Some endurance athletes switch to a high-fat diet before competition as a way to increase their muscles’ fat-burning capacity during exercise and with it their endurance. Past research has shown that it works, but does the type of fat consumed matter? Researchers at Texas Tech University recently addressed this question in a study. Subjects were placed on a high-fat diet that was rich in either saturated or monounsaturated fat for five days. Some subjects exercised two hours per day during the treatment period while others did not exercise. The authors of the study, which was published in the Journal of Applied Physiology, found that fat burning increased significantly and equally in all of the exercising subjects, whether on the saturated fat-rich diet or the monounsaturated fat-rich diet. Fat burning did not increase in the non-exercising subjects.

Several studies now have shown that competitive cyclists have abnormally low bone mineral density. The leading hypothesis to explain this phenomenon has been that the energy demands of training and racing don’t allow bone tissue to be formed as quickly as it is broken down (a natural process). It doesn’t help that cycling is a non-weight-bearing activity, as weight-bearing activities are known to increase BMD.

The results of a new study from the University of Missouri suggest that the leading hypothesis is correct, and offer hope of a simple fix. The authors of the study measured bone turnover, energy intake and energy use in cyclists throughout a six-day stage race. They found that cyclists who matched their bodies’ energy use with food energy intake maintain a healthy balance between bone formation and bone breakdown. Only those cyclists who took in fewer calories than they needed showed evidence of a bone formation deficit. Here’s another reason for cyclists to make sure they stay well fueled throughout training and racing.

The International Society of Sports Nutrition has published a new position on the use and effectiveness of caffeine as an ergogenic aid to exercise performance. Jointly authored by a veritable Who’s-Who of sports nutrition experts, the paper reaches the following conclusions:

“1.) Caffeine is effective for enhancing sport performance in trained athletes when consumed in low-to-moderate dosages (~3-6 mg/kg) and overall does not result in further enhancement in performance when consumed in higher dosages (>/= 9 mg/kg). 2.) Caffeine exerts a greater ergogenic effect when consumed in an anhydrous state as compared to coffee. 3.) It has been shown that caffeine can enhance vigilance during bouts of extended exhaustive exercise, as well as periods of sustained sleep deprivation. 4.) Caffeine is ergogenic for sustained maximal endurance exercise, and has been shown to be highly effective for time-trial performance. 5.) Caffeine supplementation is beneficial for high-intensity exercise, including team sports such as soccer and rugby, both of which are categorized by intermittent activity within a period of prolonged duration. 6.) The literature is equivocal when considering the effects of caffeine supplementation on strength-power performance, and additional research in this area is warranted. 7.) The scientific literature does not support caffeine-induced diuresis during exercise, or any harmful change in fluid balance that would negatively affect performance.”

Increased training loads increase carbohydrate needs disproportionately compared to fat and protein needs. Thus it is reasonable to speculate that increased carbohydrate intake would help runners handle the stress of increased training periods and perform better in key workouts within such periods.

Brazilian researchers recently tested this idea with a group of 24 male runners. This group was divided into two subgroups, both of which engaged in an eight-day preiod of “overload” training. During this period, one group got 61 percent of daily calories from carbs while the other got 54 percent. At the end of the overload training period both groups performed a three-part workout consisting of a 1000m time trial followed by 10 x 800m at 3000m race pace followed by another 1000m time trial. Yikes!

Members of both groups performed equally well in the first two parts, but members of the high-carbohydrate diet group saw their 1000m time increase by 5.3 percent between the first and second runnings while members of the moderate-carbohydrate diet group saw their times increase by twice that amount. Researchers also observed lower cortisol concentrations and higher post-workout blood glucose concentrations in the high-carb group. These findings suggest that increased carbohydrate intake helped runners to better handle the stress of an overload training period.

The following as an abstract of a new study published in the journal Medicine & Science in Sports & Exercise: “Purpose: Dietary supplementation with polyphenols, particularly ellagitannins, may attenuate the muscular damage experienced after eccentric exercise, producing delayed-onset muscle soreness. The purpose of this study was to determine whether ellagitannin supplementation from Wonderful variety pomegranate extract (POMx) improved recovery of skeletal muscle strength after eccentric exercise. Methods: Recreationally active males were randomized into a crossover design with either pomegranate extract (POMx) or placebo (PLA), each given during a period of 9 d. To produce delayed-onset muscle soreness, subjects performed two sets of 20 maximal eccentric elbow flexion exercises with one arm. Maximal isometric elbow flexion strength and muscle soreness as well as serum measures of creatine kinase, myoglobin, interleukin 6, and C-reactive protein were made at baseline and 2, 24, 48, 72, and 96 h after exercise. Results: With both treatments, strength was similarly reduced 2 h after exercise (i.e., 72% of baseline), and recovery of strength was incomplete after 96 h (i.e., 91% of baseline). However, strength was significantly higher in POMx compared with that in PLA at 48 h (85.4% ± 2.5% and 78.3% ± 2.6%, P = 0.01) and 72 h (88.9% ± 2.0% and 84.0% ± 2.0%, P = 0.009) after exercise. Serum markers of inflammation and muscle damage did not provide insight regarding possible mechanisms. Conclusions: Supplementation with ellagitannins from pomegranate extract significantly improves recovery of isometric strength 2-3 d after a damaging eccentric exercise.”

The so-called Western diet, with its high fat composition, is the subject of much abuse because of its connection with elevated risk for numerous chronic diseases. But a new study by researchers at the University of California-Riverside suggests that it may increase voluntary exercise, at least in creatures with an innate predisposition toward exercise. The study involved mice, and there’s no telling whether the results seen in these animals would translate to humans. Researchers bred a strain of mice that really liked to run on wheels. In fact, these mice voluntarily ran 2.5-3.0 times as much as normal mice. A bunch of these runner mice and normal mice were given either a high-fat Western diet or a low-fat control diet for two months. Their total caloric intake, weight and adiposity, and running volume were tracked.

The Western diet was found to increase weight and adiposity in both the runner mice and normal mice, but much less so in the runner mice. Mice on the Western diet ate significantly more total calories during the first month of the study, but not the last month. But the most interesting finding was that runner mice on the Western diet voluntarily ran 75 percent more than runner mice on the control diet. The authors of the study, which was published in the International Journal of Obesity, speculated that the high fat content of the diet might have given the mice the endurance needed to run more or it might have somehow increased their psychological motivation to exercise.

Does this mean that human runners are better off on a Western diet? Who knows?

Exercise scientists use the body’s testosterone-cortisol ratio (T:C) as one marker of overreaching and overtraining. Testosterone is an “anabolic” hormone, and testosterone levels tend to be higher when the body is being built up. Cortisol is a “catabolic” hormone, and cortisol levels tend to be higher when the body is being broken down. Thus, a low T:C ratio is associated with classic symptoms of overtraining, including performance decline. Carbohydrate intake influences the T:C ratio in athletes, mostly indirectly, by providing fuel for training and recovery. When carbohydrate intake is inadequate for any given training load, the T:C ratio is likely to decrease.

This was shown in a new study by researchers at the University of North Carolina. Twenty male subjects were subjected to three consecutive days of unaccustomedly challenging endurance exercise. Twelve of the 20 were placed on a 60 percent carbohydrate diet during this crash training camp, while the other eight were placed on a 30 percent carbohydrate diet. The authors of the study, which was published in the European Journal of Applied Physiology, found that the T:C ratio did not change over the three days of heavy training in the high-carbohydrate group but declined significantly in the low-carbohydrate group.

This is evidence that, to a point, the more carbohydrate you consume, the more training your body can handle.

Everyone knows that successful runners are always light and lean, but a new study by researchers at the University of Zaragosa, Spain, suggests that body fat percentage is as important to running performance as any physiological factor. The Spanish scientists used skinfold measurements to estimate body fat percentage in 12 elite male and 12 elite female Ethiopian distance runners and compared these estimates to their race performances. They found an 80 percent correlation between skinfold measurements and race times in the men and a 78 percent correspondence in the women. All of these runners were very lean, but the leanest among them were the fastest. Body fat estimates were comparable to other physiological measurements such as forced expiratory volume in predicting performance. The study was published in the Journal of Sports Medicine and Physical Fitness.

The European Journal of Applied Physiology has published a new study on the effects of caffeine on supramaximal cycling performance. Researchers from Australia’s Griffith University recruited highly trained cyclists to complete indoor rides to exhaustion at 120 percent VO2max. They performed the test on two occasions, once after taking caffeine and once after taking placebo. Time to exhaustion was significantly greater following caffeine ingestion.

The researchers took several measurements to determine the cause of the performance increase with caffeine. No significant physiological differences were found except that circulating levels of potassium ions (K+) were lower during the warm-up in the caffeine trial. Since the accumulation of potassium ions outside muscle cells contributes to fatigue at very high exercise intensities, the apparent lowering of K+ levels after caffeine ingestion may have increased the amount of time it took for K+ accumulation to reach critical levels during the performance trial.

One of the leading researchers on the effects of protein intake on exercise performance, fitness adaptations and recovery is Richard Kreider at Texas A&M University. Kredier has authored a new review of research in his area of expertise summarizing what we know. Here’s the abstract of his paper:

“Dietary protein is required to promote growth, repair damaged cells and tissue, synthesize hormones, and for a variety of metabolic activities. There are multiple sources of proteins available; however, animal sources of protein contain all essential amino acids and are considered complete sources of protein, whereas plant proteins lack some of the essential amino acids and are therefore classified as incomplete. There is a significant body of evidence to indicate that individuals who are engaged in intense training require more dietary protein than sedentary counterparts (ie, 1.4-2 g/kg/day). For most individuals, this level of protein intake can be obtained from a regular and varied diet. However, recent evidence indicates that ingesting protein and/or amino acids prior to, during, and/or following exercise can enhance recovery, immune function, and growth and maintenance of lean body mass. Consequently, protein and amino acid supplements can serve as a convenient way to ensure a timely and/or adequate intake for athletes. Finally, adequate intake and appropriate timing of protein ingestion has been shown to be beneficial in multiple exercise modes, including endurance, anaerobic, and strength exercise.”

The review was published in The Physician and Sports Medicine.