The motivational spectrum of exercise: Dissociable gradients of autonomous and controlled motivation across its amount, form, and durability

Sustaining physical activity, not merely starting it, is the harder half of the public health problem. Self-determination theory holds that the quality of motivation is tied to which half succeeds, yet population evidence is scarce. We designed and conducted the 2020 China National Fitness Survey and analysed 74,407 exercising adults aged 19 to 101 from every mainland province, measuring the motivational spectrum, psychological need satisfaction, and three axes of behaviour: amount, form, and durability. The autonomous-to-controlled continuum replicated across an independent adolescent sample, residence, and sex with full scalar invariance. Among exercising adults, autonomous motivation was associated with all three axes, and more strongly with a routine maintained for a year or longer than with meeting 150 min/week (OR per SD 1.47 against 1.34). Controlled motivation was associated with amount and form and showed no detectable association with durability. Amotivation showed its strongest inverse association with durability (0.78). Interaction tests confirmed the dissociation, the controlled gradient being weaker on durability than on amount within residence, chronic disease, and age strata below 80. Motivation quality is associated more with the durability of exercise than with its weekly volume.