The Effects of Repeated-Sprint Training vs. Short-Bout High-Intensity Interval Training on Hamstring Architecture and Physical Fitness
Bibliographic record
Abstract
ABSTRACT: Thurlow, F, Timmins, R, McLaren, SJ, Lawton, B, Cowley, N, Townshend, A, and Weakley, J. The effects of repeated-sprint training vs. short-bout high-intensity interval training on hamstring architecture and physical fitness. J Strength Cond Res 39(5): e620-e627, 2025-The aim of the study was to quantify and compare the effects of repeated-sprint training (RST) vs. short-bout high-intensity interval training (HIIT) on hamstring architecture and physical fitness in rugby league players. A parallel, 2-group, pretest posttest design was used, whereby 24 representative U20 players were assigned to either RST or short-bout HIIT for a 6-week intervention delivered alongside usual training. Assessments of biceps femoris long-head (BFlh) muscle architecture, countermovement jump (CMJ), eccentric hamstring strength, sprint force-velocity power (FVP) profiles, and 1,200 m shuttle run time (i.e., aerobic fitness) were performed. Compared with baseline, the RST group was associated with moderate improvements in aerobic fitness (change ±90% confidence interval [CI]: -4 ± 5 seconds) and maximal theoretical velocity (0.11 ± 0.10 m·s-1), as well as a moderate increase in BFlh fascicle length (1.05 ± 0.46 cm), a small increase in BFlh muscle thickness (0.12 ± 0.16 cm), and a moderate reduction in the BFlh pennation angle (-0.85 ± 0.64°). The short-bout HIIT group was associated with a moderate improvement in aerobic fitness (-10 ± 4 seconds) and a small improvement in CMJ peak power (1.4 ± 1.4 W·kg-1), as well as a large increase in BFlh fascicle length (0.99 ± 0.44 cm), a moderate increase in BFlh muscle thickness (0.15 ± 0.13 cm), and a small reduction in the BFlh pennation angle (-0.67 ± 0.50°). Changes in aerobic fitness were greater for short-bout HIIT when compared to RST, and this difference was moderate (effect size ±90% CI: 0.89 ± 0.82; pMET 0.108). Conversely, changes in 10-m sprint (0.82 ± 0.66; pMET 0.062), 20-m sprint (0.95 ± 0.71; pMET 0.043), 30-m sprint (0.104 ± 0.73; pMET 0.031) times, and certain FVP characteristics, were greater for RST, and these differences were moderate. Both groups increased fascicle length, but RST was more effective at improving sprint speed, while short-bout HIIT was more effective for improving aerobic fitness. Collectively, our findings demonstrate the potential benefits of these conditioning methods, which may cause morphological, physiological, and neuromuscular adaptations in athletes when applied alongside usual training practice.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".