Use It Or Lose It

Statement

Why it matters

Establishes movement as maintenance, not optional enhancement --- baseline function requires ongoing stimulus

Why Foundational

Foundational because tissue adaptation is bidirectional — strength, endurance, mobility, and bone density all decline without regular stimulus. Sarcopenia progresses ~1%/year after 30, accelerating after 60 without resistance training. Bone density requires ongoing mechanical loading (immobilised limbs lose density rapidly; astronauts in microgravity lose 1–2%/month). Mobility loss tracks position-time (sitting → hip flexor shortening, sedentary → ankle dorsiflexion loss). Establishes movement as maintenance, not optional enhancement — baseline function requires ongoing stimulus. Clinical implication: missing weeks of training during illness or injury produces measurable detraining within 2–4 weeks. Without sustained use, the loss is the rule.