The aim of the present study was to assess whether the critical speed calculated by the slope of the distance–time relationship (Sd–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 V˙O2 of 3866±529mLmin−1) performed, (a) four fixed-distance (100–200–400–800m) all-out efforts to determine Sd–t and peak V˙O2; (b) three constant-speed efforts to exhaustion (TTE) at and 5% above and below Sd–t (Sd–t+5% and Sd–t−5%, respectively); (c) a set of 10×400m at Sd–t with 40-s recovery in between. Capillary blood lactate concentration ([La]B), oxygen uptake (V˙O2), and RPE remained stable at Sd–t−5% (TTE=48.9±14.1min) with end values of 3.8±1.9mmolL−1, 87±14% peak V˙O2, and 4.7±1.3. TTE decreased at Sd–t+5% (8.6±3.1min), with end [La]B of 10.2±1.9mmolL−1. Peak V˙O2 was reached at exhaustion. Similarly, Sd–t could only be maintained for 24.3±7.7min with an increase in RPE and [La]B, V˙O2 reaching its peak (95±5% peak V˙O2). RPE increased but [La]B remained stable throughout the ten 400m blocks performed at Sd–t (overall time of 53.9±2.7min). The physiological responses when swimming 5% below and 5% above Sd–t are those characterising the heavy and severe intensity domain, respectively. While Sd–t lies within the severe intensity domain, intermittent swims at this intensity induce [La]B steady state alongside high rates of perceived exertion.

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.

We examined changes in mood and personality characteristics in a sample of cocaine-dependent women being treated in a therapeutic community (TC). Forty-six women completed the Beck Depression Inventory (BDI), the Hamilton Anxiety Scale (HAM-A), and the Millon Clinical Multiaxial Inventory-II (MCMI-II) on admission and 12 months after discharge from the TC. On admission, the group was characterized by clinically significant scores on the BDI, HAM-A, and the MCMI-II Avoidant, Dependent, Antisocial, Passive-aggressive, Self-defeating, and Borderline scales. On follow-up, significant improvement in functioning was suggested by decreases in scale scores on the BDI, HAM-A, and MCMI-II Avoidant, Dependent, Self-Defeating, and Borderline Scales, but not for the MCMI-II Antisocial and Passive-Aggressive scales. These results suggest substantial positive effects of TC treatment on personality characteristics and functioning, but also indicate that TC treatment may not habilitate all critical personality deficits.

The purpose of the present study was to test the validity of average power output measurement by a new stationary ergometer, the Elite Axiom, against the SRM Powermeter. An experienced cyclist completed, firstly, a series of 3 min square wave exercises at different powers output at 90rpm, and secondly, a series of 3min square wave exercises at an identical target power output with different imposed cadences. For all the tests, the cyclist's bicycle, fitted with a SRM Powermeter, was attached to the Elite Axiom ergometer. Results indicated that average power output measured by the Elite Axiom ergometer was significantly higher compared with the SRM Powermeter (20.3%). However, the average power output values measured by both SRM and Elite Axiom were strongly related (r(2)=0.975; p<0.01). A corrective equation makes it possible to adjust the overestimation in average power output by Elite Axiom ergometer (average power output=83.1% of average power output by Elite Axiom). These characteristics make the Elite Axiom a useful measurement system of the cycling average power.

This study aims to determine whether the arm coordination observed at different stroke rates (SR, number of arm stroke cycles per minute) differs according to the level of expertise. Thirteen non-expert (G(NE)) and 14 expert (G(E)) swimmers swam crawl five 25-m lengths at five stroke rate values: 35, 40, 45, 50, and 55 cycles.min(-1). Results show that the pattern of 45 % of G(NE) switched from the catch-up (a lag time is performed between the propulsive phases of the two arms) to the superposition coordination mode (both arms pushing simultaneously during a short period of the cycle) between 45 and 50 cycles.min(-1). Patterns of 62.4 % of G(E) switched in the same way between 50 and 55 cycles.min(-1). Significant differences in coordination patterns were found between G(NE) and G(E) only when SR was set at 45 cycles.min(-1). As non-expert swimmers seldom produce the superposition mode, but adopt this pattern when required to swim at high stroke rate values, it is suggested that this coordination mode is an emergent property of the movement.

The purpose of this study was to analyse the effects of an exhaustive exercise on arm coordination and intracyclic velocity variations (IVV) to better understand the ways in which they are modified under fatigue conditions. Seventeen competitive swimmers performed a 200-m all-out test and a set of two 25m (before and after the 200-m) at maximal intensity to measure stroking parameters, IVV, and the relative duration of the different parts of the stroke cycle and identify the model of arm coordination by using the index of coordination (IdC). Results showed an increase in the relative duration of the propulsive time, which induced a change in arm coordination as fatigue developed in re-lation to a decrease in stroke length (SL) and stroke rate (SR) (p < 0.05). The evolution of IdC corresponds to a reduction of the non-propulsive lag time between the two arms' propulsive actions. Despite these modifications, IVV were not significantly modified (p < 0.05). The present results highlighted that IdC and relative durations of each part of the cycle (particularly the pull phase) could be assessed to complete the "SL x SR" model and to partly understand the technique modifications under fatigue condition.

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.

The purpose of this study was to determine whether preferred pedal rate (PPR) could be used as an index of cycling performance. Thirteen competitive cyclists cycled at PPR during a graded test and a supra-threshold constant power test (CPT). The results showed that PPR values reported in CPT were correlated to both peak power determined from the graded test and exhaustion time assessed in CPT. Furthermore, multiple regression revealed that PPR values and Ppeak were two predictors of exhaustion time in CPT. Hence, this study suggests that coaches and sports scientists have to take into account PPR values complementary to Ppeak in order to evaluate the capacity of cycling performance.

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.

The aim of this study was to examine the response of physiological parameters during exercise to exhaustion at Critical Power (CP). Eight male trained subjects performed a test to exhaustion on a cycle ergometer at a constant power corresponding to their previously determined CP. Mean CP value was 283.6 +/- 20W and corresponded to 85.4 +/- 4.8% of VO(2)max. Time to exhaustion was 22.1 +/- 10.1 min and was associated with a pattern in lactate concentration, redox state, ammonia concentration, minute ventilation, respiratory rate, heart rate. Likewise, a decrease of [HCO3-] PaCO2 and base excess was observed between the 10th min and the end of the test, associated with an acidosis which cannot be compensated. The rise in these parameters could lead to exhaustion and the inability to maintain the exercise intensity. VO2 did not change after the 10th min of the test but was higher than the level expected for this intensity, due to a VO2 slow component though VO2 max level was not attained. These results demonstrated that CP does not correspond to a sustainable and physiological steady state intensity.

AIMThe 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).METHODSTen 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.RESULTSS4 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.CONCLUSIONSConsidering 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.

The aim of the present study was to compare electromyographic responses during arm exercises with a crank rate chosen spontaneously (TS) or set at 20% below or above (T−20, T+20) the spontaneously chosen crank rate (SCCR). Ten male physical education students performed arm exercises with intensities ranging from 20% to 80% of maximal power. Muscular activity levels were analysed for the biceps brachii and the triceps brachii muscles using integrated rectified surface electromyography (iEMG). All values were presented as the mean and standard deviation. During TS, the sum of iEMG for the two muscles studied was significantly (P<0.05) lower than during T+20 for each power output. No significant differences were observed in iEMG values between TS and T−20. The hypothesis that SCCR relates to a minimisation of muscle activation during an upper body exercise was not confirmed. Variations superior or inferior to a 20% increase of the iEMG responses do not influence it. Moreover, the selection of crank rates depends on the power output and the SCCR increased significantly (P<0.05) with increasing power output.

The aim of this study was to evaluate the effect of a 15% increase in preferred pedal rate (PPR) on both time to exhaustion and pulmonary O(2) uptake (VO(2)) response during heavy exercise. Seven competitive cyclists underwent two constant-power tests (CPT) at a power output that theoretically requires 50% of the difference in VO(2) between the second ventilatory threshold and VO(2)max (Pdelta50). Each cyclist cycled a CPT at PPR (CPTPPR) and a CPT at +15% of PPR (CPT+15%) in a randomized order. The average PPR value was 94 +/- 4 rpm, and time to exhaustion was significantly longer in CPTPPR compared with CPT+15% (465 +/- 139 vs. 303+/- 42 s, respectively; p = 0.01). A significant decrease in VO(2) values in the first minutes of exercise and a significant increase in VO(2) slow component was reported in CPT+15% compared with CPT(PPR). These data indicate that the increase of 15% PPR was associated with a decrease in exercise tolerance and a specific VO(2) response, presumably due to an increase of negative muscular work, internal work, and an altering of motor unit recruitment patterns.

The purpose of the present investigation was to determine to what extent the protocol (incremental and constant load exercises) affects the ratings of perceived exertion for a given submaximal intensity on a cycle ergometer. 10 healthy and well-trained male students ( M age = 23 yr., SD = 2.9) performed an incremental exercise to determine maximal oxygen uptake (VO2max), maximal aerobic power, and the ratings of perceived exertion (CR10) corresponding to 70% and 75% VO2max (CR1070iand CR1075i). Two 30-min, constant load exercises set at these intensities were performed to establish the corresponding CR10 values. CR1070i(5.6 ± 1.9) and CR1075i(6.2 ± 1.9) were significantly higher than all CR10 values collected at Minutes 5, 10, 15, 20, 25, and 30 of the constant load exercises. These results indicate that, for a given exercise intensity (70% and 75% VO2max), subjects are rated higher during an incremental exercise than during a 30-min. submaximal constant load test. Therefore, when coaches and physiotherapists want to use CR10 values reported during an incremental standard exercise to set training loads, they have to be prudent since the same relative exercise intensity does not seem to be perceived identically during a submaximal constant exercise as during an incremental one.

Aim : To compare plasma lactate concentration recovery kinetics when measured and corrected for variations in plasma volume between children and adults. Methods : Nine boys (11.3 ± 1.1 y) and 8 men (21.9 ± 1.9 y) performed a maximal and a supramaximal exercise until exhaustion. Plasma lactate concentrations, haemoglobin and haematocrit were measured at rest, immediately on completion of exercise and after the 2nd, 5th, 12th and 30th minute of recovery. The plasma lactate concentrations and the rate of recovery were corrected for variations in plasma volume. Results : The maximal decreases in plasma volume were significantly higher in adults than in children for maximal exercise (–18.7 ± 2.6% vs – 14.5 ± 3.2%; p < 0.05), but similar for the supramaximal exercise (–16.9 ± 3.4% vs –15.2 ± 3.4%). During recovery, measured and corrected plasma lactate concentrations were significantly higher in adults. The rate of plasma lactate recovery was higher in adults for maximal exercise only. The same results were obtained when the rates of plasma lactate decrease were calculated from corrected plasma lactate concentrations. Conclusion : The correction of the plasma lactate concentrations for variations in plasma volume did not influence the comparison of the concentrations obtained in adults and children, or their rate of recovery.

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.

Critical power (CP) and the second ventilatory threshold (VT2) 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 VT2 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 (V̇O2max), maximal aerobic power (MAP) and the first and second ventilatory thresholds (VT1 and VT2) associated with break points in minute ventilation (V̇E), carbon dioxide production (V̇CO2), V̇E/V̇CO2 and V̇E/V̇O2 relationships. Exhaustion tests at 90%, 95%, 100% and 110% of V̇O2max and several 30-min constant work rates were performed in order to determine CP and MLSS, respectively. MAP and V̇O2max values were 344 (29) W and 53.4 (3.7) ml·min−1·kg−1, respectively. CP [278 (22) W; 85.4 (4.8)% V̇O2max] and VT2 power output [286 (28) W; 85.3 (5.6)% V̇O2max] 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)% V̇O2max] and VT1 power output [159 (23) W; 52.9 (6.9)% V̇O2max]. MLSS work rate was significantly correlated (p<0.05) with those noted at VT1 and VT2 (r=0.74 and r=0.93, respectively). VT2 overestimated MLSS by 10.9 (6.3)% V̇O2max which was significantly higher than VT1 [+21.4 (5.6)% V̇O2max; p<0.01]. CP calculated from a given range of exhaustion times does not correspond to MLSS.

The present study assessed whether the first and the second ventilatory thresholds (VT 1 and VT 2 ) were dependent on the muscle groups solicited when spontaneously chosen crank and pedal rates are used. 20 physical education male students (22 ± 2.2 yr.) performed two maximal incremental tests randomly assigned using an increment of 15 and 30 W every minute for arm and leg exercises, respectively. These tests were used to measure the maximal oxygen uptake (VO 2 max) and to identify VT 1 and VT 2 . The absolute oxygen uptake (VO 2 ) values measured at VT 1 , VT 2 , and at maximal workload were significantly ( p<.05) lower during arm and leg exercises. However, VT 1 and VT 2 expressed in percent of VO 2 max were not significantly different between arm and leg exercises (54.1 ± 8.2 vs 57.2 ± 11.4%; and 82.5 ± 6.4 vs 84.6 ± 5.1% at VT 1 and VT 2 , respectively). In addition, at the two thresholds, none of the variables measured during arm and leg exercises were significantly correlated with the exception of spontaneously chosen crank and pedal rates ( p<.01; r=.75 and r=.69 for VT 1 and VT 2 , respectively). Probably due to the different training status and skill level, no extrapolation can be made to specify the arm thresholds from the leg. These results underline the need to specify the ventilatory thresholds from specific arm ergometer measures obtained from tests performed with spontaneously chosen crank and pedal rates and, thus, close to sport and recreational activities, when they are used for training and rehabilitation programs.