Lactate threshold heart-rate

Lactate Threshold Heart-rate: A question of distance, and how to work out your lactate threshold heart rate.

Continuing our occasional series, we answer questions from two PP subscribers. The first is Timothy Kirk of Worcester, who writes:

'At the 400-metre track where I work out, we are not allowed to use the first lane - to prevent overuse injuries to the track, I assume. So, I often do my repeats in the second, third, or even fourth lane. However, by moving to the non-inside lane, I'm actually running further than 400 metres per lap. My friends say the difference is fairly trivial, but I think it could make a big difference in my interval pacing. So, how far am I actually running when I'm not in the inside lane?'

Answer: Here's what Pete Riegel of the Road Running Technical Council in the US has to say:

'The extra distance one runs when doing a lap in lane two, three, four, and so on depends on the width of the lane. In order to figure the actual distance, two things need to be known initially:

1. Does the track have a kerb? Some tracks have kerbs, while some do not. Some without kerbs have sockets set in place so that kerbing can be installed when an event is imminent.

2. What is the lane width?

'If you give me the answers to these questions, I can give you the actual distances. For a rough estimate, assuming an unkerbed track with no sockets, figure that a lane width of 1.25 metres (49 inches, a common value) adds an increment of 7.854 metres to the original 400-metre length, and each lane adds one more increment. Thus:

Lane 1 = 400 m
Lane 2 = 407.9 m
Lane 3 = 415.7 m
Lane 4 = 423.6 m
Lane 5 = 31.4 m
Lane 6 = 439.3 m
Lane 7 = 447.1 m
Lane 8 = 455.0 m

'Of course, the exact numbers for your track would depend on the precise lane width and the configuration of the track, as mentioned above.'

Our second question comes from Dick Stockbridge of Los Angeles:
'I have just purchased a heart monitor and would like to use it to carry out some very good lactate-threshold (tempo) training. Should I just try to keep my heart rate at 90 per cent of maximum when I carry out a threshold workout? And should I use my maximal heart rate (MHR) to figure the 90-percent beating figure, or is it more effective to use the Karvonen formula?'
Answers: heavens no, and it doesn't matter. While many athletic-minded people think that lactate threshold coincides with about 90 per cent of maximal heart rate, the truth is that it varies tremendously from person to person, and of course it also varies according to your fitness level. If you're a real stud, your LTHR (lactate-threshold heart rate) might actually be at 95 per cent of MHR; if you're a beginner, it could be at 65 to 70 per cent. If you're neither, LTHR could be nearly anywhere, depending on your previous training, overall fitness, and individual characteristics.

Even among people of similar ability levels, LTHR roams all over the map. For example, if we examined a group of runners, all of whom are able to finish the 10K in 40 minutes flat, some of those individuals would reach their LTHR at 80 per cent of MHR. Others would be at 85, some would arrive at LTHR at 90 per cent, and - of course - the rest would be somewhere in between (or perhaps even below 80).

You might think that one solution would be to bring you into the lab and begin pricking your finger as you ran at different paces on the treadmill. We could indeed reckon a LTHR for you in that way, but there would be just one little problem: heart rate varies tremendously according to environmental conditions. If the lab temperature were 20 degrees Centigrade, with 40-per cent humidity, and you tried to run in 30-degree air, with 60-per cent humidity (or 2-degree air, with 20-per cent humidity), your heart rate at your actual lactate threshold running pace could be far different than it was in the lab. If you utilised the 'LTHR' you obtained in the laboratory, you would be training nicely and precisely at a specific heart rate, but unfortunately that heart rate would not be your actual LTHR.

Many athletes who use the Karvonen formula (which subtracts resting heart rate from MHR, takes a percentage of the difference, and adds the result to resting heart rate to obtain goal pulse rate for a workout) believe that they are training more 'scientifically' and sensibly, compared to the more common use of a straight percentage of MHR. However, the Karvonen disciples run into exactly the same problems outlined above: LTHR varies tremendously from person to person and according to fitness level and environmental conditions. When you use Karvonen to get LTHR, you still have to come up with a number (some percentage of your heart-rate reserve), and unfortunately that number will usually be wrong.

So what should you do? Well, forget about the wild and capricious beatings of your heart. If you're a cyclist, your lactate-threshold intensity is roughly the one you can sustain for an hour of biking - but not longer. If you're a runner, your lactate threshold pace will be about 10 to 15 seconds SLOWER per mile than your current 10-K race velocity. True, just as pulse rate wanders hither and yon, cycling and running ability also vary according to environmental conditions. For example, if you're a runner, the lactate-threshold pace you calculate after a hilly or hot-humid 10K will be different from the one you reckon after a flat or cool-dry race. However, at least you'll be pegging your lactate-threshold intensity to something YOU do - YOUR ACTUAL PERFORMANCE. And you'll be including information from your heart and your leg muscles - a wise thing to do since both are involved in determining your actual performance. You won't be relying on a collection of cardiac cells which can behave pretty unevenly, nor will you be putting your hopes on a somewhat mystical rate of cardiac pounding which 'experts' contend is your LTHR, even though it may be 20 beats above or below the true figure.

Jim Bledsoe

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