Achilles tendon ruptures (ATR) are among the most dramatic injuries in sport, usually happening during explosive movements like sprinting or jumping. Surgical repair is often necessary, but the real work is the recovery. At PFPT, we run a four-phase model built to protect the repair while preparing the athlete for high-level performance from day one.
Why tendons behave differently than muscle
Tendons connect muscle to bone and are built mostly from type I collagen, giving them the capacity to absorb and to transmit force. They operate on a spectrum of stiffness (better for power) and elasticity (better for change-of-direction, jumping, and cutting). The Achilles needs to be able to handle the dual demands of both sides of this spectrum. A rupture usually happens as the calf lengthens under tension (eccentric dorsiflexion), then quickly transitions into a forceful push-off (concentric plantarflexion); the audible “pop” is the excess energy that would have loaded the tendon converting to sound instead.
After the rupture, the tendon rebuilding process begins with weaker type III collagen fibers before progressively remodeling toward stronger type I collagen.
Between 60–80% of Achilles tendinopathy cases follow a rapid spike in training load or inadequate recovery (Silbernagel et al., 2015), and about 4% of tendinopathy cases progress to a full rupture (Yasui et al., 2017). In soccer players specifically, reinjury rates after return to sport range from 27–44%, especially when the process is rushed (Silbernagel et al., 2015). Pain with tendon loading, especially under sprinting, jumping, or sudden deceleration, is not something to push through.
The four-phase rehab model
Phase I · Protection & Foundation (0–2 weeks post-op). Protect the repair, manage swelling, restore gentle motion. Weight-bearing as prescribed, gentle passive range of motion, scar mobilization, cross-education, strength training the uninjured side to keep neural drive flowing to the healing limb.
Phase II · Early Loading (2–6 weeks). Controlled active range of motion, ankle isometrics, and 4-way ankle resistance work. Dr. Keith Baar’s research shows even light loads in a limited range of motion can meaningfully increase collagen synthesis. Dr. Baar’s research also shows that tendon cells respond best to shorter, more intense bursts: about 6–10 total minutes of isometric work.
Phase III · Strength & Capacity (6–12 weeks). Slow eccentrics, overcoming isometrics, calf raise progressions, and direct hip/knee strength work (split squats, RDLs, step-downs). Baar and Cook’s tendon-loading model recommends heavy isometric holds (>80% of 1RM) for about 30 seconds, accumulating 5 minutes total. The 30-second hold allows stress relaxation so mechanical signal reaches the weaker, healing region instead of being shielded by stronger fibers. Return-to-jogging criteria: 25 single-leg heel raises with under 20% height asymmetry, 95% dorsiflexion/plantarflexion symmetry, and normalized gait.
Phase IV · Return to Practice → Return to Sport → Return to Performance (12+ weeks). This phase is a continuum, not a single clearance: controlled practice, then sport with a pitch count, then sport with no limitations, then back to prior performance level, then surpassing it. Plyometrics prioritize force absorption before force production, and both slow plyometrics (brute force) and fast plyometrics (stretch-shortening cycle) are trained to meet the Achilles’ dual demand for stiffness and elasticity. Return-to-sport testing looks for under 10% plantarflexion strength asymmetry, at least 90% symmetry on the Y-Balance Test, and physician clearance.
This only scratches the surface of what ATR rehab actually requires. Every plan gets tailored to the individual’s deficits, sport, and goals. We’re not just getting athletes back to activity; we’re preparing them to perform at, or above, where they left off.