This result suggests that low-glycogen training offers no advantage, but the Danish researchers also gave each leg a test that involved working for as long as possible at a sizzling intensity of 90 percent of the final Wmax. When this test was carried out, the leg that had trained with low glycogen, now well stocked with glycogen for the actual test, performed much better than the leg that had always trained under high-glycogen conditions. In fact, time to exhaustion was twice as long for the low-glycogen leg compared with high-glycogen leg. Naturally, total work performed during this rugged test at 90 percent of Wmax was also much greater for the leg that had driven glycogen way down during training. The low-glycogen leg was the better one for performance!
The investigators noticed some interesting changes in hormone production associated with the low-glycogen training. Specifically, when the low-glycogen leg worked out for an hour by itself, plasma epinephrine and norepinephrine levels were significantly higher, compared with the case when the high-glycogen leg went solo. Epinephrine and norepinephrine are potent boosters of nervous system activity and can also increase the force which muscles produce when they contract.
Differences were also apparent at the molecular level when two key mitochondrial (i.e., aerobic) enzymes were monitored in each leg. The activity of hydroxyacyl CoA dehydrogenase (HAD), a very important aerobic enzyme, increased significantly only in the low-glycogen leg over the course of the 10-week study. In addition, the relative increase in activity of citrate synthase (CS), another key aerobic enzyme, was significantly more pronounced in the low-glycogen leg compared with the high-glycogen leg. On top of these molecular changes, the percent number and percent area of type II-X (fast-twitch) fibers decreased significantly in the high-glycogen leg but not in the low-glycogen leg. This was possibly because the slow-twitch muscles in the low-glycogen leg became so glycogen depleted during workouts that they had to rely on their fast-twitch cells to complete the sessions, creating a stimulus for preserving the II-X fibers.
What is the possible molecular mechanism underlying all these positive changes in the low-glycogen legs? Several transcription factors in muscle cells (i.e., chemicals that cause certain genes to be read) are naturally bound to glycogen molecules within the muscle fibers. When glycogen becomes low (i.e., the signal), these factors are released and trigger the transcription of key genes, including the genetic material that codes for aerobic enzymes such as HAD and CS.8 As a result, the activities of these enzymes increase, oxygen can be processed at a higher rate, fuel can be provided to muscle cells at greater speed, and endurance at quality intensities may improve significantly—as was the case in the performance test in this study.
In summarizing the Danish results, it is clear that carrying out two workouts every second day, with the end of the first workout separated from the beginning of the second workout by just 2 hours and with no glycogen fill-ups permitted, was superior to training once per day, even though total work performed and actually training intensities were the same in the two cases.
What molecular biology does not tell us is that such training should be approached with caution. For one thing, training schedules that permit muscle glycogen stores to diminish to very low levels have been linked with staleness and the overtrained syndrome.9 In addition, it is not illogical to think that closely coupled workouts that maximize fatigue in the second session might increase the risk of injury although this has not been meticulously studied in a controlled scientific setting.
Practical Implications for Training Twice Per Day
On a day when quality training and a double are planned, a reasonable approach is to make the first workout of the pair the more intense session. Attempting high-quality training with very low muscle glycogen stores might produce muscle damage. In addition, it would be difficult to reach planned high-quality speeds during a low-glycogen workout.
A question that remains from this research is whether it is really necessary to recover for approximately 45 hours after the second of the coupled sessions as the Danish subjects did. Many runners would ask whether it would be possible to train on the following day, too, in most cases with a single session.
Of course, it would be possible for some runners—those with good recovery powers—to do this. It can be assumed that the benefits that showed up in the Danish study were present in response to the low-glycogen conditions, not because of the 45-hour rest between the end of the second workout and the start of the next session 2 days later. However, getting right back to the workout grind on the day after double workouts is not ideal for runners with poor running-specific strength because they may damage their leg muscles with such extra running. Most runners are adapted to a certain number of workouts per week, and sudden increases in the number of weekly sessions can create adaptation and recovery problems that lead to injury or the overtraining syndrome.
For the runner who is already carrying out two daily sessions and handling them without problem, it would make sense to couple those workouts, putting them just 2 hours apart, so that the molecular effects of extra-low glycogen concentration can be produced; however, the second exertion should be the easier one. From the standpoint of the glycogen transcription mechanism, this schedule would work better than the usual practice of doubling with a session in the morning and another in the late afternoon or evening, with at least one meal intervening.
What would be the optimal frequency for doubling? The Danes gave their subjects regular rests, so the twice-a-days occurred no more than three times a week and sometimes just twice a week. Bear in mind also that major gains occurred in enzyme levels and performance even though the 45-hour furloughs were part of the plan. Such findings suggest that a couple of doubles per week might easily be enough to significantly increase performances, with these doubles separated by rest or light days of training. Overall, the low-glycogen legs in the Danish study hit the lowest glycogen concentrations just five times in each 14-day period, three times during one week and two times during the other.
The following guidelines are important to the strategy of two workouts a day:
Timing of the second workout matters. The second workout of the day has to be carried out a couple of hours after the first one with no significant glycogen loading of the muscles in between. Stocking up on carbohydrate between workouts would eliminate the boosting effect on fitness and performance of low glycogen detected by the Danish investigators. If a runner had to eat something between workouts, it would have to be very light—and biased toward fat rather than carbohydrate. Protein would not be acceptable between sessions because the human body is actually very good at stripping the nitrogens from proteins and treating them as expensive carbohydrate.
Second workout is more moderate than the first. There is an element of risk associated with the Danish strategy. Glycogen-depleted muscles are weak muscles, and muscles with subpar force production are more prone to injury. The second workout of the day would ideally be moderate in intensity to temper the stress on fatigued muscles, and any tightness and soreness that developed would need to be closely monitored. It is important to complete a program of running-specific strength training before embarking on a program that emphasizes glycogen-depleting workouts twice a day because such strength training is protective of muscles and connective tissues.
Glycogen loading needs to occur after the second workout. Following the second workout of the day, quick glycogen loading is optimal. Intramuscular glycogen synthesis is highest during the two hours after an exertion, so ample carbohydrate should be ingested during that time. The use of a high-carbohydrate recovery drink would speed carbs to the muscles. An intake of approximately 1 gram of carbohydrate per pound (.45 kg) of body weight, along with 10 to 20 grams of protein, during the 20- to 30-minute period following the second workout is recommended. Remember that the strategy is not to consistently train in the low-glycogen state. The correct strategy is to induce low glycogen levels with the second workout of the day. After that, ample glycogen building sh
ould occur to prepare for the next quality workout or Danish double.
Recovery efforts are essential. The first use of the two-a-day strategy will generally induce a significant amount of unusual fatigue. This will necessitate extra rest and the faithful pursuit of a diet rich in carbohydrates, antioxidants, and healthy fats, and which is adequate in protein. Doubles should not be undertaken during periods when nonrunning life stresses are high.
Novice runners must work up to a double training load. Because of the likely presence of inherent muscle and connective tissue weaknesses, inexperienced runners should not plunge into the two-a-day strategy. Some novice runners might be able to carry out an hour of easy walking 2 hours after their regular workouts, however, to create a similar low-glycogen effect. They can gradually build up their running-specific strength by using the correct strength training sessions (described in chapter 14), preparing themselves for the possibility of running twice a day on selected occasions as experience and strength are enhanced.
Conclusion
The molecular biology approach to training has already been helpful in resolving the debate over resistance versus endurance training; has pointed to the need for varied, balanced training; and has identified a unique strategy of doubling workouts that produces major gains in endurance performance. In the future, additional advances in the understanding of ways in which specific workouts produce transformations in cell signaling, gene expression, and protein production are certain to enhance the quality and productivity of endurance training for runners.
Part VIII
Sports Medicine for Runners
Chapter 32
Training for 800 Meters
In spite of the brevity of the race, training for 800 meters bears some remarkable similarities to preparing for the longer distances. As is the case with all events, 800-meter training requires a proper periodization of strength training, following the optimal sequence of general, running-specific, hill, and explosive strengthening. Running workouts for 800 meters are similar to those utilized for greater distances, but a special premium is placed on extremely fast training speeds at the expense of submaximal running.
Best Predictors of 800-Meter Performance
Highly informative research concerning 800-meter running has been carried out by Gordon Sleivert and A.K. Reid at the University of Otago in New Zealand.1 Sleivert and Reid evaluated 17 good-quality middle-distance runners, comparing their 800-meter times with key predictors of performance, including lactate-threshold velocity, running economy, and O2max.
Running experts often preach that maximal aerobic development is critical for achieving one’s best 800-meter performances; their argument is partly based on the fact that about half of the energy required to race 800 meters is generated aerobically. However, Sleivert and his colleagues found that O2max was totally unrelated to 800-meter time. In other words, the runners in their study who had high O2max values didn’t run 800 meters any faster than individuals with more mediocre O2max data. In this study, the two best predictors of 800-meter performance turned out to be 400-meter time and lactate-threshold speed, the velocity above which lactate begins to accumulate in the blood (Sleivert and colleagues did not measure vO2max).
The Otago findings should not be surprising given that 400-meter time is a measure of muscle contractility, muscle explosiveness, and overall neuromuscular function, three factors that are extremely important for running performance (discussed in chapters 11, 16, and 28). If an athlete can run a fast 400 meters, he or she has the neuromuscular characteristics so highly prized by Heikki Rusko, Tim Noakes, and other groundbreaking exercise scientists and has the potential to run quickly over 800 meters and longer distances, too.
Lactate-threshold speed, which is a great predictor of success not only for 800-meter competitions but also for lengthier races, is a function of the rate at which lactate moves out of the muscles into the blood during running and of the rapidity with which muscles and the heart remove lactate from the blood. As explained in chapter 10, lactate is a key fuel for the muscles. It provides a rich store of adenosine triphosphate (ATP), the high-energy compound that triggers muscle contractions, so it is easy to understand why having a high lactate-threshold speed when running would be a good thing. Establishing a lofty lactate-threshold speed means that muscles are unwilling to let energy-rich lactate slip away into the blood and that they are great at clearing lactate from the blood once it gets there. As a result, the muscles have a tremendous source of fuel to use at high rates during powerful 800-meter running.
800-Meter Workouts
It’s clear that two key goals of 800-meter training are to optimize both muscular power—a surrogate for 400-meter time—and lactate-threshold velocity. The following workouts, with their emphasis on high-velocity running, develop neuromuscular power steadily over time. Because of their high intensity, they also enhance running economy and generate high blood-lactate levels. Both of these factors lead to advances in lactate-threshold speed.
Lactate Stacker
A workout that accomplishes both goals (upswings in power and lactate-threshold velocity) simultaneously is an exciting session called the lactate stacker. To do a lactate-stacker workout, a runner simply warms up thoroughly and then blasts off for 1 minute at a pace faster than vO2max and almost as fast as maximal running speed. A runner should not strain as he or she does this; it is important to be relaxed and yet produce close to maximal power in the leg muscles.
The distance covered during the 1-minute interval is not of paramount importance: The key to the workout is to run at a pace faster than vO2max during each 1-minute interval. Since a runner does not have to reckon the distance covered per work interval, it is possible to conduct this workout anywhere. A good choice would be an area where an individual really loves to run—for example, on trails or walkways with good footing in a beautiful park or forest.
Once 1 minute has elapsed, the runner jogs easily for 2 minutes to recover; the actual recovery jogging pace doesn’t matter, as long as it is easy. The runner then repeats this pattern of 1 minute of fast running alternating with 2 minutes of easy loping. For the first workout, a runner usually completes six 1-minute surges and then ends the session after a proper cool-down. Over time, a runner can increase the number of 1-minute accelerations to about 15 to 18.
An interesting aspect of this workout is that the 2-minute recoveries will often feel shorter than the 1-minute intervals: During the 1-minute intervals, the runner is trying hard to hold on while during the recoveries he or she is hoping for a slightly longer break. Another interesting facet of the session is that most runners consider it to be fun! Many athletes love to run really fast especially if they have been existing on a diet of inchmeal-paced longer runs. This workout is an excuse to run the way a runner did when he or she was an exuberant child with quick sprints followed by satisfying recoveries.
Lactate stackers work well as preparations for 800-meter competitions because they improve raw running power and upgrade coordination at high speed, which enhances running economy at an 800-meter pace and adds some power to muscle contractility. Anecdotal evidence suggests that 400- and 800-meter race times improve, frequently by a sizable margin, when a runner regularly carries out lactate stackers.
A critical aspect of lactate-stacker work is the effect on lactate dynamics. After each 1-minute surge, blood lactate levels increase because of the powerful running that has occurred. Perhaps surprisingly, blood lactate does not fall during the subsequent 2-minute recoveries, which means that each succeeding 1-minute interval at top speed stacks up even more lactate in the blood. The result is a an extremely potent stimulus for muscles to get better at clearing lactate from the blood and breaking it down for energy within their interiors, which of course heightens lactate-threshold speed, one of the two key predictors of 800-meter success.
Classic 400-Meter Session
Since 400-meter time is a fine predictor of 800-meter performance, a second great workout for 800-m
eter runners is a classic 400-meter session. A runner simply warms up and begins reeling off 200-meter intervals at a pace that is 1 second per 200 meters faster than his or her best 400-meter tempo. For example, if the best 400-meter time is 60 seconds (30 seconds per 200 meters), the runner could start with 4 × 200 in 29 seconds each and gradually build up to 8 × 200. It is fine to take relatively long recoveries when this workout is performed; the runner is not trying to maintain high oxygen-consumption rates throughout the workout but rather is attempting to ensure that each interval is completed at the appropriate pace, which will create an excellent stimulus for neuromuscular advancement.
If a runner does not know his or her best 400-meter time and thus is not sure about setting the split time for the intervals, the runner can cover 400 meters at all-out speed on the track on a day when he or she is feeling great. If that is not appealing, it is possible to guesstimate 400-meter time from 800-meter personal best, remembering that personal best 400-meter pace will generally be 4 seconds per 400 meters faster than 800-meter speed. If a runner has raced 800 meters in a personal best of 2:20, for example (70 seconds per 400 meters), the estimated 400-meter personal best would be 66 seconds (33 seconds per 200 meters). For the classic 400-meter workout, the runner would then begin with 4 × 200 in 32 seconds each, with 2- to 3-minute recoveries between the 200-meter intervals.
Running Science Page 45