Eleven RCTs (n=289) were included in the review.
The methodological quality of the included trials was relatively good, with trials scoring between 4 and 7 points of a possible 10 on the PEDro scale. The authors explained that the intervention of eccentric exercise does not allow for blinding of the patient or therapist, thus reducing the 10-point quality score to a maximum of 8 points.
There were no significant differences between the groups when eccentric exercise was compared with no treatment (1 RCT of patellar tendinosis), alternative eccentric exercise (1 RCT of patellar tendinosis), stretching (1 RCT of patellar tendinosis and 1 RCT of Achilles tendinosis) and night splints (1 RCT of Achilles tendinosis).
Eccentric versus concentric exercise.
Three trials compared eccentric exercise with concentric exercise for the treatment of Achilles tendinosis. There were no differences in pain scores between the treatment groups in any of the trials at any of the individual follow-up times. However, one study showed that when pain scores were averaged across all follow-up times, the eccentric exercise group exhibited significantly less pain.
There were no differences in strength between the groups. However, interim results (week 6 of a 12-week protocol) for one study showed significantly higher vertical jump scores in the concentric exercise group compared with the eccentric exercise group.
Two further RCTs investigated patellar tendinosis. One study showed no difference between groups for any outcome, while the other showed a large treatment effect for pain for eccentric exercise.
Eccentric exercise versus non-thermal ultrasound versus frictional massage.
One trial of patellar tendinosis showed significant improvements in pain scores in the eccentric exercise group.