everal studies relative to endurance running have recently been published, and the following provides a brief synopsis of each. Eo * * Kusy, K., and J. Zielinski. 2014. “Sprinters Versus Long-Distance Runners: How to Grow Old Healthy.” Exercise and Sport Sciences Reviews 43(1):57-64. Much research has focused on the manifold health benefits of exercise, and research indicates that the incidence and risk of various chronic diseases, such as diabetes, metabolic syndrome, and coronary heart disease, are lower in those who exercise through adulthood and into the senior years as compared with sedentary individuals. In a recent review, Kusy and Zielinski indicated that most studies so far have focused on changes in aerobic capacity and health characteristics in endurance sports and little research attention has been paid to sprint-trained athletes, such as those who perform short-term (about 30 seconds), maximal-intensity exercise. Such training may be related to the relatively recent introduction of High Intensity Interval Training (HIIT), which may involve short bouts of sprinting at top speed as a means of attaining fitness with less time commitment. Based on their own and other research, here are some of the key points of their review:

In general, older endurance-trained athletes have a higher maximal aerobic capacity compared with sprint-trained peers, but the latter have higher capacity than untrained peers.

Both aging endurance runners and aging sprinters preserve a high level of insulin sensitivity essential to effective blood-glucose regulation and also maintain an optimal serum-lipid profile.

Older endurance runners and sprinters both have a similarly low body-fat percentage, but sprinters have a greater proportion of muscle mass. Relative to competitive performance in their respective sports, increased muscle mass may be advantageous to sprinters but disadvantageous to endurance runners.

In general, bone-mineral density is somewhat higher in sprinters than in endurance athletes, but bone loss still occurs with advanced age and beyond age 80, bone characteristics are comparable to untrained individuals.

¢ Neuromuscular function, such as maximal force and power development, was higher in sprinters. It declined in both groups with aging, but power remained considerably higher among sprinters across the age span of 35 to 90.

¢ Injury rates, such as tendon injuries, seem to be higher in sprinters and middle-distance runners compared with endurance athletes, but the overall injury rate is low and does not increase with age.

¢ Increased risk of osteoarthritis of the hip and knee in old age is a common adverse effect in those who start sport competition at an early age, but the other overall health benefits outweigh the risk.

¢ Both endurance and sprint training programs seem to reduce the risk of coronary heart disease, with endurance athletes being best protected in the later stages of life.

In summary, the authors note that comparable to the endurance-training model, the sprint-training model also results in optimal health outcomes in a long-term perspective.

As an aside, most distance runners know that in order to run faster, you need to run faster during training. Doing interval workouts, such as fast 200-meter repeats, once or twice weekly can help improve your distance-running performance. Such training, an example being repetition training, is advocated by many renowned distance-running coaches, including Jack Daniels in his renowned book, Daniels’ Running Formula.

Eo * * Hansen, E. A., et al. 2014. “Improved Marathon Performance by In-Race Nutritional Strategy Intervention.” /nternational Journal of Sport Nutrition and Exercise Metabolism 24(6):645-655.

Intake of both fluids and carbohydrate is an important consideration for marathon and ultramarathon runners, and over the course of several decades literally hundreds of studies by sports scientists have evaluated the effects of such strategies as carbohydrate loading, prerace hydration, and in-race fluid and carbohydrate intake on distance-running performance. Through experience most of us have developed our own personal strategies in attempts to optimize fluid and carbohydrate intake during a marathon, but our strategy may not be optimal.

In this well-designed study with non-elite marathon runners, Ernst Hansen and his colleagues from Aalborg University in Denmark compared the effects of two nutritional strategies on performance in the 2013 Copenhagen Marathon. The investigators used a strict pairing procedure to match two groups of runners. The matching criteria included a number of variables, including age, height, body mass, and previous running experience, but sex and 10-kilometer running time were the two key matching variables.

One group of runners used their own freely chosen nutritional strategy (FREE) to consume fluids and carbohydrate during the race. The other group used a scientifically based nutritional strategy (SCIENCE), which included two energy gels and 0.2 liter of water 10 to 15 minutes before the start of the marathon and subsequently one gel every 20 minutes during the remainder of the race. The gel contained 20 grams of maltodextrins and glucose, 20 milligrams of sodium, and 30 milligrams of caffeine. Water intake was scheduled at preestablished stations and approximated 750 milliliters per hour, which is about 25 fluid ounces. To familiarize the runners with this overall protocol, the same nutritional strategy was used by the runners in a half-marathon approximately four to five weeks prior to the marathon as well as during training.

The investigators were meticulous in their assessment of the runners, testing for blood-glucose levels before and after the race, assessing gastrointestinal symptoms, and using a sophisticated statistical analysis.

Overall, the SCIENCE group (3:38:11) completed the marathon nearly 11 minutes faster than the FREE group (3:49:26), a difference approximating 5 percent. Although the total fluid intake was comparable between the two groups, averaging approximately 2.4 liters during the race, the SCIENCE group consumed significantly more carbohydrate, approximately 234 grams compared with only 145 grams by the FREE group.

The investigators did note that the gels contained caffeine, which has been shown in other studies to enhance endurance performance. However, the amount of caffeine consumed in the gels averaged about | milligram per kilogram body weight per hour, which the investigators noted was much less than the amounts used in caffeine studies showing improved endurance performance. They also noted it was unlikely that all runners in the FREE group ingested completely caffeine-free products and thus suggested the difference in marathon performance between the two groups could be attributed to the higher level of carbohydrate intake in the SCIENCE group.

It is important to note that the investigators ensured that the subjects became acquainted with the procedure for consuming the gels during their training for the marathon. The occurrence of gastrointestinal symptoms in both groups was generally low, and there were no differences between the two groups.

Optimizing your carbohydrate intake during a marathon may help improve your performance, but it is important to experiment with the protocol during training.

ES Eo * Hyponatremia is a major health concern of marathon and ultramarathon runners, as well as some other athletes. A group of worldwide experts recently held a conference with the purpose of revising the Consensus Statement on ExerciseAssociated Hyponatremia. The following summary of the Third International Exercise-Associated Hyponatremia Consensus Development Conference was

written by the lead author of the Consensus Statement, Tamara Hew-Butler, DPM, PhD, from Oakland University in Rochester, Michigan.

Hew-Butler T., et al. 2015. “Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference.” Clinical Journal of Sport Medicine 25(4): 303-320, and British Journal of Sports Medicine (2015) doi: 10.1136/bjsports-2015-095004.

The 2015 International exercise-associated hyponatremia (EAH) consensus conference served to update the 2008 (second) EAH Consensus Statement. Key changes were made based upon new evidence that evolved our understanding of how EAH develops (etiology), how to diagnose EAH, how to treat EAH, and strategies to prevent EAH. A synthesis of the latest EAH Consensus guidelines, highlighting the key 2015 updates, is summarized below:

Definition and epidemiology. EAH is defined as any blood-sodium concentration that is below the normal range for the laboratory (or instrument) analyzing the blood sample. For most labs, this cutoff value is 135 mmol/L. Therefore, any runner with a blood-sodium concentration below 135 mmol/L is, by definition, hyponatremic.

First reported in the 1980s, EAH was once a rare sodium imbalance seen in desert hikers, ultramarathon runners, and Ironman triathletes. By the year 2000, EAH was reported in clusters of marathon runners, with five deaths confirmed from EAH-associated brain swelling (encephalopathy). Since publication of the second EAH Consensus Statement, symptomatic EAH has been reported after half-marathons, cycling, trekking, canoeing, swimming, yoga, weightlifting, and American football practice sessions. Additionally, multiple blood samples taken from ultramarathon runners, rugby players, and elite junior rowers (all for research purposes) revealed that more than half of the athletes tested were hyponatremic at one point during races or training. Thus, over the past decade, EAH has been detected with increasing frequency and across a wider variety of sports.

Etiology. The main cause of both symptomatic and asymptomatic EAH is drinking too much fluid during exercise combined with an inability to “pee out” any excess water to keep blood-sodium levels within the normal range. Dilutional hyponatremia has also been called “water intoxication” because all drinks—including sodium containing sports drinks—have far less sodium (10-38 mmol/L) compared with blood-sodium concentrations (135-145 mmol/L). It is important to note that exercise above the intensity of a brisk walk will stimulate secretion of the body’s natural antidiuretic hormone (arginine vasopressin, or AVP). Exerciseinduced AVP secretion makes evolutionary sense, because moderate to vigorous physical activity induces sweating, which is necessary for evaporative cooling. In order to preserve total body water, the body instinctively “shuts off” urinary

water losses to compensate for sweat water losses. More practically speaking, if we drink too much fluid at rest, we promptly pee off the excess to maintain blood-sodium levels. However, if we drink too much during exercise (above sweat water losses), urinary free-water excretion is impaired due to exercise-associated antidiuretic hormone secretion. Thus, sustained fluid intake above sweat water losses, combined with the inability to pee out any fluid excess during exercise, is the main cause of dilutional EAH in runners.

Of note, recent evidence suggests that runners who are not heat acclimatized and participate in longer (>18 hours), hotter races will lower their individual threshold for the amount of (extra) fluid necessary to dilute body-sodium levels. From a training standpoint, a fluid-intake plan that may have worked well in the past may cause hyponatremia when both environmental temperature and AVP secretion are abnormally high. In these rare instances, sustained sweat-sodium losses do not actually cause hyponatremia but reduce the amount of circulating plasma water (because blood sodium attracts water into the vascular space). This decrease in circulating plasma volume (hypovolemia) is a strong stimulus for antidiuretic hormone secretion. The presence of sustained hypovolemia would then explain why runners may not voluntarily drink as much fluid as they typically would (or plan to) during long, hot races: to prevent further dilution of blood-sodium levels. This unusual variant of hyponatremia is associated with body-weight loss. Thus, hypovolemic hyponatremia can also be attributed to a relative overdrinking with respect to sustained, underreplaced, sweat-sodium and water losses.

Classification and diagnosis. Hyponatremia that is detected through routine blood testing (as for research) but without symptoms is referred to as “asymptomatic” hyponatremia. Conversely, “symptomatic” hyponatremia is associated with clinical signs and symptoms and classified according to the severity of these signs and symptoms, rather than the actual numerical value for blood-sodium concentration. This is an important update from the previous Consensus Statement and is designed to more properly align diagnoses with treatment. The authors thereby classified symptomatic EAH into two categories: mild and severe, depending on the presence or absence of neurological signs and symptoms. Accordingly, mild EAH is characterized by vague signs and symptoms such as dizziness, lightheadedness, bloating, and nausea. These symptoms overlap with many other causes of exercise-associated collapse, which makes the diagnosis of EAH difficult without a blood test. Severe EAH is diagnosed when neurological signs and symptoms of acute brain swelling are present, which include vomiting, altered mental status, combativeness, seizures, and coma. Sometimes, respiratory symptoms associated with fluid in the lungs (pulmonary edema) are present and include signs and symptoms such as wheezing and pink frothy sputum. Severe EAH is an urgent, life-threatening emergency. Thus, if any of the above-mentioned symptoms are

present in a runner, especially when associated with body-weight gain and/or a history of high fluid intake, a blood-sodium test is highly recommended to rule out hyponatremia.

Treatment. Once EAH is diagnosed, the most appropriate treatment is guided by the severity of symptoms, as detailed above. When asymptomatic EAH is encountered, fluid should be restricted until the runner starts to urinate freely. Alternatively, highly concentrated saline solutions can be given, making sure that the sodium concentration of these broths is well above normal blood sodium concentrations (>140 mmol/L; or a “hypertonic” saline solution). One study showed that four bouillon cubes dissolved in 4 ounces (half a cup) of water improved blood-sodium levels within 30 minutes of ingestion. When mild EAH is diagnosed, runners should be given small amounts of hypertonic salty broth until their symptoms resolve. If athletes with mild EAH cannot tolerate oral fluids, then a small amount (100 mL, or less than half a cup) of hypertonic saline should be administered through an arm vein (intravenously) until they feel better and/or start to urinate freely. Since athletes diagnosed with asymptomatic or mild EAH can deteriorate within a few hours of race finish, either fluid restriction or hypertonic salty broths are encouraged despite somewhat vague symptomatology. Last but not least, severe EAH is a life-threatening medical emergency. Runners with signs and symptoms of severe EAH should be promptly treated with intravenous hypertonic saline until their condition improves, or at least stabilizes, before immediate transport to a hospital. The aim of this life-saving hypertonic saline treatment is to reduce fatal brain swelling (the sodium will attract water out of the brain cells and into the vascular space) rather than restore blood-sodium levels back into the normal range. Thus, brain swelling from water intoxication can be quickly reversed with prompt administration of hypertonic saline. lf EAH-associated brain swelling exceeds 5-8 percent, a runner will likely die from brain-stem herniation.

Prevention: Drinking fluids only when thirsty will prevent virtually all cases of EAH. Overzealous fluid consumption before, during, or immediately following exercise will not prevent heat stroke or muscle cramps nor enhance performance. Hyponatremia—or water intoxication—is both deadly and preventable.

As such, a wide variety of fluids should be available during races, at refueling stations spaced five kilometers apart, with instructions to drink whatever beverage is most appealing and only when thirsty. For athletes who desire a rough estimate of fluid-replacement needs (to match losses), weighing before and after 60 minutes of running—at expected race pace and ambient temperature—is a good starting guide. Thus, THE best hydration, fueling, and racing strategy is to start with a plan and then adjust accordingly.

For safe and optimal training and racing: drink to thirst and salt to taste. ©}