Is lactate testing a reliable method for determining the lactate threshold in healthy adult athletes?

Lactate Testing for Threshold Determination in Athletes

Yes, lactate testing is a reliable and valuable method for determining intensity thresholds in athletes, particularly when proper protocols and standardized methods are used. 1

Evidence Supporting Reliability

Lactate threshold testing demonstrates excellent reliability across multiple testing sessions, with intraclass correlation coefficients ranging from 0.98 to 0.99 for velocity measurements and standard errors of only 0.06 to 0.14 km/hr. 2 The 2023 Sports Medicine guidelines explicitly state that lactate is "valuable for determining intensity thresholds in physiological exercise testing" and is "one of the most used and studied blood biomarkers in sports science." 1

Key Reliability Metrics

• Velocity at lactate threshold: ICC 0.98-0.99, demonstrating near-perfect reproducibility 2
• VO2 at lactate threshold: ICC 0.91-0.96, showing strong reliability 2
• Heart rate at lactate threshold: ICC 0.75-0.96, with acceptable to excellent reliability 2

Optimal Testing Protocols

The lactate minimum test shows superior accuracy compared to traditional threshold concepts, with mean differences from maximal lactate steady state of only 0.01±0.14 m/s and an ICC of 0.964. 3 This outperforms both OBLA (4 mmol/L fixed threshold) and modified Dmax methods. 3

Standardized Approaches

The standardized lactate threshold methods (LTSDs and LTSDp) demonstrate:

• High relative reliability: ICC ≥ 0.98 4
• Excellent absolute reliability: Coefficient of variation ≤ 1.9% 4
• Strong correlation with race performance: Within 2.3% of 10-15 km time trial speeds 4

Critical Technical Considerations

Proper sampling technique is essential for reliable results. The ATS/ACCP guidelines emphasize that "determination of the point of rise in lactate requires multiple blood samples" and recommend "visual inspection of the plot of [La] versus VO2 to verify reliability of the computed AT." 1

Sampling Site Consistency

• Fingertips, toes, and earlobes are all acceptable sites, but practitioners must choose one and maintain consistency throughout longitudinal monitoring 1
• Slight but potentially significant differences exist between sites during graded exercise, making site-switching problematic 1
• Different portable lactate systems from various manufacturers may yield different values, requiring consistency in equipment selection 1

Sample Handling Requirements

• Collect in prechilled fluoride-oxalate tubes 5
• Transport on ice and process within 4 hours 5
• Draw without tourniquet application or fist-clenching to avoid artifactual elevation 5
• Never draw from lines carrying glucose-containing solutions, as contamination creates serious risk of falsely elevated values 5

Important Confounding Factors

Multiple variables can affect measured lactate levels beyond actual threshold changes, requiring careful interpretation. 1

Nutritional Influences

• Low-carbohydrate availability shifts lactate thresholds toward higher workloads on short-term low-carb diets compared to mixed diets 1
• Glycogen depletion during repeated high-intensity training may lower lactate levels in subsequent sessions, which should not be interpreted as improved training status 1

Physiological Variables

• Lactate production, elimination, transportation, and blood flow all influence measured values 1
• The combination of lactate and heart rate measures correlates well with RPE during high-intensity soccer exercise but not during submaximal cycling 1

Clinical Application for Athletes

The lactate threshold normally occurs at approximately 50-60% of predicted VO2max in sedentary individuals, with a wide normal range of 35-80%, and trained athletes typically demonstrate higher thresholds. 6 Work rates below the lactate threshold can be sustained essentially indefinitely without significant lactate accumulation. 6

Alternative Testing Methods

When direct lactate measurement is not feasible:

• Standard bicarbonate from arterial blood gases can substitute, as bicarbonate decreases almost reciprocally with lactate increase 1, 6
• The 30-minute time trial method provides accurate estimation of both running velocity (SEE 0.21 m/s) and heart rate (SEE 8.0 bpm) at lactate threshold 7

Common Pitfalls to Avoid

• Do not assume a blunted lactate response indicates pathology without first confirming that exercise intensity exceeded the threshold 6
• Avoid changing sampling sites or equipment during longitudinal monitoring, as this introduces measurement variability 1
• Do not interpret lower lactate values during glycogen-depleted states as training improvements 1
• Ensure adequate exercise intensity during testing; the threshold cannot be determined if the athlete does not reach sufficient workload 6

Despite the lack of rigorous analytical and clinical validation of lactate as a surrogate endpoint in all sports contexts 1, the extensive evidence base, excellent reliability metrics, and strong correlation with performance outcomes support its use as a primary tool for threshold determination in athletes when proper protocols are followed.