# The effect of exercise training modalities on the morphological and mechanical properties of the achilles tendon: a systematic review and network meta-analysis

## TL;DR

This study reviews how different types of exercise affect the Achilles tendon's structure and strength, finding that specific training methods like plyometric jumps and isometric exercises are most effective.

## Contribution

The paper provides a network meta-analysis comparing the effectiveness of various exercise modalities on Achilles tendon adaptations in healthy adults.

## Key findings

- Short-term plyometric jump training most effectively increases Achilles tendon cross-sectional area.
- Long-term isometric plantar-flexion training is best for improving tendon stiffness.
- Gait retraining shows the highest ranking for increasing tendon length and strain.

## Abstract

The Achilles tendon (AT) is vital for sports performance yet highly susceptible to injury. Exercise can induce structural and mechanical adaptations, but the relative effectiveness of different protocols remains uncertain. This systematic review and network meta-analysis evaluated exercise-based interventions targeting AT morphology and mechanics in healthy adults.

PubMed, Web of Science and Scopus were searched from inception to 18 Feb 2025. Randomized controlled trials (RCTs) were synthesized using random-effects network meta-analysis (Hedges' g). Risk of bias was assessed using a modified Downs and Black Quality Index.

Forty-nine trials were included in the systematic review; 31 RCTs (n = 1,388) contributed to the network across five intervention categories (15 subtypes). Short-term plyometric jump training ranked highest for increasing AT cross-sectional area (SUCRA 95.6%; SMD 1.33 vs. control). Long-term isometric plantar-flexion training ranked highest for improving stiffness (SUCRA 89.3%). Gait retraining ranked highest for AT length, elongation and strain (SUCRA 59.6%–77.1%), although networks for several outcomes were sparse and estimates imprecise. Stretching-focused programs generally ranked low across outcomes.

In healthy adults, progressive, higher-dose loading, particularly isometric plantar-flexion training and plyometric jump training, shows the most favorable rankings for AT adaptation. Rankings should be interpreted cautiously given heterogeneity and sparse networks for some outcomes; well-powered head-to-head RCTs with harmonised outcome definitions are needed.

https://www.crd.york.ac.uk/prospero, PROSPERO CRD420251009672.