Muscle power — the product of force and velocity — declines earlier and more steeply with age than either strength or lean mass, making it a more sensitive marker of functional decline. A new framing term, performancespan, defines the years during which a person retains the physical capacity to do what daily life requires, and positions power as the endpoint of interest for both training programs and drug developers pursuing muscle preservation.
Key Points
- Muscle power declines earlier and faster than strength or mass
- Performancespan measures years of retained functional physical capacity
- Power may outperform mass as a muscle-preservation endpoint
Longevity Analysis
Rising from a chair, climbing stairs unassisted and recovering from a stumble depend on rate of force production, not peak load — a distinction that separates the capacity to live independently from numbers on a scan. Power output integrates motor unit recruitment speed, contractile tissue quality and mitochondrial capacity, which is why it degrades before mass does and why it responds to velocity-oriented resistance training rather than volume alone. Treating the ability to move quickly under load as a trackable signal, and training it deliberately across decades, reframes functional capacity as something measured and maintained rather than assumed.
Original published by Longevity.Technology, by Eleanor Garth.