Tri-axial loading response to anti-gravity running highlights movement strategy compensations during knee injury rehabilitation of a professional soccer player

Anti-gravity treadmills have been used in rehabilitation to manipulate exposure to loading and to prescribe return to outside running. Analysis is typically restricted to the vertical plane, but tri-axial accelerometry facilitates multi-planar analysis with relevance to injury mechanism. In this case a professional male soccer player, 4 weeks post-operative surgery to repair a medial meniscectomy, 8 months after ACL reconstruction to the same knee, completed anti-gravity treadmill running at 70-95% bodyweight (BW) at 5% increments. Tri-axial accelerometers were placed proximal to the Achilles tendon of the injured and healthy leg, and at C7. The planar acceleration at touchdown highlighted an increase at 85%BW, identifying 70% and 85%BW as discrete loading progressions. C7 (3.21±0.68 m·s-2) elicited lower (P<0.001) vertical acceleration than the lower limb (9.31±1.82 m·s-2), with no difference between limbs suggesting bilateral symmetry. However, in the medio-lateral plane the affected limb (-0.15±1.82 m·s-2) was exposed to lower (P=0.001) medio-lateral acceleration than the non-affected limb (2.92±1.35 m·s-2) at touchdown, indicative of bilateral asymmetry. PlayerLoad during foot contact was sensitive to accelerometer location, with the affected limb exposed to greater loading in all planes (P≤0.082), exacerbated at 90-95%BW. Tri-axial accelerometry provides a means of assessing multi-planar loading during rehabilitation, enhancing objective progression.