Plyometric Readiness After ACL Reconstruction
Ms. P., 22, is a collegiate soccer player 9 months after right ACL reconstruction with a hamstring graft. Her surgeon has cleared her for sport, but she wants to add box jumps and depth jumps before preseason. She has no effusion, full knee extension, and 130° flexion. Single-leg hop for distance symmetry is 82% (right/left), quadriceps limb symmetry index is 78%, and on a 30-cm drop landing her right knee shows 10° more valgus than the left. She trains four days/week and has access to boxes, bands, and a force plate. She reports no pain during jogging but fatigue in the right quadriceps with repeated hopping. Her goal is to play 60 minutes in 8 weeks.
1. Is she ready for 45-cm depth jumps next week? Justify using landing biomechanics and objective criteria.
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No. A 45-cm depth jump is a high-intensity plyometric involving a rapid stretch-shortening cycle, high eccentric loading, and large vertical ground-reaction forces. Her quadriceps limb symmetry index of 78% and hop symmetry of 82% are below commonly used readiness cutoffs (often ≥90% for return to high-level plyometrics), and the 10° valgus asymmetry on landing suggests poor frontal-plane control. The quadriceps fatigue with repeated hopping is another warning sign: as the quadriceps fatigues, the knee may rely more on passive restraints and land in greater valgus.
Before depth jumps, she should demonstrate symmetrical landing, no dynamic valgus, and at least 90% quadriceps and hop symmetry. Use the force plate to check peak vertical ground-reaction force and time-to-stabilization symmetry. Depth jumps can wait; low-intensity plyometrics and landing mechanics are the appropriate next step.
2. Design a 4-week low-to-high plyometric progression with sets, reps, contacts, and landing cues, and specify one objective criterion for advancing each week.
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Week 1: pogo hops and squat-to-stand landings; 2 × 8 each, about 50–60 total contacts. Cue: land quietly through the whole foot, knees track over toes. Advance when landing is quiet and valgus is absent on video.
Week 2: low box squat landings (20–30 cm) and lateral step-and-stick; 3 × 6 each, about 70 contacts. Cue: 'hips back, chest over knees, no knee collapse.' Advance when force-plate landing asymmetry is under 10–15%.
Week 3: low box jumps (30 cm) and single-leg hop-and-stick; 3 × 5 each, about 80 contacts. Cue: stick each landing for 2 seconds. Advance when single-leg hop symmetry reaches 90% without valgus.
Week 4: box jumps to 30–40 cm and lateral bounds; 3 × 5, about 80–90 contacts, no depth jumps yet. Cue: same landing position every rep. Advance to depth jumps only after quadriceps LSI ≥90%, hop symmetry ≥90%, and no landing valgus on two consecutive sessions.