REF-653 · Papadimitriou, Kabasakalis, Papadopoulos, Mavridis & Tsalis, 2023 · Sports, · Paper · PubMed
In 18 national-level age-group swimmers (13.5 y), a USRPT set (2 × 10 × 25 m at 100 m pace) gave higher swim velocity with lower lactate, glucose, HR and RPE than a 5 × 50 m HIIT set
But also lower distance per stroke and stroke index
Participants
n=18 national-level swimmers (8 boys, 10 girls), age 13.5 ± 0.1 y, 8.0 ± 0.5 y of swimming experience.
Both protocols oriented to the 100 m freestyle: USRPT = 2 × 10 × 25 m (USRPT1 and USRPT2); HIIT = 5 × 50 m.
Protocol
Acute within-subject comparison: eighteen national-level swimmers (8 boys, 10 girls; 13.5 ± 0.1 years; 8.0 ± 0.5 years of experience) each completed a USRPT and a HIIT protocol, both oriented to the 100 m freestyle (from the abstract); the order and rest intervals are not given in the abstract.
USRPT: 2 × 10 × 25 m (USRPT1 & USRPT2); HIIT: 5 × 50 m.
Measures: swimming velocity, distance per stroke, stroke index, blood lactate and glucose, heart rate and RPE.
Key Findings
Swimming velocity was significantly higher in USRPT than HIIT (p < 0.001).
Distance per stroke and stroke index were significantly lower in USRPT (p = 0.007 and p < 0.001) — faster, but with shorter, less efficient strokes.
Blood lactate and glucose were lower after USRPT (p ≤ 0.001 and p = 0.037); HR and RPE were lower after USRPT than HIIT (p < 0.001 and p = 0.015).
Authors' reading: a 20 × 25 m set at 100 m pace induces more event-specific responses in kinematics, biomarkers, HR and RPE than a 5 × 50 m HIIT set.
Practical Application
In 18 national-level 13-year-old swimmers, a 2 × 10 × 25 m USRPT set at 100 m pace produced higher swim velocity with lower lactate, HR and RPE than a 5 × 50 m HIIT set, at the cost of lower distance per stroke and stroke index — use USRPT when the goal is race-pace speed with low acute strain, and watch stroke length, since the short reps were swum with a less efficient stroke.
Treat as an acute-response comparison, not proof that USRPT trains better: no adaptation or race outcome was measured.
Not from this paper; the base's own practice: keep harder, longer HIIT sets for aerobic-power stress and use USRPT for speed and race-pace rehearsal.
Limitations
Age-group sample (n=18, 13.5 y), acute single-session comparison; no long-term performance or seasonal outcome.
Rest intervals and total work are not stated in the abstract, so "matched" work cannot be assumed.
How this entry was checked and changed
Why this level
regraded 2026-09-27 from C: acute crossover, n=18, no training-adaptation outcome
Content correction 2026-09-27
Entry omitted that distance per stroke and stroke index were significantly LOWER in USRPT (abstract) — added, since it changes the practical reading.
Removed "matched HIIT" and "generous rest" (not in the abstract); added the protocols (2 × 10 × 25 m vs 5 × 50 m), n=18 (8 boys, 10 girls, 13.5 y) and lower glucose.
Level regraded C -> B (acute crossover, n=18) per the 2026-09-26 rubric; the "small sample, acute" caveat stays in Limitations.
2026-09-28: added Protocol from the abstract (Europe PMC PMID 37755863).
2026-09-28: PMID 37755859 belonged to an unrelated paper; replaced with 37755863, the PubMed record for this entry's own DOI.