Relationship of post-exercise muscle oxygenation and duration of cycling exercise

Stöcker et al. BMC Sports Science, Medicine and Rehabilitation (2016) 8:9 DOI 10.1186/s13102-016-0036-y RESEARCH ARTICLE Open Access Relationship of post-exercise muscle oxygenation and duration of cycling exercise Fabian Stöcker1*, Christoph Von Oldershausen1, Florian Kurt Paternoster2, Thorsten Schulz3 and Renate Oberhoffer3 Abstract Background: Aerobic adaptations following interval training are supposed to be mediated by increased local blood supply. However, knowledge is scarce on the detailed relationship between exercise duration and local post-exercise blood supply and oxygen availability. This study aimed to examine the effect of five different exercise durations, ranging from 30 to 240 s, on post-exercise muscle oxygenation and relative changes in hemoglobin concentration. Methods: Healthy male subjects (N = 18) performed protocol of five exercise bouts (30, 60, 90,
: an experimental 120, and 240 s) at 80 % of peak oxygen uptake V O2peak in a randomized order, separated by 5-min recovery periods. To examine the influence of aerobic fitness, we compared subjects with gas :exchange thresholds (GET) : : above 60 % V O2peak (GET60+) with subjects reaching GET below 60 % V O2peak (GET60−). V O2 and relative changes in concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, and total hemoglobin were continuously measured with near-infrared spectroscopy of the vastus lateralis muscle. Results: Post-exercise oxygen availability and local blood supply increased significantly until the 90-s exercise duration and reached a plateau thereafter. Considering aerobic fitness, the GET60+ group reached maximum post-exercise oxygen availability earlier (60 s) than the GET60− group (90 s). Conclusions: Our results suggest that (1) 90 s has evolved as the minimum interval duration to enhance local : oxygen availability and blood supply following cycling exercise at 80 % V O2peak ; whereas (2) 60 s is sufficient to trigger the same effects in subjects with GET60 + . Keywords: Muscle oxygenation, Hyperemia, Near-infrared spectroscopy, Interval training, Prior exercise Background High-intensity training (HIT) and high-intensity interval training or aerobic interval training (HIIT or AIT) are commonly accepted stimuli for improving anaerobic [1, 2] and aerobic [3–7] functions. Although the terms HIT and HIIT are sometimes used interchangeably, HIT usually refers to near-maximal or supramaximal exercise in: tensities (>90 % peak rate of oxygen uptake, V O2peak ) [6], whereas HIIT or AIT is often used in the context of exer: cise intensities between 80 % and 90 % V O2peak [3, 7, 8]. Acute microvascular responses to exercise (e.g., enhanced blood flow and local blood supply of small * Correspondence: 1 Center for Teaching and Learning, Technische Universität München, Connollystraße 32, 80809 München, Germany Full list of author information is available at the end of the article vessels in active tissue [9, 10]) have also been reported as long-term adaptations following HIT (e.g., by increased vasodilatory capacity [9] and augmented capillarization [5, 11]). Fu et al. showed these effects to be superior to those of moderate continuous training in patients with heart failure [7]. Furthermore, several studies have suggested that aerobic adaptations are facilitated by the above-mentioned microvascular mechanisms following HIIT/AIT [3, 4, 7]. Although the literature contains substantial knowledge on the acute effects of exercise on local muscle perfusion in general [10, 12–15], the acute post-exercise effects of different exercise durations on local muscle oxygen availability and blood supply have not yet been sufficiently examined. Most studies have focused on the influence of exercise intensity [16–19] or examined the © 2016 Stöcker et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Stöcker et al. BMC Sports Science, Medicine and Rehabilitation (2016) 8:9 effect of complete training sessions with only two different work-interval durations [20]. Relative changes in local, total hemoglobin concentration (ΔTHb) is a widely used parameter for bloodvolume changes in terms of capillary filling [21–23] and vasodilation [24] and can be noninvasively monitored using near-infrared spectroscopy (NIRS) [22]. With continuous-wave spectrometers, relative changes in the THb and deoxygenated (HHb) and oxygenated Hb (O2Hb) concentrations can be observed because of the distinct relative transparency of HHb and O2Hb for specific, near-infrared light wavelengths. The potential of exercise to prolong augmentation of the local blood supply could be an important determinant for metabolic adaptations. The aim of our study was to identify the association between durations of HIIT/ AIT exercise bouts and relative changes in post-exercise concentrations of THb, O2Hb, and HHb to examine (1) the post-exercise blood supply and (2) local oxygen availability. Methods Subjects A total of 18 healthy, physically active males volunteered to participate in the present study (see Table 1). Participants exercised at least 2 times per week in various sports, whereas aerobic exercise contributed an average of 4 ± 3 h per week. The inclusion criteria included age (18–35 years) and a physically active background. Exclusions included acute or chronic diseases (such as chronic heart disease), diabetes type II, epilepsy, and relevant diseases of the liver and kidney, as well as smoking and excessive alcohol consumption. All subjects were familiar with cycling exercise and exhaustive exercise testing. They received detailed information on the purpose and procedures of the study and their written informed consent was obtained. The local Ethics Committee of the Technische Universität München approved the study protocol (#67/14). Page 2 of 11 Test design and procedures Subjects reported to the laboratory for two sessions. We conducted preliminary tests (see section preliminary maximal testing) during the first session. During the second session, we aimed to examine the local blood supply in relation to exercise duration. Both sessions had to be completed within one week and had to be separated by at least 48 h to enable full recovery. The subjects were instructed not to perform exhaustive activity 24 h before each session and to avoid caffeinated and highcarbohydrate beverages 2 h before each session. Special bicycle shoes and pedals were not allowed during the ergometer tests (...truncated)