Pain, motion and function comparison of two exercise protocols for the rotator cuff and scapular stabilizers in patients with subacromial syndrome

Key points

1. 01Both groups improved significantly in pain, active range of motion, and Constant-Murley Score after 4 weeks
2. 02No significant between-group differences were found for any outcome (all P > .05)
3. 03Effect sizes for between-group differences were small across all variables (VAS = 0.09; Constant-Murley = 0.21; range of motion = 0.12-0.43)
4. 04The protocol combined eccentric rotator cuff exercises, scapular stabilization exercises, and upper trapezius stretching
5. 05This appears to be the first RCT directly comparing painful vs. pain-free eccentric exercise in subacromial syndrome

How it was conducted

Design

Prospective parallel-group randomized clinical trial

Participants

22 adults (mean age 59 years, 54.5% women) with subacromial syndrome; recruited from health centers in Valencia, Spain (March-May 2016)

Groups

Not-painful eccentric exercise group (NPEE, n = 11, VAS = 0 mm) vs. painful eccentric exercise group (PEE, n = 11, VAS < 40 mm)

Intervention

5 sessions per week for 4 weeks (~30 min/session); eccentric rotator cuff exercise, scapular stabilization exercises, and upper trapezius stretching

Primary outcomes

Shoulder pain (VAS) and active range of motion (goniometer)

Secondary outcome

Shoulder function via modified Constant-Murley Score (max 75 points; minimum clinically important difference = 17 points)

What they found

• NPEE group: VAS improved from median 55.0 to 28.0 (P = .003); Constant-Murley Score improved from median 36.0 to 65.0 (P = .003)
• PEE group: VAS improved from median 37.0 to 12.0 (P = .003); Constant-Murley Score improved from median 35.0 to 59.0 (P = .003)
• All active range of motion measures improved significantly in both groups (P < .05 for all directions in both groups)
• Between-group comparison showed no significant differences for any variable (all P > .05)
• Between-group effect sizes were small: VAS = 0.09, Constant-Murley scale = 0.21, range of motion differences = 0.12-0.43
• VAS between-group difference (pre-post): NPEE median 26.0 vs. PEE median 29.0 (P = .718, effect size = 0.09)
• Constant-Murley between-group difference: NPEE median 30.0 vs. PEE median 26.0 (P = .393, effect size = 0.21)
• Internal rotation range of motion difference showed the largest effect size at 0.43 (NPEE median 30.0 vs. PEE median 17.0, P = .086), though still non-significant
• No adverse effects were reported in either group; all 22 participants completed the program

Limitations

• Very small sample (n = 22 total, 11 per group), limiting statistical power and generalizability
• No placebo or passive control group, so the contribution of natural disease course cannot be separated from the intervention effect
• Assessor was not blinded, which may have introduced measurement bias
• Follow-up was only 1 day after the final session, with no long-term monitoring to determine durability of effects

Why it matters

For patients

Patients with subacromial syndrome can expect meaningful pain relief and improved shoulder movement from a supervised eccentric exercise program regardless of whether they exercise through mild pain or keep exercise completely pain-free.

For clinicians

Clinicians do not need to prescribe painful eccentric loading to achieve benefit in subacromial syndrome; a pain-free protocol produces equivalent short-term outcomes, which may improve patient adherence and comfort.

For readers

This small RCT challenges the assumption that pain during eccentric exercise is necessary for tendon adaptation in subacromial syndrome, though the very small sample and short follow-up mean results should be interpreted cautiously.