Toward the unity of pathological and exertional fatigue: A predictive processing model.

Fatigue is a common experience in both health and disease. Yet, pathological (i.e., prolonged or chronic) and transient (i.e., exertional) fatigue symptoms are traditionally considered distinct, compounding a separation between interested research fields within the study of fatigue. Within the clinical neurosciences, nascent frameworks position pathological fatigue as a product of inference derived through hierarchical predictive processing. The metacognitive theory of dyshomeostasis (Stephan et al., 2016) states that pathological fatigue emerges from the metacognitive mechanism in which the detection of persistent mismatches between prior interoceptive predictions and ascending sensory evidence (i.e., prediction error) signals low evidence for internal generative models, which undermine an agent's feeling of mastery over the body and is thus experienced phenomenologically as fatigue. Although acute, transient subjective symptoms of exertional fatigue have also been associated with increasing interoceptive prediction error, the dynamic computations that underlie its development have not been clearly defined. Here, drawing on the metacognitive theory of dyshomeostasis, we extend this account to offer an explicit description of the development of fatigue during extended periods of (physical) exertion. Accordingly, it is proposed that a loss of certainty or confidence in control predictions in response to persistent detection of prediction error features as a common foundation for the conscious experience of both pathological and nonpathological fatigue.

Interactions between perceptions of fatigue, effort, and affect decrease knee extensor endurance performance following upper body motor activity, independent of changes in neuromuscular function.

Prior exercise has previously been shown to impair subsequent endurance performance in non-activated muscles. Declines in the neuromuscular function and altered perceptual/affective responses offer possible mechanisms through which endurance performance may be limited in these remote muscle groups. We thus conducted two experiments to better understand these performance-limiting mechanisms. In the first experiment, we examined the effect of prior handgrip exercise on the behavioral, perceptual, and affective responses to a sustained, sub-maximal contraction of the knee extensors. In the second experiment, transcranial magnetic stimulation was used to assess the neuromuscular function of the knee extensors before and after the handgrip exercise. The results of the first experiment demonstrated prior handgrip exercise increased the perceptions of effort and reduced affective valence during the subsequent knee extensor endurance exercise. Both effort and affect were associated with endurance performance. Subjective ratings of fatigue were also increased by the preceding handgrip exercise but were not directly related to knee extensor endurance performance. However, perceptions of fatigue were correlated with heightened effort perception and reduced affect during the knee extensor contraction. In the second experiment, prior handgrip exercise did not significantly alter the neuromuscular function of the knee extensors. The findings of the present study indicate that motor performance in the lower limbs following demanding exercise in the upper body appears to be regulated by complex, cognitive-emotional interactions, which may emerge independent of altered neuromuscular function. Subjective fatigue states are implicated in the control of perceptual and affective processes responsible for the regulation of endurance performance.

The reliability of a heat acclimation state test prescribed from metabolic heat production intensities.

Acclimation state indicates an individual's phenotypic response to a thermally stressful environment, where changes in heat dissipation capacity are determined during a heat acclimation state test (HAST). Variations in thermoregulatory and sudomotor function are reported while exercising at intensities relative to maximal oxygen uptake. This inter-individual variation is not true when intensity is prescribed to elicit a fixed rate of metabolic heat production (Hprod). This study investigated the reliability of peak Tre and two composite measures (sweat gain and sweat setpoint) derived from indices of thermosensitivity during a HAST prescribed from Hprod intensities. Fourteen participants (mean±SD; age 23±3 years, stature 174±7cm, body mass 75.0±9.4kg, body surface area 1.9±0.1m(2), peak oxygen consumption [V̇O2peak] 3.49±0.53Lmin(-1)) completed a lactate threshold-V̇O2peak test and two duplicate Hprod HASTs on a cycle ergometer. The HAST consisted of three, 30-min periods of exercise at fixed Hprod intensities relative to body mass (3, 4.5 and 6Wkg(-1)), within hot dry conditions (44.7±1.8°C and 18.1±4.7% relative humidity). Peak Tre (38.20±0.36 vs. 38.16±0.42°C, p=0.54), sweat setpoint (36.76±0.34 and 36.79±0.38°C, p=0.68) and sweat gain (0.37±0.14 and 0.40±0.18gs(-1)°C(-1), p=0.40) did not differ between HASTs. Typical error of measurement (TEM), coefficient variation (CV) and intra-class coefficient of correlation (ICC) were 0.19°C, 0.5% and 0.80 for peak Tre, 0.21°C, 0.6% and 0.65 for sweat setpoint and 0.09gs(-1)°C(-1), 28% and 0.68 for sweat gain, respectively. The use of fixed Hprod intensities relative to body mass is a reliable method for measuring Tre and ascertaining sweat setpoint during a HAST, whereas, sweat gain displays greater variability. A Hprod HAST appears sufficiently reliable for quantifying heat acclimation state, where TEM in peak Tre and sweat setpoint are small enough to identify physiologically meaningful improvements post-intervention.

Stroking parameters during continuous and intermittent exercise in regional-level competitive swimmers.

This study aimed to determine whether maximal lactate steady state (MLSS) represents a boundary above which not only physiological but also technical changes occur. On different days, 13 male swimmers (23 ± 9 years) performed the following tests: 1) a 400-m all-out swim, to determine maximal aerobic speed (S-400); 2) a series of 30-min sub-maximal swims, to determine continuous MLSS (MLSSc), and; 3) a series of 12×150 s sub-maximal swims, to determine intermittent MLSS (MLSSi). Stroke rate (SR), distance per stroke cycle (DS) and stroke index (SI) were analyzed at and above (102.5%) MLSSc and MLSSi. MLSSi (1.17 ± 0.09 m.s (- 1)) was significantly higher than MLSSc (1.13 ± 0.08 m.s (- 1)) while blood lactate concentration (mmol.L (- 1)) was similar between the 2 conditions (4.3 ± 1.1 and 4.4 ± 1.5, respectively). The increase in SR and decreases in DS and SI were significant during MLSSi, 102.5% MLSSc and 102.5% MLSSi. During MLSSc, DS also decreased significantly (- 3.6%) but with no change in SR or SI. Thus, stroking technique of regional-level competitive swimmers changes over time when they swim at or above MLSS. This is the case during both continuous and intermittent swimming, despite steady state blood lactate concentrations.

Influence of moderate hypoxia on tolerance to high-intensity exercise.

It remains uncertain as how the reduction in systemic oxygen transport limits high-intensity exercise tolerance. 11 participants (5 males; age 35 ± 10 years; peak [Formula: see text] 3.5 ± 0.4 L min(-1)) performed cycle ergometry to the limit of tolerance: (1) a ramp test to determine ventilatory threshold (VT) and peak [Formula: see text]; (2) three to four constant-load tests in order to model the linear P-t (-1) relationship for estimation of intercept (critical power; CP) and slope (AWC). All tests were performed in a random order under moderate hypoxia (FiO(2) = 0.15) and normoxia. The linearity of the P-t (-1) relationship was retained under hypoxia, with a systematic reduction in CP (220 ± 25 W vs. 190 ± 28 W; P < 0.01) but no significant difference in AWC (11.7 ± 5.5 kJ vs. 12.1 ± 4.4 kJ; P > 0.05). However, large individual variations in the change of the latter were observed (-36 to +66%). A significant relationship was found between the % change in CP (r = 0.80, P < 0.01) and both peak [Formula: see text] (CP: r = -0.65, P < 0.05) and VT values recorded under normoxia (CP: r = -0.65, P < 0.05). The present study demonstrates the aerobic nature of the intercept of the P-t (-1) relationship, i.e. CP. However, the extreme within-individual changes in AWC do not support the original assumption that AWC reflects a finite energy store. Lower hypoxia-induced decrements in CP were observed in aerobically fitter participants. This study also demonstrates the greater ability these participants have to exercise at supra-CP but close to CP workloads under moderate hypoxia.

Characterising the slope of the distance-time relationship in swimming.

The aim of the present study was to assess whether the critical speed calculated by the slope of the distance-time relationship (S(d-t)) represents the boundary between the heavy and severe intensity domains in swimming and would be sustainable during intermittent exercise. Nine competitive male swimmers (mean+/-SD: aged 21.2+/-2.6 yrs; peak (.)VO2 of 3866+/-529 mL min(-1)) performed, (a) four fixed-distance (100-200-400-800 m) all-out efforts to determine S(d-t) and peak (.)VO2; (b) three constant-speed efforts to exhaustion (TTE) at and 5% above and below S(d-t) (S(d-t)(+5%) and S(d-t)(-5%), respectively); (c) a set of 10 x 400 m at S(d-t) with 40-s recovery in between. Capillary blood lactate concentration ([La](B)), oxygen uptake ((.)VO2), and RPE remained stable at S(d-t)(-5%) (TTE=48.9+/-14.1 min) with end values of 3.8+/-1.9 mmol L(-1), 87+/-14% peak (.)VO2, and 4.7+/-1.3. TTE decreased at S(d-t)(+5%) (8.6+/-3.1 min), with end [La](B) of 10.2+/-1.9 mmol L(-1). Peak (.)VO2 was reached at exhaustion. Similarly, S(d-t) could only be maintained for 24.3+/-7.7 min with an increase in RPE and [La](B), (.)VO2 reaching its peak (95+/-5% peak VO2). RPE increased but [La](B) remained stable throughout the ten 400 m blocks performed at S(d-t) (overall time of 53.9+/-2.7 min). The physiological responses when swimming 5% below and 5% above S(d-t) are those characterising the heavy and severe intensity domain, respectively. While S(d-t) lies within the severe intensity domain, intermittent swims at this intensity induce [La](B) steady state alongside high rates of perceived exertion.

Why does exercise terminate at the maximal lactate steady state intensity?

OBJECTIVE: The purpose of this study was to measure physiological responses during exercise performed until exhaustion at the exercise intensity corresponding to the maximal lactate steady state (MLSS) in order to determine why subjects stopped. METHODS: Eleven male trained subjects performed a test at MLSS on a cycle ergometer until exhaustion. RESULTS: Time to exhaustion was 55.0 (SD 8.5) min. No variation was observed between the 10th and the last minute for arterial pyruvate, bicarbonate, and haemoglobin concentrations, redox state, arterial oxygen pressure, arterial oxygen saturation, osmolality, haematocrit, oxygen uptake, carbon dioxide output, and gas exchange ratio (p>0.05). Arterial lactate concentration and arterial carbon dioxide pressure decreased significantly whereas pH, base excess and the Ratings of Perceived Exertion (RPE) increased significantly (p<0.05). Although respiratory rate, minute ventilation and heart rate increased significantly until exhaustion (p<0.05), values at termination of the MLSS test were significantly lower than values measured during a maximal exercise test (p<0.05). Blood ammonia concentrations rose progressively during the MLSS test. However, there is no known mechanism by which this change could cause peripheral fatigue. CONCLUSIONS: Exercise termination was not associated with evidence of failure in any physiological system during prolonged exercise performed at MLSS. Thus the biological mechanisms of exercise termination at MLSS were compatible with an integrative homoeostatic control of peripheral physiological systems during exercise.

Kinematic measures and stroke rate variability in elite female 200-m swimmers in the four swimming techniques: Athens 2004 Olympic semi-finalists and French National 2004 Championship semi-finalists.

The aim of this study was to assess stroke rate variability in elite female swimmers (200-m events, all four techniques) by comparing the semi-finalists at the Athens 2004 Olympic Games (n = 64) and semi-finalists at the French National 2004 Championship (n = 64). Since swimming speed (V) is the product of stroke rate (SR) and stroke length (SL), these three variables and the coefficient of variation of stroke rate (CV(SR)) of the first and second 100 m were determined (V1, V2; SR1, SR2; SL1, SL2; CV(SR)1, CV(SR)2) and differences between the two parts of the events were calculated (DeltaV; DeltaSR; DeltaSL; DeltaCV(SR)). When the results for the four 200-m events were analysed together, SR1, SR2, SL1, and SL2 were higher (alpha = 0.05, P< 0.001) and DeltaV, DeltaSR, and DeltaCV(SR) were lower (P< 0.01) in the Olympic group than in the National group. The Olympic-standard swimmers exhibited faster backstrokes and longer freestyle strokes (P < 0.05). Both CV(SR)1 and CV(SR)2 were lower for freestyle and backstroke races in the Olympic group than in the National group (P < 0.001). Our results suggest that stroke rate variability is dependent on an interaction between the biomechanical requisites of the task (techniques) and the standard of the swimmer.

Assessment of maximal aerobic power and critical power in a single 90-s isokinetic all-out cycling test.

The purpose of this study was to establish the validity of a 90-s all-out test for the estimation of maximal oxygen uptake (V.O (2max)) and submaximal aerobic ability as represented by critical power. We hypothesized that the fall in power output by the end of the 90-s all-out test (end power) would represent the exhaustion of anaerobic work capability, and as such, would correspond with the critical power. Sixteen active individuals (mean +/- SD: 30 +/- 6 years; 69.6 +/- 9.9 kg) carried out a series of tests: (i) an incremental ramp test to determine V.O (2max), (ii) three fixed-work rate trials to exhaustion to determine critical power, and (iii) two 90-s all-out tests to measure end power and peak V.O (2). End power (292 +/- 65 W) was related to (r=0.89) but was significantly higher (p<0.01) than critical power (264 +/- 50 W). The mean +/- 95 % limits of agreement (29 +/- 65 W) were too low to use these variables interchangeably. The peak V.O (2) in the 90-s trial was significantly lower than the V.O (2max) (3435 +/- 682 ml x min (-1) vs. 3929 +/- 784 ml x min (-1); p<0.01); mean +/- 95 % limits of agreement was equal to 495 +/- 440 mL x min (-1). The 90-s all-out test cannot, therefore, assess both V.O (2max) and critical power in adult performers. The duration of all-out exercise required to allow V.O (2) to attain its maximum is longer than 90 s.

The distance-time relationship over a century of running Olympic performances: A limit on the critical speed concept.

We analyse the evolution of the slope (critical speed) and the y-intercept (anaerobic distance capacity) of the linear distance-time relationship over a century of Olympic running performances. The distance-time relationship of each Olympic Games (1920-2004) was plotted using the performances in the 800-, 1500- and 5000-m track events. Values for critical speed and anaerobic distance capacity were determined by linear modelling. Mean performances for the 800, 1500 and 5000 m were 104.9 +/- 1.5 s (1.4%), 217.2 +/- 2.8 s (1.3%) and 808.9 +/- 18.4 s (2.3%), respectively. Critical speed improved during the first three-quarters of the twentieth century to reach a plateau in 1984. This is in accordance with the literature (Peronnet & Thibault, 1989) and suggests that "human aerobic endurance" has improved within the century (+13.4%) and tends to stabilize. Anaerobic distance capacity was highly variable over the century (coefficient of variation = 9.4%) and did not show a linear improvement over the years as has previously been suggested (Peronnet & Thibault, 1989). This could be due to an artefact in the application of the two-parameter model to only three Olympic performances. A limitation to the use of this linear mathematical model to fit physiological data may have been demonstrated.

Reproducibility of variables derived from a 90 s all-out effort isokinetic cycling test.

AIM: The aim of this study was to examine the reliability of the power output profile obtained from a 90 s all-out isokinetic cycling test. METHODS: Within a 10 day period, 16 participants (-x+/-s: age 30.1+/-6.4 years; body mass 69.2+/-10.6 kg) performed an incremental VO2 max ramp test and two 90 s all-out efforts on an isokinetic cycle ergometer. Peak power (PP), mean power (MP), end power (EP) and fatigue index (FI) were determined. RESULTS: There were no significant differences between tests for MP, EP and FI values (P > 0.05) but PP was higher on the second test (P = 0.003). Ratio limits of agreement suggested that a repeated measurement might be expected in 95% of cases to be between 0.92 to 1.21 times the initial PP measurement and 0.97 to 1.07 times the initial MP measurement. The 95% limits of agreement for EP and fatigue were -23 to +33 W (1.8+/-9.7% of the mean) and -6.5% to 8.8% (2+/-7.6% of the mean), respectively. CONCLUSIONS: The 90 s all-out test appears to be a reliable test for given aspects of the physiological profile, with the exception of PP.

Reproducibility of performance in three types of training test in swimming.

A variety of testing procedures are used to assess the effects of particular treatments on the training status of athletes. The present study aims to investigate the reproducibility of selected tests in swimming. Sixteen trained swimmers performed three kinds of test: 1) Constant Distance Test (CDT), 2) Constant Time Test (CTT), and 3) Constant Velocity Test (CVT). The analysis of the reproducibility was based on a test-retest procedure. The test-retest performances were highly correlated for the three kinds of test (r = 0.98, 0.98, and 0.93 for CDT, CTT and CVT, respectively). The mean Coefficient of Variation (CV) was computed between test-retest for each subject and each procedure. A repeated measures one-way ANOVA showed that CVT was significantly less reliable (CV = 6.46 +/- 6.24 %) than CDT and CTT (CV = 0.56 +/- 0.6 0 % and 0.63 +/- 0.54 % respectively) (p < 0.001). Psychological factors and a lack of familiarity with CVT (not extensively used during training session) could explain its greater variability. Thus, CDT and CTT seem to be the most reliable tests to detect the smallest meaningful change in the training status of swimmers. Post-hoc power calculations of the experimental design showed the sample size would have to increase to 80, 113, and 228 subjects for CWT, CDT and CPT respectively, to reach a power of 80 %. The minimal detectable differences have to be calculated to ensure a real effect of a particular treatment on a group of swimmers, according to the kind of test used.

Validity of the two-parameter model in estimating the anaerobic work capacity.

The curvature of the power-time (P-t) relationship (W') has been suggested to be constant when exercising above critical power (CP) and to represent the anaerobic work capacity (AWC). The aim of this study was to compare W' to (1) the total amount of work performed above CP (W (90s)') and (2) the AWC, both determined from a 90s all-out fixed cadence test. Fourteen participants (age 30.5 +/- 6.5 years; body mass 67.8 +/- 10.3 kg), following an incremental VO(2max) ramp protocol, performed three constant load exhaustion tests set at 103 +/- 3, 97 +/- 3 and 90 +/- 2% P-VO(2max) to calculate W' from the P-t relationship. Two 90s all-out efforts were also undertaken to determine W (90s)' (power output-time integral above CP) and AWC (power output-time integral above the power output expected from the measured VO(2)). W' (13.6 +/- 1.3 kJ) and W (90s)' (13.9 +/- 1.1 kJ; P = 0.96) were not significantly different but were lower than AWC (15.9 +/- 1.2 kJ) by 24% (P = 0.03) and 17%, respectively (P = 0.04). All these variables were correlated (P < 0.001) but great extents of disagreement were reported (0.2 +/- 6.4 kJ between W' and W (90s)', 2.3 +/- 7.2 kJ between W' and AWC, and 2.1 +/- 4.3 kJ between W (90s)' and AWC). The underestimation of AWC from both W' and W (90s)' can be explained by the aerobic inertia not taking into consideration when determining the two latter variables. The low extents of agreement between W', W (90s)' and AWC mean the terms should not be used interchangeably.

Self selected speed and maximal lactate steady state speed in swimming.

AIM: The purposes of this study were to ascertain whether physiological and stroking parameters remain stable during a 2-hour exercise performed at self-selected swimming speed (S4) and whether this speed corresponds to those associated with the maximal lactate steady state (SMLSS). METHODS: Ten well-trained competitive swimmers performed a maximal 400-m front crawl test, 4 30-min swimming tests in order to determine S(MLSS) and a 2-hour test swum at their preferred paces to determine self-selected swimming speed (S4), stroke rate (SR4), and stroke length (SL4) defined as the mean values observed between the 5th and the 15th min of this test. The stroking, metabolic and respiratory parameters, and ratings of perceived exertion (CR10) were reported throughout the 2-hour test. RESULTS: S4 and SMLSS were not significantly different and were highly correlated (r=0.891). S4 and SL4 decreased significantly after a steady state of 68 min and 100 min, respectively, whereas SR4 remained constant. Mean VO2, dioxide output, and heart rate values did not evolve significantly between the 10th and 120th minute of the test whereas capillary blood lactate concentration (La) decreased significantly (p<0.05). Moreover, respiratory CR10 did not evolve significantly between the 10th and the 120th minute of the test whereas general CR10 and muscular CR10 increased significantly. CONCLUSIONS: Considering the (La), SL4 and CR10 values variations, muscular parameters and a probably glycogenic depletion seem to be the main limiting factors that prevent maintaining the self selected swimming speed.

Critical swimming speed does not represent the speed at maximal lactate steady state.

Critical power and critical swimming speed (CSS) are mathematically defined as intensities that could theoretically be maintained indefinitely without exhaustion. Several investigations have been conducted to attribute a physiological meaning to these variables, but results in swimming remain equivocal. Thus, the purpose of this study was to compare CSS with direct determination of the speed at maximal lactate steady state (S (MLSS)). Eight well-trained swimmers (aged 18.6 +/- 1.9 years) performed four tests to exhaustion (95, 100, 105, and 110 % of maximal aerobic speed [MAS]) in order to determine CSS from the distance-time relationship. S (MLSS) was determined from four sub-maximal 30-min constant intensity tests (ranging from 75 % to 90 % MAS). CSS (92.7 +/- 2.6 % MAS) was significantly higher than S (MLSS) (88.3 +/- 2.9 % of MAS) and the bias +/- 95 % limits of agreement for comparisons between CSS and S (MLSS) (0.07 +/- 0.13 m x s(-1)) indicated that the extent of disagreement was too great to use these two variables interchangeably. However, CSS and S (MLSS) were strongly correlated (r = 0.87; SEE = 0.033 m x s(-1); p < 0.01). Results from the present study demonstrate that in swimming, CSS does not represent the maximal speed that can be maintained without a continuous rise of blood lactate concentration and direct determination of S (MLSS) is necessary if precision is required in experimental studies.

Stroking parameters in front crawl swimming and maximal lactate steady state speed.

In order to increase or maintain speed at sub-maximal intensities, well-trained swimmers have an increase in their stroke rate, thus a decrease in their stroke. The purposes of this study were i) to ascertain whether the maximal speed from which the stroke length decreases significantly (SSLdrop) corresponds to the maximal lactate steady state swimming speed (SMLSS), and ii) to examine the effect of the exercise duration on the stroking parameters above, below, and at SMLSS. Eleven male well-trained swimmers performed an all-out 400-m front crawl test to estimate maximal aerobic speed (MAS) and four sub-maximal 30-min tests (75, 80, 85, and 90 % MAS) to determine SMLSS and SSLdrop and to analyse the evolution of the stroking parameters throughout these tests. SMLSS (88.9 +/- 3.3 % MAS) and SSLdrop (87.3 +/- 4.5 % MAS) were not significantly different from each other (p=0.41) and were highly correlated (r=0.88; p <0.001). Moreover, a slight stroke rate increase, and a stroke length decrease, were observed above S (MLSS) but were only significant for the 5 swimmers unable to maintain this speed for 30 min (p >0.05). During the 30-min tests swum below and at SMLSS, a steady state of stroking parameters was statistically reported. Thus, SMLSS seems to represent not only a physiological transition threshold between heavy and severe sub-maximal intensities but also a biomechanical boundary beyond which the stroke length becomes compromised.

Maximal lactate steady state does not correspond to a complete physiological steady state.

The purpose of this study was to verify whether the maximal lactate steady state (MLSS) corresponds to a physiological steady state. Eight male trained subjects performed a 30-min test on a cycle ergometer at a constant power corresponding to their own MLSS which had been previously determined. No significant variation was observed between the 10th and the 30th min for arterial lactate concentration, redox state, arterial oxygen pressure, arterial oxygen saturation, bicarbonates concentration, base excess, hematocrit, hemoglobin concentration, plasma volume, oxygen uptake, carbon dioxide output, gas exchange ratio, minute ventilation, ventilatory equivalents for oxygen and carbon dioxide, and arterial systolic blood pressure values. However, arterial carbon dioxide pressure and pH values were significantly different between the 10th and the 30th min (p < 0.01). Respiratory rate values and heart rate significantly increased (p < 0.01). These results indicate that MLSS does not correspond to a complete physiological steady state.

Maximal lactate steady state, respiratory compensation threshold and critical power.

Critical power (CP) and the second ventilatory threshold (VT(2)) are presumed to indicate the power corresponding to maximal lactate steady state (MLSS). The aim of this study was to investigate the use of CP and VT(2) as indicators of MLSS. Eleven male trained subjects [mean (SD) age 23 (2.9) years] performed an incremental test (25 W.min(-1)) to determine maximal oxygen uptake (.VO(2max)), maximal aerobic power (MAP) and the first and second ventilatory thresholds (VT(1) and VT(2)) associated with break points in minute ventilation (.V(E)), carbon dioxide production (.VCO(2)), .V(E)/.VCO(2) and .V(E)/.VO(2) relationships. Exhaustion tests at 90%, 95%, 100% and 110% of .VO(2max), and several 30-min constant work rates were performed in order to determine CP and MLSS, respectively. MAP and .VO(2max) values were 344 (29) W and 53.4 (3.7) ml.min(-1).kg(-1), respectively. CP [278 (22) W; 85.4 (4.8)% .VO(2max)] and VT(2) power output [286 (28) W; 85.3 (5.6)% .VO(2max)] were not significantly different (p=0.96) but were higher (p<0.05) than the MLSS work rate [239 (21) W; 74.3 (4.0)% .VO(2max)] and VT(1) power output [159 (23) W; 52.9 (6.9)% .VO(2max)]. MLSS work rate was significantly correlated (p<0.05) with those noted at VT(1) and VT(2) (r=0.74 and r=0.93, respectively). VT(2) overestimated MLSS by 10.9 (6.3)% .VO(2max), which was significantly higher than VT(1) [+21.4 (5.6)% .VO(2max); p<0.01]. CP calculated from a given range of exhaustion times does not correspond to MLSS.

Validity and reliability of critical speed, critical stroke rate, and anaerobic capacity in relation to front crawl swimming performances.

The purpose of this investigation was to determine whether the concepts of critical swimming speed, critical stroke rate and anaerobic swimming capacity could be used by coaches as a reliable index in order to monitor endurance performances in competitive swimmers. The results of this study conducted with well-trained swimmers showed that the 30-min test velocity (V30) is not different from the critical swimming speed determined from 200- and 400-m tests but is overestimated by 3.2 %. Furthermore, a regression analysis of the number of stroke cycles on time calculated for each swimmer showed a linear relationship (r(2) greater than 0.99 and p less than 0.01). The 30-min stroke rate test (SR30) was not different from the critical stroke rate determined from 200- and 400-m tests after a correction of minus 3.9 %. These data suggest that the slope of this regression line represents the critical stroke rate defined as the maximal stroke rate value, which can theoretically be maintained continuously without exhaustion. Coaches could easily use critical swimming speed combined with critical stroke rate in order not only to set aerobic training loads but also to control the swimming technique during training. Besides, anaerobic swimming capacity (ASC) values defined as the y-intercept of the regression line between distance and time were not correlated (p > 0.05) with the determined distance over which a significant drop in the maximal speed could be noticed on a 25-m test. Thus, ASC does not provide a reliable estimation of the anaerobic capacity.