As recommended by Joe Friel (among many others), I attempt to conduct
physiological tests several times throughout the training calendar.
One of the measures I have difficulty determining, in particular, is
lactate threshold heart rate. Since I don't have access to expensive
lab facilities or equipment to measure power output, the best method I
have available is a 30-minute TT (while marking HR and PE). In
general, the method suggests riding at the highest sustainable HR for
about 30 minutes. Supposedly, the average HR achieved over last 20
minutes is a good estimate of your LTHR. Admittedly, I have relatively
weak anaerobic endurance so I'm not a very good time-trialer.
Therefore, don't compete in any TT events. Its brand of suffering just
isn't any fun for me. So I usually attempt this test without the
motivation of competition. Consequently, 158-160 bpm is the highest
average HR I can seem to achieve. However, this result doesn't seem to
agree with a couple other methods that have been suggested to me.
One method is to use the results of an in-race criterium. Naturally, a
criterium requires varying degrees of intensity, depending upon
whether I'm pulling, bridging a gap, sitting-in, or recovering off the
back. Occasionally, I'll use a crit as an interval session.
Consequently, depending upon a given effort, my HR will fall somewhere
between 150-180bpm. During a rare attempt at a prime- or field sprint,
I will hit my MaxHR of 192. Although I'm suffering during the entire
race, my average HR is about 172bpm (depending on a number of
variables) and it is also about where I begin feel a sudden
accumulation of lactate (intense quad pain) and feel the physiological
trigger to back off. My average cadence is about 90-95rpm. I usually
warm up for about 20-30 minutes of moderate spinning before the race.
Since I usually use crits as a training session, I usually finish
somewhere in the middle of a 35-40 man pack.
Another method that has been suggested is to use my average HR on a
long hard climb. Since I live near the Laurel Highlands of
Pennsylvania, there are plenty of routes that consist of 2-3 mile
climbs with varying grades of slope (sometimes as much as 20%). The
average gradient is 8-10% on most climbs lasting about 15-25 minutes.
I frequently alternate between sitting and climbing out of the saddle.
My average cadence is about 65-70rpm. I usually hit one of these
climbs during the course of a 3-hour endurance ride, so I'm pretty
well warmed up (if not reaching exhaustion). Again, my average HR will
be about 172-175bpm (usually at the lower end on a later climb,
ironically). And again, 172bpm is about where I feel the need to back
off.
My question is which result I can trust as a good estimate of my LTHR?