Underwater near-infrared spectroscopy measurements of muscle oxygenation: laboratory validation and preliminary observations in swimmers and triathletes

Abstract

Abstract. The purpose of this research was to waterproof a near-infrared spectroscopy device (PortaMon, Artinis Medical Systems) to enable NIR measurement during swim exercise. Candidate materials were initially tested for waterproof suitability by comparing light intensity values during phantom-based tissue assessment. Secondary assessment involved repeated isokinetic exercises ensuring reliability of the results obtained from the modified device. Tertiary assessment required analysis of the effect of water immersion and temperature upon device function. Initial testing revealed that merely covering the PortaMon light sources with waterproof materials considerably affected the NIR light intensities. Modifying a commercially available silicone covering through the addition of a polyvinyl chloride material (impermeable to NIR light transmission) produces an acceptable compromise. Bland-Altman analysis indicated that exercise-induced changes in tissue saturation index (TSI %) were within acceptable limits during laboratory exercise. Although water immersion had a small but significant effect upon NIR light intensity, this resulted in a negligible change in the measured TSI (%). We then tested the waterproof device in vivo illustrating oxygenation changes during a 100 m freestyle swim case study. Finally, a full study compared club level swimmers and triathletes. Significant changes in oxygenation profiles when comparing upper and lower extremities for the two groups were revealed, reflecting differences in swim biomechanics. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Performance comparison of the MOXY and PortaMon near-infrared spectroscopy muscle oximeters at rest and during exercise

“…The MOXY devices report a greater absolute ΔTSI change when compared with the PortaMon at both 30% and 50% MVC. The ΔTSI observed with the current PortaMon devices is similar to that of a previous study, also utilizing a PortaMon device, 8 reporting a ΔTSI reduction of ∼6% and 11% from baseline at 30% and 50% MVC, respectively. Very few studies have utilized the MOXY device, however, of those available, the present ΔTSI at 30% MVC is similar to that observed in the gastrocnemius by supine individuals undertaking a plantar flexion exercise against a 6-kg weight (∼37% versus ∼38%).…”

“…4 In support of this, positive peripheral muscle oxygenation adaptations have been reported as a consequence of cycling sprint interval training, demonstrating that NIRS has the potential to assess the effectiveness of training interventions at the level of the individual athlete. 7 To be effective outside the research laboratory, in an applied exercise environment, there is a requirement for low-cost, portable NIR technology with telemetric capability with the ability to withstand the rigors of sporting environments such as in swimming, 8 short track speed skating, 9 and trail running.…”

Electrically evoked wrist extensor muscle fatigue throughout repetitive motion as measured by mechanomyography and near-infrared spectroscopy

“…It reflects the dynamic balance between oxygen supply and oxygen demand in the tissue microcirculation [35][36][37]. Previous studies have shown that TSI reflects muscle oxygenation more accurately than HHb [35,38].…”

Recent developments in near-infrared spectroscopy (NIRS) for the assessment of local skeletal muscle microvascular function and capacity to utilise oxygen

“…The technology has been developed in small, wireless instruments showing good intra- and inter-subject reproducibility39, 40 and recently, the TSI signal was found to be stable despite waterproofing and water submersion when a portable CW NIRS device was used during swimming 41 …”