Exercise training comprising of single 20-s cycle sprints does not provide a sufficient stimulus for improving maximal aerobic capacity in sedentary individuals.

PURPOSE: Sprint interval training (SIT) provides a potent stimulus for improving maximal aerobic capacity ([Formula: see text]), which is among the strongest markers for future cardiovascular health and premature mortality. Cycling-based SIT protocols involving six or more 'all-out' 30-s Wingate sprints per training session improve [Formula: see text], but we have recently demonstrated that similar improvements in [Formula: see text] can be achieved with as few as two 20-s sprints. This suggests that the volume of sprint exercise has limited influence on subsequent training adaptations. Therefore, the aim of the present study was to examine whether a single 20-s cycle sprint per training session can provide a sufficient stimulus for improving [Formula: see text]. METHODS: Thirty sedentary or recreationally active participants (10 men/20 women; mean ± SD age: 24 ± 6 years, BMI: 22.6 ± 4.0 kg m(-2), [Formula: see text]: 33 ± 7 mL kg(-1) min(-1)) were randomised to a training group or a no-intervention control group. Training involved three exercise sessions per week for 4 weeks, consisting of a single 20-s Wingate sprint (no warm-up or cool-down). [Formula: see text] was determined prior to training and 3 days following the final training session. RESULTS: Mean [Formula: see text] did not significantly change in the training group (2.15 ± 0.62 vs. 2.22 ± 0.64 L min(-1)) or the control group (2.07 ± 0.69 vs. 2.08 ± 0.68 L min(-1); effect of time: P = 0.17; group × time interaction effect: P = 0.26). CONCLUSION: Although we have previously demonstrated that regularly performing two repeated 20-s 'all-out' cycle sprints provides a sufficient training stimulus for a robust increase in [Formula: see text], our present study suggests that this is not the case when training sessions are limited to a single sprint.

Determining the partial photoionization cross-sections of ethyl radicals.

Using a crossed laser-molecular beam scattering apparatus, these experiments photodissociate ethyl chloride at 193 nm and detect the Cl and ethyl products, resolved by their center-of-mass recoil velocities, with vacuum ultraviolet photoionization. The data determine the relative partial cross-sections for the photoionization of ethyl radicals to form C2H5+, C2H4+, and C2H3+ at 12.1 and 13.8 eV. The data also determine the internal energy distribution of the ethyl radical prior to photoionization, so we can assess the internal energy dependence of the photoionization cross-sections. The results show that the C2H4++H and C2H3++H2 dissociative photoionization cross-sections strongly depend on the photoionization energy. Calibrating the ethyl radical partial photoionization cross-sections relative to the bandwidth-averaged photoionization cross-section of Cl atoms near 13.8 eV allows us to use these data in conjunction with literature estimates of the Cl atom photoionization cross-sections to put the present bandwidth-averaged cross-sections on an absolute scale. The resulting bandwidth-averaged cross-section for the photoionization of ethyl radicals to C2H5+ near 13.8 eV is 8+/-2 Mb. Comparison of our 12.1 eV data with high-resolution ethyl radical photoionization spectra allows us to roughly put the high-resolution spectrum on the same absolute scale. Thus, one obtains the photoionization cross-section of ethyl radicals to C2H5+ from threshold to 12.1 eV. The data show that the onset of the C2H4++H dissociative photoionization channel is above 12.1 eV; this result offers a simple way to determine whether the signal observed in photoionization experiments on complex mixtures is due to ethyl radicals. We discuss an application of the results for resolving the product branching in the O+allyl bimolecular reaction.