report on blood lactate

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Keeping up with athletes with higher VO2maxes
This ability of older athletes to make big advances in LT no doubt explains a fascinating piece of research carried out several years ago by researchers at Washington University in St. Louis. In that investigation, eight veteran athletes (average age 56) were compared with eight young runners (average age 25) who trained the same number of miles per week (41) and happened to have the same 10-K performance ability (mean 10-K finishing time for both groups was around 41:30). As it turned out, VO2max in the older competitors was almost 10-per cent lower, compared to the youngsters, and running economy was identical in the two groups. So why were the gray-haired harriers able to keep up with the rosy-cheeked saplings?

If you're guessing LT, you're right! Both the old and young runners reached LT at a speed of about 230 metres per minute (about seven minutes per mile), so it was no surprise that both groups ran their 10Ks at a pace of around 6:42 per mile (LT and 10-K pace are predictably linked together). The higher VO2max values of the younger runners were irrelevant for predicting performances (those lofty VO2maxs should have foretold faster 10-K times for those young whippersnappers, but they didn't), because the LTs of the senior runners occurred at a higher percentage of VO2max! In fact, average LT for the vets settled in at 85 per cent of VO2max, while LT for the younger ones rested at only 79 per cent. As a result, the older runners were able to complete their 10Ks at about 90 per cent of VO2max, while the youngsters could only handle 81 per cent ('Lactate Threshold and Distance-Running Performance in Young and Older Endurance Athletes,' Journal of Applied Physiology, vol. 58(4), pp. 1281-1284, 1985).

However, it really doesn't matter if you're young or old: you can do the same thing. Giving your LT a hefty shove to a higher running, cycling, or swimming speed (eg, to a higher percentage of your VO2max) will allow you to keep pace with - or beat - individuals with higher maximal aerobic capacities and will also help you reach the PBs you have always dreamed about.

LT training recommendations
So how do you actually cure a sickly LT - or take a pretty good LT and make it sensational? Although athletes have traditionally believed that prolonged, moderate exercise represents the ultimate LT therapy, the truth is that fairly intense training is the best LT booster, because such workouts improve the heart's capacity to deliver oxygen and the muscles' ability to use oxygen once it's delivered, as well as the ability of the heart and muscles to 'clear' lactate from the blood. For example, in a study carried out at the University of North Carolina at Greensboro, runners who raised their average training intensity by completing two fartlek sessions and one interval workout per week boosted LT significantly in eight short weeks and shaved over a minute from average 10-K time. The fartlek work involved two- to five-minute bursts at 10-K pace; the intervals were completed at about 5-K speed ('Increased Training Intensity Effects on Plasma Lactate, Ventilatory Threshold, and Endurance,' Medicine and Science in Sports and Exercise, vol. 21(5), pp. 563-568, 1989).

The idea that intense workouts are best for boosting LT was even more strongly reinforced in research carried out at York University by Stephen Keith and Ira Jacobs ('Adaptations to Training at the Individual Anaerobic Threshold,' Medicine and Science in Sports and Exercise, vol. 23(4), Supplement, no. 197, 1991). In the York investigations, one group of athletes trained exactly at LT, a very popular way to attempt to heighten LT, for 30 minutes per workout. A second group divided their 30-minute workouts into four intervals, each of which lasted for seven and a-half minutes. Two of the intervals were completed at an intensity above LT, while the other two were carried out below LT. Each group of athletes worked out four times per week for a total of eight weeks.

In the second group, the 'below-LT' intensity (which was used for two of the four 7.5-minute intervals) corresponded to an intensity of about 60 to 73 per cent of VO2max, a very, very moderate intensity which is used by many runners during their long, slow runs and easy, shorter efforts - and which is unlikely to have much impact on LT. The 'above-LT' intensity (also used for two 7.5-minute intervals per workout) was set at about 30 per cent of the difference between lactate threshold and actual VO2max. 30 percent of the LT-VO2max difference would actually represent an intensity of up to 87 per cent of VO2max, or about 88 to 93 per cent of maximal heart rate. In terms of actual running velocity, it would correspond to a running speed which is almost exactly the same as 10-K pace (or perhaps a few ticks per mile slower). In contrast, actual LT intensity is more like 15-K to 10-mile race pace.

An amazing result
Which strategy was better for boosting LT - working at LT intensity or putting in the time above it? After eight weeks of workouts, both sets of athletes achieved similar increases in VO2max and LT. The actual gains in LT were absolutely tremendous, averaging 14 per cent in both groups! Advances in muscle-cell enzymes were also rather splendid - and nearly identical in the two groups. In an endurance test in which group members exercised for as long as possible at an intensity which corresponded to their pre-training LT, the above-LT trainees seemed to hold an edge, continuing for a total of 71 minutes, while the at-LT subjects could last for only 64 minutes. However, this difference was not statistically significant.

At first glance, these results seem to suggest that there's not much advantage to be gained by sweating through above-LT workouts, but wait! If you've been following carefully, you probably noticed that the above-LT athletes really logged only 60 minutes of quality work per week (4 x 15 minutes), while the at-LT subjects put in 120 weekly minutes of quality exertion (4 x 30 minutes). To put it another way, the above-LT athletes achieved the same gains in LT and VO2max as the at-LT folks (and perhaps enjoyed a slight advantage in endurance) - with only HALF the total training time. It's reasonable to assume that had the above-LT athletes stepped up their volume of above-LT work a little bit, they would have outdistanced the mundane at-LT trainees.

What happens above LT?
Why does roaming above LT during training seem to be so effective at lifting lactate threshold? Research carried out with animals provides part of the answer. In investigations at the University of Missouri, several groups of rats hustled along on laboratory treadmills at a variety of different paces, which ranged from 15 to 37 metres per minute (43 to 100 minutes per mile). The faster (by rat standards) velocities produced a flood-tide of lactate in the rodents' bloodstreams, as expected, but the Missouri researchers also noticed something very interesting: high lactate levels were linked with glycogen depletion of the rats' 'fast-twitch' muscle fibres, not their 'slow-twitch' cells. In other words, fast-twitch fibres were primarily responsible for the huge upswing in blood lactate.

Of course, fast-twitch fibres aren't heavily utilized during moderately paced running but play a larger and larger role as running speeds increase beyond LT pace. Compared to their slow-twitch brethren, these fast-twitch cells are ordinarily somewhat low on mitochondria and aerobic enzymes, so it makes sense that they would begin belching out lactate as they are called into play. If they are very, very poor at oxidizing pyruvate, massive amounts of lactic acid will be produced, and LT will be reached at a very mediocre pace. As they get better at breaking down pyruvate, less lactate will be produced and LT speed will of course increase, but there's only one way to stimulate the fast-twitchers to get better: it's to use them during training, specifically at fairly sustained, fast paces. To put it another way, fast-twitch muscle cells can be the 'culprits' behind a low LT, and the only way to upgrade their oxygen-processing machinery is to hammer away at them during training. You'll get more 'bang from your buck' with faster-paced training, compared to slower efforts; after all, your slow-twitch cells are usually pretty good at the oxygen game; it's your fast-twitchers which need to do their homework.

The advantages of faster training were also illustrated in research completed at the State University of New York at Syracuse. In this study, which was carried out over an eight-week period, the concentration of a mitochondrial enzyme called cytochrome c increased by about 1 per cent per minute of daily LT training, as long as training intensity was set at 85 to 100% of VO2max (eg, for 10 minutes of daily training within this intensity zone, subjects boosted cytochrome c by 10 per cent after eight weeks; with 27 minutes of daily training, cytochrome c advanced by 27 per cent). In contrast, working at only 70 to 75% of VO2max increased cytochrome c by only 2/3 per cent per minute of daily training (upswings in cytochrome c should be correlated with improvements in LT).

In the Syracuse study, if one looked at fast-twitch muscle fibres only, the gains associated with faster training were even more impressive: 10 minutes of daily running at 100% VO2max roughly tripled cytochromec concentrations, while running 27 minutes per day at 85% VO2max expanded cytochrome c by 80 per cent, and 90 daily minutes at 70% VO2max boosted cytochrome c by just 74 per cent ('Influence of Exercise Intensity and Duration on Biochemical Adaptations in Skeletal Muscle,' Journal of Applied Physiology, vol. 53(4), pp. 844-850, 1982).

A range of optimal intensities
Overall, the scientific research suggests that the range of intensities from about 5-K pace down to about 10-mile race pace is great for improving LT, with the faster paces within this zone being 'better' for raising LT when the improvement is plotted as a gain per minute of training. However, the advantage of the 'slower' paces within this zone is that they can be used for many more minutes of weekly training, sometimes overcoming their per minute disadvantage (for example, it is much easier to complete 40 minutes of training at one's 10-mile race pace during a week of training than it is to charge through 40 minutes at 5-K pace, and the risk of overtraining and injury is also lower). The 'slower' paces may also be used for very long intervals and for up to 30 minutes of continuous running, which helps athletes develop the ability to sustain quality speeds for longer periods of time. In contrast, shorter intervals may have a more productive intensity but they don't simulate race situations as well (few races feature recovery intervals).

For cyclists and swimmers, the range of heart rates between 85 and 95 per cent of maximal appears to be optimal for heightening LT. As with runners, the higher end of this heart-rate zone is more productive for boosting LT when the improvement is plotted as a gain per minute of training. However, the lower heart rates can be used for many more minutes of weekly training.

Supporting the idea that the moderate end of the LT-raising zone can be great for spurring performance, research carried out at Charles University in Prague, Czechoslovakia, determined that runners improved their LTs and performances most dramatically when they augmented the amount of weekly running carried out at velocities which fell between 10-K and 10-mile race speeds (10-K velocity is about 2 to 3 per cent above LT pace, while 10-mile velocity is very close to actual LT speed, as mentioned). In this Czech research, a group of seven experienced runners reduced the amount of aerobic training they carried out (aerobic workouts were defined as those conducted at a pace slower than 10-mile race speed) from 80 to 72 per cent of all miles over a four-month period. Meanwhile, the quantity of LT training (defined as runs of five miles or less at a pace somewhere between 10-K and 10-mile race speeds) advanced from just 6 to 16 per cent of all miles (the remaining, basically unchanging volume of 12 to 14 per cent was always reserved for short, speedy intervals on the track at faster than 10-K pace). As a result of the increase in LT training, LT velocity improved by a full 10 per cent in four months, and 10-K race times sharpened by almost a half-minute - from 28:45 to 28:20 ('Ventilatory Threshold and Mechanical Efficiency in Endurance Runners,' European Journal of Applied Physiology, vol. 58, pp. 693-698, 1989).

It is important to note that the more temperate end of the 'LT training zone' (eg, paces which are closer to 10-mile than 5-K velocity or heart rates which are nearer 85 per cent of max rather than 95 per cent) seems to work best when these 'cooler' paces are sustained in a continuous manner for periods of 20 minutes or more. An example of this is the classic study carried out at the famed Karolinska Institute in Stockholm, Sweden, many years ago. In this research, Swedish runners added just one thing to their usual training - a weekly 20-minute run completed at a pace which was about 10 to 12 seconds slower per mile than 10-K race speeds, which happens to be just about 10-mile race speed, or the bottom end of the LT zone. After a total of 14 weeks, the Swedes' LTs improved by 4 per cent, and 10-K times were trimmed by over a minute ('Changes in Onset of Blood Lactate Accumulation (OBLA) and Muscle Enzymes after Training at OBLA,' European Journal of Applied Physiology, vol. 49, pp. 45-57, 1982).

In addition to being a good duration for a long, LT-boosting interval, 20 minutes may just be a threshold for the amount of weekly LT-type work needed to heighten LT significantly. Research at the University of Ulm in Germany determined that investing 20 minutes or more per week in LT training can lead to large LT lift-offs, while completing less than 20 minutes of weekly LT work is linked with mediocre thresholds.

Owen Anderson

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