Iso-duration determination of D´ and CS under laboratory and field conditions

Whilst Critical Speed (CS) has been successfully translated from the laboratory into the field, this translation is still outstanding for the related maximum running distance (D´). Using iso-duration exhaustive laboratory and field runs, this study investigated the potential interchangeable use of both parameters, D´ and CS. After an incremental exercise test, ten male participants (age: 24.9±2.1 yrs; height: 180.8±5.8 cm; body mass: 75.3±8.6 kg; V ̇O2peak 52.9±3.1 mL∙min-1∙kg-1) performed three time-to-exhaustion runs on a treadmill followed by three exhaustive time-trial runs on a 400 m athletics outdoor track. Field time-trial durations were matched to their respective laboratory time-to-exhaustion runs. D´ and CS were calculated using the inverse-time model (speed=D´/t+CS). Laboratory and field values of D´ and CS were not significantly different (221±7 m vs. 225±72 m; P = 0.73 and 3.75±0.36 m∙s-1 vs. 3.77±0.35 m∙s-1, P = 0.68), and they were significantly correlated (r = 0.86 and 0.94). The 95% LoA were ±75.5m and ±0.24 m∙s-1 for D´ and CS, respectively. Applying iso-durations provides non-significant differences for D´ and CS and a significant correlation between conditions. This novel translation testing method can consequently be recommended to coaches and practitioners, however a questionable level of agreement indicates to use D´ with caution

Methodological Approaches and Related Challenges Associated With the Determination of Critical Power and Curvature Constant

The relationship between exercise intensity and time to task-failure (P-T relationship) is hyperbolic, and characterised by its asymptote (critical power, CP) and curvature constant (W’). The determination of these parameters is of interest for researchers and practitioners, but the testing protocol for CP and W’ determination has not yet been standardised. Conventionally, a series of constant work-rate tests (CWR) to task-failure have been used to construct the P-T relationship. However, the duration, number, and recovery between predictive CWR, and the mathematical model (hyperbolic or derived linear models) are known to affect CP and W’. Moreover, repeating CWR may be deemed as a cumbersome and impractical protocol. Recently, CP and W’ have been determined in field and laboratory settings using time-trials, but the validity of these methods has raised concerns. Alternatively, a 3-min all-out test (3MT) has been suggested, as it provides a simpler method for the determination of CP and W’, whereby power output at the end of the test represents CP, and the amount of work performed above this end-test power equates to W’. However, the 3MT still requires an initial incremental test, and may overestimate CP. The aim of this review is, therefore, to appraise current methods to estimate CP and W’, providing guidelines and suggestions for future research where appropriate

The oral contraceptive cycle and its influences on maximal and submaximal endurance parameters in elite handball players

The usage of the oral contraceptive pill is widespread among athletes of various levels. However, there is limited knowledge on how the intake of the pill alters the submaximal and maximal endurance parameters between the oral contraceptive phases. Therefore, the aim of this study was to examine potential differences between the pill intake and withdrawal phase on endurance-related parameters in first-division handball players. In total, 15 female team handball players performed two graded exercise tests until volitional exhaustion on a motorized treadmill. Tests were performed during the pill intake (days 16–17) and withdrawal phase (day 2–3). Throughout the test, respiratory gases were measured breath-by-breath, and the heart rate was measured continuously. Before and after the graded exercise test, blood samples were obtained in order to assess the blood lactate concentration. Before each test, venous blood samples were taken to determine endogenous sex hormone levels. Ventilatory parameters (V˙O2, V˙CO2, and V˙E, and respiratory equivalents for V˙O2 and V˙CO2) were measured, and the oxidation of fat and carbohydrates was calculated. A paired-sample t-test was used to assess differences between the two time points, and the significance was accepted as p < 0.050. Significant differences with lower values during the consumption phase were found for absolute (mean difference ± SD: 88 ± 131 mL∙min−1; p = 0.021) and relative V˙O2peak (mean difference ± SD: 1 ± 2 mL∙min−1∙kg−1; p = 0.012). Higher values during the consumption phase were found for submaximal respiratory equivalents for V˙O2 (mean difference ± SD: −1.1 ± 1.7; p = 0.028) and V˙CO2 (mean difference ± SD: −0.9 ± 1.5; p = 0.032). No differences were found for all other parameters, including differences for endogenous sex hormones (p > 0.050). The results of the current study suggest only marginal and physiologically insignificant differences in endurance-related parameters between oral contraceptive phases

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

Author's Response

Peer reviewedFinal Accepted Versio

Differences in Muscle Metabolism Between Triathletes and Normally Active Volunteers Investigated Using Multinuclear Magnetic Resonance Spectroscopy at 7T

Purpose: The influence of endurance training on skeletal muscle metabolism can currently be studied only by invasive sampling or through a few related parameters that are investigated by either proton (1H) or phosphorus (31P) magnetic resonance spectroscopy (MRS). The aim of this study was to compare the metabolic differences between endurance-trained triathletes and healthy volunteers using multi-parametric data acquired by both, 31P- and 1H-MRS, at ultra-high field (7T) in a single experimental protocol. This study also aimed to determine the interrelations between these MRS-derived metabolic parameters. Methods: Thirteen male triathletes and ten active male volunteers participated in the study. Proton MRS data from the vastus lateralis yielded concentrations of acetylcarnitine, carnosine, and intramyocellular lipids (IMCL). For the measurement of phosphodiesters (PDEs), inorganic phosphate (Pi), phosphocreatine (PCr), and maximal oxidative capacity (Qmax) phosphorus MRS data were acquired at rest, during 6 min of submaximal exercise and following immediate recovery. Results: The triathletes exhibited significantly higher IMCL levels, higher initial rate of PCr resynthesis (VPCr) during the recovery period, a shorter PCr recovery time constant (τPCr), and higher Qmax. Multivariate stepwise regression analysis identified PDE as the strongest independent predictor of whole-body maximal oxygen uptake (VO2max). Conclusion: In conclusion, we cannot suggest a single MRS-based parameter as an exclusive biomarker of muscular fitness and training status. There is, rather, a combination of different parameters, assessable during a single multi-nuclear MRS session that could be useful for further cross-sectional and/or focused interventional studies on skeletal muscle fitness and training effects

Relationships (panels a and b) and Bland-Altman plots of the differences (panels c and d) between repeated tests of CP.

<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

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