principles of training
Why does a body get fitter? Not from any single magic exercise, but from a handful of simple rules about how the body adapts when you ask more of it. These are the principles of training, and they hold whether you are coaching an athlete or rebuilding a patient's strength after surgery.
Five principles do most of the work. Overload: to improve, you must regularly stress the body a bit beyond its current comfort — gentle activity maintains but does not build. Specificity: you get better at what you actually practise, so training the legs builds the legs and aerobic work builds endurance, not strength. Progression: as the body adapts, the challenge must gradually increase, or improvement stalls. Reversibility: the gains are rented, not owned — stop training and the body fades back toward where it started ('use it or lose it'). Individuality: people respond differently to the same programme depending on age, genetics, illness, and starting point.
In rehabilitation these principles are the quiet logic behind every good exercise plan, and ignoring them causes real failures. Apply too little overload and a weak patient never gets stronger; ignore specificity and you build a skill the person never needed; forget reversibility and you let hard-won function slip away during a hospital stay. They are also a humbling reminder that there is no shortcut: adaptation takes repeated, progressive, relevant effort over weeks, and it can be lost far faster than it was gained.
A therapist rebuilding a patient's quadriceps after knee surgery keeps nudging the resistance up each week (overload and progression), chooses sit-to-stand because that is the task that matters (specificity), and warns the patient that skipping two weeks will undo much of the gain (reversibility).
The principles of training quietly govern every rep, set, and rest day of a good rehab plan.
Overload must be matched to a fragile patient: too little and nothing improves, too much and you provoke injury, pain, or a setback — judging the right dose is the art that distinguishes training from harm.