Myotonometry for the evaluation of Achilles tendon mechanical properties: a reliability and construct validity study.

OBJECTIVE

This study evaluates the intra-rater and inter-rater reliability of the MyotonPRO and its construct validity for the assessment of Achilles tendon stiffness.

DESIGN

Reliability and construct validity study.

METHODS

Forty healthy participants were assessed using the MyotonPRO by two raters on two different occasions. Tendon was evaluated in three different positions (relaxed, 0° plantarflexion and standing) and during different isometric contractions (range 0-3 kg). Reliability was calculated using intraclass correlation coefficient (ICC and 95% CI) standard error of measurement and minimal detectable change. Construct validity was evaluated between the different positions and the different contraction intensities using Friedman test.

RESULTS

Intra-rater reliability was very high ICC 0.87-0.98. The reliability of the 0.5 kg contraction was moderate with an ICC of 0.59. Inter-rater reliability ranged from high to very high with an ICC of 0.76-0.86. The reliability of the 0.5 kg, 1 kg contraction and the standing position was moderate with an ICC of 0.55, 0.54 and 0.56 respectively. Inter-session reliability ranged from high to very high with an ICC of 0.70-0.89. The reliability of the 0.5 kg contraction was moderate with an ICC of 0.54. Construct validity was demonstrated between different contraction levels and different positions.

CONCLUSION

MyotonPRO is a reliable tool for the evaluation of Achilles tendon stiffness during different contraction levels and in different positions. Construct validity was supported by changes of tendon stiffness during the explored conditions. MyotonPRO can be implemented, as a ready to use device, in the evaluation of tendon tissue mechanical properties.