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Summary Nutrition and Sports
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By: francadronten • 5 year ago
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Lecture 1: Introduction: Fit for the fightSport nutrition science is the application of nutrition principles for the purpose of improving training,
recovery and performance. Nutrition plays a role directly related to performance and indirectly via
physical training. The main aim of sport science is to improve sporting performance.
Pyramid of sport nutrition: lowest level balanced diet (e.g. quark), middle: sports nutrition (e.g.
protein bar, specific food to increase performance), highest: supplements.
Nutritional supplements encompasses:
- Sport nutrition products: energy/recovery drinks, bars, (protein) shakes
- Dietary supplements: vitamins, minerals, fatty acids
- Ergogenic aids: creatine, caffeine, beetroot (compounds increasing exercise performance)
In practice, athletes:
- Will practice well-designed dietary plans that are nutritionally sound (and on scientific
principles or perceived to be correct and beneficial, but not be based upon scientific data)
- Will focus on ritualistic behaviours that previously led to success (based on rituals)
- Will adopt scientific recommendations based upon misinformation
- May consider nutrition and food selection an inconsequential component of their training
(e.g. with team sports, nutrition might play a less important role for the athletes)
- Will blend actual food with an array of dietary supplements
Sport nutrition science is a new research area (started ~ ’80). New perspectives in sport nutrition:
- Nutrition goals and requirements are not static but depends on athletes and their goal
- Nutrition plans need to be personalized and periodized to the individual athlete
- A key goal of training is to adapt the body to develop metabolic efficiency and flexibility,
while competition nutrition strategies focus on providing adequate substrate
Recent developments and future:
- ‘Customized nutrition’: eating strategies for athletes must take account of each athlete's
physiological, biochemical characteristics, training load and competition goals
- Nutrition strategies are used to modulate training-induced muscle adaptations
- Opportunities to apply these same practices and principles to other population groups who
have no interest in sport (e.g. train people before major surgery)
Key aspects sport science:
- Measuring (the predictor of) performance in controlled settings
- Translation into practice (implementation)
- Controlling diet and exercise
Performance is affected by endogenous and exogenous factors (physical, mental, technical and
tactical) factors. Performance components are speed, strength, coordination, flexibility and
endurance. These components can be measured different ways e.g. endurance capacity, fat
oxidation, spares muscle glycogen, energy balance, blood flow, etc.
Endurance capacity is the exercise time to volitional fatigue (time to exhaustion).
Endurance performance relates to completing a certain task as fast as possible.
Running is easy to measure, but soccer is much harder. To evaluate measurements, the following
aspects should be reviewed:
- Validity (accuracy): resembles the performance that is simulated
- Reliability (precision, reproducability): CV, ICC, Pearsons r
- Sensitivity: to detect small but important differences.
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,External factors should be controlled when doing performance testing:
- Familiarization: training session(s) should be used to correct for the learning effect
- Verbal encouragement
- Music
- Feedback (preferably none)
- Additional measurements
- Diet: should be standardized
o Think about overnight-fast or pre-event meals, CHO, energy, protein, hydration
status, caffeine intake/withdrawal, alcohol consumption and supplement use
o Consider the advantages and disadvantages, match the level of dietary control with
the logistics and resources of the study, provide the food, measure and report
compliance
- Exercise
o Training status subjects (trained or untrained)
o Habitual training (should they change their habitual training?)
o Last exercise bout
o Experimental exercise intensity (relative vs absolute intensity?)
2
,Lecture 2 & 3: Energy Metabolism
Types of sports are explosive power (weight lifting), sprinting (short-term with high intensity), middle
distance (skating), endurance and game playing.
ATP → ADP + Pi + energy, ADP → AMP + Pi + energy
The conversion of ATP to ADP is needed for amongst others muscle contraction, Ca-pump (for the re-
uptake of calcium) and Na/K-pump. ADP to converted back to ATP by mitochondrial fuel oxidation.
PCr= phosphor creatine, SNS = sympathetic nervous system
Gluconeogenesis is the generation of glucose. Glycolysis is glucose breakdown and glycogenolysis is
glycogen breakdown. PDH (pyruvate dehydrogenase) transforms pyruvate into acetyl-CoA, PFK
(fosfofructokinase) regulates glycolysis and CPT controls enzymes.
Local factors such as calcium, protons and ‘energy change’ in skeletal muscle influence the
breakdown of ATP. They influence the rate limiting enzymes. With ‘energy change’ (ATP/ADP,
NADH/NAD+, AMP and AcetylCoA/CoA), the change in ratio is more important than the absolute
amounts.
Hormones are released during exercise and can control the availability of substrate. Hormones have
more influence on the long term than the local factors. Hormones regulating the energy metabolism:
- Insulin / glucagon
- (nor)adrenalin
- Growth hormone
- Cortisol (more linked to exercise, more long term than other hormones)
During exercise, there is an increase in adrenalin, increase in glucagon, increase in cortisol/growth
hormone and a decrease in insulin. Especially the decrease in insulin causes an increase in lipolysis,
glycogen breakdown and gluconeogenesis. The decrease in insulin also causes a decrease glucose
uptake, but during exercise the uptake of glucose is independent of insulin.
(Muscle) tissue growth (protein synthesis) is induced by growth hormone and testosterone.
The response (the increase/decrease in hormones) is related to relative exercise intensity.
For very high force contractions lasting 1-2 seconds, the initial energy source is from ATP stores. The
amount of ATP in your muscles stored is only present for 1-2 seconds. Afterwards the
phosphocreatine is used as energy source. After 1-1.5 min maximal dynamic exercise (high intensity),
energy metabolism become predominantly aerobic.
There are four sources of energy:
1. ATP breakdown (for 1-2 seconds, very fast)
2. Phosphocreatine → creatine + Pi
3. Anaerobic glycolysis
o Glucose-6-P is converted into pyruvate and lactate is escape
4. Oxidative phosphorylation (oxidative)
o Carbohydrates, lipid, protein and alcohol are the substrates
3
, 2+3+4 are energy resynthesis systems
1+2 are phosphagen systems (high energy phosphate)
2+3 are substrate-level phosphorylation (no oxygen needed)
Phosphocreatine has a high resynthesis of energy. For anaerobic glycolysis and especially oxidative
metabolism this lower. The phosphocreatine is directly available. The anaerobic glycolysis take a
short while, because some steps need to be taken. The delay of the oxidative metabolism depends
on its energy source. After two hours lipids are the only energy source left, however lipids are
already used earlier. All the systems are activated at the same time, but it take some time for e.g. the
aerobic system to be working. But all are activated.
The capacity is the amount of substrate that is available. With combining the rate and capacity, you
can see how long the substrate is present. Phosphocreatine is only for a small time of exercise
available. It is higher for the anaerobic glycolysis, however the acidification causes a capacity of 1.6.
The oxidative metabolism has a high capacity, especially the lipids stored in adipose tissue.
If you are trained, your muscles can store more glycogen and you have more immediate and short-
term energy systems. However, if you are trained, you often have more intense workouts which
deplete them more faster.
Absolute ATP-resynthesises gives a different picture than the % capacity of energy systems.
Fatigue is the inability to maintain the same power output or force during
repeated muscle contractions. It is the increase in the perceived effort
necessary to exert a desired force or power output, and the eventual inability
to produce that force or power output. Picture right: possible sites of fatigue.
Main types:
- Central fatigue
- Excessive endurance training
- Nutrition and central fatigue
- Peripheral fatigue
Exercise begins and ends in the brain. With central fatigue (placed in central
nervous system), there is a reduction in motor unit activation and firing frequency. The central
nervous system arousal can alter the state of fatigue. Central fatigue can be reduced by increasing
motivation or physical/mental diversion.
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