Abstract

Eccentric loading of the ankle plantar Flexor’s (PF) has demonstrated clinical efficacy in the conservative treatment of Achilles tendinopathy, however, its mechanism of therapeutic benefit remains unclear. The purpose of this study was to examine the effects of PF eccentric loading on PF angle to peak torque (AtPT), peak torque (PT) and lower limb vertical stiffness. Thirty healthy volunteers were randomised to an eccentric (n=15) or concentric (n=13) exercise group. A 10-week loading programme of the ankle plantar flexors was completed. AtPT, PT and vertical stiffness were compared within and between groups before and after the interventions. AtPT increased in the eccentric group by 3.2° dorsiflexion (p=0.001) and decreased by 0.7° dorsiflexion (p=0.528) for the concentric group with significant post-intervention group differences (p<0.001). PT levels were unchanged following the interventions for both groups (p>0.2); however, post-intervention the eccentric group showed a greater PT than the concentric group (p>0.05). Between group comparison showed no significant difference in vertical stiffness (p>0.5). However, the concentric group demonstrated a vertical stiffness increase of 765kNm-¹ (p ≥ 0.05). This study demonstrates that a clinically derived eccentric loading programme can produce an adaptive shift in AtPT of the ankle plantar flexors in a healthy population. These results support the theory that in part, eccentric loading derives its therapeutic benefit from mechanisms that influence plantar flexor motor performance.

Keywords

Achilles tendinopathy, eccentric exercise, Plantar flexors, muscle performance

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