Physiological reportsApr 24, 2026

Reduced oxygen delivery to muscles during moderate exercise in adults with long COVID

Long Covid Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Jun 27, 2026

Abstract

Essence

Adults with long COVID showed abnormal calf muscle oxygenation and poorer second-day response during repeated submaximal exercise testing.

Evidence

Repeated-exercise physiology study of 46 people with long COVID and 10 controls used two CPETs 24 hours apart with gastrocnemius NIRS monitoring and found shorter TSI elevation during exercise in long COVID, worsening on day 2.

Caveat

The small control group and NIRS/CPET endpoints identify an oxygenation pattern, not the causal mechanism of long-COVID symptoms.

Simplified

Long COVID (LC) is a multisystem condition that is linked to distinct pathologies including viral persistence, immunological dysfunction, endothelial damage, and mitochondrial dysfunction. To date, limited research has assessed peripheral tissue hypoxia to better understand LC symptom exacerbation. Forty-six people with LC and 10 controls (CON) completed two submaximal cardiopulmonary exercise tests (CPETs), separated by 24-h. Near-infrared spectroscopy (NIRS)-derived signals from the left gastrocnemius muscle were continuously monitored before, during, and after 2-day incremental CPET. CPET outcomes demonstrated impaired physical function on day 2 compared with day 1 for the LC cohort at rest and VT1. LC tissue saturation index (TSI%) remained elevated above rest for a shorter duration of exercise compared to CON on day 1 (2nd minute vs. 5th minute). On day 2, this response worsened for LC (Rest vs. 1st exercise minute: 63 ± 5% vs. 65 ± 5%; p < 0.05); meanwhile, CON exhibited sustained TSI% elevation throughout exercise above rest (Rest vs. 12th exercise minute: 62 ± 5% vs. 67 ± 4%; p < 0.05). LC TSI% remained elevated above rest for a shorter duration of exercise compared to CON, worsening for LC on day 2. LC showed rapid normalization of TSI%, suggesting impaired muscle oxygenation and recovery during repeated exercise.

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Reduced oxygen delivery to muscles during moderate exercise in adults with long COVID

Abstract

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