The calf muscles (plantarflexors) are the most important muscles for walking, running and daily activities. Weakness of these muscles through aging and disease significantly impact a person's ability to walk and complete daily activities. By assessing calf strength, it is possible to identify people at risk of falls, and a condition called sarcopenia (which means loss of muscle mass, strength and function). Unfortunately, most of the studies that have examined this have used specialist equipment unavailable to hospital staff. Our study aims to use commercially available equipment to explore the relationship between plantarflexor muscle strength and physical performance in adults living with or without sarcopenia, including those at risk of it. The study will determine if stronger/weaker calf muscles associated with sarcopenia influence the ability to walk and do things more easily. We will complete strength tests of the calf, thigh and hand, assess walking using a special camera system, use an ultrasound scan to look at the Achilles tendon, use a scan to look at how stiff your calf muscles are, assess your body composition, complete a physical performance test and some questionnaires. Each participant will complete the measures during one clinic visit