2.0, P < 0.01). Repeated ANOVA revealed no systematic bias between the three tests for RPE, and other measures of reliability were also favorable. These included intraclass correlation coefficients ranging from 0.78 to 0.87 and sample coefficients of variation of between 4.4% and 6.0%. The 95% limits of agreement ranged between 0.0 +/- 2.3 and 0.0 +/- 2.5. CONCLUSION: ST RPE displays a positive linear response during the first 2 min. The measurement of ST RPE appears to be reliable and could thus add a new dimension to ST investigations.     

Effect of marathon training on the plasma lactate response to submaximal exercise in middle-aged men.

Twenty-one previously sedentary male volunteers (aged 35-50 years) undertook a defined marathon training programme lasting 30 weeks. At weeks 0 (T1), 15 (T2) and 30 (T3) they underwent measurement of maximal oxygen uptake (VO2 max), submaximal VO2 and submaximal plasma lactate concentration during cycle ergometry. No exercise was taken for 24-48 hours prior to testing. During training aerobic power increased significantly (p less than 0.001) from an initial VO2 max at T1 of 33.9 +/- 6 (mean +/- sd) ml.kg-1min-1 to 39 +/- 5.6 ml.kg-1min-1 at T2 but the T3 value of 39.2 +/- 5.2 ml.kg-1min-1 was not significantly different from that at T2. Plasma lactate concentration of 4 mmol.l-1 (OBLAw) occurred at a significantly (P less than 0.05) higher workload (155 +/- 28 w) at T2 compared with T1 (132 +/- 30 w) but the T3 figure was 137 +/- 34 w. OBLA VO2 at T1 was 2.04 +/- 0.42 l.min-1, at T2 was 2.24 +/- 0.04 l.min-1 but at T3 was 2.03 +/- 0.30 l.min-1 (T1:T2 P less than 0.05, T1:T3 NS). OBLA % VO2 max at T1 was 75 +/- 12%, at T2 was 73 +/- 11% but at T3 was 62 +/- 10% (T1:T2 NS, T1:T3 P less than 0.01).