Determination of swimming training intensity zones using different physiological testing methods: a systematic review

Introduction: The prescription of training intensity in swimming based on different intensity zones defined by physiological thresholds constitutes a key factor in training adaptations. However, the wide variety of tests used to estimate these parameters hinders the establishment of a consensus. Objective: The aim of the study was to analyse the scientific evidence about the determination of training zones in swimming, comparing the different physiological methods and variables used to define them. Methods: To this end, a systematic review was conducted following the PRISMA guidelines. Three databases were analysed, and the PEDro and AXIS scales were applied for quasi – experimental and observational studies respectively. A total of 5629 articles were identified, of which 26 were included in the review. Results: The available evidence suggests that a three-zone model may be applicable defined by lactate thresholds (Aerobic Threshold (AeT) ≈ 1 mmol/L lactate/Anaerobic Threshold (AnT) ≈ 3–6 mmol/L lactate), which are broadly associated with, respectively, the ventilatory thresholds Gas Exchange Threshold (GET) and Respiratory Compensation Point (RCP). Zone 1 was characterized by values below 70% of maximal oxygen uptake (VO 2 max) and heart rate (HRmax) between 50–74%; Zone 2 ranged between 70–83% VO 2 max and 74–81% HRmax; and Zone 3 was defined as >83% VO 2 max and between 81–100% HRmax. In addition, MLSS and CS corresponded to higher exercise intensities than AnT (≈87-90% and ≈92% VO 2 max, respectively, versus ≈83% for AnT) were generally located within Zone 3, although MLSS has also been proposed as a marker close to the boundary between Zones 2 and 3. Conclusion: The scientific evidence analysed shows that, despite the diversity of physiological variables and protocols used in swimming, there is a general trend toward a three-zone training-intensity framework.