In order to further compare shod versus barefoot running, 35 subjects ran two bouts of 4 minutes at 3.33 m · s^-1 on a treadmill dynamometer. Parameters were measured on about 60 consecutive steps. Barefoot showed mainly lower contact and flight time (p < 0.05), lower passive peak (1.48 versus 1.70 body weight, p < 0.05), higher braking and pushing impulses (p < 0.05), and higher pre-activation of triceps surae muscles (p < 0.05) than shod. It was concluded that when performed on a sufficient number of steps, barefoot running leads to a reduction of impact peak in order to reduce the high mechanical stress occurring during repetitive steps. This neural-mechanical adaptation could also enhance the storage and restitution of elastic energy at ankle extensors level. 1 The work was undertaken at the Laboratoire de Physiologie - GIP E2S, Pavillon 12, Hôpital St Jean Bonnefonds, 42055 Saint-Etienne Cedex 2, France

Background:The therapeutic efficacy of non-surgical treatment strategies in Achilles tendinopathy (AT) has not been well clarified. Time-consuming and costly combinations of treatment for pain, physiotherapy and biomechanical procedures are often applied.Objective:To analyse the efficacy of single therapeutic regimens commonly used over a short period of 4 weeks.Methods:31 male runners (mileage >32 km/week) with unilateral, untreated AT completed 4 weeks of either physiotherapy (10 treatments: deep-friction, pulsed ultrasound, ice, sensory motor training; (P)), wearing custom fit semirigid insoles (I) or remained without treatment (control group C). Before and after treatment, all patients underwent a treadmill test and a plantar flexion strength exercise. Subjective pain (Pain Disability Index, Pain Experience Scale), as well as strength performance capacity (peak torque), was analysed (mean, 95% CI, repeated measures analysis of variance, α = 0.05).Results:Pain was reduced to <50% of the baseline value after physiotherapy or after wearing insoles (p50% (25%) in 89% (100%) of subjects in I and 55% (73%) in P. Higher eccentric plantar flexion peak torques after treatment were observed in I and P.Conclusions:Most patients with AT experience a reduction in pain after only 4 weeks of differentiated, non-surgical treatment consisting of physiotherapy or semirigid insoles.

When mechanical parameters of running are measured, runners have to be accustomed to testing conditions. Nevertheless, habituated runners could still show slight evolutions of their patterns at the beginning of each new running bout. This study investigated runners' stiffness adjustments during shoe and barefoot running and stiffness evolutions of shoes. Twenty-two runners performed two 4-minute bouts at 3.61 m·s^–1shod and barefoot after a 4-min warm-up period. Vertical and leg stiffness decreased during the shoe condition but remained stable in the barefoot condition,p< 0.001. Moreover, an impactor test showed that shoe stiffness increased significantly during the first 4 minutes,p< 0.001. Beyond the 4th minute, shoe properties remained stable. Even if runners were accustomed to the testing condition, as running pattern remained stable during barefoot running, they adjusted their leg and vertical stiffness during shoe running. Moreover, as measurements were taken after a 4-min warm-up period, it could be assumed that shoe properties were stable. Then the stiffness adjustment observed during shoe running might be due to further habituations of the runners to the shod condition. To conclude, it makes sense to run at least 4 minutes before taking measurements in order to avoid runners' stiffness alteration due to shoe property modifications. However, runners could still adapt to the shoe.