Reviewed by John Baur, PT, DPT, OCS, CSCS, FAAOMPT
This narrative review explains how the 3‑minute all‑out exercise test (3MT) operationalizes the critical speed (CS) and critical power (CP) framework so coaches can prescribe precisely targeted high‑intensity interval training (HIIT) from a single test session. In brief, CS/CP represents the highest intensity at which a metabolic steady state can be sustained during continuous exercise; above CS/CP, time to task failure becomes predictable. The 3MT exploits this relationship by letting an athlete go “all‑out” for three minutes and deriving CS/CP and the finite work/distance capacity above that threshold—W′ (cycling/rowing) or D′ (running/swimming)—from the speed/power trace. That makes it possible to individualize intervals using exact fractions of W′/D′ rather than crude percentages of maximums or reserves.
Conceptual basis and what the 3MT estimates.
In running, the classic approach regresses multiple time‑trial distances to obtain a linear distance–time slope (CS) and an intercept (D′). The 3MT replaces those multiple visits: early in the test, the athlete uses up D′ while running above CS; as D′ nears depletion, speed falls to a plateau that reflects CS. Thus, the average speed over the final 30 seconds equals CS, whereas the mean speed above CS earlier in the test quantifies D′. Figure 2 in the article illustrates this with an example where CS = 4.0 m·s⁻¹ and D′ = 180 m. The review frames CS/CP as the organizing metric of sustainable vs. non‑sustainable intensities and argues it offers more physiological specificity for interval work than percent max schemes.
Procedures and measurement quality.
For the running 3MT, the athlete runs all‑out for three minutes while speed or distance is monitored (e.g., GPS, timing splits); pace cues are concealed to discourage conscious pacing. Quality checks include reaching near‑max speed in ≈10 s, attaining ≈90% of 40‑m sprint speed at peak, and expending ≈90% of D′ in the first 90 s. The test shows strong reliability and validity (CS and D′ intraclass correlations ≈0.92–0.96). The cycling 3MT uses a fixed flywheel load (typically ~2–5% of body mass), originally requiring two visits but now supported by validated single‑visit load‑setting approaches. Rowing and swimming versions exist with acceptable agreement, although they are less studied than running/cycling.
Prescribing HIIT from CS/CP.
The 3MT enables interval design by specifying how much W′/D′ to deplete per bout and allowing precise rest for reconstitution. For cycling, power for a given interval duration can be set with
Power = (W′% / time) + CP, with rest (e.g., 5 min) chosen to standardize metabolic responses across sets (e.g., 60% vs. 80% W′ depletion). The review cites work where a mere 7‑W difference separated protocols that allowed completion of 3 vs. 4 five‑minute intervals, underscoring the fine control this method provides. For running, coaches can fix distance and compute target time that expends a specified D′ fraction, or fix time and compute the necessary speed above CS; both approaches produced similar physiological outcomes and robust improvements after 6 weeks.
Load carriage applications.
Tactical and occupational settings often require running with extra load. The review shows how the CS derived from an unloaded 3MT can be adjusted downward by a simple regression tied to load as % of body mass, accurately predicting the decline in performance under load and allowing interval prescriptions that match the new (loaded) CS. Example calculations in Table 1 show how CS of 4.0 m·s⁻¹ would fall to ≈3.74 m·s⁻¹ with 15% and ≈3.10 m·s⁻¹ with 25% body mass added.
Shuttle running and field sports. For team sports where changes of direction are intrinsic, a shuttle 3MT (25–70 m switch‑backs) is preferable for prescription to account for the energetic cost of accelerations, decelerations, and turning. The shuttle‑based CS derived from a shuttle 3MT predicts performance, aligns better with VO₂‑related measures than common field tests (e.g., CS–VO₂max r ≈ 0.90 vs. Yo‑Yo IR1 r ≈ 0.55), and avoids the overestimation of CS/D′ that occurs if a linear 3MT is used to set shuttle training.
Training effects, frequency, and caution.
Across studies using CS/CP‑guided HIIT, meaningful improvements in VO₂max, speed at VO₂max, gas‑exchange threshold, CS, and fatigue tolerance are typically achieved in 4–6 weeks with 2–3 sessions per week. However, placing too much training above CS/CP without adequate relief can promote progressive metabolic strain, elevating the risk for overreaching/overtraining, so monitoring of internal and external load remains essential.
Safety and contraindications.
The test is self‑moderating (athletes can’t exceed their capacity by definition), but caution is warranted. The cycling 3MT likely carries a lower musculoskeletal risk because it relies predominantly on concentric contractions; athletes should remain seated to avoid forceful accessory motions. The running 3MT should be avoided during musculoskeletal recovery; if an athlete isn’t cleared to sprint 40 m, they shouldn’t perform the test. The high ventilatory demand can trigger symptoms in athletes with asthma or vocal‑cord dysfunction, and the test is contraindicated with sickle‑cell trait.
Future directions.
The authors anticipate closer integration of CS/CP, D′/W′ and wearable technologies for “live” energetic modeling in sport and tactical environments, including potential match‑play applications and periodized modulation of severe‑intensity work to optimize adaptation while minimizing risk. Figure 1 in the paper also shows the rapid growth in CS/CP literature since the early 2000s, coinciding with the rise of the 3MT.
Bottom line:
The 3MT–CS/CP approach compresses testing into one efficient session, yields individualized, physiologically anchored interval prescriptions across running, cycling, swimming, rowing, and shuttle running, and now includes load‑carriage corrections for tactical use—all with strong measurement properties and practical guardrails for safe implementation.
- What is the primary reason the 3-minute all-out test was developed?
Answer: b. To estimate the time for onset of momentary fatigue at a given intensity.
Rationale: The 3MT was designed to estimate when momentary fatigue occurs for speeds/powers exceeding CS/CP.
- Which of the following best describes critical speed and critical power?
Answer: a. They indicate an exercise intensity associated with a maximal steady state for continuous exercise.
Rationale: CS/CP correspond to the maximal metabolic steady state for continuous work.
- What is a key advantage of using the 3-minute all-out test over other traditional exercise testing methods?
Answer: a. It provides an efficient way to assess and prescribe high-intensity exercise without multiple laboratory visits.
Rationale: The 3MT replaced multi‑trial protocols by yielding CS/D′ or CP/W′ from a single session.
- How is critical speed (CS) derived from the 3-minute all-out running test?
Answer: c. By analyzing the average speed during the last 30 seconds in the test.
Rationale: The final 30‑s mean speed plateaus at CS as D′ is effectively exhausted.
- The cycling version of the 3-minute all-out test requires the athlete to pedal against a fixed load on a flywheel, typically between _______________ body mass.
Answer: b. 2 and 5%.
Rationale: Fixed flywheel loads of about 2–5% body mass are indicated.
- Why does the CS/CP concept make an effective method for prescribing individualized HIIT?
Answer: a. It represents the metabolic rate that determines exercise sustainability, allowing for precise interval training.
Rationale: Intervals can target exact W′/D′ depletion above CS/CP.
- Why is the shuttle 3-minute all-out test preferred for prescribing HIIT in shuttle-based training rather than relying on a linear 3MT?
Answer: a. It accounts for the added energy expenditure with acceleration, deceleration, and turning.
Rationale: Linear CS/D′ overestimates sustainable shuttle work; shuttle 3MT corrects for stop‑and‑go costs.
- Research consistently demonstrates training improvements from HIIT using the CP/CS concept within _______________ with a frequency of __________________.
Answer: a. 4–6 weeks, 2–3 times per week.
Rationale: The review recommends cautious application, noting typical gains over 4–6 weeks at 2–3 sessions weekly.
- There is a lower risk of musculoskeletal injuries when performing the ______________3-minute all-out test due to its reliance on concentric muscular contractions.
Answer: b. Cycling.
Rationale: Cycling emphasizes concentric actions and is recommended to minimize MSK risk.
- What is a key concern when implementing HIIT within the severe intensity domain (exceeding CP/CS) too frequently?
Answer: a. It can lead to progressive metabolic strain, increasing the risk of overreaching/overtraining.
Rationale: The article cautions against excessive severe‑domain loading without adequate monitoring and relief.
References:
Pettitt RW, Dicks ND, Kramer M. Applications of the 3‑Min All‑Out Exercise Test for Prescribing High‑Intensity Interval Training: A Narrative Review on a Decade of Research Progress. Strength Cond J. 2025;47(1):45‑55.