Eccentric exercise is more effective than other exercises in mid-portion Achilles tendinopathy

Key points

1. 01Eccentric exercise reduced pain more than comparison exercises, with a pooled mean difference of -1.21 on a pain scale favouring eccentric exercise.
2. 02Four of the eight included trials favoured eccentric exercise for pain; one found it similar to heavy slow resistance training.
3. 03Continuing physical activity or load during the program did not appear to worsen outcomes.
4. 04Wait-and-see (no active treatment) was likely inferior to eccentric exercise.
5. 05Confidence is tempered by small sample sizes, very high statistical heterogeneity, and risk of bias in the trials.

How it was conducted

Design

Systematic review and meta-analysis of randomized controlled trials (PRISMA, AMSTAR 2)

Included studies

8 RCTs, searched November 2022 across PubMed, BIREME, SportDiscus, Cinahl, Web of Science and PEDro

Participants

371 patients (401 Achilles tendons), mean age 46.6 years, symptoms 3 months or longer

Comparison

Eccentric exercise versus other conservative exercise (concentric, light training, heavy slow resistance, other eccentric protocols, shockwave, vibration, wait-and-see)

Primary outcome

Pain (VAS/NVS) and function/disability (most often VISA-A)

Risk of bias

Cochrane RoB2: 62.5% some concerns, 37.5% high risk

What they found

• Pooled pain (5 studies, VAS/NVS): mean difference -1.21 (95% CI -2.72 to -0.30), favouring eccentric exercise.
• Pain meta-analysis showed very high heterogeneity (I2 91%), analysed with a random-effects model.
• Mafi 2001: eccentric exercise was significantly better than concentric exercise for pain (p<0.002).
• Beyer 2015: eccentric exercise versus heavy slow resistance training showed no between-group difference.
• Risk of bias: allocation concerns in 50% of studies, no blinding of participants or clinicians, and some concerns in selection of reported result in 3 studies.

Limitations

• Only the pain outcome could be pooled; disability could not be meta-analysed.
• Very high statistical heterogeneity (I2 91%) means the trials differed substantially in design and results.
• All trials carried risk of bias, with half showing allocation concerns and 37.5% rated high risk.
• Small individual sample sizes and varied comparison interventions limit the strength of conclusions.

Why it matters

For patients

If you have ongoing mid-portion Achilles pain, an eccentric calf-strengthening program is a reasonable first-line option that may ease pain better than other exercise routines.

For clinicians

Eccentric loading is supported as a primary exercise approach for mid-portion Achilles tendinopathy, with heavy slow resistance as a comparable alternative and continued loading not harming outcomes.

For readers

The pooled signal favours eccentric exercise, but small, heterogeneous, bias-prone trials mean the effect size should be read cautiously.