Heavy-Load Eccentric Calf Muscle Training for the Treatment of Achilles Tendinosis.

Alfredson H, Pietila T, Jonsson P, Lorentzon R (Sports Medicine Unit, Department of Orthopaedic Surgery, University Hospital of Northern Sweden, Umea, Sweden), Am J Sports Med. 1998;26:360-366.

The authors of this study investigated the short-term effect of heavy-load eccentric calf muscle strengthening on patients with chronic Achilles tendinosis. Fifteen subjects (12 men, 3 women) were chosen as the experimental group for this prospective study. The inclusion criteria were the following: recreational athlete, a diagnosis of Achilles tendinosis, a history of pain during running of a long duration, and utilization of conventional therapies (including physical therapy) without improvement in the symptoms. In addition to the experimental group, a control group of 15 consecutive recreational athletes (11 men, 4 women) were chosen to undergo surgery. They had a similar diagnosis and duration of symptoms and met the other inclusion criteria. All subjects underwent ultrasonography to determine degenerative changes to the Achilles tendon.

The study's independent variables were tendon pain during activity and concentric and eccentric strength of the calf muscles. Calf strength was measured by isokinetic testing. A test-retest reliability study of ankle plantar-flexion and dorsiflexion measurements was done prior to this study and resulted in excellent reliability for concentric and eccentric plantar flexion only. Therefore, concentric plantar flexion peak torques and total work measurement were collected at 90[degrees]/s and 225[degrees]/s, whereas measurements of eccentric plantar flexion peak torque and total work were obtained at 90[degrees]/s only. Pain during running was assessed using a 100-mm visual analog scale. All testing was done at baseline for both the experimental group and the control group. Retesting of the independent variables occurred at week 12 for the experimental group and week 24 for the control group.

The experimental group participated in eccentric training twice per day, 7 days per week, for 12 weeks. The program incorporated eccentric training of both the gastrocnemius and soleus muscles. The patient's body weight was the initial resistance level. Additional weight (using a backpack) was added when the subject experienced minimal or no pain while performing the exercises. If a very high level of resistance was needed, the subjects were encouraged to use a weight machine. The rehabilitation program of the control group following surgery consisted of a previously published stepwise training regimen. Control group subjects were seen once per week initially, once per month after 6 months, and at 1 year after the surgery.

Statistical analysis was performed using the Wilcoxon signed rank test to determine the differences between injured and non-injured sides and between the different testing periods for the injured side.

The results of this study demonstrated significant differences in peak torque between sides at both speeds in both the experimental and control groups at the start of the study. After 12 weeks of eccentric training, the experimental group showed significant improvement in plantar-flexion strength measures, but no significant differences in concentric and eccentric plantar-flexion strength between the injured and non-injured sides. In addition, the authors found no difference in the concentric and eccentric plantar-flexion strength of the non-injured side between testing periods. The control group continued to show significantly lower plantar-flexion strength in the injured side at 24 weeks after surgery compared with the non-injured side.

Total average work was reported for the experimental group only. Before the start of the training program, the authors found significantly lower concentric plantar-flexion average work at both speeds. After 12 weeks of training, the concentric plantar-flexion average total work increased significantly on the injured side at 90[degrees]/s only. As with peak torque, the researchers found no significant differences in average total work between the injured and non-injured sides after 12 weeks. Finally, the authors found no statistical difference in concentric and eccentric plantar-flexion average work in the non-injured side over the course of training.

Both groups demonstrated a statistically significant decrease in the amount of pain during activity at the end of the training or rehabilitation period. All subjects returned to their premorbid activity levels and were pleased with their restored status.

The authors discussed the major differences between the 2 groups. They focused on the time each group needed to return to pre-injury level: 3 months for the experimental group and 6 months for the control group. They were unable to answer the question concerning the effect that eccentric strengthening had on return to activity. The authors noted that all patients had reduced pain in the Achilles tendon. However, they could not determine if this was the effect of higher eccentric muscle strength or a mechanism that related to the eccentric loading of the tendon.

The authors discussed the relationship between Achilles tendinosis and running activities. The authors illustrated the pathophysiologic causes of the tendinosis and discussed theories regarding the resulting impairments of pain and decreased muscle performance. The authors concluded that the short-term effects of this treatment technique were patient safety, no need for immobilization or surgery, and low cost.

Aimee Klein, PT, OCS MGH Institute of Health Professions Boston, Mass