Shaun J. McLaren

The term training load first appeared within the cycling literature during the 1980s ( Impellizzeri et al ., 2023 ), although its use among riders and coaches likely predates this. It has since been conceptualised in a way that meets the requirements to be considered a scientific construct that can be understood using the scientific method ( Impellizzeri et al ., 2022 ). ‘Training load’ is a label assigned to a construct that has been created by observing a phenomenon (training). This has been defined as: A higher-order construct reflecting the amount of physical training that was actually done or experienced by athletes. ( Jeffries et al ., 2022 )

This study examined the concurrent and criterion validity of a football-specific intermittent-variable submaximal fitness test (SMFT) as an indicator of cardiorespiratory fitness. Eighteen male senior football players were monitored over a 12-week period using a repeated measures design. Each week, a standardised Y-shape passing drill (practical SMFT) was administered immediately following a 4-min continuous run (criterion SMFT), with exercise heart rate (HRex) measured during both protocols. Laboratory-derived measures of cardiorespiratory fitness were assessed at the start and end of this period. The within-player correlation between HRex from the two SMFTs was large, with a clear improvement in the relationship (Δ r ≈0.2) and model fit (χ² = 52.1, p < 0.001; adjusted vs unadjusted model statistics: marginal-R² = 0.56 vs 0.29, Akaike information criterion = 434.8 vs 477.0, root mean square error = 1.63 vs 2.21%-points of HR_max) after adjusting for passing drill total and high-speed running distances. Adjusted HRex values from the passing drill showed stronger associations (r ≈-0.70 vs -0.35) with maximal oxygen uptake and maximal aerobic speed. A Y-shape passing drill offers a valid and practical assessment of cardiorespiratory fitness within the SMFT framework. We provide a method to guide practitioners in adjusting HRex for external training load, thereby improving agreement with criterion SMFT running protocols.

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; p _MET 0.108). Conversely, changes in 10-m sprint (0.82 ± 0.66; p _MET 0.062), 20-m sprint (0.95 ± 0.71; p _MET 0.043), 30-m sprint (0.104 ± 0.73; p _MET 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.

We examined the effects of repeated sprint training (RST) session volume on acute physiological, neuromuscular, perceptual and performance outcomes. In a randomised, counterbalanced, and crossover design, 14 healthy and trained male and female athletes (age: 23 ± 3 years) completed two sets of 10 × 40 m (10 × 40), 5 × 40 m (5 × 40), 10 × 20 m (10 × 20) and 5 × 20 m (5 × 20) sprints with 30 s rest between repetitions and 3 min rest between sets for all protocols. Average and peak heart rate, average oxygen consumption (VO₂), time >90% of maximal oxygen consumption (VO_2max), differential ratings of perceived exertion (RPE), session‐RPE training load (sRPE‐TL), percentage sprint decrement (S_dec), acceleration load and distance >90% of maximal sprint speed were recorded during each session. Neuromuscular performance (i.e. countermovement jump, lower‐limb stiffness and isometric hamstring strength) were measured post‐session, 24 h, and 48 h and compared to pre‐session. A univariate analysis of variance was used to compare within‐ and between‐protocol differences. To aid data interpretation, all effects were expressed as an effect size and accompanied by probability values (p_MET). The 10 × 40 protocol induced the greatest training load compared to all other protocols (p_MET < 0.05), including moderate to very large differences in breathlessness RPE, large differences in S_dec and time >90% VO_2max and very large differences in sRPE‐TL. The 5 × 20 protocol induced the lowest training load compared to all other protocols (p_MET < 0.05), including moderate to large differences in sRPE‐TL and leg muscle RPE. Heart rate, VO₂, sRPE‐TL, leg muscle RPE and S_dec were similar between 5 × 40 and 10 × 20 (p_MET < 0.05), but the acceleration load was greater for 10 × 20 when compared to 5 × 40 (p_MET < 0.001), and this difference was large. Changes in neuromuscular performance across all timepoints and all protocols were unclear. Larger session volumes increase the demands of RST and by manipulating volume, sprint distance and the number of repetitions, practitioners can alter the internal and external training load.

Background Repeated-sprint training (RST) is a common training method for enhancing physical fitness in athletes. To advance RST prescription, it is important to understand the effects of programming variables on physical fitness and physiological adaptation. Objectives This study (1) quantifies the pooled effects of running RST on changes in 10 and 20 m sprint time, maximal oxygen consumption (VO_2max), Yo-Yo Intermittent Recovery Test Level 1 (YYIR1) distance, repeated-sprint ability (RSA), countermovement jump (CMJ) height and change of direction (COD) ability in athletes, and (2) examines the moderating effects of program duration, training frequency, weekly volume, sprint modality, repetition distance, number of repetitions per set and number of sets per session on changes in these outcome measures. Methods Pubmed, SPORTDiscus and Scopus databases were searched for original research articles up to 04 July 2023, investigating RST in healthy, able-bodied athletes, between 14 and 35 years of age, and a performance calibre of trained or above. RST interventions were limited to repeated, maximal running (land-based) sprints of ≤ 10 s duration, with ≤ 60 s recovery, performed for 2–12 weeks. A Downs and Black checklist was used to assess the methodological quality of the included studies. Eligible data were analysed using multi-level mixed-effects meta-analysis, with standardised mean changes determined for all outcomes. Standardised effects [Hedges G (G)] were evaluated based on coverage of their confidence (compatibility) intervals (CI) using a strength and conditioning specific reference value of G = 0.25 to declare an improvement (i.e. G > 0.25) or impairment (i.e. G < − 0.25) in outcome measures. Applying the same analysis, the effects of programming variables were then evaluated against a reference RST program, consisting of three sets of 6 × 30 m straight-line sprints performed twice per week for 6 weeks (1200 m weekly volume). Results 40 publications were included in our investigation, with data from 48 RST groups (541 athletes) and 19 active control groups (213 athletes). Across all studies, the effects of RST were compatible with improvements in VO_2max (G 0.56, 90% CI 0.32–0.80), YYIR1 distance (G 0.61, 90% CI 0.43–0.79), RSA decrement (G − 0.61, 90% CI − 0.85 to − 0.37), linear sprint times (10 m: G − 0.35, 90% CI − 0.48 to − 0.22; 20 m: G − 0.48, 90% CI − 0.69 to − 0.27), RSA average time (G − 0.34, 90% CI − 0.49 to − 0.18), CMJ height (G 0.26, 90% CI 0.13–0.39) and COD ability (G − 0.32, 90% CI − 0.52 to − 0.12). Compared with the reference RST program, the effects of manipulating training frequency (+ 1 session per week), program duration (+ 1 extra training week), RST volume (+ 200 m per week), number of reps (+ 2 per set), number of sets per session (+ 1 set) or rep distance (+ 10 m per rep) were either non-substantial or comparable with an impairment in at least one outcome measure per programming variable. Conclusions Running-based RST improves speed, intermittent running performance, VO_2max, RSA, COD ability and CMJ height in trained athletes. Performing three sets of 6 × 30 m sprints, twice per week for 6 weeks is effective for enhancing physical fitness and physiological adaptation. Additionally, since our findings do not provide conclusive support for the manipulation of RST variables, further work is needed to better understand how programming factors can be manipulated to augment training-induced adaptations. Study Registration Open Science Framework registration https://doi.org/10.17605/OSF.IO/RVNDW.

Purpose: To survey team-sport practitioners on current practices and perceptions of submaximal fitness tests (SMFTs). Methods: A convenience sample of team-sport practitioners completed an online survey (September to November 2021). Descriptive statistics were used to obtain information of frequencies. A mixed-model quantile (median) regression was employed to assess the differences between the perceived influence of extraneous factors. Results: A total of 66 practitioners (74 discrete protocols) from 24 countries completed the survey. Time-efficient and nonexhaustive nature were considered the most important features of implementation. Practitioners prescribed a range of SMFTs, administered mostly on a monthly or weekly basis, but scheduling strategies appeared to differ across SMFT categories. Cardiorespiratory/metabolic outcome measures were collected in most protocols (n = 61; 82%), with the majority monitoring heart-rate-derived indices. Subjective outcome measures (n = 33; 45%) were monitored exclusively using ratings of perceived exertion. Mechanical outcome measures (n = 19; 26%) included either a combination of locomotor outputs (eg, distance covered) or variables derived from microelectrical mechanical systems. The perceived influence of extraneous factors on measurement accuracy varied according to outcome measure, and there was a lack of consensus among practitioners. Conclusions: Our survey showcases the methodological frameworks, practices, and challenges of SMFTs in team sports. The most important features for implementation perhaps support the use of SMFTs as a feasible and sustainable tool for monitoring in team sports. The wide variety of protocols, scheduling strategies, and outcome measures, along with their associated collection and analytical techniques, may reflect the absence of robust evidence regarding the application of SMFTs in team sports.

Background: Repeated-sprint training (RST) involves maximal-effort, short-duration sprints (≤ 10 s) interspersed with brief recovery periods (≤ 60 s). Knowledge about the acute demands of RST and the influence of programming variables has implications for training prescription.Objectives: To investigate the physiological, neuromuscular, perceptual and performance demands of RST, while also examining the moderating effects of programming variables (sprint modality, number of repetitions per set, sprint repetition distance, inter-repetition rest modality and inter-repetition rest duration) on these outcomes.Methods: The databases Pubmed, SPORTDiscus, MEDLINE and Scopus were searched for original research articles investigating overground running RST in team sport athletes ≥ 16 years. Eligible data were analysed using multi-level mixed effects meta-analysis, with meta-regression performed on outcomes with ~ 50 samples (10 per moderator) to examine the influence of programming factors. Effects were evaluated based on coverage of their confidence (compatibility) limits (CL) against elected thresholds of practical importance.Results: From 908 data samples nested within 176 studies eligible for meta-analysis, the pooled effects (± 90% CL) of RST were as follows: average heart rate (HR_avg) of 163 ± 9 bpm, peak heart rate (HR_peak) of 182 ± 3 bpm, average oxygen consumption of 42.4 ± 10.1 mL·kg⁻¹·min⁻¹, end-set blood lactate concentration (B[La]) of 10.7 ± 0.6 mmol·L⁻¹, deciMax session ratings of perceived exertion (sRPE) of 6.5 ± 0.5 au, average sprint time (S_avg) of 5.57 ± 0.26 s, best sprint time (S_best) of 5.52 ± 0.27 s and percentage sprint decrement (S_dec) of 5.0 ± 0.3%. When compared with a reference protocol of 6 × 30 m straight-line sprints with 20 s passive inter-repetition rest, shuttle-based sprints were associated with a substantial increase in repetition time (S_avg: 1.42 ± 0.11 s,S_best: 1.55 ± 0.13 s), whereas the effect on sRPE was trivial (0.6 ± 0.9 au). Performing two more repetitions per set had a trivial effect on HR_peak(0.8 ± 1.0 bpm), B[La] (0.3 ± 0.2 mmol·L⁻¹), sRPE (0.2 ± 0.2 au),S_avg(0.01 ± 0.03) andS_dec(0.4; ± 0.2%). Sprinting 10 m further per repetition was associated with a substantial increase in B[La] (2.7; ± 0.7 mmol·L⁻¹) andS_dec(1.7 ± 0.4%), whereas the effect on sRPE was trivial (0.7 ± 0.6). Resting for 10 s longer between repetitions was associated with a substantial reduction in B[La] (−1.1 ± 0.5 mmol·L⁻¹),S_avg(−0.09 ± 0.06 s) andS_dec(−1.4 ± 0.4%), while the effects on HR_peak(−0.7 ± 1.8 bpm) and sRPE (−0.5 ± 0.5 au) were trivial. All other moderating effects were compatible with both trivial and substantial effects [i.e. equal coverage of the confidence interval (CI) across a trivial and a substantial region in only one direction], or inconclusive (i.e. the CI spanned across substantial and trivial regions in both positive and negative directions).Conclusions: The physiological, neuromuscular, perceptual and performance demands of RST are substantial, with some of these outcomes moderated by the manipulation of programming variables. To amplify physiological demands and performance decrement, longer sprint distances (> 30 m) and shorter, inter-repetition rest (≤ 20 s) are recommended. Alternatively, to mitigate fatigue and enhance acute sprint performance, shorter sprint distances (e.g. 15–25 m) with longer, passive inter-repetition rest (≥ 30 s) are recommended.