De Jaeger D, Joumaa V, Herzog W. Intermittent stretch training of rabbit plantarflexor muscles increases soleus mass and serial sarcomere number. J Appl Physiol 118: 1467-1473, 2015. First published April 2, 2015 doi:10.1152/japplphysiol.00515.2014.-In humans, enhanced joint range of motion is observed after static stretch training and results either from an increased stretch tolerance or from a change in the biomechanical properties of the muscle-tendon unit. We investigated the effects of an intermittent stretch training on muscle biomechanical and structural variables. The left plantarflexors muscles of seven anesthetized New Zealand (NZ) White rabbits were passively and statically stretched three times a week for 4 wk, while the corresponding right muscles were used as nonstretched contralateral controls. Before and after the stretching protocol, passive torque produced by the left plantarflexor muscles as a function of the ankle angle was measured. The left and right plantarflexor muscles were harvested from dead rabbits and used to quantify possible changes in muscle structure. Significant mass and serial sarcomere number increases were observed in the stretched soleus but not in the plantaris or medial gastrocnemius. This difference in adaptation between the plantarflexors is thought to be the result of their different fiber type composition and pennation angles. Neither titin isoform nor collagen amount was modified in the stretched compared with the control soleus muscle. Passive torque developed during ankle dorsiflexion was not modified after the stretch training on average, but was decreased in five of the seven experimental rabbits. Thus, an intermittent stretching program similar to those used in humans can produce a change in the muscle structure of NZ White rabbits, which was associated in some rabbits with a change in the biomechanical properties of the muscle-tendon unit. sarcomerogenesis; muscle properties; muscle stretching REGULARLY PRACTICED by humans, passive static stretching systematically and significantly enhances specific joint range of movement (ROM) (9, 26). One single 30-s stretch applied 3 days/wk for 4 wk appears to be enough to significantly increase knee extension ROM in young adult subjects with tight hamstrings (7). However, what causes this enhanced ROM, an increased stretch tolerance or a change in the biomechanical properties of the muscle-tendon unit, is not clear (32).In humans, the effects of a stretching program on muscletendon biomechanical properties are studied through the changes in passive torque-angle curves measured before and after the stretching program. Published results regarding these curves are neither numerous nor consistent and seem to depend on the stretched muscle group or on the stretching protocol.Contrasting results have been obtained when different muscle groups were exposed to the same stretching program. Different results are obtained when different stretching programs are used on the same muscle group. Passive torque and stiffness, measured at ...

The goal of the present study was to determine the relative efficacy of verbal and auditory knowledge of results for promoting learning of a new constrained relative timing pattern. In a series of four experiments we compared the efficiency of verbal knowledge of results to that of auditory knowledge of results. The results of all four experiments revealed that verbal knowledge of result is a very effective source of information to promote learning of a new imposed relative timing pattern. Auditory knowledge of results favoured learning of a new relative timing pattern in a very limited set of circumstances. In the present study, this was only the case when movement velocity remained constant from one segment of the task to the next and if it resulted in an unfamiliar temporal pattern. The results of all four experiments also provided evidence that movement parameterization and relative timing are independent processes that can be developed in parallel.

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