Describe the optimal nutritional strategy for recovery from prolonged exercise and discuss how recovery duration would influence your recommendations.

Question 1

Is nutritional strategy during recovery more vital during short term (<8 hours) or long term recovery?

Answer 1

Short term

Question 2

Describe the nature of glycogen repletion

Answer 2

> Biphasic (fast then slow phase).
Proglycogen stored first, then macroglycogen.
Auto-regulated process, where glycogen stores determine the rate of repletion/storage.

Question 3

How does delayed (2 hour) feeding impact muscle glycogen repletion vs immediate CHO feeding in the short term (2 hrs) and long term (8hrs)?
- What’s the reference for this?

Answer 3

• Betts & Williams (2007)
  More rapid rate of muscle glycogen recovery w/ immediate feeding.
  Much higher muscle glycogen after 2 hours w/ immediate feeding. No differences after 8 hours. (also shown in Parkin et al, 1997)

Question 4

Why does immediate CHO feeding result in higher rate of glycogen repletion in early stages vs. delayed feeding?

Answer 4

Muscle is very responsive to insulin post-exercise and delaying feeding leads to rapid reversal in exercise-induced increases in glucose uptake.

Question 5

Describe the role of insulin in muscle glycogen repletion

hint: there are 4

Answer 5

> Stimulates translocation of GLUT4 from storage vesicle to plasma membrane, more GLUT4 on membrane to take up glucose.
Helps keep GLUT4 on membrane
Increases intrinsic activity of GLUT4 on membrane
Stimulates glycogen synthase, which converts G-6-P (product of incoming glucose) into muscle glycogen

Question 6

What timing recommendations would you give for post-exercise CHO intake when recovery period is short (e.g. comp day or multiple training sessions)?
- Give reference(s) to back up your point.

Answer 6

Important to ingest CHO asap post-exercise when recovery period is short as muscle is most responsive to insulin and therefore rate of muscle glycogen storage is higher.
Feeding little and often to keep insulin levels high and GLUT4 transporters on muscle membrane.
- Betts & Williams (2007)
- Ivy et al (1998)

Question 7

What timing recommendations would you give for post-exercise CHO intake when recovery period is long (e.g. the next day)?

Answer 7

Not necessary to ingest CHO immediately post-exercise.
Personal preference can be taken into account without major detriment to recovery.
This applies to both timing and type.
- Betts & Williams (2007)

Question 8

How may frequency of CHO intake post-exercise affect subsequent performance?
- Give a reference.

Answer 8

More frequent CHO ingestion during 4 hour recovery period may increase reliance upon CHO oxidation in following bout, however, no detriment to TTE in a run.
- Siu et al (2004)

Question 9

Describe the study methods and results of Blom et al (1987).

Answer 9

Cycle to exhaustion followed by 6 hr recovery with ingestion of GLU, SUC or FRU.
Glu + Suc had faster muscle glycogen synthesis than fru. Fru better for liver glycogen, therefore, ingest sucrose for muscle and liver glycogen repletion.
Glu faster than Fru because higher GI.

Question 10

How may a CHO’s GI impact recovery of muscle glycogen post-exercise?
- Give a reference

Answer 10

• Kiens et al (1990)
  Prolonged cycle followed by 6 hours recovery ingesting either LO or HI GI CHO.
  HI GI had sig higher glycogen synthesis after 6 hours, but no difference at 14 hours.

Question 11

How may GI of CHO ingested prior to exercise impact performance?
- Give a reference

Answer 11

• Wu & Williams (2006)

Low GI CHO ingested 3 hours prior to TTE run at 70% VO2 max resulted in greater TTE and fat oxidation than high GI meal.

Question 12

Describe your recommendations for GI of CHO ingested between a short and long recovery period.

Answer 12

Short term (<6-8 hours) it's important to have GI carbs to maximise glycogen synthesis. 
Longer term it doesn't matter much. 
Moderate recovery periods it may be useful to have high GI first to maximise glycogen repletion and then low GI ~3 hours prior to repeat performance to increase fat oxidation and performance (Wu &amp; Williams, 2006).

Question 13

How does glycogen repletion post-exercise differ with varying CHO forms (liquid vs. solid) ingested?
- Give a reference and describe the study

Answer 13

• Reed et al (1989)
  Prolonged cycle followed by 4 hour recovery ingesting either liquid or solid CHO.
  No sig differences between the two in terms of muscle glycogen repletion.

Question 14

Describe the limitation to Reed et al’s 1989 study into how CHO type effects muscle glycogen repletion and give the real world implications of this.

Answer 14

CHO dosages were relatively tame compared w/ modern standards (0.75 g/kg/h).
Higher dosages may mean liquid could be taken in easier and better tolerated in the gut than solid.
Also liquid gives added benefit of hydration.

Question 15

Why is it difficult to ascertain the smallest amount of CHO needed to maximise rate of muscle glycogen storage?

Answer 15

Confounding influence of other factors (e.g. type and timing of CHO ingestion).

Question 16

Describe the results of the Blom et al (1987) study into amount of CHO ingested for recovery following exercise and cover the reason why these results may have limited validity.

Answer 16

0.35 g/kg/h sufficient to maximise rate of glycogen resynthesis following exhaustive exercise.
No sig diff when ingestion raised up to and above 0.75 g/kg/h.
Limitation: feeding frequency during recovery was relatively infrequent (2 hours). This may not adequately maintain blood glucose and insulin levels for the entire period between feedings and could have caused plateau rather than actual maximal glycogen resynthesis.

Question 17

Describe the findings from Betts’ 2007 review in terms of relationship between CHO ingestion amount and glycogen resynthesis rate post-exercise.

Answer 17

Dose-response relationship between CHO ingestion and glycogen resynthesis rate limited by ingestion of ~1.1 g/kg/h

Question 18

Optimal CHO ingestion during recovery after prolonged exercise to maximise TTE?

Answer 18

dose-response relationship caps out at ~1.1 g/kg/h

Question 19

Why could ingestion of greater than optimal amount of CHO during recovery from prolonged exercise not lead to improvement in glycogen resynthesis or subsequent performance (or even lead to detriment)?

Answer 19

> Saturation of intestinal transporters limits glycogen synthesis, not gastric emptying (Hawley et al, 1994).
GI distress

Question 20

What effect does adding PRO to post-exercise CHO have on glycogen recovery?
- give reference

Answer 20

No benefit if CHO ingestion is optimal (1.1 g/kg/h).
If CHO <0.8 g/kg/h then addition of PRO (0.3-0.4 g/kg/h) improves muscle glycogen synthesis rate by stimulating a small insulin response.
- Betts & Williams (2010)

Question 21

How does PRO supplementation w/ CHO during recovery impact a second bout of exercise?
- reference

Answer 21

CHO+PRO led to lower muscle glycogen oxidation, greater glucose ad lactate oxidation and 50% greater serum growth hormone response (greater fat metabolism).
Betts et al (2008-2013)

Question 22

How does PRO intake w/ CHO post-exercise impact protein synthesis short term (<2 hours) and long term (next morning)?
- reference

Answer 22

PRO+CHO led to greater protein synthesis in the first few hours vs CHO only. However, differences were not significant next morning, similar to the rate of muscle glycogen resynthesis when feeding of CHO is immediate vs delayed.

Question 23

What are the benefits of ingesting caffeine post exercise?

-reference

Answer 23

Ingestion of 8 mg/kg of caffeine found to significantly increase muscle glycogen re-synthesis (66%) during 4 hours of recovery after exhaustive cycling when ingested alongside CHO (4 mg/kg), compared with CHO only in trained athletes.
- Pedersen et al (2008)