Heart Rate Deflection
The heart rate deflection point is a controversial way of establishing an athlete's anaerobic threshold. The anaerobic threshold is where the body starts to rely on producing energy anaerobically (literally without oxygen) rather than aerobically (literally without oxygen). The best way of measuring the anaerobic threshold is to take a blood sample and have it analyzed. This is obviously invasive, inconvenient, painful and somewhat expensive. In 1980, Italian sport scientist and medical doctor Francesco Conconi developed a test procedure for establishing an athlete anaerobic threshold based on heart rate. The idea behind the test is to have the athlete exercise of gradually increasing intensity while recording their heart rate. When the athlete starts to produce energy anaerobically, their heart rate will not go up proportionate to the intensity. This change from linear relationship between heart rate and intensity is called the Heart Rate Deflection (HRd).
1 The Conconi Test
This test should be performed on a 400 m track with a heart rate monitor that will record the test. After a thorough warm-up, the athlete should run at a comfortable pace for 200m, and then increase their pace slightly at each subsequent 200 m. Is the time to cover each 200 m segment needs to be recorded, and this can be done by hitting the lap button on the heart rate monitor. The original Conconi test called for the athlete to increase their pace by 0.5 Km/hr, which is remarkably tricky. A modified test has the athlete increasing the pace by 2 seconds per 200 m interval. The test continues until the athlete can no longer runs of the required pace.
2 Validity of the Conconi test
The Conconi test is remarkably controversial, with many potential issues.
- There is relatively little scientific support that actually validates the blood lactate levels in comparison to the HRd. Conconi's original work compared blood lactate levels at speeds above and below those seen as HRd, but the comparisons were performed on separate occasions.
- It is difficult for runners to increase their pace by precise amount and then hold that pace for a given distance.
- The changes in heart rate between each segment may be quite small.
- In many instances the HRd is difficult to identify or completely absent.
- Some studies have observed the when the HRd is discernible it can occur well above anaerobic threshold, creating a risk of overtraining.
- Other studies have shown a disassociation between HRd and the anaerobic threshold.
These concerns and issues make the usefulness of the Conconi test unclear. Personally I would suggest that it is better to either use training paces based on race performance (Jack Daniels Running Formula), or actually measure blood lactate directly.
3 Directly measuring lactate
It is possible to measure the lactate level in the blood using a device similar to a blood glucose meter. Just like a blood glucose meter, a small drop of blood must be drawn and applied to a disposable test strip. This process is rather tricky when exercising at high intensity, and stopping to draw blood will obviously interfere with the exercise level. Lactate meters cost $300-500, with this test strips costing around $2/each. There are three Lactate meters on the market, Lactate Pro, Lactate Scout, and Lactate Plus. A review indicated that the Lactate Pro and Lactate Plus had good reliability and accuracy, and the Lactate Scout was "relatively good", but not as good as the other two.
4 See Also
- Evaluation of three portable blood lactat... [Eur J Appl Physiol. 2010] - PubMed - NCBI http://www.ncbi.nlm.nih.gov/pubmed/20145946