Northius, M. E., Leon, A. S., Serfass, R. C., Walker, A. J., Crow, R. S., & Jacobs, D. R. (1999). High responders vs. low responders in cross country running training. Medicine and Science in Sports and Exercise, 31(5), Supplement abstract 1387.

This study attempted to locate variables that differentiate between high-responders (large improvements in race velocity) and low-responders (little to no improvements in race velocity) among Division I collegiate cross country runners (M = 6: F = 10) who participated in identical training programs. Two analytical multivariate models were used:

• Physiology: changes in fractional utilization of O2 during testing, running economy, and maximal lactate production.
• Performance: changes in 300m and 3000m running velocity during training, and running economy.

Changes in maximal lactate production and running economy were significantly related to changes in racing velocity. The physiology model explained 70% of variance in change in running performance velocities while the performance model explained 76%. Change in running economy accounted for ~67% in both models. Heart rate became less economical during the season (-3.5%) although maximal lactate increased by 36%. This suggests some aerobic capacity might be sacrificed with anaerobic training.

Implication. Running economy is the best predictor of competitive running performances. As many factors as possible should be considered when evaluating performances. It is most appropriate to develop concepts of training response patterns on an individual basis. In this study, all Ss trained similarly, but responded individually.

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