Impact of Training Intensity Distribution on Performance in Endurance Athletes

TLDR

The study compared two 5‑month training programs that differed in the proportion of low‑intensity versus threshold‑level volume to determine their impact on endurance runners’ performance. Twelve subelite 5,000‑m runners were randomly assigned to either a low‑intensity (80.5 % zone 1) or a moderately high‑intensity (66.8 % zone 1) program, with training intensity monitored by heart rate zones and performance assessed via a simulated 10.4‑km cross‑country race before and after the period. The low‑intensity program produced a significantly larger performance gain (−157 s) than the moderate‑intensity program (−121.5 s), supporting the benefit of a high proportion of low‑intensity training over five months when high‑intensity volume is maintained.

Abstract

The purpose of this study was to compare the effect of 2 training programs differing in the relative contribution of training volume, clearly below vs. within the lactate threshold/maximal lactate steady state region on performance in endurance runners. Twelve subelite endurance runners (who are specialists in track events, mostly the 5,000-m race usually held during spring-summer months and who also participate in cross-country races [9-12 km] during fall and winter months) were randomly assigned to a training program emphasizing low-intensity (subthreshold) (Z1) or moderately high-intensity (between thresholds) (Z2) training intensities. At the start of the study, the subjects performed a maximal exercise test to determine ventilatory (VT) and respiratory compensation thresholds (RCT), which allowed training to be controlled based on heart rate during each training session over a 5-month training period. Subjects performed a simulated 10.4-km cross-country race before and after the training period. Training was quantified based on the cumulative time spent in 3 intensity zones: zone 1 (low intensity; <VT), zone 2 (moderate intensity; between VT and RCT), and zone 3 (high intensity; >RCT). The contribution of total training time spent in zones 1 and 2 was controlled to have relatively more low-intensity training in Z1 (80.5 +/- 1.8% and 11.8 +/- 2.0%, respectively) than in Z2 (66.8 +/- 1.1% and 24.7 +/- 1.5%, respectively), whereas the contribution of high-intensity (zone 3) training was similar (8.3 +/- 0.7% [Z1] and 8.5 +/- 1.0% [Z2]). The magnitude of the improvement in running performance was significantly greater (p = 0.03) in Z1 (-157 +/- 13 seconds) than in Z2 (-121.5 +/- 7.1 seconds). These results provide experimental evidence supporting the value of a relatively large percentage of low-intensity training over a long period ( approximately 5 months), provided that the contribution of high-intensity training remains sufficient.