Microcirculatory and Metabolic Responses during Voluntary Cycle Ergometer Exercise with a Whole-Body Neuromuscular Electrical Stimulation Device
Round 1
Reviewer 1 Report
Dear Authors,
The experiment is interesting but raises some doubts about its practical implications. It involved relatively young people who are rarely affected by cardiovascular diseases, much less frequently than the elderly. Are you sure that your findings can / should be directly applied to older people, especially those with cardiovascular conditions? This aspect should be addressed the Discussion section.
While physiotherapy has been using electrical stimulation (NMES) for many years now, the way it you applied it is relatively new and raises some doubts. The electrical stimulation of any voluntarily induced contraction (or vice versa) obviously makes sense because it increases the contraction force (see your work "Effect of the Combination of Whole-Body Neuromuscular Electrical Stimulation and Voluntary Exercise on Metabolic Responses in Human " ("… .During VE, contraction and relaxation times of NMES were synchronized with voluntary exercise,…. "), but forcing muscles that should be inactive during cycle ergometer exercise or should contract with a force appropriate to the external load is very likely to disturb movement smoothness and muscle work (imagine, for instance, a long-jumper whose tibialis anterior muscle contracts following the application of NMES the same moment he or she is taking off). The muscles of the lower limbs are not the only ones to be engaged during cycle ergometer exercise; the muscles of the torso and upper limbs, which were also stimulated in the experiment, also work in some smooth, repetitive way. During the stimulation you describe, the contraction and relaxation times of NMES were not synchronized with voluntary contraction and relaxation of the muscles (right?). This aspect should be addressed in the Discussion section.
Line 12 and 13 (2.4. Study Protocol)
“The device (SIXPAD; MTG Co., Ltd., Nagoya, Japan) and WB-NMES protocol have been previously described [10].”
In line 113, you make a reference to your reportthat does not precisely describe the electrical stimulation procedure (including current parameters). I would recommend citing another work of yours, which is more informative on this point ("Effect of the Combination of Whole-Body Neuromuscular Electrical Stimulation and Voluntary Exercise on Metabolic Responses in Human").
Line 134-136
“Participants were instructed to pedal at 50–60 revolutions per minute; the session was terminated when they could no longer pedal at more than 50 revolutions per minute.”
Do you mean that the post-exercise measurements were taken at different times after the start of the test depending on when a participant completed the test? Explain it clearly, please.
Author Response
Response to Comments by Reviewer 1
Thank you for carefully reviewing our manuscript entitled “Microcirculatory and Metabolic Responses During Voluntary Cycle Ergometer Exercise with a Whole-body Neuromuscular Electrical Stimulation Device” Manuscript ID: applsci-1491934
Your comments were very helpful for revising and improving our manuscript, as well as for offering important guidance for our research. We hope that our responses and revisions have adequately addressed your concerns.
Comment 1
The experiment is interesting but raises some doubts about its practical implications. It involved relatively young people who are rarely affected by cardiovascular diseases, much less frequently than the elderly. Are you sure that your findings can / should be directly applied to older people, especially those with cardiovascular conditions? This aspect should be addressed the Discussion section.
Authors’ Response 1
Thank you for your comment regarding clinical feasibility for elderly. A large amount of evidence has been accumulated in EMNS for the vulnerable to exercise, including the elderly. The following studies are currently underway to verify the safety and clinical value of WB-EMNS + cycle ergometer exercise in elderly patients with cardiovascular diseases. We added a sentence in the conclusion section. Page 13, Lines 324-325.“Hybrid exercise provides better time-saving training according to oxygen uptake than the cycle ergometer exercise at the same level in healthy young people. Further study is planned to apply the hybrid therapy to the elderly, especially those with associated cardiovascular diseases.”
　
Comment 2
While physiotherapy has been using electrical stimulation (NMES) for many years now, the way it you applied it is relatively new and raises some doubts. The electrical stimulation of any voluntarily induced contraction (or vice versa) obviously makes sense because it increases the contraction force (see your work "Effect of the Combination of Whole-Body Neuromuscular Electrical Stimulation and Voluntary Exercise on Metabolic Responses in Human " ("… During VE, contraction and relaxation times of NMES were synchronized with voluntary exercise,…. "), but forcing muscles that should be inactive during cycle ergometer exercise or should contract with a force appropriate to the external load is very likely to disturb movement smoothness and muscle work (imagine, for instance, a long-jumper whose tibialis anterior muscle contracts following the application of NMES the same moment he or she is taking off). The muscles of the lower limbs are not the only ones to be engaged during cycle ergometer exercise; the muscles of the torso and upper limbs, which were also stimulated in the experiment, also work in some smooth, repetitive way. During the stimulation you describe, the contraction and relaxation times of NMES were not synchronized with voluntary contraction and relaxation of the muscles (right?). This aspect should be addressed in the Discussion section.
Authors’ Response 2
Thank you for your comments that approach the core of the combination therapy. I addressed this issue in the Discussion section. Page 12, Lines 272-277.　“The contraction and relaxation times of NMES were not synchronized with voluntary contraction and relaxation of the muscles. NMES causes the antagonist muscles to contract, causing more muscle fibers in the main action muscles to work. Therefore, it has been shown that a high load can be applied to the skeletal muscle by combining electrical stimulation even with low to moderate load exercise. [20]”
20.Wahl P, Hein M, Achtzehn S, Bloch W, Mester J. Acute effects of superimposed electromyostimulation during cycling on myokines and markers of muscle damage. J Musculoskelet Neuronal Interact 2015;15(1):53-9.
Comment 3
(2.4. Study Protocol)
“The device (SIXPAD; MTG Co., Ltd., Nagoya, Japan) and WB-NMES protocol have been previously described [10].”
In line 113, you make a reference to your report　that does not precisely describe the electrical stimulation procedure (including current parameters). I would recommend citing another work of yours, which is more informative on this point ("Effect of the Combination of Whole-Body Neuromuscular Electrical Stimulation and Voluntary Exercise on Metabolic Responses in Human").
Authors’ Response 3
Page 3, Lines 112-122. Thank you for your appropriate suggestion. We have corrected the references and described the electrical stimulation procedure in detail. “The device (SIXPAD; MTG Co., Ltd., Nagoya, Japan) and WB-NMES protocol have been previously described [6,10]. NMES was applied to the anterior and posterior upper arm, chest, back, abdominal, abdominal oblique, gluteus and anterior and posterior thigh muscles. The intensity of the electrical stimulation for WB-NMES was determined after three training sessions for WB-NMES. All participants underwent the experiment for a total of three days. NMES was performed at 20 Hz, with 4 seconds of stimulation followed by 4 seconds of pause. The output voltage and effective current of the device ranged from level 1 (10.6 V, 1.7 mArms) to level 100 (70.0 V, 11.4 mArms), and the intensity of the stimulation was adjustable for each site. With a numeric rating scale of 7, the stimulus intensity was set to be able to pedal a CPX warm-up electrically braked cycle ergometer (20 W). The stimulation intensity was the same from warm-up to the maximum load.”
Comment 4
- Line 134-136
“Participants were instructed to pedal at 50–60 revolutions per minute; the session was terminated when they could no longer pedal at more than 50 revolutions per minute.”
Do you mean that the post-exercise measurements were taken at different times after the start of the test depending on when a participant completed the test? Explain it clearly, please.
Authors’ Response 4
Thank you for your comment on the protocol of cardiopulmonary exercise test. In the present study, symptom limited CPX was performed with ramp protocols that are commonly used in CPX. Therefore, exercise time slightly varied depending on the subject.
Page 4 Lines 139-143.
“Symptom limited CPX was performed with ramp protocols commonly used in CPX; the session was terminated when they could no longer pedal at more than 50 revolutions per minute. Therefore, exercise time slightly varied depending on the subject. The assessment was conducted such that participants could not see the load on the cycle ergometer. Post-exercise measurements were taken just after symptom limited CPX. In the hybrid CPX, the same electrical stimulation intensity was used from warm-up to maximum exercise load.”
　
Reviewer 2 Report
In the current paper, the authors compared the effects of cycle ergonometric exercise to a hybrid approach composed of cycle ergonometric exercise to novel whole-body neuromuscular electrical stimulation (WB-NMES).
Major concerns:
- The increase of anaerobic metabolism could be due to an enhancement of the hypoxia-inducible factor (HIF). The authors should investigate the role of this player in the metabolism alterations (nuclear protein translocation and gene expression of its target genes)
- The author should analyze the increase of glycolytic enzymes gene expression.
- A study of the different responses between men and women to the treatment could improve the article's impact.
Author Response
Response to Comments by Reviewer 2
Thank you for carefully reviewing our manuscript entitled “Microcirculatory and Metabolic Responses During Voluntary Cycle Ergometer Exercise with a Whole-body Neuromuscular Electrical Stimulation Device” Manuscript ID: applsci-1491934
Your comments were very helpful for revising and improving our manuscript, as well as for offering important guidance for our research. We hope that our responses and revisions have adequately addressed your concerns.
Comment 1
The increase of anaerobic metabolism could be due to an enhancement of the hypoxia-inducible factor (HIF). The authors should investigate the role of this player in the metabolism alterations (nuclear protein translocation and gene expression of its target genes)
Authors’ Response 1
Thank you for your valuable comment. Yes, we added the following explanation and 2 references regarding hypoxia-inducible factor (HIF) 1α and glycolytic capacity. We are very sorry that we could not additional experiments for HIF because of limited time for revision (10 days). Page 12, Lines 297-305 “NMES can increase skin perfusion via vasodilation [25]. NMES has been reported to enhance hypoxia-inducible factor (HIF) 1α and vascular endothelial growth factor, which may have accelerated wound healing of diabetic foot ulcers. [26] HIF-1α is highly expressed in fast-twitch muscle (type II), which has a high glycolytic capacity. Therefore, sustained contraction of fast-twitch muscle by WB-NMES may have elevated HIF-1α and lactate production. Vasodilation due to lactate accumulation in addition to NO-induced vasodilation may have offset the deterioration of sublingual and nailfold microcirculation due to exercise induced activation of the sympathetic nervous system.”
25.　Petrofsky, J.;Schwab, E.;Lo, T.;Cúneo, M.; George, J.; Kim, J.; Al-Malty, A. Effects of electrical stimulation on skin blood flow in controls and in and around stage III and IV wounds in hairy and non hairy skin. Med Sci Monit 2005, 11 (7), Cr309-16.
26.　Asadi, M. R.; Torkaman, G.; Hedayati, M.;Mohajeri-Tehrani, M. R.; Ahmadi, M.; Gohardani, R. F. Angiogenic effects of low-intensity cathodal direct current on ischemic diabetic foot ulcers: A randomized controlled trial. Diabetes Res Clin Pract 2017, 127, 147-155.
Comment 2
The author should analyze the increase of glycolytic enzymes gene expression.
Authors’ Response 2
Thank you for your valuable comment. We are very sorry that we could not additional experiments for glycolytic enzymes gene expression because of limited time for revision (10 days). We added the sentences as shown above. Page 12, Lines 297-305.
Comment 3
A study of the different responses between men and women to the treatment could improve the article's impact.
Authors’ Response 3
Thank you for your comment. Due to the limited number of study subjects, we could not mention about the different responses to treatment between men and women. We have addressed it in the limitation section.
Round 2
Reviewer 2 Report
Thank you for your responses.
