1. Effects of Varying the Interval Duration on the Determination of Lactate Thresholds in Elite Rowers
Pitre C. Bourdon1,2,3, Sarah M. Woolford2, Jonathan D. Buckley3.
1ASPIRE Academy, Doha, Qatar. 2South Australian Sports Institute, Adelaide, Australia. 3University of South Australia, Adelaide, Australia.
Abstract
Variations in the protocol for incremental exercise testing in rowing ergometry may affect the accuracy of the determination of the lactate thresholds.
Purpose: The purpose of this study was to identify the minimum protocol duration necessary to accurately assess the lactate thresholds relative to the criterion measure of maximal lactate steady state (MLSS). Methods: Twenty-one elite rowers (12 female, 9 males) each performed a series of 8–9 rowing tests in randomised, counterbalanced order. These tests comprised: 1) five progressive incremental tests consisting of up to seven intervals of 3, 4, 5, 7 or 10 min duration; and 2) MLSS assessments using a series of at least three 30 min constant-intensity tests. Test comparisons were made using two-way ANOVA with repeated measures (p ≤ 0.05). Results: The power output (PO) calculated at the lactate threshold (LT1) was significantly higher in the 3 and 4-min step duration tests than the 10 min test. No other physiological measures were significantly different for LT1. The PO calculated at the anaerobic threshold (LT2) in the progressive incremental tests was significantly different for all step durations and was significantly higher than the measured PO at MLSS except for the 10 min incremental test. Oxygen consumption (VO2) at LT2 was significantly higher in the 3-, 4-, 5-min incremental tests. Heart rate (HR) and rating of perceived exhaustion (RPE) at LT2 were not significantly different between incremental tests. The mean peak PO during the incremental tests was inversely related to the stage durations (r2 = 0.86, p ≤ 0.02). Mean peak VO2 was significantly higher in the shorter duration incremental tests (≤ 5 min) compared with the longer duration incremental tests (≥ 7 min). Peak HR was not significantly different between tests. Conclusion: This study suggests: 1) incremental exercise tests with work increment durations shorter than 10 min overestimate MLSS exercise intensity; 2) peak physiological values are best determined during incremental exercise tests with interval durations up to 4 min; and 3) peak HR and HR at LT1 and LT2 are not affected by test duration and therefore prescription of training HR’s will not be influenced by different work increment durations.
Purpose:
The measurement of the blood lactate ([La-]) response to incremental exercise, in conjunction with heart rate (HR), oxygen consumption (VO2) and exercise intensity, and the subsequent calculation of blood lactate thresholds, is often included in the routine physiological assessment of endurance athletes. However, comparisons between studies reporting lactate thresholds and related variables are often difficult because of differences in the protocols, threshold definitions, assessment techniques and variables used.
The aims of this study were to: 1) investigate the [La-] and HR responses, as well as their peak values, in incremental rowing protocols with different stage durations, and 2) to compare the derived blood lactate thresholds and related variables obtained in the different protocols with the criterion measure of maximal lactate steady state (MLSS), in order to ascertain whether valid estimates of MLSS can be determined during a single incremental exercise test.
Methods
Subjects: Twenty-one elite rowers (12 female, 9 male, age 20.0  2.2 y, height  8.9 cm, mass 75.4  12.7 kg, volunteered to participate in the study.
 Experimental Design: All rowers performed a series of 8–9 rowing tests in randomised order. All tests were performed on the same rowing ergometer (Concept IIC) with the drag factor set according to boat class. Each athlete performed:
1): Five progressive incremental tests consisting of six submaximal intervals of 3, 4, 5, 7 or 10 min duration, with each interval separated by a one-min rest period. After the rest period following the sixth interval the athletes undertook a final maximal effort of identical duration during which they performed as much work as possible. The same intensity was used for the six submaximal intervals in each test.
2) MLSS was assessed using a series of at least three 30-min constant-intensity tests. MLSS was defined as the highest
intensity during which [La-] increased by no more than 1.0 mmol·l-1 during the final 20 min of the test. Depending on the result of first constant-intensity test the pace was adjusted in subsequent tests until MLSS had been attained.
Each test was performed at approximately the same time of day and was separated by no less than 48 hours. Body mass and height were measured prior to each test and PO, VO2, HR, [La-] and ratings of perceived exertion (RPE) were monitored during each test.
Blood Lactate Thresholds: The lactate threshold (LT1) and anaerobic threshold (LT2) were identified using ADAPT software (Australian Sports Commission).
Table 1: LT1 and related variables
a Significantly different from 10 min test
Table 2: LT2 and related variables
Table 3: Peak Test values
* Significant difference between genders; a significantly different from 3 min test;
b significantly different from 4 min test; c significantly different from 5 min test; d significantly different from 7 min test; e significantly different from 10 min test
Figure 1: Effect of workload duration on the exercise - blood lactate response curve. (Averaged data from all subjects.)
Training And Nutrition: To standardise test conditions rowers were required not to train in the 12 h preceding each test. On the day before testing, training was limited to no more than 12 km of low intensity aerobic rowing. Rowers were requested to eat a standardised high carbohydrate meal on the evening preceding the test and if scheduling allowed, also on the day of the test. Instruction was also given to maintain good hydration in the lead up to the test. All assessments were conducted during the general preparation phase of each athletes training cycle with the athletes having undertaken ~15 h of training per week in the month preceding testing.
Statistical Analysis: PO, VO2 , HR, [La-] and RPE at LT1 and LT2 were determined for all five incremental tests and at MLSS, and the values achieved during each test were compared using two-way analysis of variance (ANOVA) with repeated measures with gender used as the between subject factor. Peak values achieved in each incremental test were similarly analysed. Where ANOVA showed a significant main effect, differences between means were determined by post-hoc analysis using a test of least significant differences. Linear regression was used to determine relationships between variables where applicable. The level of statistical significance was set at an  level of p ≤ 0.05.
Results
Mean values ± SEM for the physiological indices at LT1 and LT2 determined in all five incremental tests are presented in Tables 1 and 2 respectively.
significantly higher in the 3, 4 and 5 min incremental tests compared to the longer duration 7, 10 min and MLSS assessments. While not statistically significant, the mean [La-] at LT2 tended to fall with increasing incremental test duration (r2 = 0.68, p ≤ 0.09). HR and RPE were not significantly different between tests.
Peak values for the incremental tests are reported in Table 3. The mean peak PO during the incremental tests was inversely related to the stage durations (r2 = 0.86, p ≤ 0.02). Mean peak VO2 was significantly higher in the shorter duration tests (≤ 5 min) compared with the longer duration tests (≥ 7 min). Peak HR was not significantly different between tests.
Since the blood lactate responses and resultant peak and LT2 PO values were significantly different between all 5 incremental tests, the lactate response curve obtained from each test was shifted further right the shorter the work duration (Figure 1).
Conclusions
The current study indicated that many parameters related to blood lactate thresholds vary depending on the duration of the work increments used during incremental exercise tests. These data suggest: 1) incremental exercise tests with work durations shorter than 10 min overestimate MLSS intensity; 2) peak physiological values are best determined during incremental exercise tests with interval durations up to 4 min; and 3) peak HR and HR at LT1 and LT2 are not affected by test duration and therefore prescription of training HR will not be influenced by different work increment durations.
Acknowledgements
The authors would like to thank the South Australian Sports Institute for funding this study, Mr Tom Stanef for his invaluable technical support, and the coaches and athletes who participated in this study.
Parameter
Progressive Incremental Test – Step Duration
3 min
4 min
5 min
7 min
10 min
PO (W)
177.0 ± 8.6a
176.5 ± 8.1a
168.7 ± 7.4
170.1 ± 7.6
165.1 ± 7.5
[La-] (mmol·l-1)
0.86 ± 0.05
0.90 ± 0.04
0.79 ± 0.04
0.91 ± 0.06
0.81 ± 0.04
HR (beats·min-1)
151 ± 2
153 ± 2
152 ± 2
155 ± 3
156 ± 3
VO2 (l·min-1)
2.84 ± 0.12
2.85 ± 0.12
2.79 ± 0.11
2.77 ± 0.12
2.76 ± 0.12
RPE
10.2 ± 0.3
10.4 ± 0.4
10.6 ± 0.4
10.7 ± 0.5
11.1 ± 0.3
Parameter
Progressive Incremental Test – Step Duration
3 min
4 min
5 min
7 min
10 min
MLSS
PO (W)
248.8 ± 10.8
c,d,e,f
244.8 ± 10.6
231.0 ± 9.0 a,b,d,e,f
220.7 ± 9.2 a,b,c,e,f
210.7 ± 9.7
a,b,c,d
211.5 ± 8.6 a,b,c,d
[La-] (mmol·l-1)
3.04 ± 0.08 e
3.34 ± 0.11 e,f
2.95 ± 0.10
2.95 ± 0.13
2.61 ± 0.09 a,b
2.81 ± 0.16 b
HR (beats·min-1)
178 ± 2 f
176 ± 2 
175 ± 2 
174 ± 2 a,b
VO2 (l·min-1)
3.64 ± 0.15 d,e,f
3.68 ± 0.14 d,e,f
3.61 ± 0.14 d,e,f
3.45 ± 0.14 a,b,c
3.41 ± 0.15 a,b,c
3.43 ± 0.13 a,b,c
RPE
14.1 ± 0.3 
14.7 ± 0.4 
14.8 ± 0.2 f
14.2 ± 0.5 
14.4 ± 0.3 
13.7 ± 0.2 c
The PO calculated at LT1 in the incremental tests were significantly higher in the 3 and 4 min tests than the 10 min test.
The PO calculated at LT2 in the incremental tests were significantly different between most step durations and were also significantly higher than the measured PO at MLSS except for the 10 min protocol. LT2 VO2 was
a significantly different from 3 min test; b significantly different from 4 min test; c significantly different from 5 min test; d significantly different from 7 min test; e significantly different from 10 min test; f significantly different from MLSS
Parameter
Progressive Incremental Test – Step Duration
3 min
4 min
5 min
7 min
10 min
Peak PO
(W)*
327.5±15.8 b,c,d,e
308.6±13.7 a,c,d,e
284.2±2.4 a,b,d,e
270.3±11.9 a,b,c,e
258.7±12.1 a,b,c,d
Peak [La-]
(mmol·l-1)
8.26 ± 0.27 b
9.50 ± 0.40 a,c,d,e,g,
9.30 ± 0.29
e,g
8.19 ± 0.26
7.46 ± 0.32
b,c
Peak HR
(beats·min-1)
194 ± 2
195 ± 2
192 ± 2
Peak VO2
(l·min-1)
4.14 ± 0.18
d,e
4.16 ± 0.17
4.09 ± 0.18 e
3.98 ± 0.17
a,b
3.98 ± 0.18 a,b,c
Peak RPE
17.7 ± 0.3
c,d,e,
18.1 ± 0.3 c
19.0 ± 0.2
18.7 ± 0.2 a
18.9 ± 0.2