Tolerance and effectiveness of eccentric vs. concentric muscle strengthening in rotator cuff partial tears and moderate to severe shoulder pain. A randomized pilot study

Key points

1. 01Both exercise types achieved a 96% tolerance rate even in patients with moderate to severe pain at baseline.
2. 02Eccentric training produced significantly greater improvements in Constant scale function scores at 1 month (p = 0.003) and 3 months (p = 0.004) compared with concentric training.
3. 03Eccentric training showed significantly greater strength gains at 3 months (p = 0.01); no significant between-group difference remained at 12 months.
4. 04Tendon structure (ultrasound) improved more in the eccentric group at 3 months (p = 0.05) and 12 months (p = 0.043).
5. 05Pain (VAS) improved significantly within both groups over 12 months, but no statistically significant between-group difference was found at any time point.

How it was conducted

Design

Pilot randomized controlled trial, single-centre outpatient setting

Participants

26 adults (median age 54-54.5 years) with ultrasound-confirmed partial rotator cuff tear and VAS pain >=50 mm, no prior treatment

Groups

Eccentric strengthening (n=12) vs. concentric strengthening (n=14); both groups also received heat, massage, and range-of-motion therapy

Duration

20 supervised sessions over 4 weeks, then home program to 12 months

Primary outcomes

Tolerance rate, VAS pain, Constant-Murley scale, normalised shoulder strength (dynamometer), ultrasound tendon structure

Follow-up

Baseline, 1 month, 3 months, and 12 months

What they found

• Tolerance rate: 96% in both groups overall (eccentric 92%, concentric 100%); one patient withdrew at week 2 due to worsening pain.
• VAS (mm) - eccentric group medians: 55 at baseline, 30 at 1 month, 30 at 3 months, 10 at 12 months (intra-group p < 0.001).
• VAS (mm) - concentric group medians: 50 at baseline, 30 at 1 month, 30 at 3 months, 5 at 12 months (intra-group p = 0.01); no significant inter-group difference at any time point (12-month p = 0.83).
• Constant scale (points) - eccentric: 58.5 baseline, 88 at 1 month, 93 at 3 months, 85 at 12 months (p < 0.001 intra-group); concentric: 50 baseline, 62 at 1 month, 80 at 3 months, 91.5 at 12 months (p = 0.038 intra-group); inter-group differences at 1 month (p = 0.003) and 3 months (p = 0.004).
• Normalised strength (kg/body weight) - eccentric: 0.23, 0.29, 0.73, 0.72 at baseline/1/3/12 months (p = 0.001); concentric: 0.24, 0.21, 0.54, 0.66 (p = 0.01); inter-group differences at 3 months (p = 0.01); no significant difference at 12 months (p = 0.122).
• Ultrasound at 3 months: eccentric group had 50% tendinosis and 34% normal; concentric group had 42% still partial tears and only 14% normal (inter-group p = 0.05).
• Ultrasound at 12 months: eccentric group had 33% tendinosis and 58% normal; concentric group had 28% partial tears and 35% normal (inter-group p = 0.043).

Limitations

• Small pilot sample (n=26) with convenience sampling; the study was underpowered to detect many between-group differences, particularly for pain.
• Predominantly female sample (10/12 eccentric, 13/14 concentric), limiting generalisability; strength analysis was performed only in women.
• Home-program compliance relied on patient self-report with monthly phone reminders, not objective monitoring.
• No sham or usual-care-only control arm; both groups received identical adjunct therapy, so the specific contribution of contraction type cannot be fully isolated.

Why it matters

For patients

People with partial rotator cuff tears and significant pain can safely start lightweight strengthening early in rehabilitation; eccentric exercises may speed up recovery of shoulder function and promote tendon healing faster than standard concentric exercises.

For clinicians

Eccentric strengthening produced faster functional gains (Constant scale) and better ultrasound tendon healing at 3 and 12 months compared with concentric training in this pilot RCT, supporting its use as a preferred technique in conservative management of partial rotator cuff tears, though a larger trial is needed to confirm superiority.

For readers

This small pilot study suggests eccentric exercise is at least as safe as conventional concentric exercise for painful partial rotator cuff tears and may offer an advantage for earlier recovery, but the evidence remains preliminary due to the small sample size.