Treadmill versus overground and barefoot versus shod comparisons of triceps surae fascicle behaviour in human walking and running

Studies of human locomotion are commonly performed on a treadmill or overground, as well as with or without footwear. These testing modalities have been suggested to influence kinematics, kinetics and/or spatio-temporal variables differently. However, it is unclear whether they influence contractile behaviour at the level of the muscle fascicles. This has major relevance because results from studies performed with different combinations of the testing modalities are often compared. The present study used ultrasound to examine fascicle behaviour of the medial gastrocnemius (MG) and soleus muscles of ten young, healthy males during walking and running on a treadmill and overground, as well as barefoot and shod. Barefoot conditions resulted in modestly shorter step durations than corresponding shod conditions, whereas no consistent temporal differences were observed between overground and treadmill locomotion. For both comparisons, no differences were observed in soleus or MG fascicle behaviour between corresponding conditions in walking or running, although soleus consistently exhibited smaller, lower velocity length changes than MG. It is concluded that the examined testing modalities are equally valid for studying muscle fascicle behaviour during locomotion. This conclusion is supported by a comparison of our data to the results of 16 previous studies that used various combinations of testing modalities; muscle fascicle behaviour is qualitatively similar between studies for a given muscle and gait.

► Triceps surae fascicle behaviour was examined in walking and running using ultrasound. ► Comparisons were made between treadmill - overground and barefoot - shod trials. ► No differences in fascicle behaviour were observed between testing modalities. ► Soleus consistently exhibited smaller, lower velocity length changes than MG.