Test-retest reliability of measuring the passive stiffness of the Achilles tendon using ultrasonography

The effect of eccentric and concentric calf muscle training on Achilles tendon stiffness

Objective: To compare in vivo effects of eccentric and concentric calf muscle training on Achilles tendon stiffness, in subjects without tendinopathy.

Methods: Thirty-eight recreational athletes completed 6 weeks eccentric (6 males, 13 females, 21.6 ± 2.2 years) or concentric training (8 males, 11 females, 21.1 ± 2.0 years). Achilles tendon stiffness, tendon modulus and single-leg jump height were measured before and after intervention. Exercise adherence was recorded using a diary.

Results: All data are reported as mean ± SD. Groups were matched for height and weight but the eccentric training group were more active at baseline ( P < 0.05). Tendon stiffness was higher in the eccentrically trained group at baseline compared to the concentrically trained group (20.9 ± 7.3 N/mm v 13.38 ± 4.66 N/mm; P = 0.001) and decreased significantly after eccentric training (to 17.2 ( ± 5.9) N/mm ( P = 0.035)). There was no stiffness change in the concentric group ( P = 0.405). Stiffness modulus showed similar changes to stiffness. An inverse correlation was found between initial, and subsequent, reduction in stiffness (r = −0.66). Jump height did not change and no correlation between stiffness change and adherence was observed in either group ( r = 0.01).

Conclusions: Six weeks of eccentric training can alter Achilles tendon stiffness while a matched concentric programme shows no similar effects. Studies in patients with Achilles tendinopathy are warranted.

Effect of eccentric training on the plantar flexor muscle-tendon tissue properties

PURPOSE

It has been shown that eccentric training can be effective in the rehabilitation of patients with Achilles tendonopathy. The mechanism behind these results is not clear. However, there is evidence that tendons are able to respond to repeated forces by altering their structure and composition, and, thus, their mechanical properties change. In this regard, the objective of the present study was to investigate whether eccentric training affects the mechanical properties of the plantar flexor's muscle-tendon tissue properties.

METHODS

Seventy-four healthy subjects were randomized into two groups: an eccentric training group and a control group. The eccentric training group performed a 6-wk eccentric training program for the calf muscles. Before and after this period, all subjects were evaluated for dorsiflexion range of motion using universal goniometry, passive resistive torque of the plantar flexors, and stiffness of the Achilles tendon. Passive resistive torque was measured during ankle dorsiflexion on an isokinetic dynamometer. Stiffness of the Achilles tendon was assessed using a dynamometer, in combination with ultrasonography.

RESULTS

The results of the study reveal that the dorsiflexion range of motion was significantly increased only in the eccentric training group. The eccentric heel drop program also resulted in a significant decrease of the passive resistive torque of the plantar flexors (from 16.423 +/- 0.827 to 12.651 +/- 0.617 N.m). The stiffness of the Achilles tendon did not change significantly as a result of training.

CONCLUSION

These findings provide evidence that an eccentric training program results in changes to some of the mechanical properties of the plantar flexor muscles. These changes were thought to be associated with modifications to structure rather than to stretch tolerance.

Effect of Static and Ballistic Stretching on the Muscle-Tendon Tissue Properties

PURPOSE

Many studies have been undertaken to define the effects of static and ballistic stretching. However, most researchers have focused their attention on joint range-of-motion measures. The objective of the present study was to investigate whether static- and ballistic-stretching programs had different effects on passive resistive torque measured during isokinetic passive motion of the ankle joint and tendon stiffness measured by ultrasound imaging.

METHODS

Eighty-one healthy subjects were randomized into three groups: a static-stretch group, a ballistic-stretch group, and a control group. Both stretching groups performed a 6-wk stretching program for the calf muscles. Before and after this period, all subjects were evaluated for ankle range of motion, passive resistive torque of the plantar flexors, and the stiffness of the Achilles tendon.

RESULTS

The results of the study reveal that the dorsiflexion range of motion was increased significantly in all groups. Static stretching resulted in a significant decrease of the passive resistive torque, but there was no change in Achilles tendon stiffness. In contrast, ballistic stretching had no significant effect on the passive resistive torque of the plantar flexors. However, a significant decrease in stiffness of the Achilles tendon was observed in the ballistic-stretch group.

CONCLUSION

These findings provide evidence that static and ballistic stretching have different effects on passive resistive torque and tendon stiffness, and both types of stretching should be considered for training and rehabilitation programs.

Intrinsic risk factors for the development of achilles tendon overuse injury: a prospective study

BACKGROUND

Although Achilles tendon overuse injuries occur commonly, our understanding of the pathologic changes and the factors that predispose athletes to them is limited.

PURPOSE

To identify measurable intrinsic risk factors for Achilles tendon overuse injuries.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

Sixty-nine male officer cadets followed the same 6-week basic military training. Before this training, each subject was evaluated for anthropometrical characteristics, isokinetic ankle muscle strength, ankle joint range of motion, Achilles tendon stiffness, explosive strength, and leisure and sports activity. During military training, Achilles tendon overuse injuries were registered and diagnosed by the same medical doctor. To identify the intrinsic risk factors, a multivariate analysis with the use of stepwise logistic regression was performed. The sensitivity, specificity, and cutoff values of the risk factors were evaluated by receiver operating characteristic curve analysis.

RESULTS

Ten of the 69 male recruits (14.5%) sustained an Achilles tendon overuse injury diagnosed on the basis of medical history and clinical examination. Analysis revealed that male recruits with lower plantar flexor strength and increased dorsiflexion excursion were at a greater risk of Achilles tendon overuse injury. The cutoff value of the plantar flexor strength at 85% sensitivity was 50.0 N.m, with a 4.5% specificity; the cutoff value of the dorsiflexion range of motion at 85% sensitivity was 9.0 degrees , with 24.2% specificity.

CONCLUSIONS

The strength of the plantar flexors and amount of dorsiflexion excursion were identified as significant predictors of an Achilles tendon overuse injury. A plantar flexor strength lower than 50.0 N.m and dorsiflexion range of motion higher than 9.0 degrees were possible thresholds for developing an Achilles tendon overuse injury.