Non-invasive Indices for the Estimation of the Anaerobic Threshold of Oarsmen

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1 The Journal of International Medical Research ; 38: 91 9 [first published online as 38(3) 27] Non-invasive Indices for the Estimation of the Anaerobic Threshold of Oarsmen A ERDOGAN, C CETIN, H KARATOSUN AND ML BAYDAR Department of Sports Medicine, Medical School, Süleyman Demirel University, Isparta, Turkey This study compared four common noninvasive indices with an invasive index for determining the anaerobic threshold (AT) in 22 adult male rowers using a Concept2 rowing ergometer. A criterion-standard progressive incremental test (invasive method) measured blood lactate concentrations to determine the 4 mmol/l threshold (La4-AT) and Dmax AT (Dm-AT). This was compared with three indices obtained by analysis of respiratory gases and one that was based on the heart rate (HR) deflection point (HRDP) all of which used the Conconi test (non-invasive methods). In the Conconi test, the HRDP was determined whilst continuously increasing the power output (PO) by 2 W/min and measuring respiratory gases and HR. The La4-AT and Dm-AT values differed slightly with respect to oxygen uptake, PO and HR however, AT values significantly correlated with each other and with the four non-invasive methods. In conclusion, the non-invasive indices were comparable with the invasive index and could, therefore, be used in the assessment of AT during rowing ergometer use. In this population of elite rowers, Conconi threshold (Con-AT), based on the measurement of HRDP tended to be the most adequate way of estimating AT for training regulation purposes. KEY WORDS: SPORTS PHYSIOLOGY; ROWERS; ANAEROBIC THRESHOLD; CONCONI TEST; ROWING ERGOMETER; HEART RATE DEFLECTION POINT; RESPIRATORY GAS EXCHANGE Introduction Competitive rowing is a strength-endurance type of sport and demands high levels of both aerobic power and anaerobic capacity. 1 3 In endurance sports, the physiological responses during exercise testing are commonly used to set various threshold values to assess and predict performance, 4 6 and to regulate exercise intensity during training by either heart rate (HR) or power monitoring. 7,8 The anaerobic threshold (AT) has been the most commonly used term for describing blood lactate response to exercise and is defined as the critical work intensity above which lactate accumulation occurs, causing metabolic changes that include alterations in gas exchange. 7,8 The direct detection of AT is mainly based on repeated measurements of blood lactate concentration during incremental exercise testing, which is usually performed in the laboratory using specific equipment. In diverse laboratory settings, different types of rowing ergometers are considered valuable tools for testing oarsmen s performance. 8 Measurement of AT using blood lactate concentration has been most commonly directed on application of a fixed point at 4 91

2 mmol/l in rowing, 3,11 13 as well as in other sports. 7,8 For example, Steinacker 7 has suggested that the power that elicits a blood lactate concentration of 4 mmol/l is the most predictive parameter of rowing performance in trained rowers. Some authors have, however, criticized the use of a fixed blood lactate value of 4 mmol/l because it does not take into account the individual kinetics of the lactate concentration curve. 4,8 A variety of techniques and criteria have been published on lactate concentration8,14 18 and their relationships to rowing performance have been studied for some concepts. 19 Although there is evidence to suggest that any point consistently used from the lactate concentration curve during exercise can be used as a performance index, methods that rely on examining the shape of the lactate response curve are considered preferable to using fixed blood lactate concentrations, because the curve produced considers the dynamic change of lactate production and clearance. Cheng et al. 18 proposed a method of determining lactate threshold (LT) by calculating the maximal distance from the lactate curve and a line drawn from the first and last data points on the curve. This method, termed Dmax, was found to be an objective and reliable method for LT determination. 21,22 In order to avoid expensive invasive procedures, investigators have attempted to predict AT values from physiological measurements obtained during a noninvasive single-graded exercise test. Popular non-invasive AT procedures during different ergometries involve the use of either respiratory data or simply the HR curve Several methods have been proposed for detecting ventilatory threshold (VT), which has been reported to be coincident with the LT. 26 The VT is mainly associated with a nonlinear increase in ventilation or carbon dioxide production (VCO 2 ) in a disproportionate manner with respect to the increase in oxygen consumption ( ) When plotted against, the non-linear increase in VCO 2 is the basis of the V-slope method of identifying AT. 24 In another method, the intensity of activity that causes the first rise in the ventilatory equivalent of oxygen (V E / ) without a concurrent rise in the ventilatory equivalent of carbon dioxide (V E /VCO 2 ) 27 is considered the AT. The relationship between expired carbon dioxide and inspired oxygen (respiratory exchange ratio [RER]) can also be used, AT being where RER exceeds a certain defined cut-off value, such as 1. (RER-AT) Although the basis of the relationship between LT and VT is not clearly understood, a significant relationship between VT and directly determined AT has been presented for different sports and exercise conditions, mostly utilizing treadmills and cycle ergometers. 22,31 3 In the majority of these studies, as well as in a few studies addressing the relationship between VT and LT in rowing,,36,37 VT was detected using only one method. Different degrees of relationships have been observed, however, between values obtained from calculations of various respiratory gas indices and values corresponding with directly determined AT. 38 Results were similar both for treadmill running and cycle ergometer testing, suggesting that the relationship between VT and AT was not dependent on the mode of exercise. 38 This issue has not been studied during rowing, although it has been verified that physiological responses such as HR, 39 peak power output (PO) 4,41 and the ventilation for a given 37,42 observed during rowing were significantly different from the other two modes of exercise. The HR deflection point (HRDP) is a downward or upward change from the linear 92

3 HR work relationship evinced during progressive incremental exercise testing. HRDP is reported to be coincident with the AT. Conconi et al. 43,44 originally proposed that this phenomenon could be used in a method for non-invasively determining AT in runners. A cheap, simple to perform and non-invasive field test was developed by these researchers and it evolved into a popular method that could be expanded to include other endurance sports, including cycling, race walking, swimming and rowing. 11,44 46 In the literature, this concept has been surrounded by controversy, thought to be caused by the use of different means of defining AT and methodological problems in consistently determining the deflection points. 47 The original protocol was revised by Conconi et al. 44 to overcome these problems. Few studies incorporating rowing ergometry have yielded contradictory results on the ability of the HRDP method to assess the AT.,13,48,49 While Bourgois and Vrijens, 49 who took into account the new recommendations of Conconi et al. 44 in their study, concluded that HRDP does not reflect AT, some more recent studies have shown that measured PO 13 or HR at HRDP can be used for the training regulation of rowers. Correlations between HRDP and different AT concepts are not clear in rowing. Endurance training (training at a blood lactate concentration of 2 4 mmol/l) is the mainstay of success in rowing. 1,7,8 Blood lactate concentration measurements during laboratory and field tests have frequently been used to determine AT to elicit optimal guidelines for the intensity of endurance training. The use of lactate concentration to detect AT is, however, an invasive method and it would, therefore, be advantageous to use non-invasive ways to measure this parameter. Thus, in the present study, the criterion-standard direct progressive incremental test invasive way of measuring AT was compared with three gas analysisbased non-invasive methods and a noninvasive HRDP method, all of which used the Conconi test. The aim was to evaluate whether data obtained during a noninvasive graded exercise test could be used to estimate the PO and HR data associated with AT in male rowers whilst they rowed on Concept2 rowing ergometers. Subjects and methods SUBJECTS Oarsmen with competitive rowing experience at both national and international levels and who trained regularly on a Concept2 rowing ergometer were eligible to volunteer to participate in this study. The participants completed medical history questionnaires and provided their written consent before participation in the study. None of the subjects was on medication. All experimental procedures were approved by the Ethical Committee of Süleyman Demirel University, Isparta, Turkey, and were in accordance with the Helsinki Declaration. TESTING PROCEDURES All participants undertook two performance tests on separate days with 2 days between the tests. They were instructed to avoid hard physical training for 24 h prior to each test. Tests were performed in the participants own training environment at the same time of the day ( h). The subjects consumed a standardized carbohydrate-rich breakfast ( kcal: 8% carbohydrate, % protein, % fat) 2 3 h before each test session and were asked to drink ml of % maltodextrin solution 3 min before the tests to prevent glycogen depletion and dehydration that could affect the test results. The sequence of tests was counterbalanced 93

4 between subjects to minimize the influence of an order effect. Upon arrival at the laboratory on the first test session, anthropometric measurements were taken on each subject, including height, weight and sum of skin-folds. A Concept2 Model C rowing ergometer (Concept2, Morrisville, VT, USA) was used for all tests. Work rate (Watts) and stroke rate (strokes/min) were visible to the subjects continuously from the computer display on the rowing ergometer. The vanes were kept fully closed and the ergometers were selfcalibrated. Gas exchange during the tests was measured breath by breath with a portable gas analysing system (K4b2; COSMED, Rome, Italy). Blood lactate concentrations were measured using an automated lactate analyser (YSI SPORT ; YSI Life Sciences, Yellow Springs, OH, USA). The HR was recorded every s using a telemetric HR monitor (Polar S8i; Polar Electro, Kempele, Finland). Progressive incremental test (invasive method) Blood lactate concentration was measured using a progressive incremental test to maximal intensity on a Concept2 rowing ergometer. The test started with W and the PO was increased by W every 3 min. 9,13,49 A sample of capillary blood ( µl) was taken from the earlobe and assayed immediately for lactate at the beginning and during 3-s breaks between the 3-min stages. Stroke rate during the progressive incremental test varied between and 3 strokes/min. Conconi test (non-invasive method) The test started after a warm-up on the rowing ergometer for min. Participants decided the intensity of the warm-up period. The initial PO (initial Conconi test grade) was 7 W and the workload was increased by 2 W/min until exhaustion, resulting in a series of Conconi test grades. Subjects were verbally encouraged to perform until exhaustion. This load increment protocol was gradual to increase the corresponding HR by < 8 beats/min each min according to the new specifications of Conconi et al. 44 Exhaustion occurred when the following criteria were met: (i) the HR approached within ± beats/min of the maximal theoretical HR (2 age in years); (ii) the levelled off even with an increase in intensity; and (iii) a RER > 1. was reached. Blood lactate concentration was measured at the end of the test. DETERMINATION OF THRESHOLD POINTS La4-AT and Dm-AT (invasive index) The individual Dmax (Dm-AT) 18 and the fixed blood lactate concentration of 4. mmol/l (La4-AT) were used to determine LT. For La4-AT determination, plots of blood lactate concentration against, PO and HR variables were drawn and values were interpolated from the curve. For the Dm-AT, third-order polynomial regressions of the variables used (, HR, PO) against blood lactate concentration were determined. The slope of the straight line formed by the two endpoints of each curve was calculated and Dm-AT was defined as the maximal perpendicular distance from the curve to the straight line. Con-AT (non-invasive index) The Conconi threshold (Con-AT) was defined as the deflection point in the PO HR curve, as described by Conconi et al. 44 The HR deflection was established using Dmax, as described by Kara et al. A third-order curvilinear regression curve was calculated from the HR values versus the time, the two 94

5 endpoints of the curve were connected by a straight line and the most distant point of the curve to the line was considered as the Con-AT. Vs-AT (non-invasive index) Respiratory exchange data obtained from the Conconi test were used. The VT point was detected using the V-slope method as described by Beaver et al. 17 The VCO 2 versus curve was divided into two regions, each of which was fitted by linear regression, and the intersection between the two regression lines was regarded as the Vs-AT. The software of the K4b2 portable gas analysing equipment automatically established the regression lines and their crossing points. VEq-AT (non-invasive index) Respiratory exchange data obtained from the Conconi test were used to determine the VEq-AT point, which was defined as the PO at which an increase occurred in the V E / without a corresponding increase in V E /VCO 2 when plotted against time. 27 The VEq-AT point was assessed visually by two independent investigators. RER-AT (non-invasive index) Respiratory exchange data obtained from the Conconi test were used to determine RER- AT, which was defined as the at the time when RER stabilized at > 1. and did not return to levels of < STATISTICAL ANALYSIS Data were analysed using the SPSS statistical package, version 13. (SPSS Inc., Chicago, IL, USA) for Windows. Histograms and Q Q plots were used to check for normal distribution of data. A paired Student s t-test was used to compare the variables between different methods. Pearson s two-tailed correlation test was used to test the correlation between, HR and PO corresponding to La4-AT and Dm-AT, and the data corresponding to other threshold measurements. The significance level was set at P <. for all analyses. Bland and Altman plots 1 were used to visualize the association between the La4-AT and Dm-AT invasive index and the four non-invasive indices for PO and HR. Results A total of 22 male rowers participated in this study and their characteristics are shown in Table 1. All had competitive rowing experience, ranging from 3 to years (mean ± SD 7.3 ± 4. years). The maximal HR and blood lactate concentration (mean ± SD) achieved on the Conconi test were similar to those achieved on the progressive incremental test (197 ±. and 196 ± 4.7 beats/min for HR and 12. ± 1.8 and 12.7 ± 1.6 mmol/l for blood lactate concentration, respectively). The maximal PO (PO max ) achieved was higher on the Conconi test (mean ± SD 42 ± 4 W; P <.1) than on the progressive incremental test (mean ± SD 366 ± 36 W). Mean ± SD exhaustion time was 14.1 ± 1.8 min on the Conconi test. The mean ± SD maximal (max ) and weight-related max were 468 ± 929 ml/l and 9.2 ±.9 ml/kg per min, respectively. Mean ± SD blood lactate concentration as assessed by Dm-AT was 3.6 ±.66 mmol/l; TABLE 1: Descriptive characteristics of the adult male rowers (n = 22) Age (years) 22.2 ± 6. Height (cm) 186. ±. Weight (kg) 79.6 ± 11.3 Body mass index (kg/m 2 ) 23. ± 2.9 Body fat (%) 12.2 ± 2.2 Duration of practice (years) 7.3 ± 4. Data presented as mean ± SD. 9

6 this value was significantly lower (P <.1) than that observed with La4-AT (4. ±. mmol/l). In all subjects, the Conconi test protocol resulted in a HR deflection at high PO. The mean ± SD increase in HR between the Conconi test grades was.1 ± 2.9 beats/min. The mean, PO and HR values and percentage PO max and max (%PO max and %max, respectively) at AT are shown in Table 2 for the various invasively and non-invasively determined AT indices. No statistically significant differences were noted for and %max between Con-AT and La4-AT, for PO between RER-AT and La4-AT, and for HR between Con-AT and Dm-AT. There were significant differences among the other AT indices: HR and for RER-AT were significantly higher than for La4-AT and Dm-AT (P <.1), and VEq-AT and Vs-AT gave significantly lower ATs than La4-AT and Dm-AT (P <.1). Moderate-to-high positive correlations between the indices were obtained with respect to the absolute values of HR, PO and, whereas the correlations decreased when the ATs were expressed in terms of percentages (%PO max or %max ) (Table 3). In the Bland and Altman 1 plots for HR and PO (Figs 1 and 2), almost all data points fell within ± 2SD from the mean, which suggests a strong agreement between the invasive and non-invasive indices. Good correlation was also demonstrated between lactate and all ventilatory measurements of AT; however, bias of the measurements varied over a wide range, reaching as high as 24 beats/min for HR, and 13 W for PO when La4-AT was plotted against VEq-AT (Figs 1 and 2). For both HR and PO, good correlations (r =.963 and r =.846 for HR; r =.862 and r =.829 for PO at La4-AT and Dm-AT, respectively; P <.1) and precision expressed as coefficient of variance (CV =.9 and CV = 1.8 for HR; CV = 6. and CV = 7.4 TABLE 2: Oxygen uptake ( ), heart rate (HR) and power output (PO) for the invasively and non-invasively determined aerobic thresholds (ATs) for the adult male rowers (n = 22) Invasively determined ATs Non-invasively determined ATs Variable La4-AT Dm-AT Con-AT RER-AT Vs-AT VEq-AT (ml/l) 49 ± ± 733** 4126 ± ± 772** 3766 ± 714** 334 ± 66** Power output (W) 322 ± 3 32 ± 3** 283 ± 38** 328 ± ± 34** 214 ± 3** Heart rate (beats/min) 177 ± ± 6** 17 ± 6** 181 ± 6** 17 ± 6** 9 ± 6** %max 87.6 ± ±.6** 88.7 ± ± 7.4** 8.6 ± 4.** 71. ±.1** %PO max 8.2 ± ± 4.2** 7. ± 6.** 82. ±.4* 6.3 ± 6.9** 3.3 ± 4.2** Data are presented as mean ± SD. *P <. and **P <.1, significantly different from La4-AT; P <. and P <.1, significantly different from Dm-AT., oxygen uptake; %max, percentage of maximal O 2 uptake; %PO max, percentage of maximal ergometer power output. Details of the various indices for AT are given in the Subjects and methods. 96

7 TABLE 3: Correlation coefficients between the various invasively and non-invasively determined aerobic thresholds (ATs) for various measures of the physiological response to exercise in adult male rowers (n = 22) Physiological response measure La4-AT Dm-AT Con-AT RER-AT Vs-AT (ml/l) Dm-AT.979** Con-AT.97**.949** RER-AT.947**.98**.933** Vs-AT.967**.96**.963**.97** VEq-AT.963**.929**.92**.877**.884** Power output (Watt) Dm-AT.984** Con-AT.862**.829** RER-AT.96**.89**.881** Vs-AT.77**.8**.711**.911** VEq-AT.896**.96**.79**.811**.814** Heart rate (beats/min) Dm-AT.877** Con-AT.963**.846** RER-AT.686**.22*.717** Vs-AT.46*.14*.4**.879* VEq-AT.94**.9**.872**.637**.677** %max Dm-AT.88** Con-AT.464*.471* RER-AT.678**.3*.6** Vs-AT.618**.664**.34*.727** VEq-AT.749**.77**.477* ** %PO max Dm-AT.923** Con-AT.43**.414 RER-AT.722**.64**.639** Vs-AT.643**.733** ** VEq-AT.74**.778** ** *P <.; **P <.1., oxygen uptake; %max, percentage of maximal oxygen uptake; %PO max, percentage of maximal ergometer power output. Details of the various indices for AT are given in the Subjects and methods. for PO at La4-AT and Dm-AT, respectively) and the smallest mean bias (2.6 and.9 beats/min for HR; 39. and 19.7 W for PO at La4-AT and Dm-AT, respectively) were obtained at Con-AT using either La4-AT or Dm-AT for comparison (Figs 1 and 2, Table 4). Discussion Both PO and HR correspond to AT and can be used for regulating ergometry training intensity; however, apart from measuring stroke rate (strokes/min), the measurement of HR is the only practical and accurate means to monitor exercise intensity during 97

8 2 La4-AT vs Con-AT Dm-AT vs Con-AT La4-AT vs RER-AT Dm-AT vs RER-AT La4-AT vs Vs-AT Dm-AT vs Vs-AT La4-AT vs VEq-AT Mean HR (beats/min) 2 Dm-AT vs VEq-AT Mean HR (beats/min) FIGURE 1: Bland and Altman 1 comparison between anaerobic threshold (AT) determined by the non-invasive indices (Con-AT, RER-AT, VEq-AT and Vs-AT) versus blood lactate-detected AT (La4-AT and Dm-AT). Graphs plot the respective difference between heart rate (HR) obtained from La4-AT (left panel) or Dm-AT (right panel) and that obtained from Con-AT, RER-AT, VEq-AT and Vs-AT (y-axis) for each individual against the mean of the La4-AT or Dm-AT values. The middle horizontal line represents the mean of the differences (bias). The upper and lower dashed lines show the 9% limit of agreement and ± 2 SD range from the mean. Details of the various indices for AT are given in the Subjects and methods 98

9 La4-AT vs Con-AT Dm-AT vs Con-AT La4-AT vs RER-AT Dm-AT vs RER-AT La4-AT vs Vs-AT 1 Dm-AT vs Vs-AT La4-AT vs VEq-AT Dm-AT vs VEq-AT Mean PO (W) Mean PO (W) FIGURE 2: Bland and Altman 1 comparison between anaerobic threshold (AT) determined by the non-invasive indices (Con-AT, RER-AT, VEq-AT and Vs-AT) versus blood lactate-detected AT (La4-AT and Dm-AT). Graphs plot the respective difference between power output (PO) obtained from La4-AT (left panel) or Dm-AT (right panel) and that obtained from Con-AT, RER-AT, VEq-AT and Vs-AT (y-axis) for each individual against the mean of the La4-AT or Dm-AT values. The middle horizontal line represents the mean of the differences (bias). The upper and lower dashed lines show the 9% limit of agreement and ± 2 SD range from the mean. Details of the various indices for AT are given in the Subjects and methods 99

10 TABLE 4: Comparative statistics for the anaerobic threshold (AT) measured using the four non-invasive indices compared with the invasive La4-AT and Dm-AT method in adult male rowers (n = 22) Comparison with La4-AT Comparison with Dm-AT Physiological response No. of subjects Statistical No. of subjects Statistical measure and AT indices r CV within ± 2 SDs significance r CV within ± 2 SDs significance (ml/l) La4-AT P <.1 Dm-AT P <.1 Con-AT NS P =.1 RER-AT P = P <.1 Vs-AT P < P =.1 VEq-AT P < P <.1 Power output (W) La4-AT P <.1 Dm-AT P <.1 Con-AT P < P <.1 RER-AT NS P <.1 Vs-AT P < P <.1 VEq-AT P < P <.1 Heart rate (beats/min) La4-AT P <.1 Dm-AT P <.1 Con-AT P = NS RER-AT P < P <.1 Vs-AT P < P <.1 VEq-AT P < P <.1 r, correlation coefficient; CV, precision expressed as coefficient of variance; P-value, paired t-test probability value for difference; NS, not statistically significant (P >.);, oxygen uptake; No. of subjects within ± 2 SDs, the number of subjects in which the difference between invasive and noninvasive methods was within ± 2 SDs of the mean difference. Details of the various indices for AT are given in the Subjects and methods. 9

11 an endurance on-water rowing training session. 9,,2,3 This is particularly true when inconsistent training conditions (current, wind) are present. 9,2 Although there is a lack of consensus on how best to use blood lactate data when designing training programmes, on the basis of experience in training rowers there has been a focus on using fixed blood lactate concentrations of 2 mmol/l and 3 4 mmol/l for low- and highintensity endurance rowing, respectively. 9,4, In order to take into account the lactate kinetics of individuals, individual AT concepts such as the Dm-AT have also been used to obtain threshold values on a rowing ergometer. 16,22,3,6 Although the two criterion indices (La4-At and Dm-AT) in the present study differed slightly with respect to blood lactate concentration,, PO and HR, the yielded AT values were highly correlated, both with each other and with the four different noninvasive indices. Interestingly, the mean 3.6 mmol/l value found for Dm-AT in the present study was very close to that reported by Jürimäe et al. 19 (3.7 mmol/l) using a logarithmic method for determining individual AT; AT log is the PO at which blood lactate begins to increase when log [blood lactate] is plotted against log [power output]. The VT versus LT difference data, graphically shown in Bland and Altman 1 plots (Figs 1 and 2), clearly demonstrated that Dm-AT and La4- AT had very similar agreement levels with the ventilatory non-invasive indices. The purpose of the present study was to determine which of the commonly used noninvasive methods best predicts HR and PO at AT during rowing. Overall, the findings support and extend previous work in the area and support the use of the HRDP method and some respiratory indices as powerful predictors of HR and PO at AT. The present study indicated that PO and HR at Con-AT compared best with the values of La4-AT and Dm-AT. A HRDP was observed in all 22 rowers and this high rate may be attributed to the implementation of increments which did not increase the pulse rate of subjects by more than 8 beats/min, as recommended by Conconi et al. 44 This finding was in accordance with previous studies incorporating rowing ergometries. 48,49 The Dmax index for HRDP determination has been shown to be useful with a cycle ergometer and the present study extended this to a rowing ergometer and found it useful. Compared with Dm-AT, the HR significantly correlated (r =.846) and was similar for the two measures (HR at Con-AT, 17 ± 6 beats/min; HR at Dm-AT, 174 ± 6 beats/min). The HR at Con-AT was strongly correlated (r =.963) and was only 2 beats/min lower than for La4-AT. Bland and Altman 1 analysis showed small but significant biases of 2.6 beats/min (La4-AT) and.9 beats/min (Dm-AT), with the smallest spread for the limits of agreement (limits of agreement.7 and.47 beats/min for Con-AT versus La4-AT, and.4 and 7.2 beats/min for Con-AT versus Dm-AT). The observed biases were, therefore, within the practical range of beats/min, which is usually chosen in setting target HR for the determination of training intensities. In spite of the existence of statistical significances, with regard to the HR the practical differences between Con-AT versus La4-AT and Dm-AT seem to be negligible. The mean PO for Con-AT was significantly lower than for La4-AT and Dm-AT (12.1% and 12.9%, respectively), despite significant correlations (r =.862 and r =.829, respectively) and good agreements for these values. There is, therefore, discrepancy between these results and previous studies where running velocity 7 9 or PO (on cycle ergometry; 6 on a MicRow rowing 911

12 ergometer; 49 or on a Concept2 rowing ergometer 13 ) at HRDP was shown to be greater than work rate at individual AT or La4-AT. In the present study, however, PO at La4-AT and Dm-AT were found to be 8.2% and 7.4%, respectively, of their peak values and this finding is consistent with studies in highly-trained rowers which have shown that the La4-AT occurs in the range of 7 8% of their %PO max. 7,8 The discrepancy between the present studies and others may be related to testing protocols, subjects endurance level, site of blood sampling or methods used to determine HRDP. Correlation coefficients and Bland and Altman 1 analysis showed that HR at Con-AT was a more valid parameter than PO at Con-AT for estimating AT. This contrasts with Çelik et al., 13 who reported a higher correlation coefficient for PO and Con- AT than for HR and Con-AT, indicating that PO was more reliable than HR for the determination of exercise intensity in highlytrained rowers. A high degree of relationship has been reported between HRDP and VTs when physiological variables are derived concurrently from the same graded testing procedures.,34,61,62 Moderate-to-high relationships (r =.4.963) between Con-AT and the three gas exchange-based indices were observed in the present study. These relationships were not, however, stronger than those observed between Con-AT and La4-AT (or Dm-AT) derived from the two different incremental tests (invasive incremental test and non-invasive Conconi test), supporting the validity of using HRDP. The present study once more proved that, in a population of elite rowers, Con-AT is an adequate method for estimating AT for training regulation purposes. Examination of data presented in Tables 2 and 3 shows that there were significant differences and different degrees of significant correlation between RER-AT, Vs-AT and VEq- AT. The AT detected by RER-AT, Vs-At and VEq-AT averaged 92.%, 8.6% and 71.% of the max, respectively. These differences may be related to the procedures used for detecting ventilatory-based AT points. Determination of RER-AT was based on a fixed value, was very simple and yielded the highest AT detection in the present study, which is in accordance with other authors. 38,63 The Vs-AT was automatically detected by the K4b2 software in the present study. The determination of RER-AT and Vs-AT both arise from the same physiological concept, i.e. VCO 2 versus values and, therefore, theoretically ought to be concordant. Indeed, the highest correlation coefficients (r =.97, r =.911 and r =.879 for, PO and HR, respectively), good agreement and precision were achieved between these two respiratory indices. The Vs-AT resulted in a HR that was 11 beats/min lower and a PO that was.4% lower compared with those for RER-AT, which could be attributed to the chosen cut-off value for the RER-AT. Taking into account previous studies 64,6 where the VT was detected before the LT (as it was in the present study for the Vs-AT and VEq-AT indices), a cut-off value of 1. for RER-AT could be questioned. In these studies, disproportionate increases in ventilation caused by H + extraction from the muscle cells, independently of the lactate transporter, was proposed as the mechanism responsible for eliciting the rise in VT before the rise in LT. 64,6 The underestimation of HR at Vs-AT compared with at La4-AT and Dm- AT was in agreement with the results of Plato et al. 22 who also reported higher HR values at Dm-AT. The present study demonstrated a significant relationship and good agreement between all variables measured at both VT and LT (Figs 1 and 2). Furthermore, the correlation coefficients between the variables 912

13 for both VT and LT were in the range r = (Table 4). Several studies agree that the ventilatory equivalent is the best method for detecting VT; 66,67 Caiozzo et al. 32 reported the highest correlation between the respiratory gas exchange indirect measurements and the direct measurement of blood lactate concentrations for VEq-AT (r =.93). In the present study, strong correlations (r = ) and good precision between, PO and HR values for VEq-AT and the direct La4-AT and Dm-AT indices were observed, corroborating the data from these studies. Despite these high correlations, the VEq-AT values were lower than those for La4-AT and Dm-AT. Using one of the many different LT concepts associated with a typically low blood lactate concentration (around 2 mmol/l) than the one used in the present study (4 mmol/l) might close up these difference. In the present study, VEq-AT was determined visually however this is subjective in nature and may present some difficulty in the interpretation of variations because of indeterminate linearity changes, or lack of discernible changes in the linearity of the metabolic data. 68 This may also have contributed to the variations observed in the present study. The high correlations seen between the AT indices were decreased but in most cases remained statistically significant when expressing as %PO max or %max, which is in accord with the findings of Tokmakidis et al., and considered to be caused by the increase in the relative homogeneity of the data. In conclusion, as shown in other sports and laboratory investigations, measured HR and PO at the AT determined either by respiratory gas indices or the HRDP method gave comparable results with AT determined by blood lactate concentrations and could, therefore, be used for guiding the appropriate intensity of rowing training. Data from the present study suggested that a non-invasive graded exercise test allows for a valid assessment of AT in rowers using a rowing ergometer. In this population of elite rowers, Con-AT, based on the measurement of HRDP, tended to be the most adequate way of estimating AT for training regulation purposes. Conflicts of interest The authors had no conflicts of interest to declare in relation to this article. Received for publication February Accepted subject to revision 2 February Revised accepted May Copyright Field House Publishing LLP References 1 Secher, NH: Physiological and biomechanical aspects of rowing: implications for training. Sports Med 1993; : Secher NH: Rowing. In: Endurance in Sport (Shephard RJ and Astrand PO, eds). Oxford: Blackwell Science, ; pp Ingham SA, Whyte GP, Jones K, et al: Determinants of m rowing ergometer performance in elite rowers. Eur J Appl Physiol 2; 88: Coyle EF: Integration of the physiological factors determining endurance performance ability. Exerc Sport Sci Rev 199; 23: Roecker K, Schotte O, Niess AM, et al: Predicting competition performance in long-distance running by means of a treadmill test. Med Sci Sports Exerc 1998; 3: Riechman SE, Zoeller RF, Balasekaran G, et al: Prediction of m indoor rowing performance using a 3 s sprint and maximal oxygen uptake. J Sports Sci 2; : Steinacker JM: Physiological aspects of rowing. Int J Sports Med 1993; 1: 3. 8 Mäestu F, Jürimäe J, Jürimäe T: Monitoring of performance and training in rowing. Sports Med ; 3: Urhausen A, Weiler B, Kindermann W: Heart rate, blood lactate, and catecholamines during ergometer and on water rowing. Int J Sports Med 1993; 14(suppl 1): S S23. Hofmann P, Jürimäe T, Jürimäe J, et al: HRTP, 913

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