Publications (18)46.31 Total impact
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Article: A test to assess aerobic and anaerobic parameters during maximal exercise in young girls.
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ABSTRACT: The Wingate cycle test (WAnT) is a 30-s test commonly used to estimate anaerobic work capacity (AWC). However, the test may be too short to fully deplete anaerobic energy reserves. We hypothesized that a 90-s all-out isokinetic test (ISO_90) would be valid to assess both aerobic and anaerobic capacities in young females. Eight girls (11.9 ± 0.5 y) performed an exhaustive incremental test, a WAnT and an ISO_90. Peak VO2 attained during the ISO_90 was significantly greater than VO2peak. Mean power, end power, fatigue index, total work done and AWC were not significantly different between the WAnT and after 30 s of the 90-s test (i.e., ISO_30). However, 95% limits of agreement showed large variations between the two tests when comparing all anaerobic parameters. It is concluded that an ISO-90 may be a useful test to assess aerobic capacity in young girls. However, since the anaerobic parameters derived from the ISO_30 did not agree with those derived from a traditional WAnT, the validity of using an ISO_90 to assess anaerobic performance and capacity within this population group remains unconfirmed.Pediatric exercise science 05/2012; 24(2):262-74. · 1.71 Impact Factor -
Article: Limitations to high intensity exercise prescription in chronic heart failure patients.
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ABSTRACT: Interval training is recommended for chronic heart failure patients (CHF), but specific guidelines on setting appropriate workloads have not been fully established. The aim of this study was to compare a traditional method of interval training prescription with a protocol specifically designed for CHF. Ten CHF and 7 healthy controls performed 2 maximal incremental cycle tests to determine interval training workload; a standard test (10Wmin(-)(1)) and a steep test (25W.10(-)(s)). Peak work rate and oxygen uptake (VO(2 peak)) were determined. Training workloads were defined as 100% standard test and 50% steep test peak work rate. Training workload determined from the standard test was higher than from the steep test in healthy controls (151 ± 17W vs 118 ± 13W; P<0.01), whereas in CHF there was no significant difference between methods (88 ± 10W vs 96 ± 9W; P>0.05). Steep test VO(2peak) reached 91 ± 5% of standard test VO(2 peak) in controls, and 99 ± 4% in CHF, with no significant differences between tests in either group. Prescribing interval training from a standard test results in higher workloads than from a steep test in healthy individuals, but in CHF both methods prescribe similar workloads. However it should not be assumed that the two tests can be used interchangeably for CHF. This small-sized study raises issues about interval training prescription that may be hypothesis-generating for future larger-scale studies.European journal of cardiovascular nursing: journal of the Working Group on Cardiovascular Nursing of the European Society of Cardiology 09/2011; 10(3):167-73. -
Article: Time to exhaustion and time spent at a high percentage of VO2max in severe intensity domain in children and adults.
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ABSTRACT: The aim of the study was to compare time spent at a high percentage of VO2max (>90% of VO2max) (ts90%), time to achieve 90% of VO2max (ta90%), and time to exhaustion (TTE) for exercise in the severe intensity domain in children and adults. Fifteen prepubertal boys (10.3 ± 0.9 years) and 15 men (23.5 ± 3.6 years) performed a maximal graded exercise to determine VO2max, maximal aerobic power (MAP) and power at ventilatory threshold (PVTh). Then, they performed 4 constant load exercises in a random order at PVTh plus 50 and 75% of the difference between MAP and PVTh (PΔ50 and PΔ75) and 100 and 110% of MAP (P100 and P110). VO2max was continuously monitored. The P110 test was used to determine maximal accumulated oxygen deficit (MAOD). No significant difference was found in ta90% between children and adults. ts90% and TTE were not significantly different between children and adults for the exercises at PΔ50 and PΔ75. However, ts90% and TTE during P100 (p < 0.05 and p < 0.01, respectively) and P110 (p < 0.001) exercises were significantly shorter in children. Children had a significantly lower MAOD than adults (34.3 ± 9.4 ml · kg vs. 53.6 ± 11.1 ml · kg). A positive relationship (p < 0.05) was obtained between MAOD and TTE values during the P100 test in children. This study showed that only for intensities at, or higher than MAP, lower ts90% in children was linked to a reduced TTE, compared to adults. Shorter TTE in children can partly be explained by a lower anaerobic capacity (MAOD). These results give precious information about exercise intensity ranges that could be used in children's training sessions. Moreover, they highlight the implication of both aerobic and anaerobic processes in endurance performances in both populations.The Journal of Strength and Conditioning Research 02/2011; 25(4):1151-8. · 1.83 Impact Factor -
Article: Critical power is not attained at the end of an isokinetic 90-second all-out test in children.
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ABSTRACT: The purpose of this study was to establish whether critical power, as traditionally determined from the performance of three constant-load tests to exhaustion, is attained at the end of a 90-s all-out test in children. Sixteen healthy children (eight males and eight females; mean age 12.3 years, s(x) = 0.1; body mass 39.6 kg, s(x) = 1.8; peak VO(2) 2.0 litres . min(-1), s(x) = 0.1) completed an incremental test to exhaustion to determine peak oxygen uptake (peak VO(2)), three separate constant-load tests to exhaustion to calculate critical power, and an isokinetic 90-s all-out test. The end power of the 90-s test averaged over the last 10 s (140 W, s(x) = 8) was significantly higher than critical power (105 W, s(x) = 6; t = 6.8; P < 0.01), yet the two parameters were strongly correlated (r = 0.74; P < 0.01). After 60 s, there were no further reductions in power output during the 90-s test (P < 0.0001). In conclusion, at the end of a 90-s all-out test, children are able to produce power outputs well above critical power. This suggests that 90 s is not long enough to completely exhaust the anaerobic work capacity in children.Journal of Sports Sciences 03/2009; 27(4):379-85. · 1.93 Impact Factor -
Article: Critical power in adolescent boys and girls--an exploratory study.
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ABSTRACT: The purpose of the study was to identify critical power (CP) in boys and girls and to examine the physiological responses to exercise at and 10% above CP (CP+10%) in a sub-group of boys. Nine boys and 9 girls (mean age 12.3 (0.5) y performed 3 constant-load tests to derive CP. Eight of the boys then exercised, in random order, at CP and CP+10% until volitional exhaustion. CP was 123 (28) and 91 (26) W for boys and girls, respectively (p < 0.02), which was equivalent to 75 (6) and 72 (10) % of peak oxygen uptake, respectively (p > 0.47). Boys' time to exhaustion at CP was 18 min 37 s (4 min 13 s), which was significantly longer (p < 0.007) than that at CP+10% (9 min 42 s (2 min 31 s)). End-exercise values for blood lactate concentration (B[La]) and maximal oxygen uptake were higher in the CP+10% trial (5.0 (2.4) mmol.L-1 and 2.15 (0.4) L.min-1, respectively) than in the CP trial, (B[La], 4.7 (2.1) mmol.L-1; maximal oxygen uptake, 2.05 (0.35) L.min-1; p > 0.13). Peak oxygen uptake (expressed as a percentage of the peak value) was not attained at the end of the trials (94 (12) and 98 (14) % for CP and CP+10%, respectively). These results provide information about the boundary between the heavy and severe exercise intensity domains in children, and have demonstrated that CP in a group of boys does not represent a sustainable steady-state intensity of exercise.Applied Physiology Nutrition and Metabolism 12/2008; 33(6):1105-11. · 2.13 Impact Factor -
Article: Physiological and performance effects of low- versus mixed-intensity rowing training.
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ABSTRACT: To examine the impact of low-intensity and a mixture of low- and high-intensity training on physiological and performance responses in rowing. Eighteen experienced rowers undertook a 12-wk program of 100% < or = lactate threshold (LT) training (LOW) or 70% training at < or = LT and 30% at halfway (50%Delta) between the V O2 at LT and V O2peak (MIX). Responses were assessed before and after training by a progressive exercise test to exhaustion; multiple "square-wave" rest-to-exercise transitions of 6-min duration at 50%Delta; and a maximal 2000-m ergometer time trial. Improvements (P < 0.001) in 2000-m ergometer performance and V O2peak occurred independently of groups (P = 0.8 and 0.42, respectively). LOW improved the power at LT (23.5 +/- 12.2 vs 5.1 +/- 5.0 W, P = 0.013) and power at a [blood lactate] of 4 mM (32.3 +/- 6.9 vs 13.1 +/- 3.7 W, P = 0.03) compared with MIX. The time constant and gain of the primary component were unchanged with training, whereas the gain of the V O2 slow component was reduced with training, but independently of group. Both LOW and MIX training programs improved performance and V O2peak by the same magnitude, whereas LOW attenuated the blood lactate response to a given exercise intensity more so than MIX.Medicine & Science in Sports & Exercise 04/2008; 40(3):579-84. · 4.43 Impact Factor -
Article: A comparison of methods to determine maximal accumulated oxygen deficit in running.
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ABSTRACT: The aim of this study was to compare maximal accumulated oxygen deficit (hereafter O2 deficit) estimated from the methods of Whipp et al. (1986), Medbo et al. (1988), and Hill et al. (1998) to determine whether they agree sufficiently to be used interchangeably. Nineteen moderately to highly trained endurance runners first performed an incremental test to exhaustion for the determination of maximal oxygen uptake ([Vdot]O(2max)) and peak treadmill speed, followed by six randomly ordered constant-speed tests at 95, 100, 105, 110, 110, and 120% of peak treadmill speed. All tests were separated by at least 72 h and were performed within 4 weeks. The method of Whipp produced an O(2) deficit estimate that was lower than that derived from the method of Hill or Medbo (bias +/- 95% limits of agreement: -29.6 +/- 36.6 and -26.1 +/- 32.8 ml . kg(-1), respectively; P < 0.001). The O2 deficit did not differ between the methods of Hill and Medbo (bias +/- 95% limits of agreement: 3.5 +/- 41.6 ml . kg(-1); n.s.). However, poor correlations (0.21 < r < 0.33; n.s.) together with wide limits of agreement between O2 deficit estimates (70 - 80% of the mean response) clearly question using these methods interchangeably.Journal of Sports Sciences 04/2008; 26(6):663-70. · 1.93 Impact Factor -
Article: Comparison of the oxygen uptake kinetics of club and olympic champion rowers.
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ABSTRACT: To test the hypothesis that elite rowers would possess a faster, more economic oxygen uptake response than club standard rowers. Eight Olympic champion (ELITE) rowers were compared with a cohort of eight club standard (CLUB) rowers. Participants completed a progressive exercise test to exhaustion, repeated 6-min moderate and heavy square-wave transitions, and a maximal 2000-m ergometer time trial. The time constant (tau) of the primary component (PC) was faster for the ELITE group compared with CLUB for moderate-intensity (13.9 vs 19.4 s, P = 0.02) and heavy-intensity (18.7 vs 22.4 s, P = 0.005) exercise. ELITE rowers consumed less oxygen for moderate (14.2 vs 15.6 mL x min(-1) x W(-1); P = 0.009) and heavy (12.1 vs 13.7 mL x min(-1) x W(-1); P = 0.01) exercise. A greater absolute slow component was observed in the ELITE group (P = 0.009), but no differences were noted when the slow component was expressed relative to work rate performed (P = 0.14). Intergroup correlation with time trial performance speed was significant for tauPC during heavy-intensity exercise (r = -0.59, P = 0.02). Compared with CLUB rowers, the shorter time constant response and greater economy observed in ELITE rowers may suggest advantageous adjustment of oxidative processes from rest to work. Training status or performance level do not seem to be associated with a smaller slow component when comparing CLUB and ELITE oarsmen.Medicine & Science in Sports & Exercise 06/2007; 39(5):865-71. · 4.43 Impact Factor -
Article: Effect of prior exercise above and below critical power on exercise to exhaustion.
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ABSTRACT: The aim of the present study was to ascertain whether the intensity of prior exercise altered the time to exhaustion at critical power (CP). Eleven participants volunteered to take part in the study (mean +/- SD: VO2max 4.1 +/- 0.5 L x min(-1); age 30.1 +/- 7.2 yr; body mass 74.6 +/- 9.1 kg) and completed three trials to exhaustion at their CP under differing prior exercise conditions: 1) a control trial (CON); 2) a trial preceded by three 60-s efforts at 110% CP (severe); and 3) a trial preceded by three 73-s efforts at 90% CP (heavy). All trials followed a 5-min baseline at 50 W. Time to exhaustion was significantly lengthened after prior heavy exercise (1071 +/- 18 s) when compared with CON (973 +/- 16 s, F = 9.53, P = 0.006). However, there was no effect on TTE after prior severe exercise (967 +/- 16 s). Oxygen deficit was significantly reduced from that in CON (3.8 +/- 0.2 L) after prior heavy (3.2 +/- 0.3 L) and prior severe exercise (3.1 +/- 0.3 L, F = 10.95, P = 0.001). Concurrently, there was a significant reduction in the magnitude of the VO2 slow component (SC) in the trials with prior exercise (197 +/- 34 and 126 +/- 19 mL x min(-1) after heavy and severe exercise, respectively) when compared with CON (223 +/- 31 mL x min(-1), F = 9.62, P = 0.006). Prior heavy exercise does appear to improve the time to exhaustion at CP by approximately 10% and is associated with a reduction in the VO2 SC. However, the reduction in the SC, with no change in performance after prior severe exercise, suggests that a reduced SC may not necessarily lead to improved TTE.Medicine & Science in Sports & Exercise 06/2005; 37(5):775-81. · 4.43 Impact Factor -
Article: Muscle glycogen depletion alters oxygen uptake kinetics during heavy exercise.
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ABSTRACT: To test the hypothesis that muscle fiber recruitment patterns influence the oxygen uptake (VO2) kinetic response, constant-load exercise was performed after glycogen depletion of specific fiber pools. After validation of protocols for the selective depletion of Type I and II muscle fibers, 19 subjects performed square-wave exercise at 80% VT (moderate) and at 50% of the difference between VT and VO2max (heavy) without any prior depleting exercise (CON), after HIGH (10 x 1-min exercise bouts at 120% VO2max), and after LOW (3 h of exercise at 30% VO2max) exercise. Differences in VO2 kinetic parameters were only observed in heavy exercise AFTER HIGH: the VO2 primary component was higher (1.75 +/- 0.12 L x min) compared with CON (1.65 +/- 0.11 L x min, P < 0.05), and the VO2 slow component was lower (0.18 +/- 0.03 L x min) compared with CON (0.24 +/- 0.04 L x min, P < 0.05). The results indicate that the VO2 response to heavy constant-load exercise can be altered by depletion of glycogen in the Type II muscle fibers, lending support to the theory that muscle fiber recruitment influences both the VO2 primary and slow component amplitudes during heavy intensity exercise.Medicine & Science in Sports & Exercise 06/2004; 36(6):965-72. · 4.43 Impact Factor -
Article: Oxygen uptake kinetics during moderate, heavy and severe intensity "submaximal" exercise in humans: the influence of muscle fibre type and capillarisation.
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ABSTRACT: The purpose of the present study was to test the hypothesis that muscle fibre type influences the oxygen uptake (.VO(2)) on-kinetic response (primary time constant; primary and slow component amplitudes) during moderate, heavy and severe intensity sub-maximal cycle exercise. Fourteen subjects [10 males, mean (SD) age 25 (4) years; mass 72.6 (3.9) kg; .VO(2peak) 47.9 (2.3) ml kg(-1) min(-1)] volunteered to participate in this study. The subjects underwent a muscle biopsy of the vastus lateralis for histochemical determination of muscle fibre type, and completed repeat "square-wave" transitions from unloaded cycling to power outputs corresponding to 80% of the ventilatory threshold (VT; moderate exercise), 50% (heavy exercise) and 70% (severe exercise) of the difference between the VT and .VO(2peak). Pulmonary .VO(2) was measured breath-by-breath. The percentage of type I fibres was significantly correlated with the time constant of the primary .VO(2) response for heavy exercise (r=-0.68). Furthermore, the percentage of type I muscle fibres was significantly correlated with the gain of the .VO(2) primary component for moderate (r=0.65), heavy (r=0.57) and severe (r=0.57) exercise, and with the relative amplitude of the .VO(2) slow component for heavy (r=-0.74) and severe (r=-0.64) exercise. The influence of muscle fibre type on the .VO(2) on-kinetic response persisted when differences in aerobic fitness and muscle capillarity were accounted for. This study demonstrates that muscle fibre type is significantly related to both the speed and the amplitudes of the .VO(2) response at the onset of constant-load sub-maximal exercise. Differences in contraction efficiency and oxidative enzyme activity between type I and type II muscle fibres may be responsible for the differences observed.Arbeitsphysiologie 06/2003; 89(3-4):289-300. · 2.15 Impact Factor -
Article: Effect of pedal rate on primary and slow-component oxygen uptake responses during heavy-cycle exercise.
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ABSTRACT: We hypothesized that a higher pedal rate (assumed to result in a greater proportional contribution of type II motor units) would be associated with an increased amplitude of the O(2) uptake (Vo(2)) slow component during heavy-cycle exercise. Ten subjects (mean +/- SD, age 26 +/- 4 yr, body mass 71.5 +/- 7.9 kg) completed a series of square-wave transitions to heavy exercise at pedal rates of 35, 75, and 115 rpm. The exercise power output was set at 50% of the difference between the pedal rate-specific ventilatory threshold and peak Vo(2), and the baseline power output was adjusted to account for differences in the O(2) cost of unloaded pedaling. The gain of the Vo(2) primary component was significantly higher at 35 rpm compared with 75 and 115 rpm (mean +/- SE, 10.6 +/- 0.3, 9.5 +/- 0.2, and 8.9 +/- 0.4 ml. min(-1). W(-1), respectively; P < 0.05). The amplitude of the Vo(2) slow component was significantly greater at 115 rpm (328 +/- 29 ml/min) compared with 35 rpm (109 +/- 30 ml/min) and 75 rpm (202 +/- 38 ml/min) (P < 0.05). There were no significant differences in the time constants or time delays associated with the primary and slow components across the pedal rates. The change in blood lactate concentration was significantly greater at 115 rpm (3.7 +/- 0.2 mM) and 75 rpm (2.8 +/- 0.3 mM) compared with 35 rpm (1.7 +/- 0.4 mM) (P < 0.05). These data indicate that pedal rate influences Vo(2) kinetics during heavy exercise at the same relative intensity, presumably by altering motor unit recruitment patterns.Journal of Applied Physiology 04/2003; 94(4):1501-7. · 3.75 Impact Factor -
Article: The effect of interdian and diurnal variation on oxygen uptake kinetics during treadmill running.
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ABSTRACT: The aim of this study was to examine the variability of the oxygen uptake (VO2) kinetic response during moderate- and high-intensity treadmill exercise within the same day (at 06:00, 12:00 and 18:00 h) and across days (on five occasions). Nine participants (age 25 +/- 8 years, mass 70.2 +/- 4.7 kg, VO2max 4137 +/- 697 ml x min(-1); mean +/- s) took part in the study. Six of the participants performed replicate 'square-wave' rest-to-exercise transitions of 6 min duration at running speeds calculated to require 80% VO2 at the ventilatory threshold (moderate-intensity exercise) and 50% of the difference between VO2 at the ventilatory threshold and VO2max (50% delta; high-intensity exercise) on 5 different days. Although the amplitudes of the VO2 response were relatively constant (coefficient of variation approximately 6%) from day to day, the time-based parameters were more variable (coefficient of variation approximately 15 to 30%). All nine participants performed replicate square-waves for each time of day. There was no diurnal effect on the time-based parameters of VO2 kinetics during either moderate- or high-intensity exercise. However, for high-intensity exercise, the amplitude of the primary component was significantly lower during the 12:00 h trial (2859 +/- 142 ml x min(-1) vs 2955 +/- 135 ml x min(-1) at 06:00 h and 2937 +/- 137 ml x min(-1) at 18:00 h; P < 0.05), but this effect was eliminated when expressed relative to body mass. The results of this study indicate that the amplitudes of the VO2 kinetic responses to moderate- and high-intensity treadmill exercise are similar within and across test days. The time-based parameters, however, are more variable from day to day and multiple transitions are, therefore, recommended to increase confidence in the data.Journal of Sports Sciences 11/2002; 20(11):901-9. · 1.93 Impact Factor -
Article: Oxygen uptake kinetics during horizontal and uphill treadmill running in humans.
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ABSTRACT: The aim of this study was to examine the effect of increasing the ratio of concentric to eccentric muscle activation on oxygen uptake (VO(2)) kinetics during treadmill running. Nine subjects [2 women; mean (SD) age 29 (7) years, height 1.77 (0.07) m, body mass 73.0 (7.5) kg] completed incremental treadmill tests to exhaustion at 0% and 10% gradients to establish the gradient-specific ventilatory threshold (VT) and maximal oxygen uptake (VO(2max)). Subsequently, the subjects performed repeated moderate intensity (80% of gradient-specific VT) and heavy intensity (50% of the difference between the gradient specific VT and VO(2max)) square-wave runs with the treadmill gradient set at 0% and 10%. For moderate intensity exercise, there were no significant differences between treadmill gradients for VO(2) kinetics. For heavy intensity exercise, the amplitude of the primary component of VO(2) was not significantly different between 0% and 10% treadmill gradients [mean (SEM) 2,940 (196) compared to 2,869 (156) ml x min(-1), respectively], but the amplitude of the VO(2) slow component was significantly greater at the 10% gradient [283 (43) compared to 397 (37) ml x min(-1); P < 0.05]. These results indicate that the muscle contraction regimen (i.e. the relative contribution of concentric and eccentric muscle action) significantly influences the amplitude of the VO(2) slow component.Arbeitsphysiologie 11/2002; 88(1-2):163-9. · 2.15 Impact Factor -
Article: Effect of creatine supplementation on oxygen uptake kinetics during submaximal cycle exercise.
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ABSTRACT: The purpose of this study was to test the effect of oral creatine (Cr) supplementation on pulmonary oxygen uptake (VO(2)) kinetics during moderate [below ventilatory threshold (VT)] and heavy (above VT) submaximal cycle exercise. Nine subjects (7 men; means +/- SD: age 28 +/- 3 yr, body mass 73.2 +/- 5.6 kg, maximal VO(2) 46.4 +/- 8.0 ml. kg(-1). min(-1)) volunteered to participate in this study. Subjects performed transitions of 6-min duration from unloaded cycling to moderate (80% VT; 8-12 repeats) and heavy exercise (50% change; i.e., halfway between VT and maximal VO(2); 4-6 repeats), both in the control condition and after Cr loading, in a crossover design. The Cr loading regimen involved oral consumption of 20 g/day of Cr monohydrate for 5 days, followed by a maintenance dose of 5 g/day thereafter. VO(2) was measured breath by breath and modeled by using two (moderate) or three (heavy) exponential terms. For moderate exercise, there were no differences in the parameters of the VO(2) kinetic response between control and Cr-loaded conditions. For heavy exercise, the time-based parameters of the VO(2) response were unchanged, but the amplitude of the primary component was significantly reduced with Cr loading (means +/- SE: control 2.00 +/- 0.12 l/min; Cr loaded 1.92 +/- 0.10 l/min; P < 0.05) as was the end-exercise VO(2) (control 2.19 +/- 0.13 l/min; Cr loaded 2.12 +/- 0.14 l/min; P < 0.05). The magnitude of the reduction in submaximal VO(2) with Cr loading was significantly correlated with the percentage of type II fibers in the vastus lateralis (r = 0.87; P < 0.01; n = 7), indicating that the effect might be related to changes in motor unit recruitment patterns or the volume of muscle activated.Journal of Applied Physiology 06/2002; 92(6):2571-7. · 3.75 Impact Factor -
Article: Oxygen uptake kinetics during treadmill running across exercise intensity domains.
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ABSTRACT: The purpose of the present study was to examine comprehensively the kinetics of oxygen uptake (VO2) during treadmill running across the moderate, heavy and severe exercise intensity domains. Nine subjects [mean (SD age, 27 (7) years; mass, 69.8 (9.0) kg; maximum VO2, VO2max, 4,137 (697) ml x min(-1)] performed a series of "square-wave" rest-to-exercise transitions of 6 min duration at running speeds equivalent to 80% and 100% of the VO2 at lactate threshold (LT; moderate exercise); and at 20%, 40%, 60%, 80% and 100% of the difference between the VO2 at LT and VO2max (delta heavy and severe exercise). Critical velocity (CV) was also determined using four maximal treadmill runs designed to result in exhaustion in 2-15 min. The VO2 response was modelled using non-linear regression techniques. As expected, the amplitude of the VO2 primary component increased with exercise intensity [from 1,868 (136) ml x min-( 1) at 80% LT to 3,296 (218) ml x min-(1) at 100% delta, P < 0.05]. However, there was a non-significant trend for the "gain" of the primary component to decrease as exercise intensity increased [181 (7) ml x kg(-1) x km(-1) at 80% LT to 160 (6) ml x kg(-1) x km(-1) at 100% delta]. The time constant of the primary component was not different between supra-LT running speeds (mean value range = 17.9-19.1 s), but was significantly shorter during the 80% LT trial [12.7 (1.4) s, P < 0 .05]. The VO2 slow component increased with exercise intensity from 139 (39) ml x min(-1) at 20% delta to 487 (57) ml x min(-1) at 80% delta (P < 0.05), but decreased to 317 (84) ml x min(-1) during the 100% delta trial (P < 0.05). During both the 80% delta and 100% delta trials, the VO2 at the end of exercise reached VOmax [4,152 (242) ml x min(-1) and 4,154 (114) ml x min(-1), respectively]. Our results suggest that the "gain" of the primary component is not constant as exercise intensity increases across the moderate, heavy and severe domains of treadmill running. These intensity-dependent changes in the amplitudes and kinetics of the VO2 response profiles may be associated with the changing patterns of muscle fibre recruitment that occur as exercise intensity increases.Arbeitsphysiologie 02/2002; 86(4):347-54. · 2.15 Impact Factor -
Article: Effects of Prior Exercise and Recovery Duration on Oxygen Uptake Kinetics During Heavy Exercise in Humans
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ABSTRACT: Prior heavy exercise (above the lactate threshold, LT) reduces the amplitude of the pulmonary oxygen uptake (V̇O2) slow component during heavy exercise, yet the precise effect of prior heavy exercise on the phase II V̇O2 response remains to be established. This study was designed to test the hypotheses that (1) prior heavy exercise increases the amplitude of the phase II V̇O2 response independently of changes in the baseline V̇O2 value and (2) the effect of prior exercise depends on the amount of external work done during prior exercise, irrespective of the intensity of the prior exercise. Nine subjects performed two 6 min bouts of heavy cycling exercise separated by 6 min baseline pedalling recovery (A), two 6 min heavy exercise bouts separated by 12 min recovery (6 min rest and 6 min baseline pedalling, B), and a bout of moderate exercise (below the LT) in which the same amount of external work was performed as during the prior heavy exercise, followed by 6 min heavy exercise (C). In both tests A and B, prior heavy exercise significantly increased the absolute V̇O2 amplitude at the end of phase II (by ∼150 ml min−1), and reduced the amplitude of the V̇O2 slow component by a similar amount. Following 12 min of recovery (B), baseline V̇O2, but not blood [lactate], had returned to pre-exercise levels, indicating that these effects occurred independently of changes in baseline V̇O2. Prior moderate exercise (C) had no effect on either the V̇O2 or blood [lactate] responses to subsequent heavy exercise. The V̇O2 response to heavy exercise was therefore dependent on the intensity of prior exercise, and the effects on the amplitudes of the phase II and slow V̇O2 components persisted for at least 12 min following prior heavy exercise.Experimental physiology 04/2001; 86(3):417 - 425. · 3.17 Impact Factor -
Article: A disproportionate increase in O2 coincident with lactate threshold during treadmill exercise
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ABSTRACT: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Medicine and Science in Sports and Exercise, published by and copyright Lippincott Williams & Wilkins. Purpose: The purpose of this study was to assess the relationship between pulmonary O2 and running speed over a range of exercise intensities. During constant-load cycle exercise above the lactate threshold (Tlac), it has been shown that O2 does not attain a steady state within 3 min but continues to rise until either a delayed but elevated steady-state O2 is attained or exhaustion occurs. Since this greater oxygen cost of exercise ( O2 slow component) has only been demonstrated at discrete exercise intensities above Tlac, it was hypothesised that the onset of the O2 slow component would coincide with Tlac during an incremental test if the stage durations were of sufficient length. Methods: Five male subjects (mean +/- SD age 31 +/- 2 yr; O2peak 60.1 +/- 5.8 mL[middle dot]kg-1[middle dot]min-1) performed four identical treadmill tests within an 8-d period. The tests involved the completion of six stages of 7-min duration. Running speed was increased by 0.5 km[middle dot]h-1 between stages. In the first test, fingertip capillary blood was sampled at the end of each stage for determination of Tlac. For all tests expired air was collected into Douglas bags from 3.0 to 3.75 min and from 6.0 to 6.75 min of each stage to determine any increase in O2 (ΔO2) over the duration of the stage. Results: The mean Δ O2 for each stage over the four tests was determined for each subject. Repeated measures ANOVA with post-hoc Tukey tests revealed a significant increase in Δ O2 at running speeds above, but not below, Tlac. Conclusions: The results of this study confirm the close association between the O2 slow component and the onset of lactic acidosis and demonstrate alinearity in the O2-exercise intensity relationship above Tlac for incremental treadmill exercise.
Top co-authors
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Institutions
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2004–2009
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University of Brighton
- Centre for Health Research
Brighton, ENG, United Kingdom
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2008
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University of Exeter
- Department of Sport and Health Sciences
Exeter, ENG, United Kingdom -
Université de Montréal
- Department of Kinesiology
Montréal, Quebec, Canada
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2007–2008
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Loughborough University
Loughborough, ENG, United Kingdom
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2002–2003
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Manchester Metropolitan University
- Department of Exercise and Sport Science
Manchester, ENG, United Kingdom
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2001–2002
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University of Roehampton
London, ENG, United Kingdom
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