Durability of the Major Determinants of Endurance Performance Is Not Different After 15 kJ·kg−1 of Moderate or Heavy Exercise

Durability, or resilience to deteriorations in physiological endurance characteristics during exercise, is posited to have important implications for endurance performance. However, little is known about the effects of exercise intensity on the durability of important endurance parameters. The aim of this study was to compare changes in peak ramp power (power achieved at the end of a ramp test), $$O_2max, lactate threshold, critical power, gross efficiency and W′ after work-matched moderate and heavy exercise bouts. Twelve competitive cyclists ($$O_2max = 62.1 ± 4.4 mL·kg⁻¹ min⁻¹) performed exercise testing before and after completing 15 kJ·kg⁻¹ work bouts in the moderate (duration = 4837 ± 675 s) and heavy (4000 ± 537 s) exercise domain. Significant declines were seen in peak ramp power (baseline = 412.6 ± 64.5 W, moderate = 380.2 ± 59.7 W and heavy = 374.8 ± 59 W) and W’ (baseline = 7.8 ± 4 kJ, moderate = 4 ± 3.6 kJ and heavy = 3.6 ± 2.4 kJ)—all other parameters did not change. There were no significant differences in the magnitude of decline between the moderate and heavy work bouts for any variable. For the first time, we show that durability of important determinants of endurance performance is not different when 15 kJ·kg⁻¹ of moderate or heavy work is performed, suggesting that exercise domain does not influence durability for exercise lasting ∼60–90 min. Further research is needed to explore exercise of longer durations and associated physiological mechanisms for deteriorations in relevant parameters.