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The present study was designed to investigate whether a protein hydrolysate enriched in branched chain amino acids and antioxidants, trace and mineral elements, and vitamins would affect performance and fatigue. Eighteen sportsmen underwent testing before and after 28 days supplementation with either treatment in protein hydrolysate or placebo. Testing included exhaustive aerobic and anaerobic exercises with determination of blood lactate concentration through exercise and recovery and antioxidant status, but also measurements of maximal oxidative capacity (V. (max)) and citrate synthase activity (CS) from a resting muscle biopsy. Protein hydrolysate resulted in a significant decrease in fatigue indices, without affecting performances. A significant increase in enzymatic antioxidant and a decrease in oxidative damage were observed at rest after treatment but not with a placebo. Decrease in maximal blood lactate and improvement of blood lactate removal were only observed after protein hydrolysate treatment. Furthermore, CS increased significantly, whereas no change was observed in V. (max). In conclusion, this protein hydrolysate treatment induced adaptations that may promote a decrease in fatigue during exercises, potentially explained by changes in parameters used to represent oxidative damage and antioxidant status at rest and changes in lactate metabolism.

Sickle cell trait (SCT) is a genetic disease affecting the synthesis of normal hemoglobin (Hb) marked by the heterozygous presence of HbA and HbS. It is thought that exercise tolerance and aerobic capacity could be limited in SCT carriers, but that the co-existence of alpha-thalassemia with SCT (SCTAT) could improve exercise response. To examine these issues, we compared the characteristics of VO2 kinetics during a constant heavy exercise among athletes carrying either the SCT (n = 6), the SCTAT (n = 9), or the normal Hb (control group; n = 10). After determination of maximal power output (Ppeak), all subjects underwent a constant heavy cycling exercise lasting 9 min at approximately 70 % Ppeak. Pulmonary VO2 and cardio-respiratory parameters were measured breath-by-breath and the VO2 response was modelled using non-linear regression techniques. The time constant of the VO2 primary component and oxygen deficit were not significantly different among the three groups. The VO2 slow component was 28 % and 33 % higher (p < 0.05) in SCT and SCTAT than in the control groups, respectively. Altogether, athletes with the SCT and the SCTAT had higher heart rate at the beginning (+ 5.2 %) and the end (+ 7.4 %) of the slow component compared to the control group (p < 0.05). These results suggest that SCT and SCTAT subjects are not limited during the first exercise minutes, but are prone to exercise intolerance and to lower aerobic capacity thereafter, due to a higher VO2 slow component, and that alpha-thalassemia does not improve exercise response. The finding of a higher slow component in SCT and SCTAT athletes was possibly due to the loss of O2 availability to muscles, additional fiber recruitment and/or higher cardiac load with time.

This study aimed to examine the effects of wearing compression compared to classic elastic tights and conventional shorts (control trial) on oxygen cost and sensation responses during submaximal running exercise. In part I, aerobic energy cost was evaluated in six trained runners at 10, 12, 14, and 16 km x h(-1). In part II, the increase in energy cost over time (i. e., slow component expressed as difference in VO2 values between min 2 and end-exercise) was determined in six trained runners at a constant running pace corresponding to 80% of maximal VO2 for 15 min duration. All tests were performed on a 200-m indoor track with equivalent thermal stress conditions. VO2 was determined with a portable metabolic system (Cosmed K4b2, Rome, Italy) during all testing sessions. Runners were asked their ratings of perceived exertion (RPE) and perceptions for clothing sweating, comfort, and whole thermal sensations following each trial. Results showed in part I a significant lower energy cost only at 12 km x h(-1) by wearing compression and elastic tights compared to conventional shorts. During part II, wearing compression tights decreased significantly VO2 slow component by 26 and 36% compared to elastic tights and conventional shorts, respectively. There were no differences in sweating and comfort sensations, RPE, and for whole thermal sensation between clothing conditions in parts I and II. Wearing compression tights during running exercise may enhance overall circulation and decrease muscle oscillation to promote a lower energy expenditure at a given prolonged submaximal speed.

This study aimed (i) to quantify the spontaneous coordination between breathing and hand rim wheelchair propulsion, (ii) to manipulate arm movement frequency and assess its effects on spontaneous coordination, and (iii) to investigate the hypothesis that entrainment of breathing improves economy of locomotion and leads to a lower rate of perceived exertion (RPE) compared with spontaneous breathing. Nine male, able-bodied participants completed four bouts of 6 min submaximal steady state exercise at 60 % of maximal propulsion velocity on a wheelchair ergometer, with spontaneous breathing and arm frequencies (Fspont), with 20 % higher and lower arm frequencies (F +20 and F -20, respectively) compared to Fspont accompanied with spontaneous breathing frequency, and by synchronising expiration phase with pushing time and inspiration phase with upper limb recovery time (C). Oxygen uptake and propulsion frequency were continuously recorded. The degree of coordination was expressed as a percentage of inspiration starting in the same phase of the wheelchair propulsion cycle (i.e. pushing and recovery times). No difference in degree of coordination was observed between Fspont, F -20 and F +20 conditions (49.2 +/- 12.1 %, 49.1 +/- 29.0 % and 48.2 +/- 29.4 %, respectively). Oxygen uptake increased significantly during C condition while RPE was significantly lower for C and F -20 (p < 0.05) compared to F +20 conditions. Contrary to what we expected, entrainment of breathing using a monofrequency ratio (C) induced a higher energy cost probably due to the mechanical properties of the wheelchair propulsion activity itself. In conclusion, this study showed that the same locomotor-respiratory coupling occurred during hand rim wheelchair propulsion regardless of the arm movement frequency, and that entrainment of breathing did not improve economy of locomotion.

This study examined the influence of moderate hypoxia on the oxygen uptake (V.O(2)) kinetic response (primary time constant and slow component amplitude) during moderate and heavy cycle exercise in twenty-seven male subjects with various training status. Nine endurance trained (21.5 +/- 2.6 yr), nine sprint trained (22.9 +/- 5.7 yr), and nine untrained controls (24.0 +/- 4.4 yr) completed incremental tests to exhaustion in normoxia (inspired gas concentration or FIO (2) = 21 % O(2)) and hypoxia (FIO (2) = 13 % O(2)) to establish the FIO (2)-specific ventilatory threshold (VT) and maximal VO(2). Subsequently, the subjects performed repeated constant work rate cycling exercises during 7 min at moderate intensity (80 % of FIO (2)-specific VT) and heavy intensity (midway between the FIO (2) specific VT and maximal VO(2)). Pulmonary gas exchange was measured breath-by-breath during all exercise sessions. For both moderate and heavy intensities, the time constant of the primary VO(2) component was significantly (p < 0.05) slowed by approximately 25 to 30 % in hypoxia compared to normoxia to the same extent in the three groups. Hypoxia produced a more important decrease in the amplitude of the slow component in endurance athletes (- 36 %) than in sprinters (- 30 %) and controls (- 12 %). These results suggest that both primary and slow components of VO(2) kinetics during the adjustment to moderate- and heavy-intensity exercise are sensitive to hypoxia while training status tended to modulate partly the slow component amplitude.

We tested the hypothesis that time course of O (2) uptake (VO (2)) measured during a supramaximal exercise performed in the field is driven to maximal oxygen uptake (VO (2max)). On an outdoor track, five middle-distance male runners first performed a test to determine VO (2max) and a supramaximal 800-m running test at least two days apart. VO (2) response was measured from the start to the end of exercise with the use of a miniaturised telemetric gas exchange system (Cosmed K4). VO (2max) was reached by all subjects 45 +/- 11 s (mean +/- SD) after the onset of the 800-m race (i.e., 316 +/- 75 m), and was maintained during the next 33 +/- 6 s (i.e., 219 +/- 41 m). The mean relative exercise intensity of the 800 m was 120 % VO (2max). An unexpected significant decrease in VO (2) (24.1 +/- 7.0 %; p < 0.05) was observed in all subjects during the final 38 +/- 17 s (i.e., the last 265 +/- 104 m). We concluded that, at onset of a simulated 800 m running event, VO (2) is quickly projected towards the VO (2max), and then becomes limited by the achievable VO (2max). This race profile shown by all athletes is in some contrast to what can be expected from earlier findings in a laboratory setting.

Several indicators are used as indices of cardiorespiratory reserve. Among them, oxygen uptake (VO(2)) at peak and ventilatory threshold (VAT) levels are the most common used. In the present study, endurance training was used to evaluate and compare the usefulness of a new index, the Oxygen Uptake Efficiency Slope (OUES) as an alternative to the previous ones. Fifteen physical education student women participated in the study (8 as a trained group [T: age (mean +/- SD) 21.9 +/- 3.3 y, height 165.1 +/- 5.5 cm, weight 60.4 +/- 3.3 kg] and 7 as a control group [C: age 21.7 +/- 1.9 y, height 165.4 +/- 7.2 cm, weight 59.6 +/- 8.6 kg]). Before and after 6 weeks of the Square-Wave Endurance Exercise Test (SWEET) training program or daily activities, they performed an incremental test (30 W/3 min) on a cycle ergometer to determined VO(2), power output and parameters associated with breathing efficiency (the respiratory equivalents, and the ventilatory dead space to tidal volume ratio [Vd/Vt]) at peak- and VAT-levels. The slope of the relationship between ventilation and carbon dioxide production was also calculated. OUES, derived from the logarithmic relationship between VO(2) and minute ventilation (V(E)), was determined at 75 % (OUES75), 90 % (OUES90) and 100 % (OUES100) of exercise duration. After endurance training in T, VO(2) and power output were significantly improved at peak- and VAT-levels while all breathing efficiency indices remained unchanged. No changes were observed in C after 6 weeks. Despite significant correlation between OUES values and VO(2) at peak- and VAT-levels, OUES75, OUES90 and OUES100 did not significantly change after endurance training. While VO(2) and power output at peak- and VAT-levels increased in all T, training-induced changes in OUES appeared more variable. We concluded that OUES was not sufficiently sensitive to highlight improvement of cardiorespiratory reserve after endurance training whereas VO(2) at peak and VAT levels did.

The aim of this study was to investigate the metabolic and physiological responses to a laboratory-based simulated 30-min individual time-trial (ITT 30 ) in cycling at a self-selected intensity. Twelve experienced triathletes (n = 4 women) performed a progressive incremental exercise test on a cycle ergometer to determine .VO2max (52 +/- 5 ml x min -1 x kg -1), maximum power output (300 +/- 12 W), and the second ventilatory threshold. Then, the subjects completed an ITT30 at self-selected work intensity on a stationary ergometer equipped with the SRM Training System. In all subjects, during the ITT30, heart rate and minute ventilation increased (p < 0.05) progressively whereas oxygen consumption and power output remained unchanged. Triathletes rode at consistent pacing corresponding to their highest steady state of blood lactate concentration that increased by no more than 1.0 mmol x l -1 during the final 20-min of ITT30. The self-selected intensity of triathletes during ITT30 represented 88 +/- 5 % (mean +/- SD) of .VO2max and was not significantly different to the energy demand corresponding to the second ventilatory threshold (84 +/- 5 % of .VO2max). Our data suggest that ITT 30 at a self-selected intensity is a good predictor of individual endurance capacity and may be used to estimate racing pace for training purposes. This performance test for the identification of the exercise intensity that demarcate "steady state" is less troublesome than some of the traditional methods, limiting testing to a single session.

The present study was performed to compare various individual muscular efficiency indices, i. e., gross (GE), net (NE), work (WE), and delta (DE), during arm cranking ergometer (ACE) and wheelchair ergometer (WERG) exercise at the same relative exercise intensities. Following a maximal test on both the ACE and WERG, 15 able-bodied subjects completed 4 submaximal bouts at 0, 40, 55 and 70 % of the mode-specific VO(2) peak. The peak power output and VO(2) values were significantly higher with ACE than WERG maximal exercise. As a consequence, the power output imposed during WERG submaximal bouts was significantly lower compared to ACE submaximal bouts. ACE exercise was found to elicit a significantly higher (p < 0.001) VO(2) (16 to 28 vs 14 to 23 ml x min(-1) x kg(-1)), GE (9 to 11 vs 6 to 9 %) and NE (14 to 13 vs 10 to 11 %) compared to WERG exercise at power output from 40 to 70 % VO(2) peak, respectively. However, WE (17 to 15 vs 17 to 14 % at 40 to 55 % VO(2)peak) and DE (12 to 13 vs 12 to 12 % at Delta 40 - 55 % to Delta 55 - 70 % VO(2) peak) values were similar between ACE and WERG exercise. The lower GE and NE observed during WERG compared to ACE exercise could be explained by the biomechanical disadvantages of the hand-rim WERG pattern movement. These findings also supported that the different indices of efficiency influenced the interpretation of the comparison between ACE and WERG propulsion.

The purpose of the present study was to examine oxygen consumption (VO(2) ) kinetics during severe-intensity running exercise through a four-phase model that considered a decrease in VO(2) at the end of the exercise in light of previous research in which this decrease was only noticed. After determination of maximal oxygen consumption VO(2) max), thirteen highly trained males performed a square-wave running to exhaustion at approximately 95 % of VO(2) max on a level treadmill. VO(2) and ventilatory gas exchange variables were determined breath-by-breath. Computerised non-linear regression techniques incorporating exponential and linear terms were used to describe VO(2) and ventilatory gas exchange variable responses. In contrast with the classical 3-component model that describes the increase in VO(2) for severe-intensity exercise, we observed a 4(th) phase characterised by a significant decrease in VO(2) before exhaustion (slope of VO(2)-time relationship significantly different from a zero value, p < 0.01) in 7 out of 13 subjects. Following a time delay of 31 +/- 44 s after the decrease in VO(2), a significant decrease of minute ventilation (V(E)) was present for 6 of the 7 subjects (p < 0.02). During the exercise for the subjects who decreased V(E), a reduction of 288 +/- 169 ml in tidal volume was associated with an increase of 10.2 +/- 2.4 min(-1) in breathing frequency. These data suggest that the respiratory system might be stressed more for some endurance-trained athletes. The specific link between reduced VO(2) and reduced V(E) remains to be explored.

The aims of this study were to test the hypotheses that 1) the aerobic energy cost of roller ski skating (CS) is significantly related to level of performance and 2) a significant part of inter-individual differences of CS can be explained by kinematic parameters of skating locomotion. Oxygen uptake, kinematics of the knee and ankle joint, EMG of the vastus lateralis (VL) and gastrocnemius lateralis (GL) muscles, and roller ski velocity were recorded in 13 skiers who roller skied at 19.0 +/- 0.1 km x h(-1). CS was found to be 2.51 +/- 0.35 J x kg(-1) x m(-1) and significantly correlated with the skiers' level of performance (r = 0.61; p < 0.05). Significant relationships were found between CS and 1) knee angular amplitude (r = 0.75; p < 0.01) during the concentric phase, 2) VL average EMG during the concentric phase (r = 0.72; p < 0.01) and 3) VL and GL average EMG during the eccentric phase (p < 0.05). The results of this study showed that a significant part of performance could be explained by the aerobic energy cost of locomotion in skating. It can also be suggested that differences in upper/lower body utilization and/or in mechanical efficiency may explain the differences in CS.

The purposes of this study were 1) to examine the occurrence of the stretch-shortening cycle (SSC) in the three principal techniques of ski skating and 2) to test the hypothesis that differences in SSC behaviour may explain the choice of a technique when the grade is altered. Ten highly skilled male cross-country skiers roller skied at 5.3+/-0.1 m x s(-1) using the V1 skate (V1), V2-alternate (V2A), and V2 skate (V2) techniques. Knee and ankle joint kinematics, EMG of the vastus lateralis (VL) and gastrocnemius lateralis (GL) muscles, and roller ski velocity were recorded during the last 40 s of each bout of roller skiing. The existence of an EMG signal during the eccentric phase prior to the thrust, as well as the lack of significant delay between the two phases, showed that SSC occurs in the three techniques of roller ski skating with the exception of 50% of the subjects at the weak side knee with V1. The VL stretching velocity over the eccentric phase was higher (p < 0.005) with V2 and V2A than V1, indicating that less elastic energy was stored in the lower limbs extensor muscles with V1. This could partly explain why this technique is not used on flat terrains during races. However, no differences of average EMG activity or IEMG existed between techniques for either GL or VL during the concentric phase, suggesting that the theoretical advantage due to the SSC behaviour is minor in roller ski skating.