KNES 337 - Unit 27 and 28 Physical Fitness and Physical Performance

adult physical activity guidelines

• 150 min of moderate to vigorous physical activity per week (2 ½ hours)

• 2 sessions of strength-training per week

children physical activity guidelines

• 60 min of moderate to vigorous physical activity everyday 

  • At least 3 days per week should be vigorous 

• Activities that strengthen muscle and bone 3 days per week

fuel sources at rest

85% from fat, 10% from CHO, 5% from protein

fuel sources during exercise

1. Muscle glycogen

2. Blood glucose

3. Plasma fatty acids

4. Intramuscular triglycerides 

extent of contribution from carbs and fat

depends on

• Intensity and duration of exercise - higher intensity, more carbohydrate used 

• Level of exercise training 

• Initial muscle glycogen stores

• Supplementation with CHO during exercise - drinking sport drinks (exogenous sources)

energy systems

includes ATP-phosphocreatine system, glycolytic system, oxidative system

ATP-phosphocreatine system

immediate energy source, short-term, explosive power activities up to 10 seconds

glycolytic system

anaerobic breakdown of glucose to lactic acid (glycolysis), any intense effort lasting up to 2 min

oxidative system

after 2 min during low to moderate intensity exercise, glycogen provides 60-70% of fuel during first 20 min of low to moderate intensity exercise, after 20 min fat is increasingly used

fatigue

• Depletion of muscle and liver glycogen levels → extreme fatigue

• Some carbohydrate is needed by muscles to generate energy from fat breakdown

• Water and glucose ingestion at point of fatigue may prolong exercise but severe limitations exist for high level of energy production needed for exercise

• Inability to maintain current level of activity, perception of effort greatly increased

dietary protein

timing and amount matter when taking protein for exercise

timing of protein intake

Best to take immediately after 

• “Longitudinal training studies currently suggest that increases in strength and muscle mass are greatest with immediate post-exercise provision of protein”

amount of protein intake

• Evidence from systematic review and meta-analysis

• No further performance benefits (strength, muscle mass) when >1.62 g protein/kg/day but 95% CI (1.03-2.20 g pro/kg/d)

  • Average of 1.62 g but variability 

pre-competition nutrition

maximize muscle and liver glycogen for endurance

goals of pre-competition meal

• Stomach should be relatively empty at start of competition 

• Minimize gastrointestinal distress

• Avoid hunger, lightheadedness or fatigue

• Adequate fuel (carbohydrate) in blood and muscles

• Adequate amount of body water

3-4 hours before competition

have a solid meal 

• CHO rich with minimal fiber, fat, and protein which can cause GI distress during exercise

• Avoid gas formers and bulky foods like bran

less than 1 hour before competition

small or liquid

• Many athletes do well with 25-30 g of CHO

foods to consume 1-4 hours before exercise

• Peanut butter and honey on crackers

• Fruit and yogurt smoothie

• Low-fat cottage cheese

• Yogurt + granola + fruit

• Chicken on a whole-wheat bun

foods to consume 30-60 minutes before exercise

• A piece of fruit

• Whole grain crackers

• Sports gel, sports bar

• Fruit puree pouch like applesauce

sports bars

energy or protein rich, no magical qualities but are convenient

• could be used as a substitute for a pre-competition meal, but not on a long-term basis to replace normal healthy eating patterns 

• Disadvantages? Artificial and natural sweeteners 

eating during competition

• Generally not needed, but depends on event

• CHO → additional energy supply 

• Water → temperature regulation 

• > 1 hour = 30-60 g/h of CHO

• If duration is 1-2 hours, have up to 30 g/h of CHO 

  • Type = rapidly oxidized (e.g. glucose, sucrose, maltodextrin)

competitions longer than 1 hour

have 30-60 g/h of CHO

competitions 1-2 hours

have up to 30 g/h of CHO that are rapidly oxidized (glucose, sucrose, maltodextrin)

post-competition for endurance sports

• Immediately post-exercise simple sugars help restore muscle glycogen and adding some protein may enhance storage (ratio of 3:1)

• In general, balanced diet will restore nutritional status after hard physical training

• need CHO in daily diet (7-12 g/kg BW)

post-competition for resistance training

focus on protein to preserve muscle mass

• 30-40 g before bed 

• casein best before bed

• Whey good for post-exercise

casein vs. whey

differ in how fast they are digested

whey is fast protein, casein is slow (will coagulate in the stomach, slower delivery of amino acids), so casein is good before bed, whey good for post-exercise