Reliability of the parameters of the power-duration relationship using maximal effort time-trials under laboratory conditions

The purpose of this study was to assess the reliability of critical power (CP) and the total amount of work accomplished above CP (W´) across repeated tests using ecological valid maximal effort time-trials (TTs) under laboratory conditions. After an initial incremental exercise test, ten well-trained male triathletes (age: 28.5 ± 4.7 yrs; body mass: 73.3 ± 7.9 kg; height: 1.80 ± 0.07 m; maximal aerobic power (MAP): 328.6 ± 41.2 W) performed three testing sessions (Familiarization, Test I and Test II) each comprising three TTs (12 min, 7 min and 3 min with a passive recovery of 60 min between trials). CP and W´ were determined using a linear regression of power vs. the inverse of time (1/t) (P = W´ ∙ 1/t + CP). A repeated measure ANOVA was used to detect differences in CP and W´ and reliability was assessed using the intra-class correlation coefficient (ICC) and the coefficient of variation (CoV). CP and W´ values were not significantly different between repeated tests (P = 0.171 and P = 0.078 for CP and W´, respectively). The ICC between Familiarization and Test I was r = 0.86 (CP) and r = 0.58 (W´) and between Tests I and II it was r = 0.94 (CP) and r = 0.95 (W´). The CoV notably decreased from 4.1% to 2.6% and from 25.3% to 8.2% for CP and W´ respectively. Despite the non-significant differences for both parameter estimates between the repeated tests, ICC and CoV values improved notably after the Familiarization trial. Our novel findings indicate that for both, CP and W´ post familiarization ICC and CoV values indicated high reliability. It is therefore advisable to familiarize well-trained athletes when determining the power-duration relationship using TTs under laboratory conditions

Different durations within the method of best practice affect the parameters of the speed-duration relationship

The aim of the study was to determine whether estimates of the speed-duration relationship are affected using different time-trial (TT) field-based testing protocols, where exhaustive times were located within the generally recommended durations of 2 to 15 min. Ten triathletes (mean±SD age: 31.0±5.7yrs; height: 1.81±0.05m; body mass: 76.5±6.8kg) performed two randomly assigned field-tests to determine critical speed (CS) and the total distance covered above CS (D´). CS and D´ were obtained using two different protocols comprising three TT that were interspersed by 60 min passive rest. The TTs were 12, 7, and 3 min in Protocol I and 10, 5, and 2 min in Protocol II. A linear relationship of speed vs. the inverse of time (s=D´x1/t+CS) was used to determine parameter estimates. Significant differences were found for CS (P=.026), but not for D´ (P=.123). The effect size for CS (d=.305) was considered small, whilst that for D´ was considered moderate (d=.742). CS was significantly correlated between protocols (r=.934; P<.001), however, no correlation was found for D´ (r=.053; P=.884). The 95% limits of agreement were ±0.28m∙s-1 and ±73.9m for CS and D´, respectively. These findings demonstrate that the choice of exhaustive times within commonly accepted durations, results in different estimates of CS and D´ and thus protocols cannot be used interchangeably. The use of a consistent protocol is therefore recommended, when investigating or monitoring the speed-duration relationship estimates in well-trained athletes

Relationships (panels a and b) and Bland-Altman plots of the differences (panels c and d) between repeated tests of <i>W´</i>.

<p>The black solid line represents the linear regression and the grey-dotted line represents the line of identity (panel a and b). The solid grey line represents the mean bias and the dotted black line represent the 95% limits of agreement (panel c and d).</p

ICC (95%CL), CoV (95%CL), mean bias and 95% LoA for <i>W´</i> and CP.

<p>ICC (95%CL), CoV (95%CL), mean bias and 95% LoA for <i>W´</i> and CP.</p

ICC (95% CL), and CoV (95% CL) for individual TT and test.

<p>ICC (95% CL), and CoV (95% CL) for individual TT and test.</p