Muscle volume, functionality and metabolic resilience during recovery following severe COVID-19

Abstract

Introduction: Following hospitalisation with SARS-Cov2 infection a large proportion of individuals report fatigue as a persisting symptom. Here, we performed a detailed study of the muscle for insight into underlying mechanisms.

Method: Adults were recruited at 5-7 months following hospital discharge for severe SARS-Cov2 infection (n=21), along with control volunteers (n=10) of a similar age, gender, ethnicity and body mass. Perceived fatigue was estimated using the fatigue severity scale. The short physical performance battery test determined habitual functionality, alongside isometric quadriceps strength normalised for appendicular mass and isokinetic force loss during 20 knee extensions (Cybex Norm dynamometer). Leg muscle volume, and phosphocreatine (PCr) resynthesis during recovery from ischemic plantar flexion exercise (an index of muscle metabolic resilience) were quantified using MRI and 31P MRS. Student t-test was used to detect differences between groups and all data are mean (SD).

Results: Patients (P) reported greater perception of fatigue and demonstrated worse habitual functionality compared to controls (C). However, leg volume [P: 2,578 (303) cm3/m2 vs C: 2,384 (289) cm3/m2, p=0.1], strength [P: 21.8 (4.1) Nm/kg vs C: 21.1 (4.5) Nm/kg, p=0.7], force loss [P: 25% (6) vs C: 21% (10), p=0.1] and PCr recovery kinetics (Qmax) [P: 25.8 (11.3) vs C: 22.8 (8.7), p=0.5] were not different.

Conclusion: Despite greater perception of fatigue and lower habitual functionality, patients recovering from severe COVID-19 infection did not have altered muscle volume, strength, fatiguability or metabolic resilience compared to controls.