Dose–Response Relationship Between Backward Treadmill Inclination and Quadriceps Strength Recovery After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Abstract

Background

Quadriceps weakness is one of the most common impairments following anterior cruciate ligament (ACL) reconstruction and may delay functional recovery and return to activity. Backward treadmill walking has been suggested as an effective rehabilitation strategy to improve quadriceps strength; however, the dose–response relationship between treadmill inclination and strength recovery remains unclear.

Objective

To investigate the dose–response relationship between graded backward treadmill inclination and quadriceps strength recovery following ACL reconstruction.

Methodology

This Randomized Controlled Trial (RCT) included 60 participants who had undergone ACL reconstruction and were randomly allocated into five groups (n=12 each). Groups A, B, C and D performed backward treadmill walking at 0°, 5°, 10° and 15° inclination respectively, while Group E received conventional rehabilitation. Training was performed for 20 minutes, three times per week for four weeks. Quadriceps strength was measured using a handheld dynamometer at baseline and weekly for four weeks. Comparisons The Friedman test was employed for within-group analyses, or the Friedman test was used for among-group assessments the Kruskal–Wallis test.

Results

All groups demonstrated progressive improvements in quadriceps strength over the four-week intervention period. Within-group analysis showed statistically significant improvements in strength in all groups (p<0.001). Among-group comparisons showed no statistically substantial differences at baseline or at weekly follow-ups (p>0.05). However, although descriptive trends in strength progression were observed across groups, no statistically substantial differences were found among the intervention groups.

Conclusion

Graded backward treadmill training was associated with improvements in quadriceps strength across all groups following ACL reconstruction. However, no statistically substantial differences were observed among groups. While descriptive trends were noted, a definitive dose–response relationship could not be established.