Longitudinal Metabolic and Perceptual Responses to an Individualized, Biochemically Guided Interval-Swimming Protocol: A Non-Randomized Controlled Pilot Study

Individualized regulation of training load may help characterize athlete-specific responses during competitive swimming. This controlled longitudinal pilot study evaluated metabolic and perceptual responses to an individualized, biochemically guided interval-swimming protocol. Twelve competitive swimmers were included (experimental group, n = 5; control group, n = 7) and completed six serial assessments (T0–T5). Group allocation was non-randomized. In the experimental group, work-bout duration was progressively modified using repeated biochemical and perceptual information, whereas the control group followed a predominantly fixed-duration protocol. The principal outcome analyzed in this report was blood lactate measured 1 min after exercise. Post-exercise blood lactate decreased from 11.78 to 7.94 mmol/L in the experimental group and from 12.19 to 11.43 mmol/L in controls. The T0–T5 reduction was greater in the experimental group (−3.84 vs. −0.76 mmol/L), with a between-group difference in change of −3.08 mmol/L (95% CI, −3.72 to −2.45; p < 0.001). Ammonia showed a supportive longitudinal difference, whereas uric acid was exploratory because it guided load adjustment. Perceived exertion showed a supportive but borderline change after multiplicity adjustment. Recorded interval pace remained broadly stable while work-bout duration increased substantially in the experimental group; however, no standardized time-trial or competitive-performance outcome was assessed. These preliminary findings support further evaluation of individualized, biochemically guided interval-training protocols in larger, prospectively standardized studies.