No difference in clinical effects when comparing Alfredson eccentric and Silbernagel combined concentric-eccentric loading in achilles tendinopathy: a randomized controlled trial

Key points

1. 01VISA-A scores improved significantly in both groups from around 60 at baseline to 89 (Alfredson) and 83 (Silbernagel) at 1 year
2. 02No significant between-group difference was found for VISA-A, pain during daily activities, or pain during sport at any follow-up
3. 03More Silbernagel participants considered themselves improved at 1 year (77% vs 50%), a statistically significant difference on global perceived effect
4. 04Adherence was high and similar in both groups (74% Alfredson vs 77% Silbernagel), supporting home-based self-management
5. 05The trial was stopped early and enrolled only 40 of a planned 86 participants, limiting the ability to detect a true difference

How it was conducted

Design

Prospective multicenter 2-arm single-blind RCT

Participants

40 recreational athletes aged 18-65 with chronic unilateral midportion Achilles tendinopathy (symptoms 3+ months)

Groups

Alfredson isolated eccentric program (n=18) vs Silbernagel combined concentric-eccentric program (n=22), both 12 weeks home-based

Primary outcome

VISA-A score at 1-year follow-up

Secondary outcomes

VAS pain during ADL and sport, EQ-5D quality of life, global perceived effect

Follow-up

12 weeks, 26 weeks, and 1 year

What they found

• VISA-A improved from 60.7 +/-17.1 to 89.4 +/-13.0 in the Alfredson group (P < .001) and from 59.8 +/-22.2 to 83.2 +/-22.4 in the Silbernagel group (P < .001)
• Treatment effect for VISA-A (Alfredson vs Silbernagel, corrected for baseline and confounders): 2.4 (95% CI, -8.5 to 13.3; P = .656)
• VAS-ADL treatment effect: -2.0 (95% CI, -11.3 to 7.3; P = .665)
• VAS-sports treatment effect: 1.3 (95% CI, -12.8 to 15.3; P = .858)
• Global perceived effect at 1 year: 77.3% of Silbernagel vs 50.0% of Alfredson participants reported much or very much improvement (P = .04)
• Adherence rate: 74.1% +/-21.6% (Alfredson) vs 77.3% +/-16.2% (Silbernagel); no significant difference (P = .197)

Limitations

• Trial was stopped before reaching target sample size (40 vs planned 86) due to slow recruitment and COVID-19, substantially reducing statistical power and increasing risk of type II error
• Groups differed at baseline: Alfredson participants were younger (mean 45 vs 50 years) and had shorter symptom duration (9.4 vs 15.1 months), which may have influenced outcomes despite covariate correction
• No imaging was used to confirm diagnosis or stage tendinopathy, and load progression was not directly monitored
• Supervision frequency was lower than in the original Silbernagel protocol (3 visits vs 12 visits over 12 weeks), potentially affecting the Silbernagel group's outcomes

Why it matters

For patients

Both exercise programs are effective home-based options for midportion Achilles tendinopathy, and patients can expect meaningful pain and function improvements with either, though full recovery (VISA-A above 90) was not achieved by most at 1 year.

For clinicians

Either the Alfredson eccentric or the Silbernagel concentric-eccentric protocol can be prescribed with confidence; contraction mode does not appear to be a decisive factor, and minimal supervision is sufficient given the high adherence rates observed.

For readers

This small underpowered RCT provides preliminary evidence that both protocols are equivalent, but an adequately powered trial is still needed before a firm conclusion about contraction mode can be drawn.