ACL injuries are common in field and court sports, however there are a limited number of accepted indicators that determine readiness to return to play sport following ACL surgery.
A new study published in The Journal of Orthopaedic Sports and Physical Therapy has evaluated the readiness to return to play based on measures of maximal voluntary isometric force (MVIC) AND rate of force development (RFD) at 30% (RFD30), 50% (RFD50) & 90% (RFD90) of MVIC. The justification for the study is simple: actions requiring maximal strength are rarely performed in most sports, whereas most sport-specific actions occur through reflexes where rapid RFD is required.
The 45 professional players in this study were measured for MVIC and RFD following ACL surgery, MVIC had recovered to 97% six months post surgery, but RFD30 was 80% (p < 0.05), RFD50 was 77% (p < 0.05) and RFD90 was 63% (<p 0.07) of pre-surgery values after six months, and returned to 90% after 12 months. This is highly likely due to a decreased neuromuscular activation.
Does this study discount current rehabilitation protocols following ACL reconstruction? Not quite.
Given that maximal strength is rarely called upon in the majority of sports, but speed & power are always required, specific RFD training should be incorporated into rehabilitation. As such, RFD could be used as an indicator of readiness to return to play following chronic injury, within the context of a sports-specific activity. Recovering RFD could provide much better protection to the athlete particularly in the initial phase of re-entry to sport where reflexes are poor but implication is maximal. At which point RFD training should be introduced into rehab warrants further investigation.