Effects of cooling or warming of the distal upper limb on skin vascular conductance and brachial artery shear profiles during cycling exercise

ABSTRACT

The relative influence of skin vascular conductance in glabrous (G; palm) and non-glabrous (NG; dorsal and forearm) regions to upstream brachial artery-shear stress (BA-SS) profile are unknown. This study aimed to elucidate the effects of G and/or NG skin vascular conductance (VC), which were modulated by warming or cooling manipulation, on BA-shear rate (SR, an estimate of SS) during cycling exercise. Seven healthy subjects performed 60-min exercise. Between 20 and 50 min of the exercise, the NG+G or G skin region were warmed to 42°C or cooled to 15°C using a water bath. Throughout the protocol, diameter and blood velocity in BA and skin VCs in forearm and palm were measured. All measurements showed that a steady-state response was reached after 20 min of exercise. Subsequently, during cooling manipulation, forearm VC was significantly decreased, and the concomitant BA-SR profile was revealed (primarily characterized by decreased antegrade SR and increased retrograde SR) in the NG+G. Such changes were not observed in G alone. During warming manipulation, forearm VC and mean BA-SR significantly increased only in the NG+G. In conclusion, vascular response in NG skin possibly plays a major role in the modulation of BA-SS profile during cycling exercise.

KEYWORDS:

• Shear stress
• exercise
• vascular conductance
• thermal manipulation

Acknowledgments

The authors are grateful to Ms. A. Honma and Ms. S. Kamimura, Prefectural University of Hiroshima, for their contribution to data collection.

Disclosure statement

The authors declare that they have no competing interests.

Authors’ contributions

KM, YF, MYE, and HK contributed to the conception and design of the study, performed the experiments, and drafted the manuscript; HK, SN, and MM contributed to data collection and analysis; KM, HK, SN, MM, and AO contributed to the data analysis and interpretation; KM, HK, AO, and YF contributed to the intellectual content of the manuscript. All authors read and approved the final manuscript.

Additional information

Funding

This study was supported in part by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan [#17K01616 to Y. Fukuba, 18K17910 to K.Miura] and the Nakatomi Foundation.