Lessons from the war on dietary fat.

UNLABELLED: Conventional dietary guidelines put forth by health care institutions and providers for the past 40 years have stressed the importance of reducing the amount of dietary fat consumed. Such a diet is purported to mitigate metabolic risk factors and optimize the ability to achieve or maintain a healthy body weight. However, over the past 35 years obesity rates in the United States have risen dramatically though the level of dietary fat consumed by U.S. adults has fallen. This review examines the potential reasons for this paradox. Various meta-analyses, controlled trials, and cohort studies have demonstrated that reducing dietary fat intake provides for very little weight loss unless accompanied by equal or greater reductions in total energy intake. Due to both psychological (e.g., the tendency for people to eat more of what they consider low fat) and physiological (e.g., the low satiety that accompanies carbohydrate intake) factors, reducing total caloric intake while simultaneously reducing fat intake is a difficult challenge. Further, reductions in total carbohydrate intake, increases in protein intake, and adoption of a Mediterranean diet seem to be more effective in inducing weight loss than reductions in fat intake. Traditional claims that simply reducing dietary fat will improve metabolic risk factors are also not borne out by research. There is some evidence that replacing dietary saturated fat with unsaturated fat may improve metabolic risk factors, but that research is not conclusive. TEACHING POINTS: • Over the past 40 years, Americans have decreased the percentage of calories they get from dietary fat while rates of overweight and obesity have risen dramatically. • It appears that a decrease in total dietary fat in ad libitum diets may induce a very small decrease in body weight. • Evidence suggests that reductions in total dietary fat intake often occur in conjunction with an increase in total caloric intake. • It seems reasonable to conclude that guiding the public to simply reduce dietary fat intake is an ineffective method to mitigate the rise in obesity and improve public health.

Acceleration endurance with pressure breathing during G with and without a counterpressure vest.

INTRODUCTION: The purpose of this study was to test whether pressure breathing during G (PBC) without a counterpressure vest negatively influences G endurance or increases breathing fatigue during extended duration high-G exposures. METHODS: While using PBG, 10 subjects underwent 2 trials of +3 Gz exposures: once when wearing a counterpressure vest and once without. The exposures consisted of a relaxed, gradual G onset run until peripheral or central light loss, a straining rapid onset GC run to +6 Gz for 15 s, and a simulated aerial combat maneuver (SACM) G profile consisting of 10-s periods varying between +5 Gz and +9 Gz, during which subjects executed a hand-eye tracking task. The SACM endpoint was light loss or exhaustion. Subjects provided ratings of subjective effort and discomfort after the SACM. RESULTS: Significant differences were found between the vest and no-vest conditions for only 3 of 19 measures: heart rate under G and two measures of tracking ability. The vast majority of data indicated no difference between the vest and no-vest conditions for performance under G. DISCUSSION: This experiment supports previous studies and expands those previous results by increasing the duration of PBG exposure shown to not be influenced by wearing of the vest. We conclude that there is likely no practical advantage to wearing a counterpressure vest during PBG.

The influence of agility training on physiological and cognitive performance.

Agility training (AT) has recently been instituted in several military communities in hopes of improving combat performance and general fitness. The purpose of this study was to determine how substituting AT for traditional military physical training (PT) influences physical and cognitive performance. Forty-one subjects undergoing military technical training were divided randomly into 2 groups for 6 weeks of training. One group participated in standard military PT consisting of calisthenics and running. A second group duplicated the amount of exercise of the first group but used AT as their primary mode of training. Before and after training, subjects completed a physical and cognitive battery of tests including V[Combining Dot Above]O2max, reaction time, Illinois Agility Test, body composition, visual vigilance, dichotic listening, and working memory tests. There were significant improvements within the AT group in V[Combining Dot Above]O2max, Illinois Agility Test, visual vigilance, and continuous memory. There was a significant increase in time-to-exhaustion for the traditional group. We conclude that AT is as effective or more effective as PT in enhancing physical fitness. Further, it is potentially more effective than PT in enhancing specific measures of physical and cognitive performance, such as physical agility, memory, and vigilance. Consequently, we suggest that AT be incorporated into existing military PT programs as a way to improve war-fighter performance. Further, it seems likely that the benefits of AT observed here occur in various other populations.

Adaptations to a new physical training program in the combat controller training pipeline.

OBJECTIVES: The United States Air Force combat controller (CCT) training pipeline is extremely arduous and historically has a high attrition rate of 70 to 80%. The primary objective of this study was to evaluate the impact of incorporating a 711 Human Performance Wing (HPW) / Biobehavior, Bioassessment, and Biosurveillance Branch (RHPF)-developed physical fitness-training program into the combat controller (CCT) 5-level training physical fitness program. METHODS: One-hundred-nine CCT trainees were tested and trained during their initial eight weeks at the 720th Special Tactics Training Squadron (STTS) at Hurlburt Field. Modifications to their physical training program were principally aimed at reducing overtraining and overuse injury, educating trainees and cadre on how to train smarter, and transitioning from traditional to "functional" PT. A battery of physiological measurements and a psychological test were administered prior to and immediately after trainees undertook an 8-week modified physical fitness training program designed to reduce overtraining and injury and improve performance. We performed multiple physical tests for cardiovascular endurance (VO2max and running economy), "anaerobic" capacity (Wingate power and loaded running tests), body composition (skinfolds), power (Wingate and vertical jump), and reaction time (Makoto eye-hand test). We used the Mental Toughness Questionnaire 48 (MTQ-48) for the psychological test. RESULTS: We observed several significant improvements in physical and physiological performance over the eight weeks of training. Body composition improved by 16.2% (p < 0.05). VO2max, time-to-exhaustion, and ventilatory threshold were all significantly higher after implementation of the new program than before it. We observed strong trends towards improvement in work accomplished during loaded running (p = 0.07) and in average power per body mass during lower body Wingate (p = 0.08). Other measures of lower body power did not change significantly over the training period, but did show mild trends towards improvement. Upper body average and peak power per kilogram of body mass both improved significantly by 5.8% and 8.1%, respectively. Reaction time was significantly better posttraining as demonstrated by a 7% improvement during the reactive test. Reactive accuracy also improved significantly with the post test accuracy percentage jumping from 61% to 76%. Furthermore, overuse injuries, a major source of attrition fell by a dramatic 67%. CONCLUSIONS: The modifications resulted in significant improvement in trainees? graduation rate. In the eight classes prior to implementation of these changes, average CCT graduating class size was nine trainees. For the eight classes following the changes, average CCT graduating class rose to 16.5 trainees, an increase of 83%. Due to its success, STTS leadership expanded the modifications from the eight weeks prior to CDS to include the entire second year of the pipeline.

Physiological and psychological characteristics of successful combat controller trainees.

OBJECTIVES: The United States Air Force (USAF) Combat Controller (CCT) training pipeline is extremely arduous and historically has an attrition rate of 70-80%. The primary objective of this study was to identify the physiological, psychological, or demographical characteristics associated with successful progression through the CCT pipeline program. METHODS: A battery of physiological measurements, biographical information, and psychological tests were used to determine the profile of a successful CCT trainee. These measures were chosen on the basis of being standard physical fitness parameters, CCT-specific physical attribute indicators or validated psychological surveys. A multiple of physical tests served as measurements for cardiovascular endurance (VO2max and running economy), ?anaerobic? capacity (Wingate power and loaded anaerobic endurance treadmill tests), body composition skinfolds measurements, power (Wingate and vertical jump), and reaction time (Makoto eye-hand test.) Each test was conducted using a standardized protocol. Psychological characteristics were explored through use of the International Personality Item Pool (IPIP-NEO) and the Mental Toughness Questionnaire 48 (MTQ 48). RESULTS: Our findings revealed the following mean characteristics of 109 CCTs who completed Phase I of the pipeline and achieved their 3-level rating: 23 years old, 1.8m tall, 81 kg, 12% body fat, VO2max of 59 ml/kg/min, vertical jump of 62 cm, able to generate 11.4 W/kg peak power and 9.3 W/Kg mean power during Wingate tests, overall mental toughness rating of 8 (out of 10) with high levels of extraversion and conscientiousness and low levels of neuroticism. The most popular competitive sport played in high school was football, followed by track, wrestling, and baseball. CONCLUSIONS: The results of the investigation confirm that CCT trainees who have achieved a 3-level rating possess much higher than average levels of aerobic and anaerobic fitness, power, mental toughness, extraversion and conscientiousness. They possess lower than average levels of neuroticism and openness to experience. These results may prove useful in refining the selection criteria and in designing training for CCT trainees.

The influence of 8 weeks of whey-protein and leucine supplementation on physical and cognitive performance.

The purpose of this study was to investigate the ability of whey-protein and leucine supplementation to enhance physical and cognitive performance and body composition. Thirty moderately fit participants completed a modified Air Force fitness test, a computer-based cognition test, and a dual-energy X-ray-absorptiometry scan for body composition before and after supplementing their daily diet for 8 wk with either 19.7 g of whey protein and 6.2 g leucine (WPL) or a calorie-equivalent placebo (P). Bench-press performance increased significantly from Week 1 to Week 8 in the WPL group, whereas the increase in the P group was not significant. Push-up performance increased significantly for WPL, and P showed a nonsignificant increase. Total mass, fat-free mass, and lean body mass all increased significantly in the WPL group but showed no change in the P group. No differences were observed within or between groups for crunches, chin-ups, 3-mile-run time, or cognition. The authors conclude that supplementing with whey protein and leucine may provide an advantage to people whose performance benefits from increased upper body strength and/or lean body mass.

Acceleration tolerance after ingestion of a commercial energy drink.

BACKGROUND: Caffeine ingestion has been demonstrated to increase physical performance in some situations. This study examined the ability of a commercial energy drink containing caffeine to enhance acceleration tolerance and strength under G load. METHODS: Eight experienced centrifuge subjects completed three separate experimental acceleration exposures following ingestion of 11.5 ml x kg(-1) bodyweight of (1) a commercial energy drink, providing 5.0 mg caffeine/kg bodyweight; (2) a commercial energy drink without caffeine; or 3) a placebo. The acceleration exposures consisted of a relaxed gradual onset run to peripheral light loss, a rapid onset run to 6 G for 15 s, and a simulated air combat maneuver (SACM) run of repeated alternations between 4.5 G for 15 s and 7 G for 15 s until volitional exhaustion. RESULTS: Relaxed G tolerance was 13% higher under the caffeinated energy drink session, whereas SACM duration did not differ among the drink conditions. Hip adductor muscle strength was 37% lower during the placebo session than during the other two sessions. CONCLUSION: Consumption of a caffeine-based energy drink may enhance relaxed G tolerance and may increase strength, but does not impact acceleration tolerance duration.

Is performance of intermittent intense exercise enhanced by use of a commercial palm cooling device?

The purpose of this study was to determine if using the CoreControl Rapid Thermal Exchange (RTX), a commercial palm cooling device, during active rest periods of multiple set training is an effective means to increase performance. Ten volunteers (5 men, 5 women) completed a VO2max test on a motorized treadmill and 3 interval running tests on a human powered treadmill. This treadmill allowed the subjects to quickly reach their running speed while allowing for measurement of distance, speed, and force. During the interval running tests the subjects completed eight 30-second intervals at a hard/fast pace followed by a 90-second walking or light jogging recovery period. During the recovery period, the subjects placed their left hand on 1 of 3 media: the RTX held at 15 degrees C (R), a 15 degrees C standard refrigerant gel pack (P), or nothing at all (C). Although there were differences in core temperature (Tc), subjective heat stress ratings, distance, and power generated between intervals, there were no significant differences (p < 0.05) found between treatments for any of these variables, nor was the interaction effect of interval*treatment found to be significant. Mean distance completed per trial was 717.1 m +/- 124.4 m (R), 724.8 m +/- 130.3 m (P), and 728.6 m +/- 110.6 m (C). Change in Tc from baseline to end-test averaged 1.41 degrees C +/- 0.37 degrees C (R), 1.41 degrees C +/- 0.39 degrees C (P), and 1.41 degrees C +/- 0.59 degrees C (C). There were no significant differences (p < 0.05) in Tc, heart rate (HR), or VO2 between intervals or treatments. We conclude that the RTX, in its current iteration, is ineffective at improving performance and/or mitigating thermal stress during high-intensity intermittent exercise.

Failure of Rhodiola rosea to alter skeletal muscle phosphate kinetics in trained men.

Rhodiola rosea is an herbal supplement purported to improve resistance to stressors and to enhance physical performance, potentially by improving adenosine triphosphate (ATP) turnover. Phosphocreatine (PCr) kinetics serves as a reflection of ATP turnover. The purpose of this investigation was to examine the effect of R rosea ingestion on human skeletal muscle PCr recovery after exhaustive exercise. Twelve resistance-trained men, aged 19 to 39 years, completed incremental forearm wrist flexion exercise to volitional fatigue, once after ingesting 1500 mg R rosea per day for 4 days, and once after ingesting an equivalent placebo dose. During exercise and recovery from exercise, muscle phosphates were examined using phosphorus 31 nuclear magnetic resonance spectroscopy. [PCr] during recovery was fit with a monoexponential function, and the resulting rate constants (k) were compared between groups. Rating of perceived exertion per stage and time to exhaustion were also compared between groups. For R rosea, k=0.3744+/-0.1532, whereas for placebo, k=0.3956+/-0.2238. Although rating of perceived exertion significantly increased within groups as workload increased, it did not differ between conditions, nor did time to exhaustion (R rosea, 10.71+/-0.54 minutes; placebo, 10.48+/-0.68 minutes). Estimates of [PCr] at time 0, 5, 10, 15, and 20 minutes of recovery were nearly identical between groups. In summary, there were no significant differences between groups for any of theparameters measured. Based on these results, we conclude that R rosea ingestion does not improve ATP turnover during or immediately after exercise.

Energy expenditure during bench press and squat exercises.

Despite the popularity of resistance training (RT), an accurate method for quantifying its metabolic cost has yet to be developed. We applied indirect calorimetry during bench press (BP) and parallel squat (PS) exercises for 5 consecutive minutes at several steady state intensities for 23 (BP) and 20 (PS) previously trained men. Tests were conducted in random order of intensity and separated by 5 minutes. Resultant steady state VO2 data, along with the independent variables load and distance lifted, were used in multiple regression to predict the energy cost of RT at higher loads. The prediction equation for BP was Y' = 0.132 + (0.031)(X1) + (0.01)(X2), R2 = 0.728 and S(xy) = 0.16; PS can be predicted by Y' = -1.424 + (0.022)(X1) + (0.035)(X2), R2 = 0.656 and S(xy) = 0.314; where Y' is VO2 X1 is the load measured in kg and X2 is the distance in cm. Based on a respiratory exchange ratio (RER) of 1.0 and a caloric equivalent of 5.05 kcal x L(-1), VO2 was converted to caloric expenditure (kcal x min(-1)). Using those equations to predict caloric cost, our resultant values were significantly larger than caloric costs of RT reported in previous investigations. Despite a potential limitation of our equations to maintain accuracy during very high-intensity RT, we propose that they currently represent the most accurate method for predicting the caloric cost of bench press and parallel squat.

Does Rhodiola rosea possess ergogenic properties?

Rhodiola rosea is an herb purported to possess adaptogenic and ergogenic properties and has recently been the subject of increased interest The purpose of this article was to review and summarize recent investigations of the potential performance-enhancing properties of Rhodiola rosea. Such studies have generated equivocal results. Several investigations conducted in Eastern Europe have indicated that Rhodiola rosea ingestion may produce such positive effects as improved cognitive function and reduced mental fatigue. Other research from this region has illustrated enhanced endurance exercise performance in both humans and rats. Studies conducted in Western Europe and in North America have indicated that Rhodiola rosea may possess substantial antioxidant properties but have produced mixed results when attempting to demonstrate an ergogenic effect during exercise in humans.