The 3-min Test Does not Provide a Valid Measure of Critical Power Using the SRM Isokinetic Mode

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The 3-min Test Does not Provide a Valid Measure of Critical Power Using the SRM Isokinetic Mode
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  304 Training & Testing  Karsten B et al. Validity of the 3-Min All-Out Test … Int J Sports Med 2014; 35: 304–309 accepted after revision May 14 , 2013 Bibliography DOI http://dx.doi.org/10.1055/s-0033-1349093Published online: November 10, 2013Int J Sports Med 2014; 35: 304–309 © Georg Thieme Verlag KG Stuttgart · New YorkISSN 0172-4622  Correspondence   Bettina Karsten  Life and Sports Science University of Greenwich Central Avenue ME4 4TB Chatham Maritime United Kingdom Tel.: + 44/208/331 7927 Fax: + 44/208/331 9805 kb20@gre.ac.uk Key words   ● ▶   critical intensity  ● ▶   exercise testing  ● ▶   anaerobic work capacity  ● ▶   reliability  ● ▶   validity The 3-min Test Does not Provide a Valid Measure of Critical Power Using the SRM Isokinetic Mode cantly higher than CP. Subsequently, Vanhatalo et al. [ 30 ] investigated the e ffi  cacy of a 3-min all-out cycling test and reported that mean power output for the Þ nal 30 s (End Power or EP) matched CP. Burnley et al. [ 9 ] further demon-strated the reliability of EP using three 3-min tests. These results led Poole [ 29 ] to state that “the 3 min test promises to herald a new era for experimental exercise physiology”. In fact, EP has already been used successfully in a range of set-tings [ 12 , 26 , 32 ] .  The work of Vanhatalo and colleagues [ 30 ] sug- gests that the power pro Þ le of all-out cycle exer-cise has a fundamental physiological basis. If this is true, similar levels of agreement between all-out end-test muscle performance and CP should be observed irrespective of the mode of meas-urement [ 25 ] . However until very recently, pub- lished studies of the 3-min test in cycling were conducted using the linear mode setting of the Lode Excalibur Sport ergometer [ 2 , 16 , 30 – 32 ] . The degree to which the high level of agreement between parameters reported by Vanhatalo et al. [ 30 ] is mechanistic or coincidental has not been independently established. Recently, Bergstrom et al. [ 4 ] performed the 3-min test using a Quin-ton ergometer, also using the linear mode, as well Introduction   ▼  Critical power (CP), de Þ ned as the highest sus-tainable rate of aerobic metabolism [ 17 ] , demar- cates the heavy and the severe exercise intensity domains [ 16 , 21 , 29 ] , and is conceived as an intensity that can be maintained over time with-out eliciting ú VO 2max  [ 21 ] . The measurement of CP and its related Þ nite quantity of ‘anaerobic’ energy ( W  ′  ), which is a marker of the build-up of fatigue-inducing metabolites to a tolerable limit, has received considerable recent research atten-tion [ 13 , 25 , 29 ] .  CP is traditionally estimated via repeated, multi-day, exhaustive exercise tests. This arguably reduces its practical utility [ 18 ] . Several authors have investigated the validity of single ‘all-out’ tests to determine CP [ 8 , 14 , 15 , 29 ] . Given that any exercise bout performed above CP should lead to the gradual expenditure of W’,  a su ffi  -ciently long all-out exercise bout should lead to the attainment of CP [ 30 ] .  Based on evidence that W  ′  depletion takes < 60 s [ 2 , 19 ] , Brickley et al. [ 8 ] hypothesized that power output at the end of a 90-s all-out test would be equivalent to CP. However, the Þ nal power output reported by Brickley et al. was signi Þ -  Authors B. Karsten 1  , S. A. Jobson 2  , J. Hopker 3  , L. Pass Þ eld 3  , C. Beedie 4  A ffi  liations 1 Life and Sports Science, University of Greenwich, Chatham Maritime, United Kingdom 2 Department of Sports Studies, University of Winchester, United Kingdom 3 Centre for Sports Studies, University of Kent, Chatham Maritime, United Kingdom 4 Department of Sport and Exercise Science, Aberystwyth University, Aberysthwyth, United Kingdom  Abstract   ▼  Recent datas suggest that the mean power over the Þ nal 30 s of a 3-min all-out test is equivalent to Critical Power (CP) using the linear ergometer mode. The purpose of the present study was to identify whether this is also true using an “iso-kinetic mode”. 13 cyclists performed: 1) a ramp test; 2) three 3-min all-out trials to establish End Power (EP) and work done above EP (WEP); and 3) 3 constant work rate trials to determine CP and the work done above CP ( W    ′ ) using the work-time ( = CP1/ W    ′ 1) and 1/time ( = CP2/ W    ′ 2) models. Coe ffi  cient of variation in EP was 4.45 % between trials 1 and 2, and 4.29 % between trials 2 and 3. Limits of Agreement for trials 1–2 and trials 2–3 were −  2 ± 38 W. Signi Þ cant di ff  erences were observed between EP and CP1 ( + 37 W, P < 0.001), between WEP and W  ′  1( −  6.2 kJ, P = 0.001), between EP and CP2 ( + 31 W, P < 0.001) and between WEP and W  ′  2 ( −  4.2 kJ, P = 0.006). Average SEE values for EP-CP1 and EP-CP2 of 7.1 % and 6.6 % respectively were identi Þ ed. Data suggest that using an isokinetic mode 3-min all-out test, while yielding a reliable measure of EP, does not provide a valid measure of CP.    D  o  w  n   l  o  a   d  e   d   b  y  :   U  n   i  v  e  r  s   i   t  y  o   f   K  e  n   t .   C  o  p  y  r   i  g   h   t  e   d  m  a   t  e  r   i  a   l .  305 Training & Testing  Karsten B et al. Validity of the 3-Min All-Out Test … Int J Sports Med 2014; 35: 304–309 as with the Monark ergometer with 3.5 % and 4.5 % of body weight as the set resistance. No agreement between estimates of EP or work done above EP (WEP) values using the Quinton and Monark ergometer were observed. The aim of the present study was to investigate whether EP esti-mated using the SRM isokinetic mode would provide a reliable estimate of CP.  Methods   ▼  Subjects  12 males and 1 female subject (mean ± SD: age 33 ± 7 year, body mass 78 ± 14 kg, height 1.79 ± 0.09 m, Maximal Aerobic Power (MAP) 345 ± 54 W, ú VO 2max  5.18 ± 0.87 L · min −  1  ) participated in this study. All volunteers were competitive road cyclists with a minimum of 2 years’ experience. Subjects refrained from heavy exercise in the 24 h prior to all tests and from food intake in the 3 h prior to all tests. The study was conducted in accordance with the ethical standards of the International Journal of Sports Medicine [ 20 ] and approved by the University Ethics Committee of the host institution. Prior to providing written informed con-sent and participation, cyclists were fully informed of the nature and risks of the study. Exercise testing was conducted on an electronically braked SRM cycle ergometer (Schober Rad Messtechnik, Jülich, Germany). Subjects visited the laboratory 7 times. During visit 1, subjects completed an incremental test to determine ú VO 2max  and MAP, as well as a 3-min all-out test for familiarization. In visits 2–7 sub- jects completed 3 constant work rate trials and three 3-min tri-als randomly assigned. A standard warm-up of 5-min at 100 W followed by 5-min passive rest and 3-min of unloaded cycling [ 9 ] was used prior to each trial. During tests the investigator pro-vided consistent and strong verbal encouragement. A post-test blood lactate concentration of ≥  8 mmol · l −  1  or heart rate (HR) within 10 beats of age-predicted HR maximum was taken as an indicator for attainment of ú VO 2max  and accepted as a successful test [ 6 ] . All visits were separated by a minimum of 24 h and were completed within a maximum period of 21 days. Each subject completed each of their 7 tests at the same time of day.  Protocol  Maximal oxygen uptake test protocol  The incremental VO 2max  test was initiated at a work rate of 150 W. Thereafter, work rate increased by 20 W · min −  1  . Subjects were instructed to maintain their preferred cadence throughout the trial. The trials were terminated when cadence fell by more than 10 rpm for more than 10 s. Pulmonary gas exchange was measured breath-by-breath. Subjects wore a facemask (Hand Rudolph, MO) and breathed through a mouthpiece and impeller turbine assembly. Before each test, the gas analyser (MetaMax 3B, Cortex Biophysik, Leipzig, Germany) was calibrated accord-ing to the manufacturer’s guidelines. ú VO 2max  was recorded as the highest mean oxygen consumption over a 30-s period, while MAP was recorded as the mean power output during this same period.  Critical Power cycling tests  CP was estimated from 3 constant work rate tests at power equivalent to 80 %, 100 % and 105 % MAP. Each trial was esti-mated to yield times to exhaustion between 2–15 min [ 21 ] . Sub-  jects were instructed to sustain the power output at their preferred cadence for as long as possible. Tests were terminated when cadence fell by more than 10 rpm −  1  for more than 5 s [ 30 ] . Test durations were recorded to the nearest 0.5 s. Blood lactate was sampled at rest before the test and immediately after its completion and analysed using a Biosen C_line (EKF Diagnostic, Barleben, Germany). Consistent with Vanhatalo [ 30 ] , linear regression was used to provide an estimate of CP and W    ′  using the work-time (W = CP t   + W’   ; equation 1) and the power −  1  /time (P = W’   (1/ t   ) + CP; equation 2) model. Estimates using equation 1 or 2 were consequently termed CP1 and CP2.  3-min all-out cycling tests  During the 3-min test the resistance on the pedals was provided by the SRM ergometer in isokinetic mode, and cadence was therefore maintained at the subjects’ preferred level throughout. Subjects were instructed to attain peak power as quickly as possible from the start, and to maintain maximum power throughout the 3 min. To facilitate this, during the Þ nal 10 s of the standard warm-up subjects increased cadence by 10–20 rev · min −  1  above preferred cadence. Consistent with Van-hatalo et al. [ 30 ] subjects were not informed of elapsed time. End Power (EP) was calculated as the mean power output over the Þ nal 30 s of the test. Work done above EP (WEP) was calculated as the power-time integral above EP. Blood lactate was sampled and analysed at rest before the test and immediately after its completion.  Statistical analysis  Data were examined using the Shapiro-Wilks’ normality test. Coe ffi  cients of variation (CoV) were derived from log-trans-formed data [ 23 ] . 95 % con Þ dence intervals were calculated for each CoV. Repeated measures ANOVA was used to test for sig-ni Þ cant di ff  erences between 3-min trial 1 and trial 2 and between trial 2 and trial 3. Consistent with Vanhatalo et al. [ 30 ] , agreement between EP and CP1, WEP and W  ′  1, EP and CP2 and WEP and W  ′  2 for both models was assessed using a paired-sam-ples t   -test and limits of agreement (LoA) [ 1 , 7 ] . Relationships were assessed using Pearson product moment correlation coef- Þ cients. Additionally, linear regression was used to calculate val-ues for Standard Error of Estimates (SEE) to estimate error associated with predicting EP and WEP values. Statistical signi Þ -cance was accepted at P < 0.05. Results are reported as mean ± SD unless otherwise stated.  Results   ▼  ANOVA indicated no signi Þ cant di ff  erences in EP between pairs of trials, F   (2, 26) = 0.83, P   > 0.05. CoV for EP was 4.45 % between trials 1 and 2 and 4.29 % between trials 2 and 3. Bland-Altman plots of the test-retest data are presented in ● ▶   Fig. 1  . The EP 95 % LoA for trials 1–2 was −  2 ± 37 W (0.99*/ ÷ 1.14 as a ratio) and for trials 2–3 it was −  4 ± 35 W (0.98*/ ÷ 1.13 as a ratio). The intrac-lass correlation coe ffi  cient for EP values was 0.97 (95 % CI = 0.92–0.99). CP and mean EP were normally distributed. Statistically signi Þ cant di ff  erences were observed between EP and CP1 (EP = 290 ± 41 W vs. CP1 = 253 ± 41 W, t(12) = −  6.16, P < 0.001) and between EP and CP2 (EP = 290 ± 41 W vs. CP2 = 259 ± 38 W, t(12) = −  4.645, P < 0.001). The SD of the di ff  erences for CP1 vs. EP was 19 W, providing 95 % LoA of 25 ± 48 W ( ● ▶   Fig. 2c  ; 0.87*/ ÷ 1.16 as a ratio) and for CP2 vs. EP the SD of the di ff  erence was 18 W, providing 95 % LoA between    D  o  w  n   l  o  a   d  e   d   b  y  :   U  n   i  v  e  r  s   i   t  y  o   f   K  e  n   t .   C  o  p  y  r   i  g   h   t  e   d  m  a   t  e  r   i  a   l .  306 Training & Testing  Karsten B et al. Validity of the 3-Min All-Out Test … Int J Sports Med 2014; 35: 304–309 20 ± 41 W ( ● ▶   Fig. 2d  ; 0.89*/ ÷ 1.14 as a ratio). The correlation coe ffi  cient for EP and CP1 was r = 0.89, P ≤  0.001 ( ● ▶   Fig. 2a  ) and for EP and CP2 r = 0.90, P ≤  0.001 ( ● ▶   Fig. 2b  ). Mean r 2  values for equation 1 were 0.99 ± 0.01 (SEE 2.94 ± 2.23) and for equation 2 0.94 ± 0.06 (SEE 11.96 ± 6.55). The SEE value for the linear rela-tionship between CP1 and EP was 19.49 W, CL (14.49–30.22) with an average error prediction of 7.7 % and for CP2 and EP it was 17.10 W, CL (12.79–26.52) with an average error prediction of 6.6 %. Signi Þ cant di ff  erences were observed between WEP and W  ′  1 (WEP = 12.5 ± 4.3 kJ vs. W  ′  1 = 18.6 ± 4.8 kJ, t(12) = −  4.65, P = 0.001) and between WEP and W  ′  2 ( W  ′  = 16.6 ± 4.8 kJ, t(12)  = −  3.3, P = 0.006). The SD of the di ff  erences was 4.78 kJ for W  ′  1 vs. WEP, providing 95 % LoA of 3.27 ± 9.06 J ( ● ▶   Fig. 3c  ; 0.64 */ ÷ 1.96 as a ratio) and for W  ′  2 vs. WEP the SD of the di ff  erences 50 a b 403020100–10–20–30–40–5050403020100–10–20–30–40–500200250300350400Mean End Test Power (W)0200250300350400Mean End Test Power (W)    T   e   s   t  -   r   e   t   e   s   t    d   i    f    f   e   r   e   n   c   e   s    (   W    )   T   e   s   t  -   r   e   t   e   s   t    d   i    f    f   e   r   e   n   c   e   s    (   W    )   Fig. 1  Bland-Altman plots of the End Power test–re-test di ff  erences between trials 1 and 2 a  and trials 2 and 3 b  . The solid horizontal lines represent mean bias, while the dashed lines represent the 95 % LoA. 400 a bc d 350300250150200100500806040200–20050100150Critical Power 1 (W)Mean of End Power and Critical Power 1 (W)Mean of End Power and Critical Power 2 (W)    3  -   m   i   n   t   e   s   t   E   n    d   P   o   w   e   r    (   W    )   D   i    f    f   e   r   e   n   c   e   i   n   p   o   w   e   r   o   u   t   p   u   t    (   e   n    d   p   o   w   e   r  -   c   r   i   t   i   c   a    l   p   o   w   e   r   1    [   W    ]    )   D   i    f    f   e   r   e   n   c   e   i   n   p   o   w   e   r   o   u   t   p   u   t    (   e   n    d   p   o   w   e   r  -   c   r   i   t   i   c   a    l   p   o   w   e   r   2    [   W    ]    ) 200 y = 0.87x + 0.66r = 0.89y = 0.83x + 19.41r = 0.90 250300350400200250300350400806040200–20200250300350400400350300250150200100500050100150Critical Power 2 (W)    3  -   m   i   n   t   e   s   t   E   n    d   P   o   w   e   r    (   W    ) 200250300350400   Fig. 2  Bland-Altman plots of the relationship (panel a  and b  ) and limits of agreement (panel c  and d  ) between End Power (W) and CP1 (Watt), and between End Power (W) and CP2 (Watt). In panel c  and d the solid horizontal line represents the mean di ff  erence between End Power and Critical Power 1 and 2, and the dashed lines represent 95 % LoA.    D  o  w  n   l  o  a   d  e   d   b  y  :   U  n   i  v  e  r  s   i   t  y  o   f   K  e  n   t .   C  o  p  y  r   i  g   h   t  e   d  m  a   t  e  r   i  a   l .  307 Training & Testing  Karsten B et al. Validity of the 3-Min All-Out Test … Int J Sports Med 2014; 35: 304–309 was 4.53 kJ, providing 95 % LoA of 1.43 ± 6.90 kJ ( ● ▶   Fig. 3d  ; 0.73 */ ÷ 1.93 as a ratio). The correlation coe ffi  cient for WEP and W  ′  1 was r = 0.43, P = 0.14 and for WEP and W  ′  2 r = 0.48, P = 0.10 ( ● ▶   Fig. 3a, b  ). The SEE value for the linear relationship between W’ 1 and WEP resulted in 4.5 kJ, CL (3.37–6.98) with an average error prediction of 24.2 % and for W’ 2 and WEP it was 4.37 kJ, CL (3.27–6.78) with an average prediction error of 26.3 %.  Discussion   ▼  The results presented above suggest that a 3-min all-out cycling test using the SRM isokinetic mode does not provide a valid measure of CP. Speci Þ cally, the mean power output during the Þ nal 30 s of the 3-min all-out test appears to be signi Þ cantly higher than estimates of CP derived from both work-time and power −  1  /time models. The 3-min test also appears to underesti-mate the ‘anaerobic’ parameter of the CP model (i. e., W    ′ ). The results presented above also suggest that the 3-min all-out test is a reliable measure of EP when studying a trained athletic pop-ulation. A 5 % coe ffi  cient of variation (CV) has been cited as an acceptable upper limit in sports science reliability studies [ 23 ] . Given that the CV values observed were below this boundary of 5 %, the EP from a 3-min all-out cycling test can be considered to be reliable. In fact, Burnley et al. [ 9 ] suggested that EP is a reproducible measure when reporting a coe ffi  cient of variation (typical error as a percentage of the mean) only a little lower than that reported here (3 % vs. ~ 4.9 %). Johnson et al. [ 24 ] reported a CV of 6.7 % for the 3-min all-out EP results, and even given this ac-cepted the test as reliable. However, caution should be taken as such a level of variation is unlikely to be acceptable when evalu-ating the relatively small training-induced changes seen in well-trained athletes [ 27 ] . Such a conclusion is supported by limits of agreement analyses which suggest that, with an approximate 95 % probability, the di ff  erences between the test and retest of EP in a well-trained cyclist will lie between −  40 W and + 36 W. Assuming that the bias is negligible, ratio limits of agreement suggest that, between any 2 tests, EP will di ff  er by as much as 14 % in a positive or negative direction. Using a magnitude-based analysis, Paton and Hopkins [ 28 ] identi Þ ed that a change of 1.7 % in performance impacts the chances of an elite road time trial cyclist winning an event. With an average SEE value for EP-CP 1 and EP-CP 2 of 7.7 % and 6.6 %, respectively, the discrepancy between the 2 measurement methods in the present study would therefore result in substantial performance di ff  erences. In a heterogeneous group of cyclists, runners and Þ tness trained subjects, Vanhatalo et al. [ 30 ] reported no di ff  erences between EP (287 ± 55 W) and CP (287 ± 56 W). In contrast, in the present study EP was signi Þ cantly higher than CP1 and CP2 (37 W and 31 W respectively). Several factors might explain this lack of agreement. First, it is possible that the use of 3 constant work 30 a bc d 25201510502015105–5–10–15–2002015105–5–10–15–2000510 y = 0.55x + 9.69r = 0.48y = 0.50x + 12.32r = 0.48 1520W’ 2 (kJ)Mean of WEP and W’ 1 (kJ)    W   E   P    (    k   J    )   W   E   P  -   W   ’    (    k   J    )   W   E   P  -   W   ’    (    k   J    ) 302520151050    W   E   P    (    k   J    ) 25300102030Mean of WEP and W’ 2 (kJ)010203005101520W’ 1 (kJ)2530   Fig. 3  Bland-Altman plots of the relation (panel a  and b  ) and limits of agreement (panel c  and d  ) between WEP (kJ) and W  ′  1 (kJ) and between WEP (kJ) and W  ′  2 (kJ). In panel c  and d  the solid horizontal line represents the mean di ff  erence between End Power and CP 1 and 2, and the dashed lines represent 95 % LoA.    D  o  w  n   l  o  a   d  e   d   b  y  :   U  n   i  v  e  r  s   i   t  y  o   f   K  e  n   t .   C  o  p  y  r   i  g   h   t  e   d  m  a   t  e  r   i  a   l .  308 Training & Testing  Karsten B et al. Validity of the 3-Min All-Out Test … Int J Sports Med 2014; 35: 304–309 rate trials resulted in an inaccurate estimate of CP and W’   . Van-hatalo et al. [ 30 ] used 5 trials, while research seeking to model the power-exhaustion time relationship commonly uses 4 or more trials [ 3 , 10 ] . However, several recent investigations have used 3 tests for CP and W’   estimation [ 2 , 15 ] . According to Hill [ 22 ] the decision as to the number of trials used depends on the Þ tness level of subjects as well as their familiarity with all-out exercise. Subjects in the present study were accustomed to all-out exercise, a fact which arguably justi Þ ed the use of 3 trials in line with Hill’s proposal. Strong correlation and low SEE values observed for each subject and model used lend further support to this decision (mean r 2  values for equation 1 was 0.99 ± 0.01/SEE 2.94 ± 2.23 and for equation 2 it was 0.94 ± 0.06/SEE 11.96 ± 6.55). Secondly, as pulmonary gases were not recorded during the 3-min all-out tests, it might be suggested that we did not meet all 3 conditions outlined by Jones et al. [ 25 ] for the attainment of a successful 3-min test (i. e., that subjects did not reach su ffi  ciently high intensity). However, the post-test lactate concentrations (12.3 ± 3.8 mmol · L −  1  ) were higher than those reported by Vanhatalo et al. [ 30 ] (10.2 ± 2.2 mmol · L −  1  ). Given that all subjects also reached values within 10 beats per minute of their age-predicted maximal heart rates, we are con Þ dent that subjects did perform at an appropriate intensity. Further-more, the group mean power pro Þ le suggests both the very high intensities achieved during the Þ rst 60 s of the all-out trials and the subsequent plateau, both of which are vital to the proposed e ffi  cacy of the 3-min test ( ● ▶   Fig. 4  ). It is also possible that the discrepancy between the present results and those of Vanhatalo et al. [ 30 ] relate to the use of dif-ferent ergometers. The isokinetic mode of the SRM allows the cyclist to maintain a Þ xed cadence while the resistance adapts to any change in pedal force. In contrast, in the linear mode of the Lode the applied resistance is cadence-dependent, and in the early stages of the 3-min test, the high power output necessi-tates a very high cadence. As a subjects’ ability to produce power declines, so too does cadence. In order to ensure that cadence does not fall to unacceptably low levels, the researcher must adjust the Lode’s power/cadence settings. This is done by adjust-ing the ‘linear factor’ α  in the equation Power = α *RPM 2  . To date, researchers have adjusted the linear factor such that preferred cadence is reached at GET + 0.5*( ú VO 2max  –GET) (i. e., 50 % Δ ), where GET is the gas exchange threshold. Given that 50 % Δ  is very close to CP (46.7 % Δ  in Vanhatalo et al. [ 30 ] ), it is possible that the use of a Lode ergometer biases the 3-min all-out test towards an End Power close to GET and therefore to CP. Estimates for EP, CP1 and CP2 reported in the present study may have been in ß uenced by the selection of subjects. While previ-ous studies [ 2 , 9 , 30 ] utilized a range of athlete abilities, the present study was conducted on a relatively homogeneous sam-ple of trained cyclists. This suggests that subjects in the present study, who are accustomed to high-intensity cycling perform-ances, may have been better able to sustain their 3-min e ff  ort to ensure that W    ′  was not depleted. Mean W    ′ 1 (18.3 kJ) and mean W    ′ 2 (16.6 kJ) were also higher than in the subject group investigated by Vanhatalo et al. [ 30 ] (16 kJ). It is possible that subjects with a higher W    ′  take longer to fully expend W    ′  than those with a smaller W    ′  using the isokinetic mode, a mode in which resistance is modulated according to fatigue level while maintaining cadence. This might suggest the need for an all-out test longer than 3 min. However, this does not appear to be supported by the power pro Þ le in the present study, in which power declined towards a relative plateau over a simi-lar time course to that described by Vanhatalo et al. [ 30 ] . Berg- strom et al. [ 5 ] recently reported 150 s EP derived from a similar method as the 3-min test using a Lode ergometer and which did not signi Þ cantly di ff  er from EP observed in the srcinal 180 s test duration. While it is not clear whether or not W    ′  describes a true ‘anaero-bic work capacity’ [ 13 ] , if valid, the 3-min test would neverthe- less provide a valuable tool for the assessment of this parameter. However, the data reported in the present study suggest that the anaerobic parameters derived from the 3-min test signi Þ cantly underestimate W  ′  . This supports Vanhatalo et al. [ 30 ] who reported a WEP markedly below W    ′  in 6 of 10 subjects. Van-hatalo et al. [ 30 ] suggested that the discrepancy might be the result of di ff  erent acceleration pro Þ les of the ß ywheel during all-out and constant work rate exercise when using the Lode ergometer. The suggestion is supported by the results in the present study as the SRM ergometer uses ß ywheel technology similar to the Lode ergometer. The generalization of the CP concept to all-out exercise is dependent upon the capacity of the all-out trial to fully deplete W  ′  . Despite satisfying the requirements of the 3-min test [ 25 ] , it might be possible that the present subjects were unable to fully deplete W  ′  . This is surprising given that a maximal accumulated oxygen de Þ cit has been demonstrated following 60–90 s of all-out exercise [ 18 , 33 ] . Such observations led Brickley et al. [ 8 ] and Dekerle et al. [ 15 ] to evaluate whether a 90-s all-out test could estimate CP in adults and children, respectively. As in the present study, testing was conducted on an SRM ergometer using the isokinetic mode, and EP was signi Þ cantly higher than CP. Despite a plateau being apparent in the Þ nal 10 s of the 90-s test, Dekerle et al. [ 15 ] suggested that power output continues to decline at the end of the test. This led to the hypothesis that a test of longer duration would allow CP to be attained [ 8 ] . The hypothesis is refuted by the observation that the results of the current inves-tigation agree so closely with those obtained when using the 90-s test to derive CP. Following the protocol proposed by Vanhatalo et al. [ 30 ] while using an isokinetic mode might explain di ff  erent outcomes between EP and CP1/CP2. To investigate the robustness of the 3-min all-out test, Vanhatalo et al. [ 31 ] manipulated the ß y-wheel resistance for subjects to achieve EP cadences which were ± 10 rev · min −  1  di ff  erent from the srcinal investigation. The authors reported no di ff  erences in EP for reduced cadence 1000800600400    P   o   w   e   r   O   u   t   p   u   t    (   W    ) 20000308090Time (s)120150180   Fig. 4  Group mean power pro Þ le of the SRM isokinetic 3-min all-out cycle test. Solid lines represent the standard deviation.    D  o  w  n   l  o  a   d  e   d   b  y  :   U  n   i  v  e  r  s   i   t  y  o   f   K  e  n   t .   C  o  p  y  r   i  g   h   t  e   d  m  a   t  e  r   i  a   l .
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