M.L. Fysh

Moderate-domain pulmonary oxygen uptake kinetics and endurance running performance

Abstract The aims of this study were to determine if the primary time constant (τ) for oxygen uptake ([Vdot]O2) at the onset of moderate-intensity treadmill exercise is related to endurance running performance, and to establish if τ 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 ([Vdot]O2max), the ventilatory threshold (VT) and running economy. In addition, runners completed six transitions from walking (4 km · h−1) to moderate-intensity running (80% VT) for the determination of the [Vdot]O2 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 τ 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 τ, 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 τ or mean response time. The velocity at [Vdot]O2max 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 τ nor mean response time is a primary determinant of endurance running performance.

Effects of high-intensity running training on soccer-specific fitness in professional male players

The purpose of this study was to investigate whether or not physiological and performance gains could be achieved with the addition of high-intensity running to an existing training programme in a group of well trained professional male soccer players. Sixteen professional male players (21.3 ± 2.1 years, stature 177.4 ± 4.2 cm, body mass 73.1 ± 8.1 kg) were randomised in training (TRA, n = 8) and control (CON, n = 8) groups. All players performed physiological assessments before and after a 6-week intervention. Outcome measures were: (i) V̇O2peak, (ii) V̇O2 kinetics during very heavy-intensity exercise, (iii) a maximal anaerobic running test, and (iv) Yo-Yo Intermittent Recovery Test level 2 (YIRT2). The only aerobic parameter to change after the intervention was the phase III time constant at exercise onset for CON, which lengthened (p = 0.012) to a value similar to that of the TRA group. However, TRA showed gains in anaerobic performance (p = 0.021), time to exhaustion (p = 0.019), and maximal running speed (p = 0.023). In the YIRT2, distance run increased for TRA over time (p = 0.015), and the TRA group were also capable of running further in the YIRT2 after the intervention compared with CON (p = 0.011). This study shows it is possible to improve the soccer-specific high-intensity running capacity of professional players when high-intensity intermittent training is added to the normal training load and that this effect is only detectable in anaerobic capabilities. The observed effects are meaningful to the training practices of elite athletes seeking a competitive edge in team sports when otherwise well matched.

Kinematics and neuromuscular recruitment during vertical treadmill exercise

The vertical treadmill (VertiRun) is an unresearched, partial weight-bearing exercise mode for lower limb rehabilitation. The user undertakes a “running-like” action whilst body weight is supported by a bench and the limb is drawn downwards against overhanging resistance cables on a vertically hung nonmotorised treadmill. This study sought to describe the kinematics and neuromuscular recruitment during VertiRun exercise in the supine, 40°, and 70° postures. Twenty-one healthy male participants (age, 25±7 years; stature, 1.79±0.07 m; body mass, 77.7±8.8 kg) volunteered for sagittal plane kinematic analysis of the ankle, knee and hip and electromyography of lower limb musculature in all three postures. Results indicated similar kinematic and neuromuscular profiles in the 40° and 70° postures which differed from the supine. Regardless of posture, a basic movement pattern was observed where the hamstrings and gastrocnemius muscles were active to extend the hip, flex the knee, plantarflex the ankle and draw the leg down the treadmill belt in the contact phase. The rectus femoris and tibialis anterior were active to flex the hip and knee, and dorsiflex the ankle to draw the leg upwards during the swing phase. The vasti muscles were not active during VertiRun exercise. The VertiRun demonstrated similar kinematic and neuro-muscular patterns to overground gait, allows workload progression based on effort and posture changes, and is a low-impact exercise mode that could maintain physical fitness without loading injured tissues. This study suggests that the VertiRun could supplement rehabilitation programmes for lower-limb injuries.

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° (± 6.37°) to -81.93° (± 10.45°) 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.

Sprint interval training on the vertical treadmill improves aerobic and anaerobic running performance

The vertical treadmill (VertiRun) is an unresearched mode of exercise where users engage in a “running-like” action whilst body weight is supported by a recumbent bench and overhanging resistance cables are tethered to the user’s ankles. The purpose of this study was to determine the effects of training on a VertiRun and any cross-training effect on running performance. Thirty active males (age, 22±4 years; stature, 1.79±0.08 m; body mass, 78.5±12.6 kg) volunteered for this study. Participants’ aerobic and anaerobic running performance were determined by incremental maximum rate of oxygen consumption (VO2max) treadmill test and a maximum anaerobic running test (MART), respectively. Participants were matched and then randomly assigned to either a VertiRun group, 20-m shuttle sprint group or control group. The intervention consisted of 4–6, 30-sec all-out efforts with 4-min recovery between bouts, 3 days a week for 6 weeks. The pre- and postintervention VO2max and MART were analysed using a mixed repeated measures analysis of variance. MART increased by 4.5% in the VertiRun group (P=0.006) and 4% in the sprint group (P<0.001). VO2max increased by 6.2% in the VertiRun group (P=0.009) and 5.5% in the sprint group (P=0.020). The MART and VO2max of the control group were unchanged (P=0.910 and P=0.915, respectively). These data suggest that the VertiRun could be an effective cross-training mode for running and could supplement training programmes. Also, as VertiRun is a low-impact exercise it might be useful in the physical preparation of athletes returning to sport following lower limb injury.

TIME DOMAIN ANALYSIS OF OXYGEN UPTAKE KINETICS IN ELITE RUNNERS BY PSEUDO RANDOM BINARY SEQUENCE (PRBS) EXERCISE

Oxygen uptake kinetics assessed in the frequency domain are known to be differentially faster in elite endurance runners than in elite sprinters. Breath-by-breath data from PRBS testing have routinely been analysed by application of Fourier methods, however, it is possible to analyse the data in the time domain in the form of a Total Lag Time (TLT). In this study, correlational techniques were applied to yield an output response to a work rate input. An autocorrelation function was performed on the input work rate (WR) and a cross correlation function was performed on input (WR) and output (vO₂). The cross correlation function was analysed by fitting a linear summation of the ramp form of a two-component exponential function to a triangular pulse. Twelve elite male sprinters and 12 elite male endurance runners completed 3 identical PRBS cycles of 300 s with 20 s work rate changes between 25 and 85 W on an electrically braked cycle ergometer at a pedal cadence of 1 Hz. Oxygen uptake was measured on a breath-by-breath basis using a respiratory mass spectrometer. Statistical analysis using the analysis of variance revealed significantly faster oxygen uptake kinetics (TLT) in the elite endurance runners compared with the elite sprinters (33.3 s 3.39SD and 39.91 s 7.14SD respectively) (p < 0.01). The results of this study show that time domain analysis represents a possible alternative to frequency analysis in the study of oxygen uptake kinetics described by PRBS exercise.