Abstract. The purpose of the study was to compare muscle oxygenation as measured by two portable, wireless near-infrared spectroscopy (NIRS) devices under resting and dynamic conditions. A recently developed low-cost NIRS device (MOXY) was compared against an established PortaMon system that makes use of the spatially resolved spectroscopy algorithm. The influence of increasing external pressure on tissue oxygen saturation index (TSI) indicated that both devices are stable between 2 and 20 mmHg. However, above this pressure, MOXY reports declining TSI values. Analysis of adipose tissue thickness (ATT) and TSI shows a significant, nonlinear difference between devices at rest. The devices report similar TSI (%) values at a low ATT (<7 mm) (PortaMon minus MOXY difference is þ1.1 AE 2.8%) with the major subsequent change between the devices occurring between 7 and 10 mm; at ATT values >10 mm the difference remains constant (−14.7 AE 2.8%). The most likely explanation for this difference is the small source-detector separation (2.5 cm) in the MOXY resulting in lower tissue penetration into muscle in subjects with higher ATT. Interday test-retest reliability of resting TSI was evaluated on five separate occasions, with the PortaMon reporting a lower coefficient of variation (1.8% to 2.5% versus 5.7% to 6.2%). In studies on male subjects with low ATT, decreases in the TSI were strongly correlated during isometric exercise, arterial occlusion, and incremental arm crank exercise. However, the MOXY reports a greater dynamic range, particularly during ischemia induced by isometric contraction or occlusion (Δ74.3% versus Δ43.7%; hyperemia MAX-occlusion MIN). This study shows that in this subject group both MOXY and PortaMon produce physiologically credible TSI measures during rest and exercise. However, the absolute values obtained during exercise are generally not comparable between devices unless corrected by physiological calibration following an arterial occlusion. © 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.

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Introduction: New Zealand Blackcurrant Extract (NZBC) is a popular ergogenic aid used to improve endurance performance. The aim of this research was to determine the effects of a single bolus of NZBC on 10-km time trial (TT) cycling performance in normobaric hypoxia. Methods: A double-blind, crossover design study was conducted with trained cyclists. The effects of acute NZBC (900 mg) were compared with a placebo in normobaric hypoxia (NH) (FiO2 = 15.5%). Testing comprised of three laboratory-based visits for (1) familiarisation (and screening of TT performance before entry into study), (2) placebo and (3) NZBC, whereby a 10-km cycling TT was completed one hour after consumption. After completion of the TT blood lactate was assessed at four time-points in the 10 minutes following. Throughout the TT, power output (PO), rating of perceived exertion (RPE) and heart rate (HR) were recorded. Results: NZBC had no effect on TT cycling performance in NH compared to a placebo (1078.4 s [1009.4, 1147.4] and 1071.0 s [1006.4, 1137.5] respectively, p=0.31; d=-0.31). Additionally, no difference was observed for mean power output (p=0.20; d=0.39), HR (p=0.76; d=0.09) or at 1-km intervals for performance time (p=0.80), PO (p=0.77) or RPE (p=0.41). Post exercise blood lactate recovery did not differ between placebo and NZBC (p=0.42). Conclusion: Acute intake of NZBC has no effect on cycling performance or blood lactate recovery in simulated altitude.

The effect of compression tights on running economy is unclear. The purpose of this investigation was to assess the influence of compression tights on economy. Following an incremental test to exhaustion to determine aerobic capacity (V̇O2max) and peak running speed (vV̇O2max), twenty-six moderately endurance-trained males (28 ± 7 years; 76.1 ± 8.4 kg; V̇O2max = 54.7 ± 4.8 mL·kg−1·min−1) were allocated to either a 60% (n = 8), 62.5% (n = 9) or 65% vV̇O2max group (n = 9) using block randomisation. Participants ran for 15 min at the allocated vV̇O2max with compression tights and a non-compression control condition in a randomised, counter-balanced order, separated by seven days. Oxygen consumption (V̇O2) and expired carbon dioxide (V̇CO2) was measured to determine economy as caloric unit cost. No difference was observed between conditions for the 60% and 62.5% vV̇O2max groups, however economy was improved with compression at 65% vV̇O2max ( P < 0.01). Combined analysis of all participants revealed ΔRE (Δ = control − compression) correlated with relative aerobic capacity (%V̇O2max) ( r = 0.50, P < 0.01) but not running speed ( r = 0.04, P < 0.84). These data suggest that compression tights influence economy at 65% vV̇O2max or at relative exercise intensities of approximately 75–85%V̇O2max.

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