This study aims to see if ultrasound can be used as a reliable and valid method to measure fatty infiltration, muscle thickness and muscle architecture to provide a quick, cheap and mobile alternative measure of muscle quality to MRI.

The MRS and MRI images will be used to validate the ultrasound images.

A key hallmark of the natural biology of ageing is a progressive loss of skeletal muscle mass, strength and aerobic capacity, termed 'sarcopenia' (Cruz-Jentoft et al. 2019a). The association between muscle loss (mass and quality) and increased incidence of falls, fractures, metabolic disease and other health complications is well established. Despite exercise and physiotherapy, recovery from these is often incomplete and studies have failed to identify fully effective countermeasures (Reeves et al, 2005). Ways to objectively measure the clinical effectiveness of the countermeasures are also limited.

Muscle quality can be measured in terms of muscle thickness, architecture (pennation angle and fascicle length) and fatty infiltration. At present ultrasound muscle thickness and architecture have been shown against MRI to be a reliable and valid but fatty infiltration can only be measured reliably using MRI. MRI is an expensive, time consuming and immobile technique limiting its use as a clinical tool in a rehabilitative setting. Finding a cheaper, quicker and mobile alternative, such as ultrasound, would enable clinicians to gather useful information on patient muscle quality in an objective manner and use this information to tailor treatment accordingly.

15 old (>50y) and 15 young (<40y) will be recruited. MRI, MRS and Ultrasound will be measured in each participant in calf and thigh muscle, at the same location within a 1 hour time frame.

MRI and MRS will provide the validation to ultrasound fatty infiltration.

Inclusion Criteria:

- Age <40y or >50yrs

Exclusion Criteria:

1. Significant cognitive deficits and the inability to follow directions during assessment.
2. Neurological, neuromuscular, or musculoskeletal disorders that could impair the quality of the muscle. eg. CP, muscular dystrophy or SCI
3. Prosthesis with metalwork, eg. metal work from surgery
4. Aneurysm clip in situ
5. No metal work anywhere, history of metal fragments in eyes, spinal cord or brain.
6. Previous exposure to metal flakes and metallic injury.
7. No external implants; cochlear implant, spinal cord simulator, pacemaker or other implanted electronic devices.
8. Non-removal hearing aids
9. FEMALE ONLY Not pregnant
10. Not claustrophobic

General population

Participant data will not be shared.