Other research suggests that bicarbonate ingestion might aid performance during 3K (1.86 mi) competitions. In a study carried out at the University of South Carolina, 10 highly trained runners (O2max = 69.4 ml • kg-1 • min-1) ran for as long as possible on a treadmill at an intensity of 100 percent of O2max after ingesting either a placebo or 0.3 grams of sodium bicarbonate per kilogram of body weight.20 Sodium bicarbonate ingestion significantly increased running time to exhaustion at 100 percent of O2max from 564 to 578 seconds, a 2.5 percent improvement.
Sodium bicarbonate as baking soda is easily and cheaply obtained, and it appears to improve performance in high-intensity competitions lasting longer than 1 minute but requiring less than 10 minutes to complete. Research suggests that the ergogenic dose is about 0.3 grams of sodium bicarbonate per kilogram of body weight ingested approximately an hour prior to intense exertion. The appropriate amount of sodium bicarbonate is dissolved in a glass of water, using just enough water to put the bicarbonate into solution, and then drunk. In addition to bolstering race performances in events lasting from 1 to 10 minutes, acute baking soda supplementation appears to boost the quality of interval workouts carried out over longer periods of time.
Unlike caffeine supplementation, sodium bicarbonate ingestion is linked with a variety of unpleasant side effects, including diarrhea, cramping, and general gastric discomfort.21 Runners intending to ingest sodium bicarbonate prior to a major race would be well advised to practice consuming it several times in less-important races in advance of the big day.
Supplements Without Scientific Backing
The list of supplements marketed to runners and other athletes is a long one, including those in the list that follow. There is no convincing scientific evidence that any of these can enhance running performance. A variety of antioxidant formulas are also sold to runners, including products containing omega-3 fatty acids. Such products may be beneficial for overall health, but their use has not been linked with increased running capacity.
acetylcholine
androstenedione
arginine
bee pollen
branched-chain amino acids
carnitine
choline
chondroitin
chromium
coenzyme Q10
conjugated linoleic acids
ginseng
glucosamine
glutamine
MCT
phosphatidylserine
octacosanol
royal jelly
sodium citrate
sodium phosphate
spirulina
vanadium
wheat germ oil
Effects of Creatine on Running
A third supplement—creatine monohydrate—can boost sprinting capacity and enhance body composition and muscle mass when it is taken over an extended period of time. Creatine monohydrate is probably the most widely used supplement taken by athletes in an attempt to improve athletic success.22
There is a logical scientific rationale for creatine’s ability to improve high-power performances. Research has revealed that supplementary creatine intake can raise muscle creatine concentrations by 20 percent or more, with a significant portion of this added creatine stored as a compound called phosphocreatine within muscles. Muscle phosphocreatine is a source of energy during sprint events; it acts by donating its phosphate group to a chemical called ADP in order to create ATP (adenosine triphosphate) within muscle fibers. ATP is the energy for muscle contractions (see chapter 43).
Just 6 seconds of all-out sprinting can deplete normal muscle phosphocreatine levels in an athlete who has not loaded creatine, explaining the fall-offs in velocity that occur near the end of a 100-meter sprint. 23 Four to six daily portions of 5 grams of creatine monohydrate over a five-day period—called a loading dose—can cause phosphocreatine concentrations to reach maximal levels inside muscles.24 Comparable advances can be attained with a lower intake of 3 grams of creatine per day sustained for a month. Three grams per day is considered to be a maintenance dose of creatine.25
One meta-analysis of peer-reviewed scientific studies, published in 2003, uncovered 18 investigations in which creatine supplementation was linked with improvements in strength, body composition, or performance;26 since then, many additional studies have documented creatine’s benefits. The creatine studies reviewed in the meta-analysis were usually 8 weeks in duration, the average loading dose was 19 grams of creatine per day for 5 days, and the mean maintenance dose was 7 grams each day.
Scientific evidence suggests that creatine supplementation can enhance sprint performances and upgrade the overall quality of high-intensity interval workouts. In a study carried out in Spain with trained male handball players, 5 days of creatine supplementation involving a loading dose of 20 grams of creatine per day improved running velocity during the initial 5 meters of 15-meter sprint (initial 16.40 ft of 49.21 ft) intervals by about 3 percent.27 Creatine loading was also linked with upgrades in lower-body maximal strength and repetitive power and heightened resistance to fatigue during repeated jumping activity. In another study, a creatine intake of 20 grams per day for 5 days augmented muscular phosphocreatine concentrations and advanced the quality of high-intensity repetitions performed during interval workouts lasting for 80 minutes; the work intervals used in this research were extremely short, taking just 4 seconds to complete.28
Creatine and Endurance Runners
Can creatine supplementation benefit endurance runners? The previously mentioned meta-analysis revealed that creatine supplementation is linked with a net weekly gain in strength of about 1.1 percent in athletes carrying out resistance work compared with carrying out strength training without any supplementation at all. While that might seem like a small effect, it could lead to substantial differences in strength over time. Although there is no scientific evidence to support the idea that creatine supplementation directly boosts endurance-running performance, distance-running success hinges on running speed. Running speed is a function of the amount of force applied to the ground by the legs, and creatine supplementation—combined with effective running-specific strength training—could magnify that propulsive force. Creatine’s ability to improve the quality of interval workouts might also aid endurance-running performance after an extended period during which interval work was emphasized.
One study carried out with middle-distance runners demonstrated the dramatic effect that creatine supplementation can have on interval training.29 Five runners at Tartu University in Estonia supplemented their diets with 30 grams of creatine monohydrate per day over a 6-day period; the creatine was taken in six 5-gram doses parceled out over the course of a day. During the 6 days, five other Estonian middle-distance runners of comparable ability supplemented their diets daily with 30 grams of a glucose placebo. The runners were unaware of the actual compositions of their supplements.
Prior to and following the 6 days of supplementation, the athletes ran four 300-meter (.19 mi) intervals and—on a separate day—four 1,000-meter (.62 mi) intervals with 3 minutes of rest between the 300-meter intervals and 4 minutes of recovery between the 1,000-meter repetitions. Compared with the placebo group, improvement in the final 300-meter interval from pre- to postsupplementation was more than twice as great for creatine users; the upgrade was more than three times as large for the runners using creatine in the final 1,000-meter interval. Total time required to run all four 1,000-meter intervals improved from 770 to 757 seconds after creatine supplementation, a statistically significant result. The placebo group slowed by 1 second after the 6 days of glucose ingestion from 774 to 775 seconds. This meant that the performance gap between the two groups over 4,000 meters (2.49 mi) of interval running had increased from 4 to 18 seconds.
A weakness in this Estonian study was that the researchers, including the highly respected Eric Hultman, who has been called the father of the strategy of carb loading for endurance runners, did not use a crossover design. In such a design, the
runners who supplemented with creatine would have crossed over and tried glucose, while those who had used glucose would have loaded with creatine. Crossing over wasn’t possible because once leg muscles are fully loaded with creatine, it can take 6 to 9 months without creatine supplementation to clear the surplus creatine from muscle fibers and return to baseline creatine concentrations.29
Weight Gain
In the meta-analysis, creatine supplementation resulted in a net gain in lean mass of 0.36 percent per week compared with placebo use. This meant that those supplementing with creatine were adding about three-fourths of a pound (340 g) of new lean tissue to their bodies every 7 days. With creatine supplementation, the average net gain in muscular strength was about 1.1 percent per week compared with placebo use.
The issue of weight gain is a primary caveat in creatine supplementation. Muscle storage of creatine is associated with water storage, which would make a creatine-loaded endurance runner a bit heavier. Creatine’s anabolic action also adds body mass. In one study carried out at the Karolinska Institutet in Stockholm, Sweden, nine well-trained runners ingested 5 grams of creatine monohydrate four times per day for 6 days, while nine other experienced runners consumed a placebo.30 After the 6 days, they all competed in a 6K (3.73 mi) race over rolling terrain. The endurance runners who supplemented their diets with creatine increased body weight by 1 percent; their 6K race times slowed by the same percentage.
More research needs to be conducted before informed advice can be given to endurance runners regarding creatine supplementation. It is possible that the weight gain and interval-training improvements resulting from creatine intake tend to balance each other out over extended training periods and that creatine therefore does not enhance endurance running. This possibility has not been examined carefully by exercise scientists.
Dosage and Contamination Concerns
Creatine is sold to the runner in various formats, including such exotic preparations as Createk, Freakit, Cell-Tech Hard Core, CellMass, but there is absolutely no evidence that special preparations of creatine monohydrate are more effective than the basic compound itself. The scientifically accepted loading dose for creatine is 20 grams per day for 5 to 7 days; the maintenance dose is considered to be 3 to 5 grams per day for 2 weeks to 6 months depending on the training being conducted.22 Although no studies have examined the effects of long-term supplementation with creatine, there is no compelling evidence that creatine supplementation is associated with adverse side effects.
Runners interested in supplementing their diets with creatine should be aware that current legislation does very little to protect them from creatine products and other supplements that might be contaminated or even contain unsafe ingredients.31 Poorly manufactured creatine may be contaminated with the by-products creatinine and dicyandiamide.32 Purity is especially important for creatine supplementation because doses taken by athletes are so large. Runners wishing to learn more about the quality of a specific creatine product may check reports published by independent testing laboratories such as ConsumerLab.com.
Conclusion
Elite Kenyan endurance runners don’t take nutritional supplements, and for good reason. Supplements are expensive, and in most cases there is little evidence that they promote higher performances. Only three compounds—caffeine, sodium bicarbonate, and creatine—have been documented as performance enhancers. Caffeine is legal and inexpensive. Sodium bicarbonate is legal and even less costly, but it can cause gastrointestinal distress and diarrhea. Creatine supplementation works well for enhancing sprint performances, but its effect on endurance running capacity is unclear. It may boost endurance running in some runners by upgrading the quality of interval workouts.
Part XI
Psychology of Running
Chapter 48
The Brain and the Experience of Fatigue
The traditional view in running is that fatigue, or the inability to continue a desired running velocity, is caused by the accumulation of metabolites in the muscles, the depletion of intramuscular energy stores, or increased body temperature. In this well-accepted conception, the muscles are believed to be the center of fatigue. One theory is that muscle fibers allow calcium to leak from them as strenuous running proceeds, lessening the force of muscle contraction. This occurs because the flow of calcium into muscle cells is a key stimulus for muscle-fiber shortening. Another frequently cited hypothesis—that science has proved to be incorrect—is that a buildup of lactic acid inside muscle cells is the dominant cause of fatigue during intense running.
A fundamental problem with the lactic acid and calcium concentrations theories is that neither corresponds to the real world. An often-forgotten implication of these conventional conceptions is that runners would slow down continuously during challenging runs as the leakiness of muscle fibers gradually increased or as lactic acid continued to pile up. If lactic acid is the true cause of fatigue, running pace should slow rather steadily over the course of a 5K or 10K race as intramuscular lactic acid concentrations increased.
The actual performances of well-trained runners reveal that race velocities vary widely over the course of a competition and are not tightly linked with calcium leaking from muscles or lactic acid level. When Haile Gebrselassie set his 10K world record, for example, his calcium leakiness and lactate level surely advanced steadily over the course of 10,000 meters of hard running, but his fastest pace was actually achieved over the last kilometer (.62 mi), which he covered in 2:31.3; most of the prior 1,000-meter segments of the race were completed in 2:37 to 2:38.1 He was running fastest when lactic acid levels and calcium leakiness had reached their apices.
The theory that fatigue during running is caused by biochemical, intramuscular factors is clearly inadequate.1 If muscle biochemistry were the true source of fatigue, there would be a clear link between muscle metabolite concentrations and actual running velocity. Some other system must be at work to explain why runners slow down during workouts and races.
Brain Regulates Pace and Fatigue
A key point to remember is that running velocity during a workout or competition is always a direct function of the rate of work performed by the muscles, but the instructions the muscles receive to work at various rates are always provided by the brain. The brain must take into account a variety of factors in order to choose the velocity at which an athlete will run. The brain might monitor body temperature, muscle metabolites, distance left to run, and other variables in order to reach a decision about running pace. The brain might even create a sensation of fatigue in order to enforce its decision—to prevent a runner from exceeding certain physiological thresholds. The brain could regulate running pace by generating strong feelings of fatigue in order to prevent physiological failure.
Anecdotal evidence that the brain acts as a regulator of fatigue and running pace is abundant although usually ignored. A classic example of the brain’s anticipatory role in running performance, presented by sports scientist Ross Tucker,2 is the case of a 40-minute 10K runner who is transported to either high altitude or a venue with hot, humid conditions and then asked to run a 10K race. In both situations, the runner’s 10K pace is much slower than usual from the very beginning of the 10K, not at some point within the race when inadequate oxygen delivery to the muscles or high internal temperatures become physiologically limiting.
Traditional theory would indicate that the slowdown in these situations was the result of oxygen depletion or high body temperature, but this is clearly wrong since the slowing occurred before either of these events. The brain must be able to anticipate physiological failure and thus slows pace and creates fatigue in certain situations in order to prevent too great a disturbance in physiological equilibrium. Since the brain anticipates and regulates, the overall process is thus called anticipatory regulation of running velocity.
A clear example of the shift in thinking that has occurred from the old model of fatigue to the new anticipatory regulation schema can be found in research carr
ied out on the role played by overheating in causing fatigue. Traditional investigations suggest that athletes run in the heat until core body temperature reaches a certain limit, usually thought to be approximately 40 degrees Celsius (104°F), at which point the brain stimulates the muscles to a lesser degree and heat-related fatigue occurs.3-5 Fatigue (i.e., the slowdown) is thus believed to be caused by a failure to maintain adequate coolness of the body during running.
However, such studies have been carried out in the unnatural situation in which athletes are required to continue exercising at a fixed rate until they are unable to continue. This is rarely the case during running workouts or races where pace varies considerably as the exertion proceeds. In fact, research carried out with athletes running in the heat when they are not forced to run at a single pace verifies the anticipatory regulation model by demonstrating that runners don’t slow down because they are overheated; rather, they decrease their pace in order to prevent themselves from getting too hot.6, 7 The failure to run as quickly in the heat as would be the case under cool conditions is thus the result of anticipatory regulation by the brain, not an overheating phenomenon within the muscles or brain itself.
If the anticipatory regulation theory of fatigue is sound, there should be studies that show that the nervous system gradually reduces its stimulation of muscles during fatiguing exercise and that this reduction parallels the actual increases in fatigue. Such a finding would be in contrast with the traditional view of fatigue, which would suggest that the nervous system continues a high level of stimulation while the muscles simply fail to continue functioning. Such investigations do exist. In one inquiry, cyclists completed a 100K ride sprinkled with all-out 1-kilometer (.62 mi) sprints.8 The quality of the sprints declined over the duration of this 100K effort. In parallel with this drop-off in sprint power, integrated EMG (IEMG ) activity also fell, which indicated that the central nervous systems of the athletes were recruiting fewer and fewer motor units as the ride progressed. This was true even though less than 20 percent of the available motor units in the cyclists’ leg muscles were being recruited at any one time even though there was an opportunity for the athletes’ nervous systems to bring more motor units into play—if they so desired.
Running Science Page 66