Sport-specific fitness testing differentiates professional from amateur soccer players where VO2max and VO2 kinetics do not.

AIM: The purpose of this study was to identify if sport-specific and cardiopulmonary exercise testing differentiated professional from amateur soccer players. METHODS: Thirty six men comprising 18 professional (mean±s: age 23.2±2.4 years) and 18 amateur (mean±SD: age 21.1±1.6 years) soccer players participated and performed four tests on separate occasions: 1) a graded exercise test to determine VO2max; 2) four exercise transients from walking to 80%Δ for the determination of VO2 kinetics; 3) the Yo-Yo Intermittent Recovery Test level 2 (Yo-Yo IR2) and 4) a repeated sprint test (RST). RESULTS: The players did not differ in VO2max (professional 56.5±2.9 mL.kg-1.min-1; amateur 55.7±3.5 mL.kg-1.min-1: P=0.484) or VO2 kinetic fundamental measures (τ1 onset, professional 24.5±3.2 s; amateur 24.0±1.8 s: τ1 cessation, professional 28.7±2.8 s; amateur 29.3±3.5 s: P=0.923). However, the amateurs were outperformed in the Yo-Yo IR2 (Professional 966±153 m; Amateur 840±156 m) (P=0.034) and RST (best time, professional 6.46±0.27 s; amateur 6.84±0.24 s, P=0.012). CONCLUSION: Performance indices derived from field-based sport-specific performance tests identified significant differences between professional and amateur players (P<0.05). However, neither tests of VO2 kinetics nor VO2max differentiated between groups, suggesting laboratory tests of cardiorespiratory parameters are probably less consequential to soccer than sport-specific field-based observations.

Relationships between pulmonary oxygen uptake kinetics and other measures of aerobic fitness in middle- and long-distance runners.

The purpose of this study was to assess the relationships between on- and off-transient pulmonary oxygen uptake kinetics and other measures of aerobic fitness in middle-distance (MD) and long-distance (LD) runners. 16 MD and 16 LD runners participated and each completed a series of tests to determine their maximal oxygen uptake (VO2max) gas-exchange threshold (GET), running economy (RE) and the primary time-constant for VO2 at the onset (tau(on)) and offset (tau(off)) of moderate-intensity treadmill exercise. Relationships between measures were established using Pearson product moment correlations (r). The relationships between VO2 kinetic parameter and other aerobic measures varied depending on classification of runner (MD or LD runner). There was a significant relationship between (VO2max) and tau(on) and tau(off) in LD runners (tau(on): r = -0.70, P = 0.003; tau(off): r = -0.55, P = 0.029), but not for MD (tau(on): r = 0.24, P = 0.366; tau(off): r = -0.09, P = 0.739). Similar relationships also existed between GET, RE and kinetic parameters for LD but not MD runners. The inconsistent relationships between VO2 kinetic parameters and other measures of aerobic fitness in MD and LD runners is intriguing. Further work is now required to identify how the volume and intensity of training influence peripheral adaptations in Type I and Type II fibres and how these may, or may not influence VO2 kinetic responses in the moderate- and heavy-intensity domain.

Moderate-domain pulmonary oxygen uptake kinetics and endurance running performance.

The aims of this study were to determine if the primary time constant (tau) for oxygen uptake (VO2) at the onset of moderate-intensity treadmill exercise is related to endurance running performance, and to establish if tau could be considered a determinant of endurance running performance. Thirty-six endurance trained male runners performed a series of laboratory tests, on separate days, to determine maximal oxygen uptake (VO2max), the ventilatory threshold (VT) and running economy. In addition, runners completed six transitions from walking (4 km x h-1) to moderate-intensity running (80% VT) for the determination of the VO2 primary time constant and mean response time. During all tests, pulmonary gas-exchange was measured breath-by-breath. Endurance running performance was determined using a treadmill 5-km time-trial, after which runners were considered as combined performers (n=36) and, using a ranking system, high performers (n=10) and low performers (n=10). Relationships between tau and endurance running performance were quantified using correlation coefficients (r). Stepwise multiple regression was used to determine the primary predictor variables of endurance running performance in combined performers. Moderate correlations were observed between tau, mean response time and endurance running performance, but only for the combined performers (r=-0.55, P=0.001 and r=-0.50, P=0.002, respectively). The regression model for predicting 5-km performance did not include tau or mean response time. The velocity at VO2max was strongly correlated to endurance running performance in all groups (r=0.72 - 0.84, P < 0.01) and contributed substantially to the prediction of performance. In conclusion, the results suggest that despite their role in determining the oxygen deficit and having a moderate relationship with endurance running performance, neither tau nor mean response time is a primary determinant of endurance running performance.

A comparison of pulmonary oxygen uptake kinetics in middle- and long-distance runners.

The purpose of this study was two-fold: 1) to compare the on- and off-transient pulmonary oxygen uptake (VO2) kinetics, in the moderate-intensity domain, of middle-distance (MD) and long-distance (LD) runners and 2) to determine the relationship between the volume of training and VO2 kinetics. With institutional ethics approval, 16 competitive male MD (800/1500 m) and 16 competitive male LD runners (5000/10 000 m) participated in the study. Each runner completed a series of tests to assess maximal VO2 (VO2max), ventilatory threshold (V(T)), and both the on- and off-transient primary time constants (tauon and tauoff, respectively) in response to moderate-intensity treadmill exercise. The results showed that tauon was significantly shorter in LD (12.3 +/- 0.5 s) than MD runners (16.4 +/- 1.0 s, p = 0.002). During recovery from exercise, tauoff was shorter in LD than MD runners (tauoff, 24.3 +/- 0.6 s vs. 26.9 +/- 0.8 s, p = 0.017). The volume of training was greater in LD (66.6 +/- 3.5 km x wk(-1)) than MD runners (43.5 +/- 3.9 km x wk(-1), p < 0.001) and was related to tauon in both groups of runner (MD: r = - 0.63, p = 0.009; LD: r = - 0.68, p = 0.004). Collectively, the results show that MD and LD runners can be differentiated on the basis of their on- and off-transient VO2 kinetics, despite similarities of VO2max and V(T). This is attributable to the greater volume of training performed by LD runners. Further investigations into adaptation(s) to training in muscle in MD and LD runners is required to determine the functional significance of such differences and the response of VO2 kinetic parameters to different training stimuli.

Characterisation, asymmetry and reproducibility of on- and off-transient pulmonary oxygen uptake kinetics in endurance-trained runners.

The purpose of this study was three-fold: (1) to characterise both the on- and off-transient oxygen uptake (V(.)O(2)) kinetics in endurance runners during moderate-intensity treadmill running; (2) to determine the degree of symmetry between on- and off-transients; and (3) to determine the reproducibility of V(.)O(2) kinetic parameters in endurance runners. Twelve endurance-trained runners [mean (SD) age 25.2 (4.7) years, body mass 70.1 (9.7) kg, height 179.5 (7.5) cm, ventilatory threshold (V(T)), 3,429 (389) ml.min(-1), maximal V(.)O(2) (V(.)O(2max)) 4,138 (625) ml.min(-1)] performed two multiple square-wave transition protocols on separate days. The protocol consisted of six (three transitions, 15 min rest, three transitions) square-wave transitions from walking at 4 km.h(-1) to running at a speed equivalent to 80% of the V(.)O(2) at the V(T) (80%V(T)). To determine the reproducibility, the protocol was repeated on a separate day (i.e. a test-retest design). Pulmonary gas-exchange was measured breath-by-breath. The V(.)O(2) data were modelled [from 20 s post-onset (or offset) of exercise] using non-linear least squares regression by a mono-exponential model, incorporating a time delay. The on- and off-transient time constants (tau(on) and tau(off)), mean response times (MRT(on) and MRT(off)) and amplitudes (A(on) and A(off)) were obtained from the model fit. On- and off transient kinetics were compared using paired t-tests. The reproducibility of each kinetic parameter was explored using statistical (paired t-tests) and non-statistical techniques [95% limits of agreement (LOA, including measurement error and systematic bias) and coefficient of variation (CV)]. It was found that the tau(on) [12.4 (1.9)] was significantly (P<0.001) shorter than tau(off) [24.5 (2.3) s]. Similarly, MRT(on) [27.1 (1.9) s] was shorter than MRT(off) [33.4 (2.2) s]. With respect to the reproducibility of the parameters, paired t-tests did not reveal significant differences between test 1 and test 2 for any on- or off-transient V(.)O(2) kinetic parameter (P>0.05). The LOA for tau(on) (1.9 s), tau(off) (2.3 s), MRT(on) (1.2 s), MRT(off) (3.2 s), A(on) (204 ml.min(-1)) and A(off) (198 ml.min(-1)) were narrow and acceptable. Furthermore, the measurement error (range, 4.3 to 15.1%) and CV (1.3 to 4.8%) all indicated good reproducibility. There was a tendency for tau(off) to be more reproducible than tau(on). However, MRT(on) was the most reproducible kinetic parameter. Overall, the results suggest that: (1) a multiple square-wave transition protocol can be used to characterise, reproducibly, both on- and off-transient V(.)O(2) kinetic parameters during treadmill running in runners; (2) the phase II time constant is independent of V(.)O(2) (max), and (3) asymmetry exists between on- and off transient V(.)O(2) kinetic parameters.

A comparison of two time-domain analysis procedures in the determination of .VO(2) kinetics by pseudorandom binary sequence exercise testing.

The purpose of this study was to apply and compare two time-domain analysis procedures in the determination of oxygen uptake (.VO(2)) kinetics in response to a pseudorandom binary sequence (PRBS) exercise test. PRBS exercise tests have typically been analysed in the frequency domain. However, the complex interpretation of frequency responses may have limited the application of this procedure in both sporting and clinical contexts, where a single time measurement would facilitate subject comparison. The relative potential of both a mean response time (MRT) and a peak cross-correlation time (PCCT) was investigated. This study was divided into two parts: a test-retest reliability study (part A), in which 10 healthy male subjects completed two identical PRBS exercise tests, and a comparison of the .VO(2) kinetics of 12 elite endurance runners (ER) and 12 elite sprinters (SR; part B). In part A, 95% limits of agreement were calculated for comparison between MRT and PCCT. The results of part A showed no significant difference between test and retest as assessed by MRT [mean (SD) 42.2 (4.2) s and 43.8 (6.9) s] or by PCCT [21.8 (3.7) s and 22.7 (4.5) s]. Measurement error (%) was lower for MRT in comparison with PCCT (16% and 25%, respectively). In part B of the study, the .VO(2) kinetics of ER were significantly faster than those of SR, as assessed by MRT [33.4 (3.4) s and 39.9 (7.1) s, respectively; P<0.01] and PCCT [20.9 (3.8) s and 24.8 (4.5) s; P<0.05]. It is possible that either analysis procedure could provide a single test measurement of .VO(2) kinetics; however, the greater reliability of the MRT data suggests that this method has more potential for development in the assessment of .VO(2) kinetics by PRBS exercise testing.

The test-retest reliability of gas exchange kinetics in humans using a pseudo random binary sequence exercise test.

The purpose of this study was to compare the test-retest reliability of oxygen uptake (VO2) kinetics with carbon dioxide output (VCO2) kinetics using a pseudo random binary sequence (PRBS) exercise test. A reliable test of gas exchange kinetics would have the potential of being applied as a sports fitness test. Ten healthy male subjects agreed to participate in the study and all subjects completed two identical PRBS exercise tests (test 1 and test 2), separated by a 30 min period of inactivity. Three consecutive 300 s PRBS cycles were completed in each test with 20 s exercise intensity changes between 25 and 85 W using an electrically braked cycle ergometer. Fourier analysis was computed for frequencies 3.3, 6.7 and 10 mHz. Statistical analysis by two-way ANOVA with repeated measures did not reveal significant differences between test 1 and test 2 for either VO2 kinetics or VCO2 kinetics. Static gain of VO2 for test 1 [9.11 (SD 0.59) ml.min-1.W-1] and test 2 [9.23 (SD 0.64) ml.min-1.W-1] did not differ significantly between tests. The 95% limits of agreement for VCO2 kinetics displayed increased variability in comparison to VO2 kinetics at each frequency of amplitude ratio and phase shift. Systematic bias ranged between 0% and 4%, except at frequency 10 mHz of VCO2 kinetics phase shift which showed a 10% bias for slower VO2 kinetics in test 2. It is possible that the increased variability of VCO2 kinetics compared to VO2 kinetics might be attributable to a lower signal to noise ratio in VCO2 kinetics, variations in ventilation or the storage mechanisms of CO2. The lower variability of VO2 kinetics compared with VCO2 kinetics suggests that the PRBS test of VO2 kinetics has the greater potential for further development as an indicator of aerobic fitness.

Exercise testing in children: an alternative approach.

In recent years there has been a call for new methods of evaluating the cardiorespiratory responses of children to exercise that complement their everyday exercise patterns. One potential method would be to use a sub-maximal, intermittent, pseudo-random binary sequence (PRBS) exercise test protocol to measure oxygen uptake kinetics (VO2 kinetics). Ten children of mean (SD) age 10.8 (+/- 1.5) years completed a 20 - 50 W cycle ergometer protocol of 17-min duration. An estimate of alveolar oxygen uptake (VO2) was calculated on a breath-by-breath basis. The VO2 kinetic parameters were expressed in the frequency domain as amplitude ratio and phase delay using standard Fourier techniques. Analysis was restricted to the frequency range 2.2 to 8.9 mHz. The mean (SD) amplitude ratio responses decreased from 10.33 (+/- 0.73) to 7.42 (+/- 0.99) ml min(-1) W(-1) and the mean phase delay increased from -26.78 degrees (+/- 6.37 degrees) to -81.93 degrees (+/- 10.45 degrees) over the frequency range 2.2-8.9 mHz. Significant correlations (p < 0.05) were found between chronological age and amplitude ratio (r = 0.68 and 0.62), and chronological age and phase delay (r = -0.62 and -0.69) at the frequencies of 2.2 and 4.4 mHz, respectively. No significant correlations were found between VO2 kinetics and stature or VO2 kinetics and body mass. The observations demonstrated the use of the PRBS technique to measure VO2 kinetics in the frequency domain in children. This approach may be a useful addition to the tests that are used to quantify the oxygen uptake responses to exercise in children.

VO2 kinetics determined by PRBS techniques differentiate elite endurance runners from elite sprinters.

The aim of the study was to examine whether a measure of oxygen uptake (VO2) kinetics could differentiate between 12 elite male endurance (3000-10,000 m) runners and 12 elite male sprint (100-400 m) runners using a pseudo random binary sequence (PRBS) exercise protocol. All exercise tests were performed on an electrically braked cycle ergometer at a constant pedal frequency of 1 Hz. The PRBS exercise intensities alternated between 25 W and 85 W for three consecutive PRBS cycles of 300 s. VO2 was measured breath-by-breath and results were analysed by Fourier techniques in the frequency domain. Blood lactate concentrations taken pre and post testing were below 2 mM. Significantly greater amplitude components were observed in the endurance runners than sprinters at frequencies 6.7 mHz (6.71 +/- 1.09 and 5.47 +/- 0.95 ml x min(-1) x W(-1), respectively) P<0.05 and 10 mHz (4.97 +/- 0.98 and 3.56 +/- 0.69 ml x min(-1) x W(-1) respectively) P<0.01. Phase shift components were significantly shorter in the endurance runners compared to the sprinters at frequency 3.3 mHz (-35.45 +/- 4.31 and -41.26 +/- 5.82 degrees respectively) P<0.05. The results of this study show that VO2 kinetics are differentially faster in elite endurance runners than in elite sprinters. This supports the development of the PRBS technique as a test of sports performance.