Comparison of the muscle oxygenation during submaximal and maximal exercise tests in patients post-[COVID-19]... 2024 Başak Kavalcı Kol et al

Full title: Comparison of the muscle oxygenation during submaximal and maximal exercise tests in patients post-coronavirus disease 2019 syndrome with pulmonary involvement

ABSTRACT

Introduction
Pulmonary involvement is prevalent in patients with coronavirus disease 2019 (COVID-19). Arterial hypoxemia may reduce oxygen transferred to the skeletal muscles, possibly leading to impaired exercise capacity. Oxygen uptake may vary depending on the increased oxygen demand of the muscles during submaximal and maximal exercise.

Objective
This study aimed to compare muscle oxygenation during submaximal and maximal exercise tests in patients with post-COVID-19 syndrome with pulmonary involvement.

Methods
Thirty-nine patients were included. Pulmonary function (spirometry), peripheral muscle strength (dynamometer), quadriceps femoris (QF) muscle oxygenation (Moxy® device), and submaximal exercise capacity (six-minute walk test (6-MWT)) were tested on the first day, maximal exercise capacity (cardiopulmonary exercise test (CPET)) was tested on the second day. Physical activity level was evaluated using an activity monitor worn for five consecutive days. Cardiopulmonary responses and muscle oxygenation were compared during 6-MWT and CPET.

Results
Patients’ minimum and recovery muscle oxygen saturation were significantly decreased; maximum total hemoglobin increased, heart rate, blood pressure, breathing frequency, dyspnea, fatigue, and leg fatigue at the end-of-test and recovery increased in CPET compared to 6-MWT (p < .050). Peak oxygen consumption (VO2peak) was 18.15 ± 4.75 ml/min/kg, VO2peak; percent predicted < 80% was measured in 51.28% patients. Six-MWT distance and QF muscle strength were less than 80% predicted in 58.9% and 76.9% patients, respectively.

Conclusions
In patients with post-COVID-19 syndrome with pulmonary involvement, muscle deoxygenation of QF is greater during maximal exercise than during submaximal exercise. Specifically, patients with lung impairment should be evaluated for deoxygenation and should be taken into consideration during pulmonary rehabilitation.

Paywall, https://www.tandfonline.com/doi/full/10.1080/09593985.2024.2327534

 

This is the Moxy system which is a commercial wearable NIRS device being used for athlete training (it's not cheap). Here is a relevant recent paper which could stay linked in this thread —

Comparing the reliability of muscle oxygen saturation with common performance and physiological markers across cycling exercise intensity
Yogev, Assaf; Arnold, Jem; Nelson, Hannah; Clarke, David C.; Guenette, Jordan A.; Sporer, Ben C.; Koehle, Michael S.

Wearable near-infrared spectroscopy (NIRS) measurements of muscle oxygen saturation (SmO2) demonstrated good test-retest reliability at rest. We hypothesized SmO2 measured with the Moxy monitor at the vastus lateralis (VL) would demonstrate good reliability across intensities. For relative reliability, SmO2 will be lower than volume of oxygen consumption (VO2) and heart rate (HR), higher than concentration of blood lactate accumulation ([BLa]) and rating of perceived exertion (RPE).

We aimed to estimate the reliability of SmO2 and common physiological measures across exercise intensities, as well as to quantify within-participant agreement between sessions. Twenty-one trained cyclists completed two trials of an incremental multi-stage cycling test with five-minute constant workload steps starting at 1.0 watt per kg bodyweight (W∙kg-1) and increasing by 0.5 W∙kg-1 per step, separated by one-minute passive recovery intervals until maximal task tolerance. SmO2, HR, VO2, [BLa], and RPE were recorded for each stage. Continuous measures were averaged over the final 60 seconds of each stage. Relative reliability at the lowest, median, and highest work stages was quantified as intraclass correlation coefficient (ICC). Absolute reliability and within-subject agreement were quantified as standard error of the measurement (SEM) and minimum detectable change (MDC).

Comparisons between trials showed no significant differences within each exercise intensity for all outcome variables. ICC for SmO2 was 0.81-0.90 across exercise intensity. ICC for HR, VO2, [BLa], and RPE were 0.87-0.92, 0.73-0.97, 0.44-0.74, 0.29-0.70, respectively. SEM (95% CI) for SmO2 was 5 (3 - 7), 6 (4 - 9), and 7 (5 - 10) %, and MDC was 12, 16, and 18%. Our results demonstrate good-to-excellent test-retest reliability for SmO2 across intensity during an incremental multi-stage cycling test. VO2 and HR had excellent reliability, higher than SmO2. [BLa] and RPE had lower reliability than SmO2.

Muscle oxygen saturation measured by wearable NIRS was found to have similar reliability to VO2 and HR, and higher than [BLa] and RPE across exercise intensity, suggesting that it is appropriate for everyday use as a non-invasive method of monitoring internal load alongside other metrics.

Link | PDF (Frontiers in Sports and Active Living) [Open Access]

 

I think this team started off with patients with clear evidence of lung injury (mild-moderate changes on CT with the majority less than 50% involved lungs), a minority having required ventilation acutely. As Hutan says, not directly comparable to our typical ME-phenotype LC situation. They confirmed abnormal lung function, as you might expect. However the findings may indicate problems distinct from (or at least not directly related to) the lung injury. I wonder if the findings could be correlated with other recent Long Covid muscle findings.

I'll re-order some of the sentence structure in their following quotes to make it easier to follow.

So they suggest the lungs might be causing a problem via simple hypoxaemia

So here, they're suggesting there may be a separate problem in the muscles and their mitochondria (which relates to Wüst et al)

Problems with peripheral oxygen extraction have been highlighted by Systrom et al (which they indeed reference in the passage above).

 

I would like to see the Moxy system applied to acutely mild/asymptomatic patients, like the Wüst cohort. However, more than just evaluating response to exercise as in this paper, I'm interested to see what happens with variations day-to-day. I wonder whether on bad days where my leg muscles feel "lactic" and fatigued there might also be a measurable difference in SmO2, perhaps part of PEM. So I'm tempted to see if I can get my hands on a Moxy device and do a little pilot trial with me and @Kiwipom vs our respective healthy age/sex-matched friends.