ATHLETE x SCIENCE
ATHLETE x SCIENCE
The debate between manipulating carbohydrate and fat metabolism for various weight loss and performance outcomes has gone back and forth by researchers for several decades, with no conclusive evidence supporting the extreme elimination diets we see so heavily marketed today. In the 1990s, high-carbohydrate nutrition was favored by the sports nutrition guidelines, recommending that at least 55% of energy come from carbohydrates in a given day (Burke, 2010). For endurance athletes, this number was recommended at greater than 60%; however, the research failed to support ‘why’ athletes needed this sort of macronutrient ratio for training (Burke, 2010). The evidence came after the millennium when it was found that higher carbohydrate intake could reduce (though not completely prevent) overreaching stress symptoms such as fatigue, sleeplessness, hormone disruption, and sub-par performance (Burke, 2010). In fact, withholding carbohydrates during the first few hours of recovery may hinder the functionality of the immune system and accentuate the immunosuppression occurring post-exercise (Burke, 2010). In addition, it was not found that moderate carbohydrate intake provided performance enhancement over a high-carbohydrate intake, so the guidelines remain in favor of carbohydrate availability for training purposes (Burke, 2010). High-fat nutrition has renewed interest once again, but is there enough to support a case for today’s endurance athlete?
The availability of a given substrate in the body largely determines our body’s fuel of choice at rest (Spriet, 2014). Exercise increases the metabolic demand on the body several-fold upon beginning a training session from rest, after which the body strives to achieve a steady state of aerobic intensity where the proportion of carbohydrates and fats finds an equilibrium in relation to an individual’s preference of fuel source (Spriet, 2014). When the power output of exercise exceeds 60% of maximal oxygen uptake (VO2max), studies have shown a decreased reliance on fat oxidation as a fuel source (Spriet, 2014). This decrease in free fatty acid release at higher intensities is likely due to a diversion of blood flow from adipose tissue to contracting muscles (Spriet, 2014). Above 75% of the VO2max, the majority of energy is derived from carbohydrate use, specifically muscle glycogen, in moderately trained individuals (Spiret, 2014). This is an important concept to consider when an endurance athlete is aiming to compete at 70-75% of maximum for extended periods of competition. The question remains whether or not it is possible to “teach” the body how to metabolically prefer fat as a fuel source at these competition intensities, which would go against the “default,” so-to-speak, of our innate preference for carbohydrates at these speeds.
Carbohydrates have gotten a bad rap for supposedly contributing to an ever-growing trend of obesity and metabolic syndrome in our country. On a physiologic level, carbohydrate intake results in a release of insulin by the body to help shunt glucose into depleted cells, or in the case of an inactive population, into the fat cells for conversion and storage, resulting in excess weight gain. Upregulated insulin inadvertently inhibits the transfer of fat across membranes, blocking fat oxidation (also known as lipolysis) during exercise and even at rest (Spriet, 2014). The reverse is true also: in the presence of high-fat, carbohydrate metabolism is down-regulated (Hawley & Leckey, 2015). The proposed theories of high-fat, low-carb exploit this physiologic mechanism as a way to increase fatty acid oxidation at the expense of restricting carbohydrate intake. The attraction to high-fat, low-carb diets for athletes has recently caught the attention of many through the media highlights of any given elite who has successfully clinched a podium spot in a championship, purely by running on a ketogenic diet or the like. While these performances are being attributed to the nutritional habits of these athletes, the research says there is no correlation between increased fat oxidation and performance (Hawley & Leckey, 2015). Carbohydrate-, not fat-based fuels, are the rate limiting factor in performance in trained endurance athletes (Hawley & Leckey, 2015). Fat-rich diets directly impair rates of muscle glycogenolysis, limiting high-intensity ATP-production necessary for energy at these paces (Hawley & Leckey, 2015).
Continue reading the full article and other sport science research at https://www.freelapusa.com/keto-or-not-to-keto-that-is-the-question/
Plyometrics and Performance
One of the topics I am most interested in relates to plyometric training for endurance runners. An article by Ebben (2001) states that due to the instability of the surface of cross country running, it is estimated that 5-10% of energy in a 3-6 mile race comes from anaerobic sources. With that being said, it is important to train for this anaerobic component, even in a primarily aerobic sport. This can be done via the use of explosive plyometric exercises. Ebben (2001) discusses the principle of specificity as it relates to training in a sport-specific manner. Force application to the ground is extremely important in cross-country running, as it directly generates power for covering the greatest horizontal distance possible with optimal efficiency (Ebben, 2001). Plyometric training, especially in the single-leg modality is highly specific to the single-leg force application that occurs in a runner’s stride (Ebben, 2001). Plyometric exercises with a greater horizontal component are even more specific to running, such as multiple reactive single-leg hops moving forward (Ebben, 2001).
A study by Ramirez-Campillo et al. (2014) examined the use of plyometric training in highly competitive middle- and long-distance runners for the purpose of developing explosive strength in performance. Plyometric training is meant to adapt the stretch-shortening cycle (SSC) and increase the rate of activation of a muscle’s motor units (Ramirez-Campillo et al., 2014). This study was initiated because prior research lacked a sufficient number of participants, failed to evaluate the effects in elite runners, applied a very high volume of plyometric activity per study length, and/or failed to include a time trial to assess distance running performance change (Ramirez-Campillo et al., 2014).
The experiment included a simultaneous application of plyometric and endurance training to test the effect on both time trial endurance performance and explosive strength adaptations (Ramirez-Campillo et al., 2014). The plyometric exercises included a drop (depth) jump from 20cm and 40cm to test for maximum jump height and minimum ground contact time, a countermovement jump (with arms) for slow SSC action, a 20m sprint test to assess horizontal explosive strength with fast SSC action, and a 2.4km endurance test on an outdoor track (Ramirez-Campillo et al., 2014). Total plyometric training time was less than 60-minutes per week for the 6-week study (Ramirez-Campillo et al., 2014). The experimental group experienced a 3-time greater improvement in time trial performance than the control group; in all other explosive metrics, the experimental group improved significantly while the control group showed a reduction in performance (Ramirez-Campillo et al., 2014). I thought this study was well-done and covered a lot of the bases that were missing in prior research to-date. It’s important to see these adaptations in the elite population, since they are already highly efficient individuals, small gains in performance are crucial and highly visible with new training strategies. In the general, untrained or even moderately-trained population, it’s very easy to manipulate variable to create positive results; this is much more difficult to achieve in elite populations.
Continue reading the full article and other sport science research at https://simplifaster.com/articles/plyometrics-performance-bone-health/
The topic of nature versus nurture presents itself in the world of elite sporting events as a sustained debate. Are world class athletes born or bred? Is there a certain amount of practice that can turn the average athlete into an elite? There are two main theories which aim to explain both arguments in the spectrum of the debate: the genetic influence model and the deliberate practice model.
The genetic model argues that athletic potential and success is predicted by a predetermined set of genetic traits. These physical traits are polygenic, or coded my many genes, producing the ultimate elite phenotype (Tucker & Collins, 2012). The four most influential traits include: gender, height, skeletal muscle composition, and VO2max (Tucker & Collins, 2012). The most obvious influence on athletic performance is the drastic segregation of male and female performances; this in itself is proof of genetic predisposition to athletic potential. Height is developed by both nature and nurture (nutrition), and is very predictive of sport-specific success; for example, the height required for basketball players is not conducive to long distance running.
Studies have found a number of VO2max genes in untrained individuals, inherently genetic, and also genes activated by training, environmentally influenced (Tucker & Collins, 2012). VO2max is a strong predictor of maximal aerobic capacity and thus performance in endurance-based events. Being genetically gifted with a superior aerobic capacity automatically places the athlete in an advantageous position for accelerated graduation to the elite level. Skeletal muscle properties are subject to similar genetic and environmental influences (Tucker & Collins, 2012). Hence, an athlete born with greater strength capacity in his or her musculature will have an easier time transitioning into strength-based sports, such as football or wrestling.
The dominance of East African runners in the middle-and long-distance events is well-known, especially in the last decade where 85% of the top 20 ranks in the world have come from this region (Vancini et al., 2014). These runners are primarily of Kenyan and Ethiopian descent and classically possess high VO2 max, hemoglobin, hematocrit, tolerance to altitude, bland diets of rice and beans, optimal running economy, and optimal muscle fiber type composition (Wilber & Pitsiladis, 2012). Much research has explored the possibility that genetic factors have yielded an advantage in this particular population, especially genes responsible for anthropometric, cardiovascular, and muscular adaptations to training (Vancini et al., 2014).
Continue reading the full article at https://simplifaster.com/articles/nature-vs-nurture-determinants-athletic-potential/