Heyer, L., Breil, F., Lehmann, A., Reichlin, L., Prisi, D., & Vogt, M. (2009). Manipulation of training intensity distribution in distance runners and its impact on endurance performance: A cross-over study. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

"The training intensity distribution between elite and moderately-trained athletes is different. Untrained or moderately-trained subjects commonly exercise following a "threshold-training" model allocating a high proportion of moderate intensity exercises while (international) elite athletes seem to prefer a “polarized training” distribution tending to minimize trainings between the first (VT1) and second ventilatory threshold (VT2)."

This study evaluated the effect of a polarized training distribution on physiological determinants of performance in endurance runners. In the first year and after a 12-week baseline period, well-trained recreational runners (N = 15) were randomly assigned to either a polarized training or a normal training period for 10 weeks. In accordance with a cross-over design, training groups were switched to the other training protocol for the same training duration one year later. During polarized training, Ss performed ~70% of all endurance sessions in zone 1 (VT2). In normal training, Ss trained ~50% in zone 1, ~26% in zone 2, and ~24% in zone 3. VO2max, maximal running speed, ventilatory thresholds, running economy, respiratory exchange ratio, and anaerobic power were measured before the baseline period and each year immediately before and after the intervention period.

VO2max increased significantly for the normal training group but not for the polarized group. Maximal running speed, ventilatory thresholds, and running economy did not change for either training group. Respiratory exchange ratio was significantly decreased at 10 km/hr, 11.5 km/hr, and at 13 km/hr only after polarized training. In the anaerobic 30-second Wingate tests, peak power output and mean power output only increased after undergoing polarized training. Despite unaltered training volume (~5 hr/wk), body fat content was significantly higher after polarized training.

Implication. When frequency of high intensity training in zone 3 is fixed at around 25% of total endurance sessions, the relative contribution of low (zone 1) and middle (zone 2) intensity training does not affect maximal endurance performance in well-trained recreational runners. The polarized training pattern seems to slightly modify substrate selection and improves anaerobic performance. Unlike elite athletes, a polarized distribution of the training intensity seems not to be preferable for recreational runners performing low to moderate training volumes. If training intensity is not high enough, anaerobic gains are quite limited. When high-intensity training is included in a program, lower-intensity training adds little, if anything, to the functioning of an endurance athlete.

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