Optimizing Maximal Aerobic Speed and Shuttle-Based Endurance Performance

Determinants of Shuttle-Based Aerobic Performance

Field- and court-sport athletes frequently rely on intermittent, shuttle-based endurance capacity rather than continuous linear aerobic capacity. Shuttle tests—such as the Yo-Yo Intermittent Recovery Tests (Yo-Yo IR1 and IR2), the 20-meter Multi-Stage Fitness Test (20m MFT), and the 30–15 Intermittent Fitness Test (30–15 IFT)—evaluate not only maximal oxygen uptake ($\dot{V}\text{O}_2\text{max}$) and maximal aerobic speed (MAS), but also repeated acceleration, deceleration, and 180° change-of-direction (COD) mechanics [1, 8, 15].

Designing effective conditioning interventions requires understanding how distinct training modalities target linear velocity, anaerobic speed reserve (ASR = maximum sprinting speed − MAS), and intermittent recovery capacity [18].

Running-Based High-Intensity Interval Training (HIIT)

Running-based HIIT allows precise calibration of external training intensities using benchmarks such as MAS, velocity in the 30–15 IFT ($V_{\text{IFT}}$), or ASR [9, 18]. Common formats include:

• Long HIIT: 90–105% MAS for 1–6 minutes [18].
• Short HIIT: 100–130% MAS for 15–60 seconds [18].
• Sprint Interval Training (SIT): Supramaximal bouts of 15–45 seconds with 2–4 minutes passive recovery [18].

In meta-analytic evaluations of trained adolescent athletes (McKay Tier $\ge$2), HIIT-based interventions produced substantial improvements in $V_{\text{IFT}}$ (SMD = 1.13, 95% CI [0.63, 1.63]) and field-based intermittent shuttle endurance (Yo-Yo IR1/IR2, 20m multistage: SMD = 0.65, 95% CI [0.07, 1.23]), alongside significant enhancements in $\dot{V}\text{O}_2\text{max}$ (SMD = 0.65) and COD speed (SMD = -0.54) [8]. In female team-sport athletes, HIIT performed at 80–100% HRmax yielded consistent increases in $\dot{V}\text{O}_2\text{max}$ (ES 0.19 to 1.08), COD speed (ES 0.34 to 0.88), and repeated sprint ability (RSA: ES 0.32 to 0.64) [5].

Network meta-analysis comparing conditioning modalities in soccer players showed that running-based HIIT ranked highest for improving shuttle-based Yo-Yo IR1 performance (SUCRA = 86.2; SMD = 0.78, p = 0.001) and $\dot{V}\text{O}_2\text{max}$ (SUCRA = 74.3; SMD = 0.53, p = 0.007) [7].

Running-Based HIIT vs. Small-Sided Games (SSGs)

Small-sided games integrate high cardiovascular loads with technical and tactical execution, naturally eliciting repeated accelerations and decelerations [9, 10]. In youth team-sport athletes, SSG conditioning significantly enhances maximal aerobic capacity (SMD = 0.78), intermittent high-intensity endurance (SMD = 1.05), sprint acceleration (SMD = -0.55), and COD ability (SMD = -0.85) [1]. In untrained young adults, handball-based SSGs (maintaining HR >85% $\text{HR}_{\text{max}}$) improved $\dot{V}\text{O}_2\text{max}$ by ~7 mL·kg⁻¹·min⁻¹ and enhanced 20m MFT performance to an extent equivalent to track-based HIIT [10].

However, when directly compared in controlled trials, running-based HIIT demonstrates specific advantages for high-end shuttle test outcomes:

• In a meta-analysis of 17 RCTs involving male adolescent team-sport athletes, HIIT demonstrated a statistically superior improvement over SSG in Yo-Yo IR1 performance (SMD = 0.42, 95% CI [0.09, 0.74], $I^2 = 0%$), while adaptations in $\dot{V}\text{O}2\text{max}$ (SMD = 0.05), $V{\text{IFT}}$ (SMD = 0.24), and COD (SMD = 0.00) remained comparable between modalities [2].
• Running-based HIIT is significantly superior to SSG for linear sprint adaptations (between-group ES = 0.42, p = 0.012), whereas neither modality reliably induces vertical jump improvements without targeted resistance training [3].

Combining MAS-based intervals with SSG training is highly effective: a 12-week intervention demonstrated that both MAS combined with SSG and MAS alone produced significant gains in Yo-Yo IR1 distance and $\dot{V}\text{O}_2\text{max}$ compared to standard routine training (p = 0.001) [4]. Conversely, unstructured concurrent implementation of HIIT and SSG within the same microcycles may impair sprint performance (20-m sprint SMD = 1.84, p = 0.002) if total volume and fatigue are unmanaged [7].

Linear HIIT vs. Change-of-Direction (COD) HIIT

Because shuttle endurance tests require 180° turns, incorporating directional changes into HIIT prescriptions is frequently explored [13, 15]. Introducing 180° turns increases the metabolic and mechanical cost of running; standard programming adjustments typically reduce interval running distance by 2–3% per directional change (e.g., a ~7% total distance reduction for three 180° turns) to maintain equivalent prescribed intensities [15].

In elite female soccer players, comparing straight-line intervals (HIIT LIN) to intervals with three 180° turns (HIIT COD) demonstrated that both modalities produced significant, equivalent improvements across 10m–30m sprint speed, agility (Pro-agility, Zig-zag), RSA, $\dot{V}\text{O}2\text{max}$, and $V{\text{IFT}}$, with HIIT COD offering no superior adaptation over linear running [13]. However, higher COD density per interval bout (e.g., three turns vs. one turn) has previously shown greater aerobic and repeated-sprint adaptations in court-based athletes [13]. Over acute microcycles, high-density shock HIIT microcycles can accelerate 30–15 IFT improvements, though they do not improve running economy [17].

Repeated Sprint Training (RST)

Repeated sprint training (RST; sprint durations <10 s, recovery <60 s at 85–100% maximum sprinting speed) targets neuromuscular power, acceleration, and phosphocreatine resynthesis [11, 18]. Meta-analytic evidence indicates that RST effectively enhances linear acceleration and speed (10-m sprint ES = 1.01; 20-m sprint ES = 0.80), COD speed (ES = 0.60), and best repeated-sprint time (ES = 0.48) in youth athletes [11]. RST also significantly improves overall repeated-sprint ability in trained adolescents (SMD = -0.70) [8].

However, RST alone is insufficient to maximize aerobic speed or shuttle endurance: it fails to induce statistically significant gains in maximal aerobic capacity compared to control training [11].

Blood Flow Restriction (BFR) Combined with Interval Training

Combining interval training with blood flow restriction (IT+BFR) can serve as an intensifier for maximal aerobic speed and aerobic power [19]. A meta-analysis of 24 studies showed that IT+BFR produces greater improvements in MAS (g = 0.74, $I^2 = 0%$) and $\dot{V}\text{O}_2\text{max}$ (g = 0.63) compared to interval training alone, alongside improvements in time to fatigue (g = 1.26) and 30-s Wingate mean power (g = 0.70) [19]. Meta-regression indicates that these adaptations depend on cuff dimensions, with a minimum cuff width threshold of 8.23 cm required to achieve significant improvements [19].

Summary of Comparative Efficacy

1. Yo-Yo IR and Intermittent Shuttle Endurance: Structured running-based HIIT provides the highest relative effect sizes and consistently outperforms isolated SSGs (SMD = 0.42 advantage for Yo-Yo IR1) [2, 7, 8].
2. Aerobic Power ($\dot{V}\text{O}_2\text{max}$ and MAS): Both running-based HIIT and SSGs yield large improvements, with running-based HIIT offering precise intensity control around 100–130% MAS [2, 9, 18]. IT+BFR serves as an effective adjunct to further enhance MAS (g = 0.74) [19].
3. Sprint and COD Transfer: Running-based HIIT and RST effectively target linear speed and acceleration [3, 8, 11]. Adding COD turns into HIIT intervals is viable when distance is adjusted (~2–3% reduction per 180° turn), although linear HIIT provides comparable transfer across field-based fitness markers [13, 15].