Li Zuo

Point:CounterpointCommentaries on Point:Counterpoint: Exercise training-induced bradycardiaINTRINSIC HEART RATE CHANGES WITH TRAINING AND AGING AFFECT RESTING AND MAXIMAL HEART RATECOMMENTARIES ON POINT:COUNTERPOINTCOMMENTARIES ON POINT:COUNTERPOINT

[Extract] TO THE EDITOR: In the recent Point:Counterpoint debate (2, 3), both research groups argued that training-induced bradycardia was a result of changes in intrinsic, sinoatrial node firing (i.e., intrinsic rate) or cardiac autonomic/parasympathetic regulation. While Billman (2) stated the possibility of a combination of these mechanisms, no further discussion of this was provided by either research group. Rather, the discussion focused on either mechanism and we would urge researchers to consider a more complex scenario – contribution of either mechanism that is moderated by other factors, or both mechanisms, potentially in combination with other elements (e.g., cardiac tructural changes). For example, training-induced bradycardia was reported in young adults with no changes in heart rate variability (HRV)(4), supporting an intrinsic rate mechanism. However, bradycardia was induced similarly with enhanced HRV in young adults following high-intensity exercise, supporting a cardiac autonomic mechanism (5).

Commentaries on Viewpoint: Could small-diameter muscle afferents be responsible for the ergogenic effect of limb ischemic preconditioning?

TO THE EDITOR: Cruz and colleagues (3) suggested that the ergogenic effect of ischemic preconditioning (IP) is in part caused by a reduced activity of sensory muscle afferents (SMA). This is an intriguing hypothesis that also further highlights some important implications of SMA for endurance performance. However, given the complex and integrative role of SMA, some points should be considered. First, unlike IP, spinal blockade of SMA did not provide any ergogenic effect on healthy subjects (1, 2), albeit the last most probably has a stronger suppression of SMA activity. Second, blockade of SMA demonstrated that perception of effort (RPE) is independent of SMA activity (4) and therefore changes in RPE after IP, should not be caused by a reduced activity of SMA. Finally, the ergogenic effect of IP might be also caused by a placebo effect. Indeed, the inability to effectively perform a sham-control IP treatment still remains. The placebo effect mainly relies on the assumption that participant believes that the intervention will alter results. For IP treatment, sham procedure commonly involves a very low cuff pressure that does not induce the same sensation experienced during IP treatment. Therefore participant expectancy about the treatment is unpredictable and might explain the improvement in performance and/or an altered pacing strategy (3, 5). Accordingly, future experiments should deserve more attention to reduce this confounding variable. In conclusion, future studies are required to confirm this hypothesis and more research is needed to understand the physiological mechanisms responsible for the ergogenic effect of IP on exercise performance.

Commentaries on Viewpoint: Origin of the forward-going “backward” waveARE CARDIOVASCULAR REFLEXES SENSITIVE TO SUBTLE ALTERATIONS IN ARTERIAL WAVEFORM PATTERNS?COMMENTARY ON VIEWPOINTTARGETING RESERVOIR-WAVE PRESSURE INDICES TO PREDICT CARDIOVASCULAR EVENTSCOMMENTARY ON VIEWPOINTCOMMENTARY ON VIEWPOINT

# ARE CARDIOVASCULAR REFLEXES SENSITIVE TO SUBTLE ALTERATIONS IN ARTERIAL WAVEFORM PATTERNS? {#article-title-2}nnto the editor: Mechanisms whereby cardiovascular reflexes might be sensitive to subtle changes in arterial waveform patterns is a fascinating area of inquiry. Fundamentally, arterial

Commentaries on Viewpoint: Could lobar flow sequencing account for convection-dependent ventilation heterogeneity in normal humans?

to the editor: Based on 4DCT imaging ([3][1]), this Viewpoint ([5][2]) investigates how lobar flow sequencing can contribute to generate a positive phase III slope. Results suggest that interlobar differences in expansion and deflation during the respiratory cycle contribute to Scond. We agree that

Commentaries on Viewpoint: Loopomics: a new functional approach to lifeTranscriptional Complexes as Functional Agents: Getting in Touch with the Genome Requires Teamwork at Multiple LevelsCommentary on ViewpointComplex Network of Redox Signaling Pathways

# Transcriptional Complexes as Functional Agents: Getting in Touch with the Genome Requires Teamwork at Multiple Levels {#article-title-2}nnto the editor: A major limitation in the integration of various “omics” data is the lack of a conceptual framework to integrate them. A new paradigm, termed

Commentaries on Viewpoint: Standardization of bed rest studies in the spaceflight context.

to the editor: The work presented by Sundblad et al. ([5][1]) is important and is likely to improve present international efforts to develop countermeasures against, for example, cardiovascular deconditioning during spaceflight. However, one aspect that is not addressed to a sufficient extent is the