Table 1.

Summary of findings related to body composition, muscle function, and quality of life related to muscle health in individuals with long COVID

Body Composition
Reference	Body Compartment	Technique	Timeline	Selected Main Findings
Tanriverdi et al,32 2021	FM and FFM	BIA	>3 mo after COVID-19	•No differences in FM and FFM by disease severity.
van den Borst et al,29 2021	FFMI	BIA	3 mo after COVID-19	•19% had low FFMI, prevalence not different by disease severity.
van Gassel et al,30 2021	SMA, SMD, and IMAT	CT	3 mo after hospital discharge	•No differences in SMA and SMD between groups of physical performance. •IMAT was higher in patients with impaired physical performance.
Farr et al,31 2021	Diaphragm muscle thickness and thickening ratio	Ultrasound	Admitted to a rehabilitation after COVID-19	•Muscle thickness was not different between cases and controls. •Thickening ratio was reduced in patients with COVID-19.

Muscle Function
Reference	Muscle Function Evaluation	Assessment Test	Timeline	Selected Main Findings
van Gassel et al,30 2021	Muscle strength and physical performance	Handgrip strength	3 mo after COVID-19	•Trend for lower relative handgrip strength (no statistical difference in patients with impaired physical function).
Tanriverdi et al,32 2021	Muscle strength and physical performance	Handgrip and quadriceps muscle strength, and 4-m gait speed	>3 mo after COVID-19	•Disease severity did not relate to muscle weakness and function.
van den Borst et al,29 2021	Physical performance	6MWD	3 mo after COVID-19	•Greater impairment in individuals with moderate and severe disease.
Mittal et al,33 2021	Muscle strength	Handgrip strength	Not specified. Average: 3 mo	•Handgrip strength was significantly reduced in patients with COVID-19 with high fatigue scores.
Bellan et al,34 2021	Physical performance	SPPB and 2MWT	4- and 12-mo postdischarge	•31.5% and 7.1% of patients had poor physical function at 4- and 12-mo follow-up. •Decrease in the prevalence of impaired physical performance at 12 mo.

Quality of Life
Reference	QOL Test	Timeline	Selected Main Findings
van den Borst et al,29 2021	Nijmegen Clinical Screening Instrument	3 mo after COVID-19	•High prevalence of functional impairment, fatigue, and low QoL
van Gassel et al,30 2021	EQ-5D	3 mo after COVID-19	•Lower QoL in patients with impaired physical performance.
Cuerda et al,35 2021	EQ-5D-5 L	Ongoing study: patients are being followed for 12 mo	•71.2% unable to move or with moderate impairment. •75.5% with problems to perform daily activities.
Vaes et al,36 2021	EQ-5D-5 L	3 and 6 mo after COVID-19	•62% with moderate-to-extreme problems performing daily activities.

Abbreviations: 6MWD, 6-minute walking distance; 2MWT, 2-minute walk test; BIA, bioelectrical impedance analysis; COVID-19, coronavirus disease, 2019; CT, computerized tomography; EQ-5D, European Quality of Life Five Dimension; EQ-5D-5L, 5-level European Quality of Life Five Dimension; FFMI, fat-free mass index; FFM, fat-free mass; FM, fat mass; IMAT, intermuscular adipose tissue; QoL, quality of life; SMA, skeletal muscle area; SMD, skeletal muscle radiodensity; SPPB, short physical performance battery.