Inter-Individual Different Responses to Continuous and Interval Training in Recreational Middle-Aged Women Runners A crucial topic in sports is the determination of interindividual differences in response to the training that would enable to create individual timetables before workout and improve the runner’s performance. We wanted to analyze the heterogeneity of individual reactions to two half marathon training programs that differ mid-ages in running volume and intensity. 20 women performed either a 12-week continuous training with moderate intensity or interval training with high intensity.They were tested before and after training with maximum stress tests in the laboratory (Vo2max) and in the field (time to exhaustion and endurance run). All women participated in the same half marathon and their conclusion times were compared to their previous times.Although the improvements of mean final times were not significant, a continuous intensity of average intensity resulted in greater reduction in the final times, with more women (70%) improved compared to their previous times than at an interval of high intensity. The laboratory tests showed more differences in the highly intensive interval group, while both groups showed homogeneous significant increases of time to exhaustion.Both in the short interval series as well as in endurance run, the interval with high intensity resulted in better individual improvements with a higher percentage of responsters compared to continuous intervals of medium intensity (100% compared to 50% in the short series and 78% compared to 38% in endurance run). In summary, a variability of the interindividual reactions was observed both after a continuous interval middle and after a high-intensity interval, with some participants showed improvements (responders), while others showed no (non-responders) in the different performance parameters, which the idea of individualizationconfirmed.To optimize performance, a training concept is required. The whole study can be found under https://www.frontiersin.org/articles/10.3389/fhys.2020.579835/full