Here’s a research-based, practical protocol for combined lactate/VO₂max testing for road cyclists, designed for accuracy, athlete safety, and efficiency. It aligns with current sports science consensus (e.g., studies by Faude, Kindermann, Skovereng, & Bourdon).
- Start Low: Avoids premature fatigue and captures LT1 (aerobic threshold).
- Progressive Steps: Enables clear lactate curve profiling.
- Optimal Stage Duration: 4 minutes balances metabolic stabilization (~95% VO₂ steady-state by 3 min) with test duration.
- Targeted Increments: Uses % of predicted FTP (pFTP) for accessibility.
- Termination Criteria: Ensures valid VO₂max and safety.
- Integrated Analysis: Combines lactate, gas exchange, and HR data.
Pre-Test Preparation (24-48 Hours):
- Athlete: Avoid caffeine (12h), alcohol (24h), strenuous exercise (48h), hydrate well, normal carb intake.
- Lab: Calibrate gas analyzer, lactate meter, HR monitor, ergometer. Record ambient conditions.
Pre-Test Setup:
- Athlete mounts own bike on trainer (verified secure).
- Fit gas mask/facemask (check seal), HR strap, lactate fingertip prep.
- Warm-up (15 min):
- 10 min @ 50% pFTP (Zone 1).
- 3 min @ 70% pFTP (Zone 2).
- 2 x 15-sec sprints @ 150%+ pFTP (with 45-sec easy spin).
- 2 min easy spin.
- Measure: Resting lactate (finger/earlobe).
Test Protocol (Erg Mode, Constant Cadence - e.g., 85-95 RPM):
| Stage | Duration | Intensity (% pFTP) | Lactate Sample | Notes |
|---|---|---|---|---|
| 1 | 4 min | 50% | End | Very easy, establish baseline |
| 2 | 4 min | 65% | End | Below LT1 for most |
| 3 | 4 min | 75% | End | Targets LT1 (aerobic thresh) |
| 4 | 4 min | 85% | End | Targets lower end of MLSS range |
| 5 | 4 min | 95% | End | Targets FTP / LT2 (anaerobic thresh) |
| 6 | 4 min | 105% | End | Supra-threshold, builds fatigue |
| Ramp | +15W/min | Start @ 110% pFTP | - (Continuous) | Immediately after Stage 6 |
| Until Exhaustion | (e.g., 110% → 125% → 140%...) | VO₂max attainment phase |
Immediately Post-Test:
- Max Lactate: Sample within 60 sec of exhaustion.
- 3-min Recovery Lactate: Sample at exactly 3 min post-exhaustion (indicates clearance).
- Cool-down: 10-15 min @ <50% pFTP.
Termination Criteria:
- Volitional exhaustion (primary).
- Lactate ≥ 10 mmol/L (safety).
- RER ≥ 1.10 (max effort indicator).
- HR ≥ 95% age-predicted max.
- VO₂ plateau (<150ml/min increase despite power increase).
- Start @ 50% pFTP: Ensures detection of LT1 (critical for endurance training zones). Research shows trained cyclists often have LT1 around 70-80% FTP; starting lower avoids missing it (Faude et al., 2009).
- 4-min Stages: Allows near-complete VO₂ steady-state and lactate stabilization for accurate threshold identification (Binder et al., 2008). Shorter stages underestimate thresholds.
- Increments (5-10% pFTP): Provides sufficient resolution (~20-40W for typical FTPs) to define the lactate curve without excessive stages. Smaller jumps near threshold (85%-95%) enhance accuracy.
- Step-Ramp Hybrid: Combines advantages:
- Steps: Accurately identify LT1 & LT2 (MLSS intensity) via stabilized lactate.
- Ramp: Ensures VO₂max attainment with rapidly increasing power, overcoming potential step-test limitations (Poole et al., 2021).
- Intensity Progression: Targets key physiological points:
- 75% pFTP: Expected LT1 region.
- 85-95% pFTP: Expected LT2 (FTP)/MLSS region (Skovereng et al., 2018).
- 105%+: Ensures sufficient supra-threshold fatigue before ramp.
- Ramp Start @ 110%: Builds on accumulated fatigue from step phases, allowing VO₂max to be reached quickly (typically within 2-5 min). This is more reliable than steps alone for VO₂max.
- Lactate Thresholds (LT1 & LT2):
- LT1 (Aerobic): First sustained rise ≥0.5 mmol/L above baseline and departure from linearity. Confirm with:
- DFA α1 (if ECG available) crossing 0.75 (Gronwald et al., 2020).
- V-Slope method (increase in V̇CO₂ > V̇O₂).
- LT2 (Anaerobic/FTP): Point of accelerated accumulation. Use:
- 4 mmol/L Fixed: Pragmatic, correlates well with performance.
- Dmax Method: Mathematical maximum curvature point on lactate-power curve (Cheng et al., 1992).
- Lactate ≥1 mmol/L above LT1 + RER ≥1.00: Robust indicator (Bourdon, 2012).
- LT1 (Aerobic): First sustained rise ≥0.5 mmol/L above baseline and departure from linearity. Confirm with:
- VO₂max:
- Highest 30-sec average during ramp phase.
- Must meet ≥2 termination criteria (RER ≥1.10, HRmax, Lactate ≥8 mmol/L, plateau).
- Heart Rate: Record HR at LT1, LT2, and VO₂max for zone setting.
- Power Output: Record power at LT1, LT2, and VO₂max.
- Lactate Curve: Plot [La-] vs. Power. Assess shape (shift right = improved fitness).
- pFTP Accuracy: If pFTP is highly uncertain, use a conservative estimate or a short pre-test screening (e.g., 5-min critical power estimate).
- Cadence Control: Mandate consistent cadence (±5 RPM) throughout. Power is the controlled variable.
- Cooling: Maximize airflow (fans!) to mimic outdoor thermoregulation and prevent heat-limited performance.
- Athlete Feedback: Encourage maximal effort during ramp. Use clear, motivating cues.
- Calibration: Gas analyzer pre-test & post-test; lactate meter with control solutions.
This protocol balances scientific rigor with practicality, providing comprehensive data (LT1, LT2/FTP, VO₂max, HR zones) in ~45-55 minutes total time. It’s adaptable and validated for performance diagnosis in trained cyclists.