PT  - JOURNAL ARTICLE
AU  - N L Grigg
AU  - S C Wearing
AU  - J E Smeathers
TI  - Eccentric calf muscle exercise produces a greater acute reduction in Achilles tendon thickness than concentric exercise
AID  - 10.1136/bjsm.2008.053165
DP  - 2009 Apr 01
TA  - British Journal of Sports Medicine
PG  - 280--283
VI  - 43
IP  - 4
4099  - http://bjsm.bmj.com/content/43/4/280.short
4100  - http://bjsm.bmj.com/content/43/4/280.full
SO  - Br J Sports Med2009 Apr 01; 43
AB  - Objective: To investigate the acute effects of isolated eccentric and concentric calf muscle exercise on Achilles tendon sagittal thickness.Design: Within-subject, counterbalanced, mixed design.Setting: Institutional.Participants: 11 healthy, recreationally active male adults.Interventions: Participants performed an exercise protocol, which involved isolated eccentric loading of the Achilles tendon of a single limb and isolated concentric loading of the contralateral, both with the addition of 20% bodyweight.Main outcome measurements: Sagittal sonograms were acquired prior to, immediately following and 3, 6, 12 and 24 h after exercise. Tendon thickness was measured 2 cm proximal to the superior aspect of the calcaneus.Results: Both loading conditions resulted in an immediate decrease in normalised Achilles tendon thickness. Eccentric loading induced a significantly greater decrease than concentric loading despite a similar impulse (−0.21 vs −0.05, p<0.05). Post-exercise, eccentrically loaded tendons recovered exponentially, with a recovery time constant of 2.5 h. The same exponential function did not adequately model changes in tendon thickness resulting from concentric loading. Even so, recovery pathways subsequent to the 3 h time point were comparable. Regardless of the exercise protocol, full tendon thickness recovery was not observed until 24 h.Conclusions: Eccentric loading invokes a greater reduction in Achilles tendon thickness immediately after exercise but appears to recover fully in a similar time frame to concentric loading.