Intraclinician Variability in Force Application During Anteroposterior Mobilization of the Ankle Joint

Objective

The purpose of this study was to quantify the variability in the force applied during 20 cycles of Maitland's grade IV anteroposterior ankle mobilization measured on 2 occasions.

Methods

Thirteen healthy adults (mean age, 25 ± 5 years; height, 170 ± 7 cm; weight, 71 ± 16 kg) received 20 cycles of Maitland's grade IV ankle mobilization on 2 sessions separated by 1 week. A force transducer was used to measure the peak force, loading rate, and impulse applied during each load cycle. Mean within-session coefficient of variation, standard error of measurement, and 95% level of agreement were estimated during each mobilization session.

Results

The mean peak force during the anteroposterior mobilization technique was 70 ± 12 N and 58 ± 10 N during sessions 1 and 2, respectively. The mean within-session coefficients of variation in peak force, loading rate, and impulse applied during 20 loading cycles were 10% to 13%, 15%, and 21% to 43%, respectively. There was a significant difference between sessions in mean peak force (−17%, t₁₂ = 2.445, P = .031) and impulse (−51%, t₁₂ = 2.306, P = .040), with large 95% levels of agreement in applied peak force (±33 N) and impulse (±128 N s) compared to their mean values (approximately ±50% and 110%, respectively).

Conclusion

The peak force and loading rate applied by an experienced practitioner during a Maitland's grade IV anteroposterior talar mobilization session varied over 20 loading cycles. Variability between repeated mobilization sessions by the same practitioner was even greater, with respect to peak applied force and loading rate. The large variability in force applied during a Maitland's grade IV talar mobilization may underpin differential clinical effects reported in the joint-mobilization literature. The findings of this study highlight the need for strategies that standardize the application of force during talar mobilization.