Which factor explains ROM variation due to the series of joints involved and functional demands?

• A. Age-related changes
• B. Individual variation
• C. Height
• D. Strength

Answer: (B)

When a movement involves a series of joints, how far you can go is shaped by your unique body and how you use it. This is individual variation: differences in anatomy (like limb length and joint structure), soft-tissue properties (tendon and ligament flexibility), and habitual movement patterns or training that influence how joints move together under functional demands. Because these personal factors vary from person to person, ROM across multi-joint tasks shows a lot of variation that is best explained by individual differences.

Age-related changes can alter ROM, but they describe a general aging trend rather than the specific differences between people. Height might influence reach in some tasks but doesn’t account for the wide ROM differences across joint chains. Strength affects how much of the available ROM you can actively achieve, but the inherent end-range limits set by joint and tissue properties are what primarily define ROM across individuals.