Running Science

by Owen Anderson

  When caloric and carbohydrate intakes are too low, performance problems can occur, and a form of energy overefficiency may be induced. Athletes should record what they eat for a several-day period and then calculate their intakes using a tool such as the USDA National Nutrient Database for Standard Reference, which can be found at the USDA website and provides nutrition information for a wide variety of foods. If carbohydrate or caloric intakes are low, optimal adaptation to training cannot occur.

  Consider the case of a 26-year-old male runner who was preparing to be competitive in 5K and 10K races and considering competing at the National Cross Country Championships. He had been a runner in college, posting a 4:16 personal record for the mile. In a 6-minute, vO2max test in an early stage of his training, he covered nearly 2,000 meters (1.24 mi) for an average pace of 72 seconds per 400 meters and an estimated vO2max of 5.56 meters (18.24 ft) per second. This would predict a 5K pace of about 74 seconds per 400 for a 5K time of 15:25, which would be reasonable for the preliminary phase of his overall progression. As he resumed serious training, his speed workouts went well. He clipped off 28- to 29-second 200s and hit 400s in 60 seconds each on the track. Predicting 5K times in the 14s did not appear to be too much of a stretch.

  As part of his effort to carry out high-quality, sustained running, he entered some 5K and 10K races, and here a problem revealed itself. He crashed badly in the last mile (1.6 km) of every 5K and over the last 2 to 3 miles (3.22-2.83 km) of the 10Ks. His interval workouts, too, had a similar pattern. The first halves of the sessions were great, but the intervals in the second halves were performed at significantly slower paces. In a vO2max session, for example, he could perform the first three 800s at 2:24, but the last two might drop to 2:37 or even 2:43. In a 4 × 1,600 session, the fall-off over the last two intervals was even more dramatic, and with a 5 × 1,600, he often had to stop when attempting to carry out the closing interval.

  The runner was training faithfully, getting plenty of sleep, and avoiding stress, but the pattern of decreased running velocity persisted during workouts and competitions. The problem turned out to be that his daily intake of calories and carbohydrate were too low. This athlete’s food choices tended to be low in fat, moderate in protein, and fairly rich in carbohydrate. His weight was stable, and so he assumed that he was taking in sufficient calories and carbohydrate. However, his dietary log revealed that this was not the case. Table 46.1 shows his total food intake for a typical day.

  Although calorie burning varies widely for individuals, estimate daily caloric needs by multiplying body weight in pounds by 15 and then adding about 100 calories per mile of training. As discussed in chapter 44, during challenging training, endurance runners should ingest a minimum of 4 grams (0.14 oz) of carbohydrate per pound of body weight on a daily basis. Top-quality Kenyan runners ingest almost 5 grams of carbohydrate per pound of weight.20 Protein intake for endurance athletes engaged in strenuous training could be as high as 1.5 to 1.6 grams per kilogram of body weight.

  The runner weighed 140 pounds (64 kg) and ran about 9 miles (15 km) per day, so his caloric intake should have been 3,000 calories per day:

  (140 pounds × 15) + 900 calories for the miles = 3,000 calories

  On the day represented in table 46.1, a typical day, he took in less than 1,900 calories, about 62 percent of the estimated caloric need. Additionally, he was ingesting just 381/140 = 2.7 grams of carbohydrate per pound, less than 70 percent of the recommended amount and barely over half of what the Kenyans would be eating. Protein intake was also somewhat low, suggesting that the muscle-repair processes that occur during recovery might be hampered. A runner should take in about 95 grams of protein; instead, he ingested a little over 58 grams on this particular day.

  The runner was counseled to gradually increase the amount of food he was eating. Gradual changes are necessary in this case because of the potential mitigating factor of energy efficiency. Since the runner had been seriously undereating, there was a good chance that his body was quite conservative in burning calories. A sudden jump to 4 grams of carbohydrate per pound of body weight might be treated by his body as a major surplus, leading to storing large quantities of body fat. An increase of just 25 grams of carbs (100 calories) per day, with this new total sustained for several days, then another similar increase, appeared to be the optimal way to proceed.

  During this period of gradual change, the athlete discovered one morning that his weight had jumped to 144 pounds (65 kg). He was reassured that he was simply storing more carbohydrate (i.e., glycogen) in his muscles and liver, that carbohydrate weighs more than twice as much as fat for the equivalent amount of calories, that glycogen storage includes water storage as well, and that the higher-quality and longer-duration training he could now perform as a result of the carbohydrate storage would ultimately keep his weight stable. He was also extremely happy when his ability to sustain quality paces during challenging workouts and races took a dramatic upswing.

  The runner also found that muscle soreness between workouts decreased. Muscle glycogen is not only a fuel during exercise, but it also provides energy for recovery processes. In addition, glycogen-poor muscles probably produce less protective joint stabilizing forces during strenuous running than glycogen-rich muscles. Thus, the amount of damage may be greater when glycogen is low, inducing soreness and necessitating longer recoveries.

  Conclusion

  Runners with low to moderate training volumes can lose weight effectively via a combination of increased training and reduced caloric intake that produces an average daily energy deficit of about 500 calories. Higher-volume runners often have difficulty increasing volume and thus must rely on changes in energy intake to achieve goal weight. A reduction in the percentage of dietary fat consumed can be an effective weight-loss strategy as long as it is not extreme, healthy fats (e.g., omega-3) are retained in the diet, and the effect is a drop in total caloric intake. Dietary plans that restrict carbohydrate should be avoided since they deplete muscle glycogen and lead to a reduction in training quality.

  Keeping an accurate dietary log can help endurance runners understand how many calories they are consuming per day. This is especially important for runners who are experiencing significant fatigue during intense or prolonged workouts or who are underperforming during competitions; such athletes’ intakes of carbohydrate and total calories may be too low. For those runners with excess body fat, knowledge of calorie consumptions permits a gradual reduction in caloric intake or a revision in dietary habits that can promote desired weight loss.

  Chapter 47

  Ergogenic Aids for Running

  More than $90 billion worth of sport supplements are sold to athletes each year around the world by an industry that is growing at a 24 percent annual rate.1 Runners and other athletes find themselves tempted by an amazing array of allegedly performance-enhancing products ranging from Andro Xtreme to Xenadrine RFA-1 and zeranol.

  Given the growth of the sport supplement business, many runners are surprised to learn that scientific research has linked only three relatively inexpensive supplements—caffeine, sodium bicarbonate, and creatine monohydrate—with improved running performances. Two of these supplements—caffeine and sodium bicarbonate—are readily available to runners without the purchase of high-priced commercial products.

  Caffeine Boost for Endurance Running

  Of the trio, caffeine has the strongest scientific support as an ergogenic aid for distance runners. Ergogenic aids are substances with the potential to improve performance, especially resistance to fatigue. In one well-designed (i.e., randomized, double-blind, crossover) study carried out in Australia, 15 well-trained and 15 recreational runners completed two randomized 5K time trials after ingesting either 5 milligrams of caffeine per kilogram (2.2 lb) of body weight or a placebo.2 The intake of caffeine significantly upgraded the 5K performances of both the well-trained and recreational runners by approximately 1 percent compared with placebo ingestion.

  In a s
econd investigation completed at Edge Hill College in the United Kingdom, eight trained male distance runners participated in an 8K race (4.97 mi) 1 hour after ingesting 3 milligrams of caffeine per kilogram (2.2 lb) of body weight, a placebo, or no supplement at all.3 This inquiry attempted to detect the mechanism underlying caffeine’s ergogenic activity by analyzing heart rate, blood lactate concentration, and rating of perceived effort (RPE) during the competition. The use of caffeine resulted in a 1.2 percent, 23-second enhancement of performance for the 8K runners compared with placebo use and no supplementation. Caffeine had no significant effect on heart rate or RPE, but it was linked with elevated blood lactate levels. Two interpretations for the higher lactate concentrations are possible: (1) The faster running associated with caffeine supplementation might have generated more lactate, or (2) the caffeine may have stimulated lactate production, increasing fuel availability during the race and thus enhancing performance.

  A third piece of research undertaken at the College of St. Scholastica in Minnesota linked caffeine use with benefits for cross country runners.4 Ten college-age cross country runners (five women and five men) completed a O2max test and then ran for 30 minutes on a treadmill at an intensity of 70 percent of O2max. In one case, the athletes ingested 7 milligrams of caffeine per kilogram of body weight prior to the submaximal run; in another, they consumed a placebo (7 mg/kg using vitamin C). The crossover treatments were randomized, and the study was completed in a double-blind manner. The results revealed that the intake of caffeine reduced perceived effort during the 30-minute runs and also augmented respiratory function, including tidal volume (i.e., the amount of air taken in per breath) and alveolar ventilation (i.e., the degree to which the lung’s small sacs filled with air during running).

  There is also evidence that acute ingestion of caffeine may be helpful in shorter-duration, higher-intensity running events such as the mile and 1,500 meters. In an exploration conducted at Christ Church College in Canterbury, United Kingdom, well-trained club-, county-, and national-level runners ran 1,500 meters on a treadmill as fast as possible and also engaged in a 1-minute finishing burst following a high-intensity run after ingesting either caffeinated or decaffeinated coffee. Drinking the caffeinated coffee reduced the amount of time needed to run 1,500 meters, heightened the velocity of the finishing burst, and also augmented the oxygen consumption rate during the 1,500-meter run compared with ingestion of decaffeinated coffee.5

  Finally, caffeine seems to boost performance during supramaximal effort, that is, during running carried out at speeds considerably faster than vO2max and thus much quicker than 1,500-meter or mile velocities. In work carried out at the University of Luton in the United Kingdom, nine well-trained male runners were able to run significantly longer at an intensity of 125 percent of vO2max after ingesting 5 milligrams of caffeine per kilogram (2.2 lb) of body weight compared with the ingestion of a placebo.6

  Caffeine is available to runners in four forms:

  As a natural constituent of regular, not decaffeinated coffee

  As a compound found in so-called energy drinks (e.g., Red Bull, Jolt, Mountain Dew Red Alert, Surge)

  In caffeinated gels (e.g., Torq Gel, Octane Energy Gel, Power Gel, Hammer Gel)

  In pill form in popular supplements (e.g., Alert, No Doz, Vivarin, Stay Awake) that are sold without prescription in many drug stores

  The pill supplements commonly provide from 50 to 200 milligrams of caffeine per tablet. The actual amount of caffeine in coffee depends on a number of factors, including the type of bean, the soil and overall environment in which the coffee was grown, the grind with which the coffee was prepared, and the method and length of brewing. A 6-ounce (177 mL) cup of coffee may have as few as 50 milligrams or as many as 200 milligrams of caffeine.

  This imprecision of caffeine content tells endurance runners interested in caffeine’s ergogenic effects that the use of caffeine tablets, gels, or caffeinated energy drinks might be preferable from a performance-enhancing standpoint compared with sipping mugs of java before competitions. Also making the use of coffee even more problematic for the endurance athlete is the evidence that coffee contains compounds that may at least partially suppress some of the physiological actions of caffeine.7 When athletes exercise at an intensity of 85 percent of O2max, they derive much more benefit, or increased endurance, from caffeine provided in pill form than from an equivalent amount of caffeine in coffee.

  A majority of endurance athletes are aware that caffeine intake prior to exercise is ergogenic but are unaware of how much caffeine must actually be ingested to produce performance enhancement.8 Exercise scientists generally agree that an ergogenic dose of caffeine is about 3 to 9 milligrams per kilogram of body weight taken one hour before running begins.9 There are few adverse side effects associated with caffeine use just before and during exercise,8 and caffeine consumption prior to performance is no longer banned by the International Olympic Committee, the IAAF, or the NCAA. Caffeine is considered to be a diuretic, but its ability to induce diuresis is blunted by exertion.

  Some exercise scientists have speculated that the chronic ingestion of coffee or caffeine-containing products might block the acute, positive effects of caffeine on performance on a specific day. Regular users of caffeine do have significantly different metabolic responses to the intake of the compound compared with nonusers.10 Nonetheless, no research has shown that caffeine-related enhancements in performance are different in caffeine users and nonusers. In one study, complete withdrawal from caffeine for 2 to 4 days had no impact on the effect of caffeine on performance; the ergogenic dose of caffeine in this investigation was 6 milligrams per kilogram of body weight.11

  There is evidence that the use of caffeine combined with another compound called ephedrine may boost running performances to a greater extent for events ranging in duration from 10 to 20 minutes compared with the ingestion of caffeine alone.12, 13 However, ephedrine supplementation has been linked with a number of deaths and adverse cardiovascular side effects, and its use is generally discouraged by sports medicine physicians. Ephedrine is also on the prohibited list published by the World Anti-Doping Agency (WADA): An athlete violates this prohibition when his or her urine level of ephedrine exceeds 10 micrograms per milliliter.14

  Sodium Bicarbonate and Middle-Distance Running

  Like caffeine ingestion, sodium bicarbonate (i.e., baking soda) supplementation is legal, and some exercise physiologists contend that bicarbonate intake may be particularly helpful to middle-distance runners. Sodium bicarbonate is a strong buffer, a chemical that can prevent the blood from becoming unusually acidic during intense running. This makes bicarbonate attractive as a supplement because upswings in blood acidity have been correlated with fatigue in some research.

  In a study carried out at Ball State University by exercise physiologist David L. Costill and his colleagues, eight healthy male athletes pedaled bicycle ergometers at the high intensity of 125 percent of O2max until they became exhausted.15 One hour prior to exertion, the individuals ingested a solution of either sodium bicarbonate or sodium chloride (table salt). All of the athletes were eventually tested with each type of solution. Ingestion of the baking soda slightly increased endurance time at 125 percent of O2max from 98.6 to 100.6 seconds, but this difference was not statistically significant. A related study revealed that ingesting bicarbonate did not upgrade performance in a 400-meter run.16

  The Ball State researchers found that the blood of the cyclists who consumed bicarbonate recovered more quickly following the intense effort (i.e., returned to a normal level of acidity more rapidly). This heightened recovery suggested to the scientists that the muscles of the exercisers might also have recovered more quickly, and they hypothesized that bicarbonate could enhance performance during workouts that involved repeated high-intensity intervals.

  In their follow-up study, 11 athletes (10 males and 1 female) completed an interval session consisting of five high-intensity intervals; this workout was compl
eted 1 hour after ingesting either sodium bicarbonate or sodium chloride.17 The workload during the intervals was again set at 125 percent of O2max, and a 1-minute recovery interval separated each minute of exercise. The first four work intervals lasted 1 minute, but the fifth interval was sustained for as long as possible.

  The athletes taking bicarbonate performed much better during the fifth interval than the sodium chloride control group. For the fifth interval, bicarbonate users exercised 160.8 seconds prior to exhaustion while control individuals managed to keep going for only 113.5 seconds. The fittest individuals benefited the most from sodium bicarbonate ingestion: The athletes who had the longest performance times with sodium chloride achieved the biggest improvements with sodium bicarbonate, perhaps because their sustained power outputs advanced blood acidity to the greatest extent and therefore needed buffering the most.

  A separate study carried out at the University of Western Australia supported the idea that ingesting sodium-bicarbonate could heighten the quality of high-intensity interval workouts.18 In this study, seven female team-sport athletes ingested sodium bicarbonate on day and a placebo on another day, both shortly before performing an intermittent-sprint workout consisting of two 36-minute halves during which high-intensity work intervals alternated with easy recovery periods. During the second halves of these training sessions, total work output was significantly greater during 7 of the 18 intervals after ingesting sodium bicarbonate rather than a placebo.

  Costill’s research team contended that bicarbonate ingestion is useless in running events lasting less than 1 minute but can enhance performance during repeated intervals of high-intensity running. The Costill group suggested that bicarbonate might also be beneficial during single runs lasting longer than a minute, a hypothesis that was supported by subsequent work with 800-meter runners.19 In this follow-up inquiry, athletes who ingested 0.3 grams of sodium bicarbonate per kilogram (2.2 lb) of body weight improved 800-meter race times by 2.9 seconds.