Quantitative weight bearing and non-weight bearing measures of stiffness in the achilles tendon and gastrocnemius muscle

Objectives. To establish quantitative values of stiffness for the Achilles tendon (AT) and Gastrocnemius muscle (GM) in participants weight bearing and non-weight bearing. Methods. Measurements of 25 participants taken bilaterally at 8 points along the AT, and 2 points at the GM included: Natural Oscillation frequency (F), dynamic stiffness (S), mechanical stress relaxation time (R), logarithmic decrement (D) and creep (C) were taken non-weight bearing (NWB) and weight bearing (WB) using the Myoton-PRO. Results. Median WB F scores were significantly higher than NWB F scores. D was significantly (P<0.005) higher NWB than WB for both AT and GM. S decreased from point 1 to point 8. GM S measurements were significantly (P<0.005) higher WB to NWB. C increased along course of tendon in the NWB condition and was significantly (P<0.005) higher at the GM. R was significantly (P<0.005) higher in the NWB condition for the AT and GM. R incrementally increased along the course of the AT in both NWB and WB conditions. Conclusions. There was an overall increased stiffness of the AT and GM during the weight bearing condition compared to the non-weightbearing condition. Further studies are required to develop a robust clinical application of this technology.