This study aimed at evaluating the homogeneity of physiological responses during swim training bouts with intensities prescribed by reference to the individual anaerobic threshold (IAT). Eighteen competitive front crawl swimmers (female 5, male 13, 10 long-distance, and 8 short-distance swimmers [LDSs, SDSs], age: 17 ± 1.7 years, training history: 7.0 ± 2.8 years, training volume per week: 35 ± 5.7 km) performed an incremental swimming test to determine the IAT. Within a maximum of 3 weeks, 4 training programs were conducted: 20 × 100-m low-intensity endurance training (EN(low), 97% IAT), 5 × 400-m high-intensity endurance training (EN(high), 101% IAT), 5 × 200 m (IT1, 105% IAT), and 10 × 100 m (IT2, 108% IAT) intensive interval training. Blood lactate concentrations (bLa) were determined during each training session. The results are given as median (25th and 75th percentiles). During EN(low) and EN(high), the mean bLas were 1.8 mmol·L(-1) (1.3/3.0 mmol·L(-1)) and 4.4 mmol·L(-1) (3.9/6.4 mmol·L(-1)). The bLas were higher during both IT programs: IT1, 6.3 mmol·L(-1) (5.6/7.2 mmol·L(-1)); IT2, 5.8 mmol·L(-1) (5.0/6.5 mmol·L(-1)). The bLas of most individuals were close to the median values (±2.4 mmol·L(-1)). However, in each of the training programs, some subjects showed bLa values that were clearly above (3-7 mmol·L(-1) higher). In particular, SDSs reached higher bLas at the same intensity compared with LDSs. It is concluded that intensity prescriptions by means of IAT seem to elicit an expected metabolic response in approximately 85% of swim training sessions. The observed average bLa is in the range of those recommended in the scientific literature.