Discussion
Tendon stiffness
The present study yielded three key findings. Firstly, six weeks of daily hopping exercise improve running economy and increase respiratory exchange ratio at higher running speeds (12 and 14 km/h) in amateur runners. Secondly, maximal aerobic capacity remains unaltered by hopping if regular running and exercise habits are maintained. Our findings are in line with earlier studies examining plyometric interventions in amateur athletesAlthough the present trial strengthens the evidence that plyometric exercise improves running economy, the relative contributions of factors driving the observed changes are still a matter of debate. Tendon stiffness has been shown to significantly correlate with running economyOur hypothesis assumed that repeated hopping would elicit morphological and functional adaptation in the tissue, which in turn improve energy storage capacity. The daily loading paradigm was chosen based on research elucidating optimal loading paradigms for collagenous connective tissuesIn addition to adaptations in the tendon, metabolic factors may have caused the alterations of REOur findings have implications for clinical practice and may open new avenues for future research. As indicated earlier, previous training paradigms predominantly focussed on complex and more time consuming interventions which are particularly used by professional athletes