What is performance diagnostics?
Performance diagnostics refers to medical and sports-scientific assessments used to objectively determine an individual's physical capacity. These tests are used not only in professional sport, but also in recreational and health-oriented activity. The aim is to define training zones, make progress measurable and identify health risks at an early stage.
Two methods have become particularly well established: the lactate test and spiroergometry. Both are usually carried out on a treadmill or cycle ergometer and show how the body responds under load – although with a different focus.
Why performance diagnostics can be worthwhile
Many recreational athletes train either too intensively or not intensively enough. Generic rules of thumb, such as "220 minus age" for maximum heart rate, are imprecise. Performance diagnostics can provide a sound basis for individually tailored training.
Typical reasons include:
- Returning to sport after a longer break
- Preparing for a competition (e.g. half marathon, cycling marathon)
- Stagnation despite regular training
- Assessing exercise tolerance in the presence of pre-existing conditions (in consultation with the treating doctor)
- A general appraisal of endurance capacity
The lactate test: focusing on metabolism
What is measured?
During a lactate test, blood is taken from the earlobe or fingertip at several exercise stages and the lactate level is determined. Lactate is a metabolic by-product that accumulates particularly when the body produces energy without sufficient oxygen – that is, during increasingly intense effort.
How is the test carried out?
The test usually starts with a light workload that is gradually increased. At each stage (typically three to five minutes), heart rate and lactate concentration are recorded. This produces a lactate performance curve, which shows the intensity at which metabolism shifts from predominantly aerobic to increasingly anaerobic.
What does the result tell us?
Several thresholds can be derived from the curve, commonly:
- Aerobic threshold: range of easy basic endurance
- Anaerobic threshold: the highest intensity that can be maintained for a longer period without a disproportionate rise in lactate
These values help to define training zones – for example, for easy long runs, intensive tempo sessions or interval training. Interpretation is always individual, as lactate values can fluctuate depending on daily form and nutrition.
Spiroergometry: breathing and energy supply
What is measured?
Spiroergometry combines an exercise test with analysis of respiratory gases. A breathing mask is used to measure oxygen uptake (VO₂) and carbon dioxide output (VCO₂), supplemented by ECG and blood pressure. This provides a detailed picture of cardiovascular and respiratory function under load.
Which values are particularly informative?
- VO₂max (maximum oxygen uptake): considered a key indicator of endurance capacity
- Ventilatory thresholds (VT1, VT2): transitions between exercise intensity zones, derived from respiratory gases
- Breathing efficiency and breathing reserve: indications of respiratory efficiency
- Respiratory quotient (RQ): shows whether fat or carbohydrate is being used predominantly for energy production
Who might benefit from spiroergometry?
The test is used in both sports medicine and internal medicine. It can help in the assessment of unclear exertional dyspnoea (shortness of breath on exertion), in estimating cardiopulmonary capacity or in fine-tuning training. In endurance sport, it provides additional information beyond a lactate test alone, such as the rate of fat metabolism.
Lactate test or spiroergometry – which is better?
There is no general answer to this question. The two methods complement each other.
- The lactate test is comparatively easy to perform and provides solid data for training control in endurance sport.
- Spiroergometry offers deeper insight into cardiovascular and respiratory function as well as energy supply.
In practice, a combination of both methods is often recommended in order to obtain as complete a picture as possible. Which test is most appropriate in an individual case should be decided together with the supervising doctor.
How are the tests organised?
Although the methods differ, the basic procedure is similar:
- Preparation: arrive well rested, avoid intense exercise on the test day, drink enough fluids, eat a light meal about 2–3 hours beforehand
- Medical history and pre-assessment: review of medical history, resting ECG, blood pressure measurement
- Incremental test: gradually increasing workload on a treadmill or cycle ergometer up to individual exhaustion or a defined stopping criterion
- Follow-up discussion: detailed review of findings with derivation of training recommendations
A complete diagnostic assessment usually takes 60 to 90 minutes.
What does the result mean for training?
The measured values are translated into individual training zones – often as heart rate or wattage ranges. This makes it easier to target when
- basic endurance is being built (long, steady sessions),
- fat metabolism is being trained,
- work is being done at threshold intensity,
- or short, intense intervals are appropriate.
A repeat assessment after a few months can show whether training is having the desired effect and whether the zones need to be adjusted.
Possible risks and limitations
Performance diagnostic tests are generally well-established procedures. As they require maximum effort, a medical assessment of exercise tolerance should be carried out beforehand – particularly in the case of cardiovascular disease, high blood pressure, diabetes, lung disease or when returning after a longer break. The validity of the values also depends on daily form, nutrition, sleep and the test protocol. Individual values should therefore always be interpreted in their overall context.
Conclusion
Lactate tests and spiroergometry are established components of modern performance diagnostics. They reveal what is happening in the body under load and provide an objective basis for individualised training. Anyone wishing to improve endurance in a structured way or to better assess their own exercise tolerance will find valuable guidance in these procedures – ideally embedded in medical consultation and a well-considered training plan.
This article does not replace medical advice.