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10 Longitudinal changes in muscle strength and rate of force development using HHD in the early phases of ACL rehabilitation
  1. Tomer Yona1,
  2. Bezalel Peskin2,
  3. Arielle Fischer1
  1. 1Technion – Israel Institute of Technology, Israel
  2. 2Rambam Medical Center, Department of Orthopaedic, Israel


Introduction Understanding muscle strength and Rate of Force Development (RFD) changes after a cruciate ligament reconstruction rehabilitation is crucial for return to sport. The Limb Symmetry Index (LSI) offers a standardized measure to compare the injured limb’s function to the uninjured side. While force and RFD are commonly measured using an expensive isokinetic device, new research shows that a hand-held dynamometer (HHD) can be used to measure them reliably. Only a few studies have used HHD and described longitudinal changes of the force and RFD during early rehabilitation.

Materials and Methods Using an HHD, 25 participants were assessed pre-surgery, two- and four-months post-surgery. We focused on peak force, early-phase RFD (100ms), and late-phase RFD (200ms). Effect sizes (ES) are reported to compare the injured and contralateral legs.

Results Pre-surgery, the injured quadriceps peak force was 383±138 newtons with an LSI of 0.81±0.26%. Two months post-surgery, the participants’ force dwindled to 257±105 (ES -1.50; LSI 0.55±0.25). By the fourth month, it rebounded to 322±145 (ES -1.01; LSI 0.67±0.26). The hamstring’s peak force at pre-surgery was 225± 78.9. At two months post-surgery, the peak force was 162±75.2 (ES -1.52; LSI 0.59±0.29), which improved to 225±103 at four months (ES -1.02; LSI 0.72±0.27). The RFD metrics followed a similar trajectory.

Conclusion Post-surgery, the injured limb’s muscle strength, and RFD decline, with some recovery by the fourth month, but as expected - still lower than the contralateral limb. Using an HHD can be valuable for clinicians as it offers insights outside the lab.

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