Contradiction between Lactate Threshold Pace and VO2MAX race prediction

Hello, I am a veteran amateur runner, I have been running for more than 3 decades, I attend about 6-7 races a year. I have never been on a sport lab to test my running performance data (VO2MAX, Lactate Threshold, etc.), but performing on races give me some good guidelines. I purchased a Fenix 5 watch 1 months age, and it collected enough data to give proper estimation of these performance values.
The recent Lactate Threshold Pace is 4:35 min/km and the Lactate Threshold Heartrate is 162 bpm. Firstbeat writes: "Lactate Threshold identifies the level of physical activity intensity above which your body will rapidly fatigue. Well-trained runners typically find their lactate threshold at 90% of their maximum heart rate and at a pace somewhere between 10k and half-marathon pace." The LaT pace value seems to be right in my case, I ran a half marathon last year with an avearge pace of 4:39 min/km and an average heartbeat of 153 bpm, and now I feel I am in similar form. But when I observe the race predictor times based on my VO2MAX estimation, those times are so fast I'm sure I can't run them. (10k - 39:48 (3:59 min/km), half marathon - 1:28:04 (4:10 min/km)). I think there is a clear contradiction between my estimated LaT Pace and the race predictor times. I mean if I accept that my LaT Pace (4:35 min/km) is correct, how could I run a half marathon in a much faster pace (3:59 min/pace) when it is said that 21km is a longer distance than you are able to keep your LaT Pace from the start to the finish line?

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0 JSRUNNER_ over 6 years ago

kilfish I believe the race predictions calculated from VO2 max are just taken from a standardised table and there is likely to be individuals for which the projection will be significantly out - it is purely a measure of maximum Oxygen usage. If you look at many endurance athletes at the top of their sports you see quite a range of VO2 max for similar performance levels. Matt Pinsent for instance had a significantly higher VO2 max than Stephen Redgrave - both of them having a higher VO2 max than your average club endurance runner yet because of their size/weight and training background both would be left far behind in a half-marathon. Lactate threshold is a much simpler relationship to maximum sustainable pace and so should be a fairly good predictor for 10k.

0 kilfish over 6 years ago

The strange thing is that before buying the Fenix 5 I had been using a Fenix 2 for years. The VO2MAX values and the race predictor values were close enough to the times I could run on 10k and half marathon. I ran an interval workout 2 months ago with the Fenix 2, and now I repeated the same workout with the Fenix 5. The average pace and the heart rates are closely the same in both workouts, and Fenix 2 estimated a VOMAX value of 50, Fenix 5 estimated a value of 53 VO2MAX. (Actually I performed a bit better on the workout with the Fenix 2) Do the 2 Fenix watches use the same algorithms to calculate VO2MAX?

0 JSRUNNER_ over 6 years ago

kilfish I don't know if the algorithms are identical - I would be surprised if they have changed much - however I don't know whether the VO2 max figure that you see against a run is solely for that run or whether it is for that run plus your recent other runs. I think it is the latter so you would not necessarily to expect two similar performance runs to give exactly the same figure. However I take your point that overall the 5+ seems to calculate a higer figure than the F2. When I switched from my 935 to the 5+ my VO2 Max stayed about the same. The data gathered by the 5 may have changed vs th 2 and that may account for the difference. Either way I see VO2 mainly as a trend indicator rather than an indicator of expected race performance.

0 mcalista over 6 years ago

As noted above, the race prediction is based on VO2Max. If you dig into the Firstbeat (who provide the algorithms Garmin use) whitepaper on VO2Max, you will note that the accuracy of the VO2Max prediction is significantly influenced by the accuracy of the HRMax datapoint.

The default 220 minus your age formula may be the average of the population as a whole, but is #$%^ at predicting the actual HRmax of any one individual. A more accurate datapoint here will improve the accuracy of the VO2Max estimate (and the race times predictor).