BACKGROUND: Near-infrared spectroscopy (NIRS) measurements of oxygenation reflect O2 delivery and utilization in exercising muscle and may improve detection of a critical exercise threshold.PURPOSE: First, to detect an oxygenation breakpoint (Δ[O2HbMb-HHbMb]-BP) and compare this breakpoint to ventilatory thresholds during a maximal incremental test across sexes and training status. Second, to assess reproducibility of NIRS signals and exercise thresholds and investigate confounding effects of adipose tissue thickness on NIRS measurements.METHODS: Forty subjects (10 trained male cyclists, 10 trained female cyclists, 11 endurance trained males and 9 recreationally trained males) performed maximal incremental cycling exercise to determine Δ[O2HbMb-HHbMb]-BP and ventilatory thresholds (VT1 and VT2). Muscle haemoglobin and myoglobin O2 oxygenation ([HHbMb], [O2HbMb], SmO2) was determined in m. vastus lateralis. Δ[O2HbMb-HHbMb]-BP was determined by double linear regression. Trained cyclists performed the maximal incremental test twice to assess reproducibility. Adipose tissue thickness (ATT) was determined by skinfold measurements.RESULTS: Δ[O2HbMb-HHbMb]-BP was not different from VT1, but only moderately related (r = 0.58-0.63, p<0.001). VT1 was different across sexes and training status, whereas Δ[O2HbMb-HHbMb]-BP differed only across sexes. Reproducibility was high for SmO2 (ICC = 0.69-0.97), Δ[O2HbMb-HHbMb]-BP (ICC = 0.80-0.88) and ventilatory thresholds (ICC = 0.96-0.99). SmO2 at peak exercise and at occlusion were strongly related to adipose tissue thickness (r2 = 0.81, p<0.001; r2 = 0.79, p<0.001). Moreover, ATT was related to asymmetric changes in Δ[HHbMb] and Δ[O2HbMb] during incremental exercise (r = -0.64, p<0.001) and during occlusion (r = -0.50, p<0.05).CONCLUSION: Although the oxygenation threshold is reproducible and potentially a suitable exercise threshold, VT1 discriminates better across sexes and training status during maximal stepwise incremental exercise. Continuous-wave NIRS measurements are reproducible, but strongly affected by adipose tissue thickness.
The results of this study indicate that whole body metabolic and cardiovascular responses to 140 min of either steady state or variable intensity exercise at the same average intensity are similar, despite differences in skeletal muscle carbohydrate metabolism and recruitment
There is increasing interest for the use of Virtual Reality (VR) in the field of sustainable transportation and urban development. Even though much has been said about the opportunities of using VR technology to enhance design and involve stakeholders in the process, implementations of VR technology are still limited. To bridge this gap, the urban intelligence team of NHTV Breda University of Applied Sciences developed CycleSPEX, a Virtual Reality (VR) simulator for cycling. CycleSpex enables researchers, planners and policy makers to shape a variety of scenarios around knowledge- and design questions and test their impact on users experiences and behaviour, in this case (potential) cyclists. The impact of infrastructure enhancements as well as changes in the surrounding built environment can be tested, analysed an evaluated. The main advantage for planners and policy makers is that the VR environment enables them to test scenarios ex-ante in a safe and controlled setting.“The key to a smart, healthy and safe urban environment lies in engaging mobility. Healthy cities are often characterized by high quality facilities for the active modes. But what contributes to a pleasant cycling experience? CycleSPEX helps us to understand the relations between cyclists on the move and (designed) urban environments”