2.5 Therapeutic Exercise Principles

Foundational Principles

Overload, Specificity, Progression

• Overload: Tissues adapt only when loaded above their habitual demand.
• Specificity (SAID — Specific Adaptation to Imposed Demands): Adaptations are specific to the stress imposed — the muscle, joint angle, contraction type, and movement speed all matter.
• Progression: Once a stimulus is tolerated, dosage advances to continue adaptation.
• Reversibility: Gains are lost when the stimulus stops (detraining begins within roughly 1-2 weeks of inactivity).
• Individuality: Age, genetics, and pathology shape the response.

FITT-VP Framework

Frequency, Intensity, Time, Type, Volume, and Progression — the PTA documents the exact dosage delivered within the plan of care (POC) using these variables, which makes session-to-session changes auditable.

Dosing for Different Goals

American College of Sports Medicine (ACSM) targets commonly tested on the NPTE-PTA:

RM (repetition maximum) is the heaviest load liftable for the stated number of repetitions with good form. A scenario that names a goal (hypertrophy) maps to one row; a scenario that names a scheme (1-6 reps at 85%+) maps back to maximal strength. Watch for distractor schemes that mix an endurance rep count with a strength load.

Closed vs Open Kinetic Chain

• Closed kinetic chain (CKC): The distal segment is fixed (foot on the floor, hand on the wall). Examples: squat, leg press, push-up, lunge. CKC co-contracts agonist and antagonist groups and approximates joint surfaces, so it is favored early after surgery to protect grafts such as the anterior cruciate ligament.
• Open kinetic chain (OKC): The distal segment is free. Examples: seated knee extension, biceps curl, leg curl. OKC isolates a muscle group but creates more shear at the moving joint — which is why open-chain knee extension is restricted early after ACL reconstruction.

Muscle Contraction Types

Eccentric training has strong support in tendinopathy: the Alfredson protocol for Achilles tendinopathy and the Tyler twist for lateral epicondylalgia are common PTA-implemented examples. Eccentric loading also generates the most force per cross-section, which is why it produces the most delayed-onset muscle soreness.

Plyometrics

Plyometric drills (box jumps, depth jumps, lateral hops) train the stretch-shortening cycle and are placed late in a progression once the patient demonstrates:

• Pain-free full ROM
• Adequate strength (often a limb symmetry index of 80%+ for lower-extremity programs)
• Adequate single-leg balance and squat control
• Surgeon clearance for impact

Volume and Recovery

• DOMS typically peaks 24-72 hours after unaccustomed eccentric loading and resolves within about 5-7 days.
• Allow 48-72 hours between heavy resistance sessions for the same muscle group.
• The PTA monitors pain, swelling, and effusion; symptoms persisting beyond 24 hours after a session signal the prior dose was excessive, and the PTA reduces dosage within the POC and documents the change rather than pushing through. This 24-hour rule is the practical bridge between exercise physiology and the PTA's day-to-day modification authority.

Sequencing a Program and Selecting Stretch Technique

Beyond dosing tables, the NPTE-PTA asks the PTA to sequence exercise correctly across a rehab episode and to pick the right flexibility technique for the situation.

Typical Rehab Sequence

1. Protect and activate: isometrics and pain-free AROM early, before tissue tolerates load.
2. Restore motion and base strength: AAROM to AROM, closed-chain strengthening, neuromuscular control.
3. Build strength and endurance: progressive resistance using the goal-matched ACSM dosage.
4. Add speed and impact: eccentrics, then plyometrics, then sport- or job-specific drills with clearance.

Moving a patient up this ladder requires meeting the phase criteria the PT wrote; the PTA can adjust dosage within a rung but does not skip rungs.

Flexibility Techniques

Linking Modalities to Exercise

The PTA uses heat before stretch to raise tissue extensibility and ice after loading to control post-exercise inflammation. Modalities support TherEx but do not replace it; an item that offers "ultrasound only, discontinue exercise" for a tendinopathy is a distractor because progressive loading is the evidence-based core. As always, the PTA delivers these within the POC and reduces or holds dosage when the 24-hour soreness rule signals overload.