Jones, A. M. (2002). Running economy is negatively related to sit-and-reach test performance in international-standard distance runners. International Journal of Sports Medicine, 23, 40-43.

The relationship between running economy and lower body flexibility were determined in international standard male distance runners (N = 34). Ss performed an incremental treadmill test to determine physiological attributes and the sit-and-reach test to measure lower body flexibility. Running speeds below lactate threshold were used to evaluate the relationship.

The results for running at 14, 15, and 16 km/hr were similar. There were no relationships between aerobic demand at 16 km/hr and age, height, body mass, or VO2max. However, there was a significant negative relationship between lower trunk flexibility and running economy. "Stiffer" athletes were more efficient runners. It was hypothesized that elastic energy was enhanced in muscles that were not overly stretched.

Implication. It is possible to have muscles that are too stretched. A loss in the elastic properties of muscle most probably results in a loss of energy production, and therefore movement efficiency, in running. It is possible to overdo stretching and flexibility training to the extent that it reduces performance potential.

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