Articles Flashcards
Carbohydrate contribution and exercise intensity? (van Loon et al. 2001)
Protocol - Contribution of CHO at different exercise intensities
Results - increasing intensity increases the contribution of energy that is generated from CHO
Relationship between muscle glycogen and exercise capacity? (Bergstrom et al. 1967)
Protocol
- mixed diet consumption and cycling performance
- high protein and CHO, high fat and mixed diet
- measured oxygen consumption (assess substrate utilisation), muscle biopsies, lactate and blood glucose
Results
- linear relationship between pre-muscle glycogen content and exercise capacity
- the higher the CHO intake the greater the exercise capacity
The effect of carbohydrate intake on exercise performance and mood state? (Achten et al. 2004)
Protocol
- 7 trained male runners
- cross-over design
- 4 days moderate intensity & 7 days intensified training
- high CHO (8.5g/kg/d) vs low CHO (5.4g/kg/day)
Results
- speed during an 8km was maintained in the high CHO group
- 16km run time was maintained in the high CHO group
- mood state was maintained in the high CHO group
Carbohydrate ingestion on muscle glycogen and exercise performance? (Bergstrom & Hultman 1966)
Protocol
- one cycling leg and one rest leg
- ingestion of CHO
Results
- cycling to exhaustion depleted muscle glycogen in the exercise leg
- CHO ingestion increased muscle glycogen stores in the exercise leg
Effects of carbohydrate ingestion on muscle glycogen stores and performance? (Sherman et al. 1981)
Protocol - moderate CHO - Low CHO and high CHO - moderate CHO and high CHO Results - all groups increased muscle glycogen stores - after 7 days all had similar levels of muscle glycogen - no effect on performance
Effect of carbohydrate loading on muscle glycogen stores over time? (Bussau et al. 2002)
Protocol
- 8 male
- high CHO (10g/kg BM/day) over 3days, remaining inactive
Results
- high increase in muscle glycogen stores of the first 24-72hrs
- no further increase after the next 2days
How does altering carbohydrate availability affect the response to training? (Wojtaszewski et al. 2003)
Protocol
- 8 athletes
- 1hr of exercise (low MG) vs 1hr rest (high MG)
- measured muscle glycogen
Results
- altering nutrient availability can alter the response of muscle signalling molecules to a bout of exercise
- AMPK activity increases in low muscle glycogen
Effects of train low, compete high on performance, citrate synthase and HAD activity? (Hansen et al. 2005)
Protocol
- knee extension
- 10wk one leg trained high MG (once a day) stores vs low (twice every other day)
Result
- no difference in max power
- significant increase in time to exhaustion with low MG
- greater increase in citrate synthase activity with low MG (oxidative metabolism)
- trend for increased HAD activity with low MG (fat metabolism)
Effects of train low, compete high on performance? (Hulston et al. 2010)
Protocol
- training with high MG vs low MG
- trained at a self-selected training intensity
Results
- time trial performance increased in both groups
- high-intensity session results in a greater increase in power output for the higher MG stores
Effects of sleep low on AMPK and p38MAPK activity? (Lane et al. 2015)
Protocol - sleep with low glycogen stores
Results - increases in AMPK and p38MAPK following exercise in the fasted state
Effects of different carbohydrate nutritional interventions and exercise performance (VO2)? (Burke et al. 2017)
Protocol - 21 elite race walkers - 3wk isoenergetic diet - high CHO - periodised CHO - low CHO, high fat Results - low CHO, high fat had a greater increase in VO2 - greater benefit from periodised
Effects of pre-carbohydrate feeding (fed vs fasted) on and muscle glycogen, blood glucose, plasma fatty acids and RER during exercise? (Coyle et al. 1985)
Protocol
- 7 subjects
- 105min cycling at 70% VO2max
- CHO meal 4hr before vs 16hr fast
Results
- muscle glycogen concentration higher in the fed condition
- blood glucose concentration dropped in the fed state prior to exercise due to insulin
- blood glucose concentration increased during exercise due to glucose uptake in the muscle
- plasma fatty acids was higher in the fasted state
- respiratory exchange ratio was higher in the fed state, indicating CHO oxidation
Effects of varying amounts of carbohydrate intake on performance and RER? (Sherman et al. 1989)
Protocol
- 0 vs 312g CHO
- 45 vs 156g CHO
- 4hrs before 45min performance test
Results
- high 312 g CHO had a greater performance than 0g CHO
- there was little difference in performance between 45 and 156g CHO
- respiratory exchange ratio was highest in the high CHO meal indicating CHO oxidation
Effects of pre-exercise feeding on performance and blood glucose concentration? (Chryssanthopoulos et al. 1989)
Protocol - 10 males - 2x 30km runs - 4hr before CHO meal - 4hr before placebo drink and CHO-E drink every 5km Results - no difference in performance - blood glucose concentration had an initial rise after the pre-exercise meal which returned to baseline during exercise
Effect of having breakfast on performance? (Mears et al. 2018)
Protocol
- CHO, placebo, and water
- short-duration aerobic exercise
Results - increased performance in both the placebo and CHO condition
Effect of either carbohydrate or water intake on resistance exercise and hunger? (Naharudin et al. 2020)
Protocol - CHO, placebo, and water
Results
- increased performance in both placebo and CHO conditions
- increased hunger in the water condition
What is the effect of carbohydrate mouth rinse on performance? (Carter et al. 2004)
Protocol
- CHO (12.5%) vs placebo
- 1hr/~40km TT with or without CHO-E
Results - time trial performance was reduced with the CHO mouth rinse
Is there a benefit to carbohydrate intake on performance? (Reviewed by Stellingwerf & Cox 2014)
Protocol
- CHO vs placebo
- 61 studies reviewed
Results
- 82% of the studies showed a performance benefit with CHO intake
- dose-response relationship
- CHO has a greater effect on performance as duration increases
What carbohydrate methods can increase exogenous carbohydrate oxidation? (Jentijen et al. 2004)
Protocol
- glucose (1.2g/min)
- maximal glucose (1.8g/min)
- equivalent glucose (1.2g/min) and fructose (0.6g/min)
- tracer to assess CHO oxidation
Results - combined glucose and fructose can increase exogenous CHO oxidation more than glucose alone
The effect of multiple glucose transporters on performance? (Currell & Jeukendrup 2008)
Protocol
- water, glucose, vs glucose and fructose
- 8 trained male cyclists
- 2hr @60% VO2max followed by a ~1hr TT
Results
- power output was higher in the glucose and fructose condition
- performance was higher in the glucose and fructose condition (19& better than water and 8% better than glucose)
Effect of natural carbohydrate sources compared to gels on performance? (Salvado et al. 2019)
Protocol - potatoes vs CHO gels
Results
- natural CHO requires a larger intake fo foot to achieve the same volume of CHO compared to the hell
- there was no difference in improvements in time trial performance
- greater GI symptoms with natural CHO
Effect of different carbohydrate drink patterns (volume and frequency) on exogenous carbohydrate oxidation? (Mears et al. 2020)
Purpose
- to determine how the pattern of CHO ingestion during running effect exogenous and total CHO oxidation rates and the reported measures of GI comfort
Protocol
- water, 50mL CHO every 5min vs 200mL CHO every 20min
- 12 males (26+/-7yrs, 67.9+/-6.7kg, 68+/-7ml/kg/min)
- 100min run @ 70% VO2max
Results
- a higher volume, low-frequency drink increased exogenous CHO oxidation, this may be due to increased gastric pressure and subsequent emptying rate
The effect of hydrogel technology on performance? (Mears et al. 2020)
Protocol - hydrogel vs drink intake in cyclists -2hr preload followed by a 20min TT Results - no difference in performance between the hydrogel and an equivalent drink
The effect of carbohydrate enriched diet on the recovery of muscle glycogen after exercise? (Peihl 1974)
Protocol
- 4 subjects
- CHO enriched diet (60g)
- 1hr endurance exercise followed by 1hr repeated efforts on the bike
Results
- very rapid initial glycogen resynthesis after exercise following CHO ingestion
- glycogen synthase activity driving glycogen synthesis is heavily influenced by muscle contraction resulting from the exercise
- insulin-independent phase from 10-15min
- levelling off after 15min
The effect of exercise on muscle glycogen resynthesis? (Bergstrom & Hultman 1966)
Protocol - exercise leg vs rest leg
Results - glycogen resynthesis is driven by muscle contraction from exercise
The effect of the timing of carbohydrate intake on glycogen synthesis and glycogen stores? (Ivy et al. 1988)
Protocol - immediate feed vs 2hr delay (depleted glycogen)
Results
- immediate feeding increased muscle glycogen storage within the first 2hrs
- the 2hr delay feeding had similar glycogen stores as the immediate feeding group after 4hrs
- total rate of muscle glycogen storage of the 4hr was increased in the immediate feeding group
- The insulin-independent phase of rapid muscle glycogen synthesis seems to be driven by low muscle glycogen and contraction-induced factors resulting in an increase in glucose transport
The effect of the timing of carbohydrate intake on glycogen stores in team sport athletes? (Bradley et al. 2017)
Protocol
- immediate feed vs 2hr delay
- 6g/kg CHO
- rugby players
Results
- post-exercise muscle glycogen stores were similar between the two groups
- 48hr post-exercise the immediate feed had a greater increase in muscle glycogen compared to the 2hr delayed feed
The effect of carbohydrate and protein ingestion on muscle glycogen resynthesis? (Van Loon et al. 2000)
Protocol
- low CHO (0.8g/kg/hr)
- high CHO (1.2)
- CHO (0.8) and protein (0.4)
Results
- CHO and protein had a bigger insulin response
- the addition of protein when CHO is insufficient can help with a full CHO resynthesis programme, due to leucine in protein
What are the effects of hypohydration on endurance and cognitive performance in temperate-warm-hot conditions? (Sawka et al. 2007?
Protocol - dehydration
Results - dehydration of 2% body mass degrades aerobic exercise and cognitive/mental performance in temperate-warm-hot environments
The effect of hypohydration on physiology? (Montain & Coyle 1992)
Protocol - 4% dehydration in a 2hr period
Results
- hypohydration decreased SV and Q
- hypohydration increases HR
- hypohydration increases core body temperature
The effect of hypohydration on the perception of effort and thrist? (Casa et al. 2010)
Protocol - outdoor run in the heat
Results - hypohydration increases perceived exertion, thermal sensation and thirst
The effect of hypohydration on running velocity? (Armstrong et al. 1985)
Protocol - a diuretic drug used to increase urine output and hypohydration
Results - running velocity is greater
The effect of hypohydration and temperature on endurance performance? (Keneflick et al. 2010)
Protocol
- 3hr of heat exposure at 50C
- dehydration vs euhydration
Results
- in all temperatures, the dehydration performance was impaired
- dehydration has a greater effect on performance as the temperature increases due to increased skin temperature
The effect of hypohydration on endurance performance? (Streams et al. 2009)
Protocol
- 24hr fluid restriction followed by exercise
- dehydration vs euhydration
Results - performance was decreased when dehydrated
The effect of hypohydration on exercise, contrasting views - weight loss? (Zouhal et al. 2011)
Protocol - marathon
Results
- an increase in weight loss results in increased performance (substantial variability)
The effect of hypohydration on exercise, contrasting views - sweat rate? (Dion et al. 2013)
Protocol - run
Results
- The faster you run the greater the sweat rate
- No relationship between running speed and drink frequency
The effect of hypohydration on exercise, contrasting views - weight loss? (Zouhal et al. 2013)
Protocol - marathon running
Results - Some elite marathon runners lost ~10% of body weight
The effect of hypohydration on plasma volume, thirst, RPE and endurance performance? (James et al. 2017)
Protocol
- blinding
- 8x 5min exercise (5min rest) followed by a 15min TT
- dehydration vs euhydration
Results
- dehydration results in a substantial loss in plasma volume compared to euhydration
- dehydration had a substantial increase in thirst compared to euhydration
- dehydration caused a greater increased RPE compared to euhydration
- dehydration decreased performance relative to euhydration
The effect of blinding and hypohydration on plasma volume, thirst, RPE and endurance? (Funnell et al. 2019)
Protocol
- blinded vs unblinded
- dehydration vs euhydration
- cycle 150min followed by TT
Results
- dehydration resulted in a substantial loss in plasma volume, an increase in thirst and an increase in RPE relative to euhydration
- there was no difference in response between the blinded and unblinded group
- dehydration resulted in similar performance deficits in the blinded and unblinded groups
The effect of thirst on performance? (Adams 2018)
Protocol
- 2hr preload provided with a small amount of fluid every 5min
- dehydration (DEY-NOT-THIRST) vs euhydration (EUH-NOT-THIRST)
Results - even in the absence of thirst dehydration impairs performance
The effect of induce-dehydration and habitual dehydration on endurance? (Fleming & James 2014)
Protocol - dehydration and euhydration - familiarisation - VO2peak Results - dehydration impaired performance by 6% - dehydration habituation impaired performance by 1%
The effect of the rate of drinking on drink retention? (Jones et al. 2010)
Protocol - drink over 1hr vs 4hrs
Results - for a given drink volume, drinking slower increases drink retention
The effect of CHO rehydration on fluid retention, plasma volume and serum osmolality? (Clayton et al. 2014)
Protocol
- rehydration following exercise
- 1% body weight loss
- 2% vs 10% CHO
Results
- more urine produced in the 2% CHO relative to the 10% CHO drink
- no recovery of plasma volume following rehydration - due to hypertonic CHO content
- serum osmolality continues to increase after 2L
Does hydration really matter in terms of recovery? (Funnell et al.)
Protocol
- voluntary recovery
- exercise bout to loss 2% BW
Results
- resting showed no change in body mass and urine serum osmolality
- exercise had a decrease in body mass and an increase in urine serum osmolality
- indicts possibly some carryover effects of hypohydration to the next day/session
The effect of a high ketosis diet with a caloric restriction on exercise performance and substrate utilisation? Limitations? (Phinney et al)
Protocol
- 10wk balanced diet vs 4wks ketogenic diet (85% fat, <20g/day CHO)
- 62-64% VO2 max to exhaustion in a fasted state
Results
- time to exhaustion was similar between diets
- substrate utilisation was preferential to fat oxidation in the ketogenic diet
- there was no detriment of a ketogenic diet on performance
Limitation
- not randomised assignment to each diet (balanced followed by ketogenic)
- balanced diet was prescribed, therefore is an intervention
- exercise task favours low CHO adaptation
The effect of a high-fat diet on substrate metabolism and exercise performance at different intensities? (Lambert et al. 1994)
Protocol -
70%fat vs 70% CHO diet for 2wks
- Wingate test followed by an 85% Wpeak to exhaustion and followed by a 50% Wpeak to exhaustion
Results
- Fat diet reduced reliance on CHO and increased fat oxidation by changing RER
- CHO stores pre-exercise were lower in the fat diet
- Wingate performance was similar
- 85% Wpeak performance was greater in the CHO diet
- 50% Wpeak performance was greater in the fat diet
- differential performance benefit depending on the intensity of exercise
The effect of a high-fat diet on substrate utilisation over 15days? (Goedecke et al. 199)
Protocol
- 69% fat diet form 15days
- 2.5hrs at 63% Wpeak
Results - shift in substrate utilisation from CHO to fat as early as 5days
The effect of a high-fat diet followed by CHO pre-loading on substrate utilisation and fat oxidation? (Burke et al. 2002)
Protocol
- high fat (4.4g/kg/day) for 5 days followed by high CHO (9.3g/kg/day) for 1 day and a high CHO pre-exercise meal
- 2hr at 70% VO2max
Results
- fat is preferentially oxidised, even after the fat adapt condition
- high CHO pre-loading replenished muscle glycogen stores
- we can shift metabolism by ingesting a higher fat diet, and CHO can still be spared when muscle glycogen stores are restored
